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diff --git a/43320-0.txt b/43320-0.txt new file mode 100644 index 0000000..87f4b8c --- /dev/null +++ b/43320-0.txt @@ -0,0 +1,11054 @@ +*** START OF THE PROJECT GUTENBERG EBOOK 43320 *** + +THE WONDER BOOK OF + +VOLCANOES AND EARTHQUAKES + +[Illustration: MOUNT VESUVIUS IN ERUPTION] + + + + +THE +WONDER BOOK +OF +VOLCANOES AND EARTHQUAKES + +BY +Professor EDWIN J. HOUSTON, Ph.D. + +NEW YORK +FREDERICK A. STOKES COMPANY +Publishers + + + + +Copyright, 1907, by +FREDERICK A. STOKES COMPANY + +_All rights reserved_ + +_October, 1907_ + + + + +ACKNOWLEDGMENTS + + +We take this opportunity of acknowledging the courtesy of the +following publishers, who have helped us in connection with the +illustrations of this book:-- + +Henry Holt and Company ("Physiography," by Rollin D. Salisbury). + +D. Appleton and Company (Figs. 13, 35, 39, 40, 41, 42, 43, 44, 45 and +46, "Volcanoes: What They Are and What They Teach," by J. W. Judd; +Fig. 15, "Principles of Geology," by Sir C. Lyell). + +The American Book Company ("Manual of Geology," by James Dwight Dana). + +G. P. Putnam's Sons ("Earthquakes in the Light of the New Seismology," +by C. E. Dutton). + +The Clarendon Press ("Geology: Chemical, Physical, and +Stratigraphical," by Joseph Prestwich). + + THE PUBLISHERS. + + + + +CONTENTS + + +CHAPTER PAGE + +I. THE VOLCANIC ERUPTION OF KRAKATOA IN 1883 1 + +II. SOME EFFECTS OF THE ERUPTION OF KRAKATOA 12 + +III. THE VOLCANIC ISLAND OF HAWAII 26 + +IV. THE VOLCANIC ISLAND OF ICELAND 46 + +V. VESUVIUS 58 + +VI. OTHER VOLCANOES OF THE MEDITERRANEAN 73 + +VII. ORIZABA, POPOCATEPETL, IXTACCIHUATL, AND + OTHER VOLCANOES OF MEXICO 85 + +VIII. COSEGUINA AND OTHER VOLCANOES OF CENTRAL AMERICA 91 + +IX. THE VOLCANIC MOUNTAINS OF SOUTH AMERICA 97 + +X. VOLCANOES OF THE UNITED STATES 105 + +XI. THE CATASTROPHE OF MARTINIQUE AND THE VOLCANIC + ISLANDS OF THE LESSER ANTILLES 117 + +XII. SOME OTHER NOTED VOLCANIC MOUNTAINS 125 + +XIII. JORULLO, A YOUNG VOLCANIC MOUNTAIN 130 + +XIV. MID-OCEAN VOLCANIC ISLANDS 137 + +XV. SUBMARINE VOLCANOES 141 + +XVI. DISTRIBUTION OF THE EARTH'S VOLCANOES 148 + +XVII. VOLCANOES OF THE GEOLOGICAL PAST 153 + +XVIII. LAPLACE'S NEBULAR HYPOTHESIS 157 + +XIX. THE EARTH'S HEATED INTERIOR, THE CAUSE OF VOLCANOES 165 + +XX. SOME FORMS OF LAVA 178 + +XXI. MUD VOLCANOES AND HOT SPRINGS 193 + +XXII. THE VOLCANOES OF THE MOON 207 + +XXIII. EARTHQUAKES 219 + +XXIV. SOME OF THE PHENOMENA OF EARTHQUAKES 231 + +XXV. THE EARTHQUAKE OF CALABRIA IN 1783 245 + +XXVI. THE GREAT LISBON EARTHQUAKE OF 1755 252 + +XXVII. THE EARTHQUAKE OF CUTCH, INDIA, IN 1819 257 + +XXVIII. THE SAN FRANCISCO EARTHQUAKE OF APRIL 18, 1906 262 + +XXIX. SOME OTHER NOTABLE EARTHQUAKES 269 + +XXX. SODOM AND GOMORRAH AND THE CITIES OF THE PLAIN 281 + +XXXI. INSTRUMENTS FOR RECORDING AND MEASURING EARTHQUAKE + SHOCKS 290 + +XXXII. SEAQUAKES 296 + +XXXIII. THE DISTRIBUTION OF EARTHQUAKES 303 + +XXXIV. THE CAUSES OF EARTHQUAKES 308 + +XXXV. EARTHQUAKES OF THE GEOLOGICAL PAST--CATACLYSMS 319 + +XXXVI. THE KIMBERLY DIAMOND FIELDS AND THEIR VOLCANIC + ORIGIN 326 + +XXXVII. THE FABLED CONTINENT OF ATLANTIS 335 + +XXXVIII. PLATO'S ACCOUNT OF ATLANTIS 344 + +XXXIX. NATURE'S WARNING OF COMING EARTHQUAKES 364 + + + + +FULL PAGE ILLUSTRATIONS + + + PAGE + +MT. VESUVIUS IN ERUPTION Frontispiece + +STONES AND LAVA THROWN UPWARDS--ERUPTION OF + MOKUAWEOWEO, HAWAII, JULY 4-21, 1899 fac. 36 + +COTOPAXI 102 + +THE LAVA FLOW OF THE CRATER OF KILAUEA, HAWAIIAN ISLANDS 184 + +A SAN FRANCISCO PAVEMENT TORN BY THE EARTHQUAKE 266 + + + + +ILLUSTRATIONS IN TEXT + + +FIG. PAGE + +1. THE SUNDA ISLANDS 3 + +2. KRAKATOA BEFORE THE ERUPTION 4 + +3. KRAKATOA AFTER THE ERUPTION 4 + +4. VOLCANIC DUST AS IT APPEARS UNDER THE MICROSCOPE 19 + +5. THE HAWAIIAN ISLANDS 27 + +6. HAWAII 29 + +7. PANORAMA OF MOKUAWEOWEO 35 + +8. VIEW OF THE CRATER OF KILAUEA FROM THE VOLCANO HOUSE 35 + +9. CRATER OF KILAUEA 40 + +10. SECTIONS OF KILAUEA AT DIFFERENT PERIODS 42 + +11. ICELAND 47 + +12. THE MEDITERRANEAN 59 + +13. THE VOLCANIC DISTRICT AROUND VESUVIUS 60 + +14. MT. ETNA 77 + +15. STROMBOLI, VIEWED FROM THE NORTHWEST, APRIL, 1874 79 + +16. MEXICO AND CENTRAL AMERICA 86 + +17. SOUTH AMERICA 98 + +18. THE UNITED STATES 106 + +19. PANORAMA FROM THE MESA AT THE EDGE OF MT. TAYLOR 110 + +20. VOLCANIC NECKS, EDGE OF MESA AT MT. TAYLOR 111 + +21. THE LESSER ANTILLES 118 + +22. GRAHAM'S ISLAND--A RECENT VOLCANIC ISLAND 143 + +23. ALEUTIAN ISLANDS 146 + +24. MAP OF THE WORLD, SHOWING LOCATION OF ACTIVE AND + RECENTLY EXTINCT VOLCANOES 150 + +25. VOLCANIC VESICLES 183 + +26. THREAD-LACE SCORIÆ FROM KILAUEA 185 + +27. THREAD-LACE SCORIÆ FROM KILAUEA 185 + +28. FROST-LIKE LAVA CRYSTALS 187 + +29. FROST-LIKE LAVA CRYSTALS 187 + +30. BASALTIC COLUMNS, ISLE OF CYCLOPS, ITALY 188 + +31. COLUMNAR AND NON-COLUMNAR BASALT 189 + +32, 33. DRIBLET CONES 190 + +34. LAVA STALACTITES 191 + +35. CRATER OF THE GREAT GEYSER OF ICELAND 202 + +36. GIANT GEYSER 203 + +37. BEE HIVE 203 + +38. BEE HIVE GEYSER OF ICELAND 205 + +39. HEAVY STONE OBELISKS TWISTED BY CALABRIAN EARTHQUAKE + OF 1783 229 + +40. CIRCULAR HOLLOW FORMED BY CALABRIAN EARTHQUAKE 239 + +41. SECTION OF CIRCULAR HOLLOW FORMED BY CALABRIAN + EARTHQUAKE 239 + +42. MAP OF THE CALABRIAN EARTHQUAKE OF 1783 246 + +43. FISSURES CAUSED BY THE CALABRIAN EARTHQUAKE 249 + +44. MAP SHOWING DISTRICT VISITED BY THE EARTHQUAKE OF + CUTCH OF 1819 258 + +45. SINDREE BEFORE THE EARTHQUAKE OF 1819 259 + +46. SINDREE AFTER THE EARTHQUAKE OF 1819 260 + +47. MAP OF WESTERN COAST OF CALIFORNIA SHOWING POSITION + OF SAN FRANCISCO 263 + +48. NEW ZEALAND 274 + +49. MAP SHOWING REGION AFFECTED BY THE CHARLESTON + EARTHQUAKE OF 1886 277 + +50. SYRIA 282 + +51. COMPLEX RECORD OF SEISMOGRAPH 293 + +52. LONG DISTANCE SEISMOGRAM 293 + +53. VICENTINI VERTICAL PENDULUM 294 + +54. VICENTINI PENDULUM AND RECORDER 295 + +55. DAVISON'S EARTHQUAKE MAP OF JAPAN 306 + + + + +THE WONDER BOOK OF + +VOLCANOES AND EARTHQUAKES + + + + +THE WONDER BOOK OF VOLCANOES + +AND EARTHQUAKES + + + + +CHAPTER I + +THE VOLCANIC ERUPTION OF KRAKATOA IN 1883 + + +Krakatoa is a little island in the Straits of Sunda, about thirty +miles west of the island of Java, and nearly the same distance east +of the island of Sumatra. It is uninhabited and very small, measuring +about five miles in length and less than three miles in width. Its +total area is only thirteen square miles. This little piece of land +made itself famous by what took place on it during the month of +August, 1883. + +Krakatoa is one of the many islands that form the large island chain +known as the Sunda Islands. The most important islands of this chain +are Sumatra, Java, Sumbawa, Flores, and Ceram. Between Sumatra and +Java, the largest two of these islands, there is a channel called the +Straits of Sunda that connects the waters of the Indian Ocean with +those of the Pacific Ocean. The Straits of Sunda is an important piece +of water that forms one of the great highways to the East. Shipping +is, therefore, always to be found in its waters. + +As can be seen by the map, Krakatoa is not far from the Equator, +being situated in lat. 6° 7' S. and long. 105° 26' E. from Greenwich. +Since there are about sixty-nine miles in every degree of latitude, +Krakatoa is about 420 miles south of the Equator, and is about +twenty-five miles from Java. Java is part of the Dutch East Indies, +which includes Java, Celebes, the Spice Islands, and parts of Borneo +and Sumatra. Batavia, the principal seaport of Java, near the +northwest coast, is a great shipping centre, visited by vessels from +nearly all parts of the world. It has, however, no harbor, but is +approached from the ocean by means of a canal two miles in length, the +sides of which are provided with massive brick walls. Besides Batavia, +which is situated about one hundred English miles east of Krakatoa, +there are many smaller towns or villages, the most important of which +is Anjer, a thriving seaport town, where sailing vessels obtain their +supplies of food and fresh water. Before the eruption of Krakatoa, +Anjer was provided with a strong, stone lighthouse. + +Java is especially noted for its production of coffee, in which it is +second only to Brazil. Its area is about the same as that of the State +of New York. Java is one of the most densely populated parts of the +world, containing nearly four times as many people as the whole State +of New York. + +These facts about the situation and surroundings of Krakatoa are +necessary to an understanding of the wonderful thing that happened on +it during the month of August, 1883. In that month Krakatoa suffered a +most tremendous explosive volcanic eruption, for it is a volcano. + +[Illustration: FIG. 1. THE SUNDA ISLANDS] + +A volcano is a mountain or hill, generally conical in shape, having +at the top a nearly central opening, called a _crater_, from which +at times melted rock and lava, vapor and gases escape. The lava +either flows down the side of the mountain in a liquid condition, or +is thrown upwards into the air. If the distance the lava is thrown +upwards is sufficiently great the melted matter solidifies before it +falls to the earth. In such cases the largest fragments form what are +called _volcanic cinders_, the smaller pieces, _volcanic ashes_, and +the extremely small particles, _volcanic dust_. If, however, the lava +is thrown to a comparatively small height, it is still melted when it +falls, and is then known as _volcanic drops_ or _driblets_. + +[Illustration: FIG. 2. KRAKATOA BEFORE THE ERUPTION] + +It is not surprising that Krakatoa is a volcanic island, since it lies +in one of the most active belts of volcanic islands in the world, and +near the coasts of the most active of these islands; i. e., Java. +This belt, as shown in the map, includes, besides the Sunda Island +chain, parts of Gilolo, Celebes, Mindanao and the Philippine Islands. +These islands lie between Asia on the northwest and Australia on the +southeast. + +[Illustration: FIG. 3. KRAKATOA AFTER THE ERUPTION] + +There is no other part of the world with, perhaps, the single +exception of Japan, where so many active volcanoes are crowded in +so small a space. The island of Java, small as it is, has nearly +fifty volcanoes, of which at least twenty-eight are active. They are +situated in a lofty range running from east to west, some of the +peaks of which are more than 10,000 feet above the level of the sea. +Volcanic eruptions are so frequent that the island is seldom free from +them. + +As will be seen from the map shown in Fig. 2, Krakatoa consists of +three groups of volcanic mountains, the southern group giving the name +of Krakatoa to the island. Strictly speaking, this mountain was called +_Rakata_, but as it is now generally known as Krakatoa, it would be +unwise to attempt to call it by any other name. The central mountain +or group of mountains is known as Danan, and consists largely of part +of an old crater. The group of mountains which lies near the northern +end of the island was known as Perboawatan. From the centre of this +latter group of mountains are several old lava streams consisting +of a variety of lava resembling a dark-colored glass, known to +mineralogists as _obsidian_, or _volcanic glass_. + +Although Krakatoa was always a volcano, yet between the years 1680 and +1883, it was in the condition of a sleeping or extinct volcano. There +had been a severe explosive eruption in the year 1680, that caused +great loss of life and property, but ever since that time all activity +had ceased and it seemed that the volcano would never again burst out. +In other words, it was generally regarded as a trustworthy, sedate, +quiet, inoffensive and perfectly safe volcano, that had become extinct. + +The long continued quiet of Krakatoa was broken on the 20th of May, +1883, when the inhabitants of Batavia on the island of Java were +terrified by noises like the firing of great guns, that were first +heard between ten and eleven o'clock in the morning. These noises +were accompanied by the shaking of the ground and buildings. The +sleeping volcano of Krakatoa was evidently growing restless, but no +great damage was done and soon all was again quiet. The disturbances +were merely the forerunner of the terrible eruption soon to follow, +and confidence was soon restored. But suddenly, on Sunday, August +26th, 1883, almost without any further warnings, Krakatoa burst into +terrible activity and began an explosive eruption that has never been +equalled in severity in the memory of man. + +That memorable Sunday of August 26th, 1883, came during a season of +the year known as the _dry monsoon_, a name given the season of the +periodical winds from the Indian Ocean. Batavia, and the surrounding +country, greatly needed rain, for in this part of the world it seldom +rains from April to October, although the air is very moist and damp. +For this reason the beginning of the wet season is always welcomed. +When, therefore, the rumbling sounds of the approaching catastrophe of +Krakatoa were heard in Batavia, the people, believing that the noises +were due to peals of thunder, rejoiced, for all thought they heralded +an earlier setting in of the wet monsoon. But when the rumbling +sounds increased and reports were heard like heavy artillery, it was +clear that the sounds were the beginning of a volcanic eruption, a +phenomenon with which they were only too well acquainted, but, as +volcanic eruptions were far from being uncommon in Java, no one was +very greatly frightened. + +But this time the noises increased to such an extent that the people +became alarmed. Throughout the night the appalling sounds continued +and were accompanied by shakings of the earth sufficiently strong to +shake the houses violently. Sleep was out of the question. Many of +the people left their houses and remained all night in the open air, +fearing the shocks would bring the houses down over their heads. + +The morning instead of heralding the dawn of a beautiful tropical day, +with its bright, cheerful sunlight, brought with it skies covered +with gray clouds that completely hid the sun. The rumbling sounds, +however, had decreased, and the people were beginning to congratulate +themselves that the dangers were over, when suddenly, the sky grew +darker, and there began a shower of ashes that soon covered the +streets and houses of the city. About seven o'clock on the morning of +August 27th, a most tremendous crash was heard. The sky rapidly became +so dark that it was soon necessary to light the lamps in the houses +of Batavia, and some of the neighboring towns in the western part of +Java. In addition to this the air was filled with vapor, while every +now and then earthquake shocks were again felt. These shocks were +accompanied by terrific noises like those produced by the explosion of +heavy artillery. The noises rapidly increased in number and intensity +until they produced a nearly continuous roar, the nature of which it +is almost impossible to describe since it is probable that such sounds +had never been heard before by man. It is a curious fact, which, I +believe, has never been satisfactorily explained, that in most cases +the people in the immediate neighborhood of the volcano, as, for +example, those on board vessels in the Straits of Sunda, did not hear +the terrific noises at all. Possibly they were too loud and simply +gave a single inward impetus to the drum of the ear and then held it +in position. + +Probably some of my readers may remember that witty description given +by Dr. Oliver Wendell Holmes of an alleged effort made by all the +people of the world to find out whether or not there is a man in the +moon. This wonderful plan was as follows: + +Careful calculations were made to ascertain when it would be the same +time over all the earth so that all the people of the earth could +simultaneously shout at the top of their voices. In this way it was +hoped that the man in the moon, if there were such a person, would +notice the noise. + +The story goes on to tell how when the time approached for the great +experiment, and all were ready to shout as loud as they could, that +each person reasoning to himself or herself, that amid so great a +noise no one could notice whether his or her voice was omitted, +determined to remain silent, so as to be able to hear the noise and +the better to observe what the man in the moon would do when the sound +reached him. The result was that every person on the earth remained +silent and simply listened, so that the earth was never so quiet +before. + +Had Oliver Wendell Holmes, or any other person conceiving the witty +idea, lived during the time of the great explosive eruption of +Krakatoa, on that memorable August 27th, 1883, he might have taken +the opportunity of observing the man in the moon, had he not been +frightened by what was occurring, for certainly never before were +such tremendous or terrifying sounds produced, for these sounds, as +we shall see shortly, were actually heard for distances of more than +3,000 miles from the volcano. + +There were two different kinds of waves produced in the air by the +tremendous forces at work in the eruption of Krakatoa; namely, +atmospheric waves and sound waves. + +The atmospheric waves showed their presence in the air by means of +changes produced in the atmospheric pressure. Now, while these +changes cannot readily be felt by man, yet their presence can be +easily shown by the use of instruments called _barometers_. + +There are in different parts of the world, buildings called +_meteorological observatories_, that are provided, among other +instruments, with recording barometers. These instruments caught +the great atmospheric waves that were produced by the eruption of +Krakatoa. In this manner, the astounding fact was learned that the +waves starting from the volcano travelled no less than seven times +around the world. When we say astounding, it must not be understood +that the formation of such waves was at all contrary to the known laws +of physics. On the contrary, provided the force of the eruption was +sufficiently great, such waves must have been produced in the great +ærial ocean. The astonishing, or wonderful thing, was that the force +setting up these waves was so great that it caused them to move seven +times around the globe. + +The atmospheric waves were so powerful that it will be worth our while +to describe them in detail. Starting from the volcano of Krakatoa, +as a centre, these waves moved outwards in all directions, becoming +gradually larger and larger until they reached a point halfway round +the globe, or 180° from Krakatoa. The waves did not, however, stop +here, but continued moving onward, now growing smaller and smaller +until they reached a point in North America, immediately opposite +Krakatoa. Such a point on a globe is called an _antipodal point_.[1] +The waves did not stop at this point, but again advanced moving toward +Krakatoa, growing larger and larger until they again reached a point +halfway around the globe, or 180° from Krakatoa, when they again +continued moving but now continually growing smaller and smaller, +until they reached Krakatoa. Here they again began moving completely +around the globe, and this was continued for as many as seven times. +It must not be supposed that the waves ceased on the seventh time +around. On the contrary, they, probably, kept on moving for many +additional times, but they were then so feeble that even the sensitive +recording barometers were unable to detect their presence. + +There was another kind of waves in the atmosphere that did not require +barometers for their detection. These were the sound waves, and can +readily be detected by the human ear. + +Now, in the case of the great eruption of Krakatoa, the intensity of +the sounds was so great that the sounds could be heard distinctly at +distances of several thousand miles from Krakatoa. + +The sound waves so closely resembled the explosion of artillery that +at Acheen, a port on the northern coast of Sumatra, 1,073 miles from +Krakatoa, the authorities, believing that an attack was being made on +the port, placed all their troops under arms to repel the invaders. +The sounds were also distinctly heard at Bangkok, in Siam, a distance +of 1,413 miles from the volcano. They were also heard at the Chagos +Islands, a group of islands situated in the Indian Ocean about 2,267 +miles from Krakatoa. + +Two steamers at Singapore, 522 miles distant, were despatched to find +the vessel that was believed to be firing guns as distress signals. + +The sounds were distinctly heard in parts of South Australia, 2,100 +miles distant, and in Western Australia, at 1,700 miles distance. + +But it will be unnecessary to give any further details of the great +distances at which these sounds were actually heard. It will suffice +to say that they were heard as far off as about 3,000 miles. + +It is difficult to picture to one's self such great distances. +Assuming the greatest distances to be in the neighborhood of 3,000 +miles, it would be as if a sound produced, say, in Boston, New York, +or Philadelphia, was so loud that it could be heard in Amsterdam, +London, or Paris. + +Some idea of the intensity of these sounds can be had from the fact +that in Batavia, when, in accordance with usage, a gun was fired from +one of the forts at eight o'clock in the morning, two hours before the +greatest intensity of the sounds had been reached, the sound of the +gun could scarcely be heard above the continuous roar. + +While, of course, the principal reason the sound waves were carried +so far was the great force causing the eruption, yet these distances +were increased by the fact that the explosion occurred in a region +almost entirely surrounded by great bodies of water. The waves could, +therefore, be readily carried along the surface of the sea. Had there +been a high mountain wall, like the Andes of South America, on one +side of the volcano they would probably have been shut off in this +direction a short distance from where they were produced. + + + + +CHAPTER II + +SOME EFFECTS OF THE ERUPTION OF KRAKATOA + + +Besides the sound waves in the air, there were waves in the waters of +the ocean. Suddenly, without any warning, the people of Batavia were +surprised by a huge wave that, crossing the Straits of Sunda, entered +the ship canal before referred to as connecting the city with the +ocean, and, rising above the brick wall, poured over the surrounding +country. + +Although Batavia was 100 English miles from Krakatoa, yet after +travelling this distance the wave was sufficiently strong to enter +the city and flood its streets with water to a depth of several feet. +Fortunately, the loss of life was small in the city of Batavia, but +very great in the surrounding towns and villages. + +The ocean waves varied in height at different times of the eruption. +The greatest were from fifty to eighty feet high. Just imagine the +effect of a wave twice the height of an ordinary house. The waves +caused great damage to the shipping in the neighborhood. In one +instance, a vessel was carried one and a half miles inland and left on +dry land thirty feet above the level of the sea. + +The total loss of life by the waves has been estimated at 35,000 +people; besides this, of course, there was a great amount of property +destroyed. The greatest loss was in the immediate neighborhood of +Krakatoa. Gigantic waves swept over the lowlands lying near the +shores of Sumatra and Java, where over areas several miles in width +nearly everything was destroyed, the houses, trees, and people being +swept away and the surface of the land greatly changed. The towns of +Karang and Anjer, as well as numerous smaller villages, were almost +completely destroyed. + +The seaport town of Anjer, by far the most important of the above +towns, was almost completely swept away. The heavy stone lighthouse +was so completely obliterated that no traces of its heavy stone +foundations could afterwards be found. The Rev. Phillip Neale, +formerly a British chaplain at Batavia, from whose account of the +eruption of Krakatoa some of the above facts have been taken, tells +of the brave action of the keeper of the lighthouse at Anjer. Besides +his work as lighthouse keeper, to see that the light was constantly +burning during the night, he was charged with telegraphing to Batavia +the names of all passing vessels. On the fateful morning of the great +catastrophe, observing that the sun did not rise, he kept the light of +the lighthouse burning, and, notwithstanding the danger to which he +was exposed, continued at his post in order to send word to Batavia of +the passing of an English steamer. While doing this the lighthouse was +swept away and the brave man perished. + +The following verbal account of the destruction of the port of Anjer +was given by a Dutch pilot stationed at Anjer. This description is +quoted by the Rev. Mr. Neale from an article prepared by him for +publication in "The Leisure Hour." + + "I have lived in Anjer all my life, and little thought the + old town would have been destroyed in the way it has. I am + getting on in years, and quite expected to have laid my + bones in the little cemetery near the shore, but not even + that has escaped and some of the bodies have actually been + washed out of their graves and carried out to sea. The + whole town has been swept away, and I have lost everything + except my life. The wonder is that I escaped at all. I can + never be too thankful for such a miraculous escape as I had. + + "The eruption began on the Sunday afternoon. We did + not take much notice at first, until the reports grew + very loud. Then we noticed that Krakatoa was completely + enveloped in smoke. Afterwards came on the thick darkness, + so black and intense that I could not see my hand before + my eyes. It was about this time that a message came + from Batavia inquiring as to explosive shocks, and the + last telegram sent off from us was telling you about + the darkness and smoke. Towards night everything became + worse. The reports became deafening, the natives cowered + down panic-stricken, and a red, fiery glare was visible + in the sky above the burning mountain. Although Krakatoa + was twenty-five miles away, the concussion and vibration + from the constantly repeated shocks were most terrifying. + Many of the houses shook so much that we feared every + minute would bring them down. There was little sleep for + any of us that dreadful night. Before daybreak on Monday, + on going out of doors, I found the shower of ashes had + commenced, and this gradually increased in force until at + length large pieces of pumice stone kept falling around. + About six A. M. I was walking along the beach. + There was no sign of the sun, as usual, and the sky had a + dull, depressing look. Some of the darkness of the previous + day had cleared off, but it was not very light even then. + Looking out to sea I noticed a dark, black object through + the gloom, travelling towards the shore. + + "At first sight it seemed like a low range of hills rising + out of the water, but I knew there was nothing of the kind + in that part of the Sunda Strait. A second glance--and a + very hurried one it was--convinced me that it was a lofty + ridge of water many feet high, and worse still, that it + would soon break upon the coast near the town. There was + no time to give any warning, and so I turned and ran for + my life. My running days have long gone by, but you may + be sure that I did my best. In a few minutes I heard the + water with a loud roar break upon the shore. Everything + was engulfed. Another glance around showed the houses + being swept away and the trees thrown down on every side. + Breathless and exhausted I still pressed on. As I heard + the rushing waters behind me, I knew that it was a race + for life. Struggling on, a few yards more brought me to + some rising ground, and here the torrent of water overtook + me. I gave up all for lost, as I saw with dismay how high + the wave still was. I was soon taken off my feet and borne + inland by the force of the resistless mass. I remember + nothing more until a violent blow aroused me. Some hard, + firm substance seemed within my reach, and clutching it, + I found I had gained a place of safety. The waters swept + past, and I found myself clinging to a cocoanut palm-tree. + Most of the trees near the town were uprooted and thrown + down for miles, but this one fortunately had escaped and + myself with it. + + "The huge wave rolled on, gradually decreasing in height + and strength until the mountain slopes at the back of + Anjer were reached, and then, its fury spent, the water + gradually receded and flowed back into the sea. The sight + of those receding waters haunts me still. As I clung to + the palm-tree, wet and exhausted, there floated past the + dead bodies of many a friend and neighbor. Only a mere + handful of the population escaped. Houses and streets were + completely destroyed, and scarcely a trace remains of where + the once busy, thriving town originally stood. Unless you + go yourself to see the ruin you will never believe how + completely the place has been swept away. Dead bodies, + fallen trees, wrecked houses, an immense muddy morass and + great pools of water, are all that is left of the town + where my life has been spent. My home and all my belongings + of course perished--even the clothes I am wearing are + borrowed--but I am thankful enough to have escaped with my + life and to be none the worse for all that I have passed + through." + +As is common in cases of earthquake waves a great depression in the +level of the sea occurred at places great distances from Krakatoa. For +example, at the harbor of Ceylon, the water receded so far that for +about three minutes the boats were left high and dry, and then a huge +wave carried them with it as it rushed over the land. + +Perhaps one of the best evidences of the immense power of ocean waves +is to be seen in the massive blocks of white coral rock that were +washed up by the waves, on parts of the coast of Java for distances of +from two to three miles from the ocean. Many of these blocks weighed +from twenty to thirty tons. Indeed, some of them reached the weight of +from forty to fifty tons. + +It is probable that the island of Krakatoa and its neighboring smaller +islands formed portions of a huge cone about eight miles in diameter, +that has been broken up at some very remote but unknown time by, +perhaps, a greater catastrophe than that of August, 1883. + +In the Straits of Sunda the water was raised fifty feet to eighty +feet above the ordinary level, and produced tremendous destruction +especially on the coasts of Java and Sumatra, sweeping away many +villages and drowning many thousands of people. The wave had a +velocity of progression of nearly 400 miles per hour, or eight times +faster than an ordinary express train. + +When it is said that the _velocity of progression of the wave_ was +nearly 400 miles per hour, it is not meant that a body floating on +the ocean, such, for example, as a ship, would have been carried +forward at this high velocity, but would merely rise and fall in a +to-and-fro swing to about the height of the wave; that is, fifty to +eighty feet according to what may have been the height. As in the +case of the sound waves these motions of water covered or passed over +nearly all the waters of the earth. The waves progressing toward the +west, crossed the Indian Ocean reaching to the coast of Hindostan, and +Madagascar, and sweeping around the southern part of Africa, finally +reached the coasts of France and England, as well as the eastern part +of North and South America. Sweeping towards the east, they reached +the coasts of Australia, New Zealand, and crossing the vast Pacific +Ocean were felt at Alaska and the western coasts of North and South +America. + +But besides the enormous waves caused by the eruption, there were +marked changes in the level of the land. Large portions of the coast +of Sumatra and Java were almost annihilated, much of the original +surface near the coast being submerged, and places that were formerly +dry land are now covered with water to a depth of from 600 to 900 feet. + +The enormous amount of material thrown into the air by the forces +of the eruption is especially characteristic of this phenomenon. +Such quantities of pumice stone and ashes fell from the clouds that, +sinking in the water and collecting on the bed of the channel, they +changed the depth of the water, so as to render navigation dangerous. +Indeed, the Sebesi Channel, lying on the north of the island of +Krakatoa was completely blocked by a huge bank of volcanic material, +portions of which projected above the water, forming two smaller +islands. These, however, have since been washed away by the waves. + +We will not attempt to give at present any explanations as to the +causes of this great volcanic eruption, since the different theories +as to the cause of volcanoes will be better understood when other +volcanic eruptions have been described. It is sufficient here to say +that if a large quantity of water should have suddenly reached a +great mass of molten rock, frightful explosive eruptions would have +occurred, and if the island was resting on a submerged crater its +sudden disappearance may be explained. + +Another great wonder connected with the explosive eruption of Krakatoa +was the enormous heights to which the fine dust was thrown up into +the air. It has been asserted that during the most intense of these +eruptions the particles reached elevations of perhaps more than +twenty-five miles above the level of the sea. Carried by the winds, +the fine particles remained suspended in the air for many months, +and gave rise to magnificent sunlight effects, such as early dawn, +lengthened twilights, lurid skies, and gorgeous sunsets of a reddish +tint. There were also caused curious haloes, as well as green and blue +moons. + +The fine dust particles consisted of minute crystals of feldspar and +other minerals, and when examined under the microscope presented the +appearance shown in Fig. 4. + +These mineral substances permitted a portion of the light to pass +through them, thus producing wonderful optical effects in the +atmosphere either because they acted like minute prisms and so +produced rainbow colors, or because they turned the rays of light out +of their course as to produce what is called interference by color +effects of a nature similar to the colors seen in mother-of-pearl, +rainbow coal, or in the wing cases of many beetles. The explanations +of these phenomena are too difficult for a book of this character. + +An explosive volcanic eruption is a very terrifying and wonderful +phenomenon. Frightful roaring sounds are suddenly heard, the earth +shakes for many miles around, when suddenly a vast quantity of molten +rock, and sometimes huge stones, are thrown out of the crater high up +into the air. So great is the force that throws these materials out +of the opening that heavy masses of rocks often are ejected very much +faster than the projectiles from the largest guns that are used in any +of the navies of the world. + +[Illustration: FIG. 4. VOLCANIC DUST AS IT APPEARS UNDER THE +MICROSCOPE] + +As the molten lava cools and falls in the form of prodigious clouds +of ashes, cinders and dust, for many miles around the volcano, even +the light of the sun is obscured, and one cannot see the hand before +the face. Some of the materials in these clouds are so light that they +remain suspended in the air for many hours, often indeed for many +days, and sometimes even for years. The heavier particles, however, +soon begin to fall, and before long the earth's surface both around +the volcano, and often at considerable distances from it, is covered +with a thick layer of ashes. + +The sounds accompanying a volcanic eruption are often terrifying. Amid +shakings and tremblings of the earth's crust, known as earthquakes, +there are occasionally heard noises like the explosion of huge guns. +Sometimes these sounds follow one another so rapidly that they produce +an almost continuous roar. Through the roar of the explosion a +curious crackling noise can be heard, due to the fragments of stone +hurled out of the crater striking against one another, especially as +the stones which are thrown out of the crater and have commenced to +fall back again to the earth, are struck by others that are still +rising. + +Immense quantities of ashes, stones, vapor and gases are thrown +upwards for great distances into the air, while, at the same time, a +lava stream pours over the lowest side of the crater. As the column +of ashes and cinders reaches its greatest height in the air, it +begins to spread outward on all sides, rapidly growing like a huge +dark mushroom. This soon shuts out the light of the sun, and from it +showers of red hot ashes and cinders fall to the earth. + +It would be extremely dangerous to be on the side of the volcanic +mountain during an explosive eruption; for, even should you escape +falling into an opening in the side of the mountain, you might be +killed by the huge stones that are constantly falling on all sides +around the opening, or might be buried under the vast showers of red +hot ashes that are poured down from the dense clouds overhanging the +mountain, or suffocated by clouds of sulphur vapor that rush down its +sides. + +When at a safe distance the sight is certainly magnificent. There is +no light from the sun. All would be in pitch darkness but for the +reddish glare thrown upwards by the red hot lava, by the glowing +showers of ashes that are being rained down on the sides of the +mountain, or by terrific lightning flashes, due to the discharge of +the immense quantities of electricity produced by the forces of the +eruption. + +Naturally a great volcanic eruption can cause a considerable loss of +life and property. When a large lava stream begins to flow down the +sides of the mountain, it cannot be stopped, and should it flow toward +a village or town it is likely to destroy the town completely. Besides +this, the vegetation of the country for many miles around is destroyed +by the showers of red hot ashes that fall from the sky. The houses of +neighboring cities are similarly ruined by the great conflagrations +thus set up. Further destruction is also caused by large streams of +mud that rush down the slopes of the mountain, or by huge waves set +up in the ocean. If the volcano is situated, as most volcanoes are, +near the coast, the showers of ashes and falling stones may set fire +to vessels in the neighborhood, or the progress of such vessels may be +seriously retarded by layers of ashes or pumice stone that float on +the surface. Sometimes these layers are so thick as actually to bring +ships to a complete standstill. + +It must not be supposed that volcanoes are in a constant state of +eruption. On the contrary, nearly all volcanoes, after an eruption, +become _quiet_ or _inactive_. The air soon clears by the ashes +settling, and the sunlight again appears. A crust forms over the +surface of the lava, which rapidly becomes hard enough to permit one +to walk over it safely. The vegetation, which has been destroyed by +the hot ashes, again springs up, and, if the volcano happens to be +situated within the tropics, where there is an abundance of moisture, +the land soon again becomes covered by a luxuriant vegetation. Most of +the people, who have escaped sudden death during the eruption, return +to the ruins of their houses; for it is a curious fact that no matter +how great has been a volcanic eruption, or how far-reaching the ruin, +the survivors, as a rule, do not appear to hesitate to return to their +old neighborhood. In a few years the fields are re-cultivated, the +villages are rebuilt, and the people apparently forget they are living +over a slumbering volcano, which may at any time again burst forth in +a dangerous eruption. + +A volcano that throws out molten rock, vapor and gases is known as an +_active volcano_. An active volcano, however, is only correctly said +to be in a state of eruption when the quantity of the molten rock, +lava or vapor it throws out is greatly in excess of the ordinary +amount. + +Sometimes the volcanic activity so greatly decreases that the molten +rock or lava no longer rises in the crater, but, on the contrary, +begins to sink, so that the top of the lava in the crater is often +at a considerable distance below its edges. The lava then begins to +harden on the surface, and, if the time is sufficient, the hardened +part extends for a considerable distance downward. In this way the +opening connecting the crater with the molten lava below becomes +gradually closed, the volcano being thus shut up, or corked, just as a +bottle is tightly closed by means of a cork driven into the opening at +its top so as to prevent the escape of the liquid it contains. + +It may sound queer to say that a volcano has its crater so corked up +as to prevent the escape of the lava, but the idea is nevertheless +correct and helpful. To realize the size of these huge volcanic corks +one must remember that the craters of some volcanoes are several miles +across. A volcano thus choked or corked up is said to be _extinct_. + +When we speak of an extinct volcano we do not mean that the volcano +will never again become active. A volcano does not cease to erupt +because there are no more molten materials in the earth to escape, but +simply because its cork or crust of hardened lava has been driven in +so tightly that the chances of its ever being loosened again seem to +be very small. But small as the chances may seem we must not forget +that the volcano may at any time become active, or go into its old +business of throwing out materials through its crater. A volcano in +an extinct condition is not unlike a steam boiler, the safety valve +of which has been firmly fixed in place. If the steam continues to be +generated in the boiler, it is only a matter of time when the boiler +will blow up, and the explosion will be all the greater because the +safety valve did not allow the steam to escape earlier. + +Sometimes an intermediate class of volcanoes called _dormant_ is +introduced between active volcanoes on the one hand and extinct +volcanoes on the other. The name dormant volcano, or, as the word +means, _sleeping volcano_, is objectionable, since it might lead one +to think that an extinct volcano is not sleeping but dead, and this is +wrong. + +Since the plug of hardened lava in the volcanic crater is generally at +a much lower level than the top of the crater, the crater will soon +become filled to a greater or less depth with water, produced either +by the rain, or by the melting of the snow that falls on the top of +the mountain. Crater lakes, often of very great depths, are common in +extinct volcanoes. + +Of course, when an extinct volcano again becomes active, two things +must happen if the eruption is explosive. In the first place, the +force of the explosion must be sufficiently great to loosen the +stopper or plug of hardened lava which stops it. In doing this the +mass is broken into a number of fragments that are thrown forcibly +upwards into the air. After rising often for great heights they soon +fall again on the sides of the mountain. + +But besides the breaking up of the stopper, the lake in the crater of +the volcano is thrown out along with the cinders or ashes, producing +very destructive flows of what are called aqueous lava or mud streams. +These streams flow down the sides of the mountain, carrying with them +immense quantities of both the ashes thrown out during the eruption, +or those that have collected around the sides of the crater during +previous eruptions. Very frequently, these streams of aqueous lava +produce greater destruction than the molten lava. + +If you have ever watched common ants at work clearing out or enlarging +their underground homes, in a piece of smooth gravel walk in your +garden, you can form some idea why the mountain immediately around a +volcanic crater is conical in shape. If the colony of ants happens +to be fairly large, you can see an almost unbroken stream of these +industrious little animals, each bearing in its mandibles a small +grain of sand or gravel brought up from some place below the surface. + +Carrying it a short distance from the opening, it throws it on the +ground, rapidly returning for another load. In this way there is +heaped up around all sides of the opening a pile of sand or gravel, +the outward slopes of which gives the pile a conical form. You have, +probably, noticed that the steepness of the slopes depends on the size +of the grains; for the larger these grains the sharper or steeper the +slopes, the very fine grains producing flat mounds or cones. + +It is the same with a volcanic cone. The materials that are thrown +upwards into the air, falling again on the mountain, collect around +the crater on all sides, thus giving it the characteristic cone-like +shape of the volcanic mountain. Where nothing occurs to disturb +the formation of the cone its height above the level of the sea +will gradually increase. Very frequently, however, during explosive +eruptions, a large part of this cone will be blown away by the +force of the eruption only to be again built up during some later +eruption. Indeed, in the case of volcanic islands, the force of a +great volcanic eruption is sometimes so great that not only is a large +volcanic mountain blown entirely away, but a hole is left, where it +had been standing, that extends further downwards below the level +of the sea than the top of the mountain extended previously above +it. The above are some, but by no means all, the wonders attending +volcanic eruptions. We shall refer to others in subsequent chapters in +describing particular eruptions. + + + + +CHAPTER III + +THE VOLCANIC ISLAND OF HAWAII + + +The volcanic island of Hawaii, the largest of the Sandwich Island +chain, is situated in the mid Pacific, south of the Tropic of +Cancer. As shown in Fig. 5, this island chain consists of Hawaii, +Maui, Molokai, Oahu, Kauai, Nihau, and about eight large islands, +together with numerous small islands, extending in a general northwest +direction from Hawaii to Nihau, a distance of about 400 miles. Like +most volcanic islands they lie in more or less straight lines, +probably along fissures, in this case in two nearly parallel lines. +The island of Nihau, however, is an exception, the direction of the +greatest length being almost straight across the two parallel lines. + +The Sandwich Islands lie 2,000 miles from San Francisco in deep water, +between 2,000 and 3,000 fathoms, or between 12,000 and 18,000 feet in +depth. This island chain consists of great volcanic mountains, that +had, at one time, fifteen active volcanoes of the first class. These +are now all extinct but three, and all of these are on the island of +Hawaii. + +In his report to the United States Geological Survey for 1882-83, +Dutton states that the summit of Mt. Haleakala on East Maui is 10,350 +feet above the sea level. Oahu has peaks on its eastern side 2,900 +feet high, and peaks on the western side 3,850 feet high. The summit +of Kauai is probably 6,200 feet above the sea. + +[Illustration: FIG. 5. THE HAWAIIAN ISLANDS _From U. S. +Geological Survey_] + +It can be shown by deep-sea soundings that all these volcanic piles +are the summits of a gigantic mountain mass that rises abruptly from +the bed of the Pacific. There are reasons for believing that this +submarine chain continues for many hundreds of miles in the same +direction beyond Kauai. + +The extinct volcano, Haleakala, on East Maui appears to have been in +eruption at a much later day than Mt. Kea, which is also an extinct +volcano. But the natives have no traditions of any eruptions. + +The volcanoes on the other islands have been extinct for a very long +time judging from the extent of their erosion. Dutton is of the +opinion that the western islands of the chain have been extinct for +much longer times than the remaining islands. + +The Sandwich Islands, also known as the Hawaiian Islands, are one of +the colonial possessions of the United States. The island of Hawaii is +about 2,000 miles from San Francisco. Honolulu, on the island of Oahu, +the principal seaport of the chain, has a pleasant climate, and is an +important coaling station for warships, commercial vessels, whalers, +and trading ships generally. + +The principal product of the island is sugar cane. + +The island of Hawaii, as shown in map, Fig. 6, consists of five +volcanic mountains and some small coral reefs. These mountains are: +Mt. Kea, on the north, 13,805 feet in height; Mt. Haulalai, in the +west central part of the island, 8,273 feet in height; Mt. Loa, in the +south central part of the island, 13,675 feet in height; Mt. Kilauea, +twenty miles east of the crater of Loa, 4,040 feet high at the Volcano +House, and 4,158 feet on the highest point on the west, and Kohala, +5,505 feet in height, running through the northwestern part of the +island, and the Kohala mountains in the northwestern part. + +[Illustration: FIG. 6. HAWAII _From Dana's Manual of +Geology_] + +Of these mountains, Mt. Loa and Kilauea are the only active volcanoes, +and are in frequent eruption. Mt. Haulalai was in eruption during +1804. Mt. Kea has not been active during historical times, while Mt. +Kohala has been inactive for so long a time that its slopes are deeply +gullied wherever the rivers flow down them. + +As you can see from the map, Hawaii is very large. It has a length of +ninety-three miles from north to south, and a breadth of eighty miles +from east to west, its area is about 6,500 square miles. With the +exception of small patches of coral reefs, Hawaii is formed entirely +of lava, and is the largest pile of lava in the world with the single +exception of Iceland. + +Where the islands of the Hawaiian chain have coral reefs extending +off their coasts, excellent harbors are found in the deep waters +between the islands and the reefs. Hawaii, however, has no extended +reefs of this character, and, consequently, no first-class harbors. +Hilo, on the eastern coast, is the best harbor, and is, therefore, the +principal settlement. + +A very brief examination of the map of Hawaii will show you that there +are no rivers on the island, except on the sides exposed to the wind, +that is, on the northern and northeastern slopes. Since the yearly +rainfall on Hawaii is large, being in the neighborhood of a hundred +inches, you will understand that considerable rain water falls on the +island. In those parts of the island where it does not run off the +surface it must drain downward through the loose piles of broken rocks +or cinders. A rainfall of one hundred inches a year means that if all +the rain which falls on each square foot of surface was collected +in a flat vessel one foot square with vertical sides it would fill +the vessel to the depth of one hundred inches, or over eight feet. +The drainage of the rainwater downwards through these parts of the +island, must, therefore, be large. + +Another curious fact you can notice on the map, is that the lava +streams of the past fifty years from Mt. Loa indicated by heavy +dotted lines, in no cases begin at the crater, but start at fairly +considerable distances from it. Later on in this chapter we shall +explain the reason for this curious fact. + +Since practically the whole of Hawaii has been formed from the streams +of lava that have flowed at one time or another, you can understand +how great these flows must have been. But to do this fully you must +not only take into consideration the portions of the island that +lie above the ocean and reach into the air at its greatest height +to 13,805 feet above its surface, you must also remember that this +mountain rises from a deep ocean, so that if all the water were +removed, you would see Hawaii towering up above the former level +of the sea to the height of about 31,000 feet, or higher than Mt. +Everest, the highest point on the earth above the present sea level. +This would be, approximately, five and eight-tenths miles. You can +understand, therefore, how great the flow of lava must have been. + +We shall begin the description of Hawaii with the active volcano of +Mt. Loa, or, as it is sometimes called in Hawaii, "The White Mountain." + +You will remember that the eruption of Krakatoa was of the explosive +type. Practically no melted rock or lava escaped from the crater. +Indeed, if it had escaped it would not have been seen; for, not only +the cone near the crater, but also much of the mountain itself was +blown completely out of sight and covered by the waters of the ocean. + +The eruptions of Mt. Loa are of an entirely different type. In Loa +there are no explosions, the eruptions being what are called the +non-explosive or quiet volcanic eruption type. It will be necessary to +explain some of the peculiarities of this kind of eruptions. + +There is a great difference in the liquidity or the ease with which +different kinds of lava flow. Some lava is very thick or viscid, +or is sticky like thick molasses or tar, and therefore flows very +sluggishly. Other lava is thin or mobile, more closely resembling +water in the ease with which it flows. Now, in the case of a volcanic +mountain of fairly considerable height, where the lava possesses +marked liquidity, the lava as it rises from great depths in the tube +of the volcano seldom flows over the top or rim of the crater. This is +not because the force that brings the lava up is unable to carry it +a few thousand feet higher, so that it can run over the brim of the +crater, but because the walls of the volcanic mountains are unable to +stand the great pressure which the mass of liquid lava exerts against +their sides. + +It can be shown that a column of liquid lava 500 feet high, will exert +a pressure on the walls of the crater of about 625 pounds to the +square inch. Therefore, in very high volcanic mountains, long before +the lava can reach the edge of the crater and overflow, the pressure +becomes so great, that cracks or fissures are made in the sides of +the mountain, through which the lava is quietly discharged; when, of +course, the level of the lava in the crater falls considerably. In +volcanoes of the explosive type, no matter what may be the condition +of lava, should a large quantity of water suddenly find an entrance to +a large body of molten lava at some distance below the surface, the +lava would be suddenly thrown explosively into the air, where being +chilled, it would afterwards descend in showers of ashes, cinders, or +volcanic dust. + +In some volcanic mountains such as Mt. Loa, the crater, instead +of being situated at the top of a conical pass of ashes or other +material, consists of a pit-like depression, generally occupying a +level tract or plain at the top of the mountain. This pit is known +as a _caldera_, or _caldron_, or what you might, perhaps, call a +huge kettle or boiler. The pit has more or less vertical sides that +extend downwards for unknown depths to the place from which the lava +comes. The vertical walls of the caldera are not, however, smooth, but +exhibit numerous horizontal ledges, that mark places where portions of +the floor of the caldera were situated at different times. + +At the bottom of the large pit or caldera on the summit of Mt. Loa +can be seen the level floor formed of hardened lava. This floor is +surrounded by vertical walls on which can be seen the broken edges of +the old lake bed. + +Captain Dutton, in a paper on Hawaiian volcanoes, prepared for the +United States Geological Survey, and published in its Fourth Annual +Report for 1882-83, thus describes the appearance at the great crater +as it was in 1882. + + "The summit of Mauna Loa (Mt. Loa), is a broad and large + platform about five miles in length and four miles in + width, within which is sunken the great caldera called + Mokuaweoweo. The distance from the point where we first + reach the summit to the brink of the pit is about a mile + and a half. The surface of the platform is much more rugged + than the slopes just ascended. It is riven with cracks, and + small faults,[2] and piles of shattered rock are seen on + every hand. Nowhere is there to be seen the semblance of + a cinder cone. Doubtless many eruptions have broken forth + from the various fissures on this summit, but only here + and there can insignificant traces of such catastrophes + be definitely distinguished. The absence of fragmental + ejecta (broken rock that are thrown out) is extraordinary. + The shattered blocks, slabs, and spalls (chips) which + everywhere cumber the surface appear to have resulted from + the spontaneous shivering and shattering of the lava sheets + by their own internal tensions as they cooled. + +Fig. 7, taken from Dutton's report, gives the general shape of this +great caldera. Dutton's description of the same is as follows: + + "The length of the main caldera is a little less than + three miles and its width about a mile and three-quarters. + Its floor, viewed from above, appears to be composed of a + series of flat surfaces occupying two distinct levels, the + higher upon the surface of the black ledge, the lower lying + within the ledge. Upon the western side is a small cinder + cone standing close upon the border of the black ledge. + It is the only one visible, either within the caldera or + upon the surrounding summit. Its height is about 125 or 130 + feet. It was seen in operation, throwing up steam, clots of + lava, and lapilli (some of the larger pieces of fragmentary + lava) in the year 1878. The only other diversifications of + the floor are many cracks which traverse it, the larger of + which are distinctly visible from above. Some of them are + considerably faulted. There is no difficulty in recognizing + the fact that the whole floor has been produced by the + sinkage of the lava beds which once continued over the + entire extent of the depression, their undersides having + been melted off most probably by the fires beneath. The + lava beds in the immediate vicinity of the brink upon the + summit platform wear the aspect of some antiquity. They + have become brown and carious by weathering, and, although + no soil is generated, little drifts of gravel are seen + here and there mixed with pumice. Since the caldera was + formed there is no indication that the lavas have anywhere + overflowed its rim. And yet it is a very strange fact that + within a half mile, and again within a mile to a mile and + a half, lavas have been repeatedly erupted within the last + forty years from the summit platform, and have outflowed + at points situated from 700 to 900 feet above the level of + the lava lake within. Traces may also be seen, at varying + distances back of the rim, of very many eruptions in which + the rocks betoken great recency, although no dates can be + assigned to their occurrence." + +[Illustration: FIG. 7. PANORAMA OF MOKUAWEOWEO _From U. S. +Geological Survey_] + +[Illustration: FIG. 8. VIEW OF THE CRATER OF KILAUEA FROM THE +VOLCANO HOUSE _From U. S. Geological Survey_] + +During his visit to this great pit, Captain Dutton succeeded in +climbing down the almost vertical walls on the side of the crater, +and, reaching the surface of the hardened lake, walked over it. It +must have required no little courage to thus venture on the thin +floor of a lake which he knew was filled to great depths with red hot +boiling lava, for he was walking over the surface of a slumbering +volcano, that might at almost any moment awaken, and opening, swallow +him and his companions. Through enormous cracks in the floor, he could +feel the heat from the molten mass, while, through the same openings +came suggestive whiffs of sulphur vapor. + +During the eruption of this mountain, on January 23d, 1859, the light +from the glowing lava streams was bright enough to read fine print at +Hilo, a distance of thirty-five miles. + +During the eruption of 1852, a stream of white-hot lava was thrown up +into the air from one of the fissures to a height of from 300 to 400 +feet. + +[Illustration: STONES AND LAVA THROWN UPWARDS--ERUPTION OF +MOKUAWEOWEO, HAWAII, JULY 4-21, 1899 _From a Stereograph, +Copyright, by Underwood & Underwood_] + +When an eruption takes place in Mt. Loa the column of lava slowly +rises in the crater, threatening to overflow its lowest edges, but +before this can take place the pressure becomes so great that some +portion of the mountain below the crater is fractured and the lava +quietly escapes. + +During some conditions of the mountain every fifteen or twenty minutes +a column of highly glowing lava is shot upwards like a fountain to +a height of 500 feet and over, falling back into the lake in fiery +spray. Unusual heights of these streams are generally followed by an +eruption. + +These curious jets of molten rock certainly cannot be due to the +pressure of higher columns of lava, since the crater itself is near +the top of a high plain. They are believed to be due to steam formed +by the penetration of the rain water that falls on this part of the +mountain. + +You can now understand why the lava streams escaping from Mt. Loa as +shown on the map, in Fig. 6, do not begin at the level of the crater; +for the discharge of the lava does not take place over the rim of +the crater, but through the cracks or fissures formed further down +the sides of the mountains. It must not be supposed, however, that +the fissures are limited to the sides of the mountain where they can +be seen. They probably occur in many places below the surface of the +water on some part of the bed of the ocean. + +The crevices that are formed in this manner in the sides of the +mountain vary greatly in size, some being so narrow that the lava +scarcely flows through them at all but simply fills up the crevice, +hardens on cooling, and mends the cracks in the mountains, in the way +that a crack is mended in a piece of china by the use of glue or in +a wall of masonry by mortar. Through the largest crevices or cracks, +however, large lava streams may continue to flow often for several +weeks, or even longer. + +Sometimes, especially towards the close of the eruptive flow, the +lava may escape disruptively, so that small cones are formed along +the lines of the fissures. Cones of this character are called lateral +cones, and in the case of a volcanic island, where the lava flows out +below the level of the water, the lateral cones sometimes project +above the water and form volcanic islands or dangerous shoals that +impede navigation. + +When the lava pours out of a crevice in the side of the mountain, a +river of molten rock rushes down the slopes, at first like a torrent, +but on reaching the more nearly level ground, it spreads out in great +lava lakes or fields, the surface of which takes on the characteristic +black appearance of basalt, a certain kind of glass, for the lavas of +Mt. Loa are generally basaltic. After an eruption the hardened floor +of lava in the caldera, being no longer supported by the liquid mass +formerly below it, falls in, leaving a large cavity with only the +edges of the old floor clinging to the sides of the pit. + +It will be interesting to give a short account of some of the great +lava streams that have been poured out at different times from Mt. Loa. + +In the great eruption of August 11th, 1855, the lava escaped through +fissures from two to thirty inches in width. Then, flowing in a +continuous stream, it did not stop until it was within five miles of +Hilo. + +In the eruption of January 23d, 1859, the lava stream flowed towards +the northwest on the east side of Haulalai, reaching the sea in eight +days. + +The eruption of March 27th, 1868, was characterized by severe +earthquake shocks, one of which, occurring on the second of April, +destroyed many houses and produced huge fissures in the earth. These +shocks produced great earthquake waves that reached distant coasts. + +Mt. Kilauea, lies at a lower level towards the east. This crater is +situated at 4,040 feet above the level of the sea, and is nearly 6,000 +feet below the caldera on the top of Mt. Loa. + +Fig. 8, taken from the United States Geological Survey, Fourth +Annual Report, for 1882-83, shows a view of Kilauea from the Volcano +House. Dutton gives the following description of the appearance of +Halemaumau, the pit crater or caldera of Kilauea. + + "In front of us and right beneath our feet, over the crest + of a nearly vertical wall, more than 700 feet below, is + outspread the broad floor of the far-famed Kilauea. It + is a pit about three and a half miles in length, and two + and a half miles in width, nearly elliptical in plan and + surrounded with cliffs, for the most part inaccessible to + human foot, and varying in altitude from a little more than + 300 feet to a little more than 700 feet. The altitude of + the point on which we stand is about 4,200 feet above the + sea.... + + "The object upon which the attention is instantly fixed + is a large chaotic pile of rocks, situated in the centre + of the amphitheatre, rising to a height which by an + eye estimate appears to be about 350 to 400 feet. From + innumerable places in its mass volumes of steam are poured + forth and borne away to the leeward by the trade wind. The + color of the pile is intensely black.... + + "Around it spreads out the slightly undulated floor of the + amphitheatre, as black as midnight. To the left of the + steaming pile is an opening in the floor of the crater, + within which we behold the ruddy gleams of boiling lava. + From numerous points in the surrounding floor clouds of + steam issue forth and melt away in the steady flow of the + wind. The vapors issue most copiously from an area situated + to the right of the central pile, and in the southern + portion of the amphitheatre. Desolation and horror reign + supreme. The engirdling walls everywhere hedge it in. But + upon their summits, and upon the receiving platform beyond, + are all the wealth and luxuriance of tropical vegetation + heightening the contrast of the desolation below...." + +[Illustration: FIG. 9. CRATER OF KILAUEA _From Dana's Manual +of Geology_] + +Fig. 9 represents the pit-like crater of Kilauea as it appeared after +the eruption of 1886. Here, as will be seen, there are several lakes +of lava, the largest of which is known as Halemaumau. The eruption of +1886, like all the eruptions of Kilauea, consisted of the escape of +the lava from an opening on the side of the mountain below the crater, +and a sinking in of the hardened floor of the crater. The figure also +shows the position of the New Lake that lies east of Halemaumau. The +extent and appearance of each of these lakes are constantly changing, +both as to height and area. + +Dutton gives the following description of the appearance of the lake +of lava, and some curious phenomena that occur on its surface. He is +describing the general appearance of the pool of molten lava covered +as it is with a hardened black crust: + + "The surface of the lake is covered over with a black + solidified crust showing a rim of fire all around its edge. + At numerous points at the edge of the crust jets of fire + are seen spouting upwards, throwing up a spray of glowing + lava drops, and emitting a dull, simmering sound. The heat + for the time being is not intense. Now and then a fountain + breaks out in the middle of the lake and boils freely for a + few minutes. It then becomes quiet, but only to renew the + operation at some other point. Gradually the spurting and + fretting at the edges augment. A belch of lava is thrown + up here and there to the height of five or six feet, and + falls back upon the crust. Presently, near the edge, a + cake of the crust cracks off, and one edge of it bending + downwards descends beneath the lava, and the whole cake + disappears, disclosing a naked surface of liquid fire. + Again it coats over and turns black. This operation is + repeated edgewise at some other part of the lake. Suddenly + a network of cracks shoots through the entire crust. Piece + after piece of it turns its edge downwards and sinks with + a grand commotion, leaving the whole pool a single expanse + of liquid lava. The lake surges feebly for awhile, but soon + comes to rest. The heat is now insupportable, and for a + time it is necessary to withdraw from the immediate brink." + +It is very curious to think of cakes of hardened lava floating on the +surface of molten lava, but, of course, this is just as natural as +cakes of ice floating on the surface of water; for a cake of hardened +lava is, as you will understand, only a cake of frozen lava, and, +being lighter than the molten lava, must, of course, float on its +surface. + +The disappearance of these cakes of frozen lava and their remelting is +still more curious, and can be explained as follows: The frozen or +solidified mass of black basalt is a trifle lighter than the lava on +which it is floating only while its temperature is high, and therefore +expanded by heat. As soon as it cools, its density increases, and when +it becomes a little greater than that of the liquid lava, it begins to +sink and soon disappears. + +[Illustration: FIG. 10. SECTIONS OF KILAUEA AT DIFFERENT +PERIODS _From Dana's Manual of Geology_] + +Professor Dana, who has made a careful study of the phenomena of +Kilauea, shows in Fig. 10, a cross section of Kilauea at different +times. Before the eruption of 1823, the depth of the crater was from +800 to 1,000 feet. At the eruption the bottom 600 to 800 feet, making +the depth of Kilauea over this deeper central part about 1,500 feet. +The varying depths at different dates are clearly marked on the +drawing. + +The eruptions of Kilauea generally occur as follows: + +First there is a slow rising of the lava in the crater. This rising +continues until the pressure is so great that the mountain is ruptured +at some lower place. Next a discharge of the lava and a sinking to a +level in the conduit that will depend on the position of the crevice. +Then a gradual falling in of the hardened floor of the lake, a portion +of the horizontal walls remaining on the sides of the caldera. + +The eruption of Kilauea, however, has not always been of the quiet +type. There was an eruption in the year 1789 that would appear to +have been of the explosive variety. The following account is given by +Dana as taken from a history of the Sandwich Islands by the Rev. I. +Dibble, published in 1843: + +"The army of Keoua, a Hawaiian chief, being pursued by Kamehamoha, +were at the time near Kilauea. For two preceding nights there had +been eruptions, with ejections of stones and cinders. The army of +Keoua set out on their way in three different companies. The company +in advance had not proceeded far before the ground began to shake and +rock beneath their feet, and it became quite impossible to stand. +Soon a dense cloud of darkness was seen to rise out of the crater, +and, almost at the same instant, the thunder began to roar in the +heavens and the lightning to flash. It continued to ascend and spread +around until the whole region was enveloped, and the light of day +was entirely excluded. The darkness was the more terrific, being +made visible by an awful glare from streams of red and blue light, +variously combined through the action of the fires of the pit and the +flashes of lightning above. Soon followed an immense volume of sand +and cinders, which were thrown to a great height, and came down in a +destructive shower for many miles around. A few of the forward company +were burned to death by the sand, and all of them experienced a +suffocating sensation. The rear company, which was nearest the volcano +at the time, suffered little injury, and after the earthquake and +shower of sand had passed over, hastened on to greet their comrades +ahead on their escape from so imminent a peril. But what was their +surprise and consternation to find the centre company a collection +of corpses! Some were lying down, and others were sitting upright, +clasping with dying grasp their wives and children, and joining noses +(the mode of expressing affection) as in the act of taking leave. So +much like life they looked that at first they supposed them merely +at rest, and it was not until they had come up to them and handled +them that they could detect their mistake." Mr. Dibble adds: "A blast +of sulphurous gas, a shower of heated embers, or a volume of heated +steam would sufficiently account for this sudden death. Some of the +narrators who saw the corpses, affirm that though in no place deeply +burnt, yet they were thoroughly scorched." As you will see in Chapter +XI, this sudden and awful death due to highly heated air and dust +particles, caused even a greater loss of life in the catastrophic +eruption of Pelée, in Martinique on May 8, 1902. + +By reason of its situation at a lower level on the slopes of Mt. Loa, +Kilauea was at one time thought to be one of the craters lower down +on the slopes of Loa. This was the opinion of Professor Dana when he +examined the district in 1840. Since this time the region has been +more carefully studied, and Mt. Loa and Kilauea, are now generally +regarded as separate and independent volcanoes, neither of which acts +as a safety valve for the other. + +We shall not attempt in this chapter to say anything concerning the +sources or places from where these great supplies of lava have been +drawn. This will be left to some subsequent chapter, after we have +described still other volcanoes. + +The outlines of mountains like Mt. Loa or Kilauea differ greatly from +mountains like Vesuvius; their slopes, like the slopes of all other +Hawaii volcanoes, have an inclination which does not exceed 10°. +The lava streams, therefore, as they flow down the mountains, move +more slowly than they would were the slopes more precipitous, as in +mountains like Vesuvius. + +There have been many eruptions of Kilauea. That which occurred in the +year 1840, was of great magnitude (see map, Fig. 6), and began in a +fissure southwest of the crater. The principal eruption, however, +broke out about twelve miles from the sea coast, and about twenty-five +miles east of Kilauea. Here an enormous mass of lava forming a stream +nearly three miles wide reached the ocean at Nanawale. + +When an eruption takes place on Mt. Loa through a fissure at the +height of 10,000 to 13,000 feet the length of the lava streams is +frequently as great as twenty-five to thirty miles. Often the lava +though hardening at the surface will continue to flow underneath +through huge tunnels, of which the top and sides are composed of +solidified parts of the same lava stream. After the flow has ceased +long hollow tunnels often remain. If the lower end of such a tunnel +containing molten lava is momentarily closed, the pressure of the +lava above may not only burst through the obstruction, but may even +throw the lava upwards in jets 300 to 700 feet high. Probably most of +you have seen illumined fountains where jets of water are beautifully +lighted up by different colored electric lights placed below them. +Such fountains, however, can but poorly compare either in beauty or +grandeur with these wonderful lava fountains, common on the slopes of +Mt. Loa during an eruption. + + + + +CHAPTER IV + +THE VOLCANIC ISLAND OF ICELAND + + +The island of Iceland consists of a number of volcanic mountains some +of which are still active. As can be seen from the map, shown in +Fig. 11, Iceland lies in the North Atlantic Ocean, immediately below +the Arctic Circle, about 250 miles east of Greenland, and 600 miles +west of Norway. Its length from east to west is about 300 miles, and +its breadth about 200 miles, its total area, including the adjacent +islands, being more than 40,000 square miles. + +Were all the water removed from the North Atlantic Ocean, it would be +seen that Iceland rests on the bed of the Atlantic, on a submarine +plateau or highland; for, in this part of the ocean the water is only +from 1,500 to 3,000 feet deep. This submarine plateau extends as far +as Norway on the east, Greenland on the north, and the island of Jan +Mayen on the northeast. Immediately north of the plateau the ocean +suddenly drops to a depth of 12,000 to 15,000 feet. + +[Illustration: FIG. 11. ICELAND] + +Toward the south the plateau extends with but few interruptions +through the middle of the ocean to a shoal known as the _Dolphin +Shoal_, as far as lat. 25° N. This part of the ocean, which can only +relatively be called a shoal, is not generally deeper than 9,600 feet, +although in some places the water is more than 12,000 feet deep. On +each side of the Dolphin Shoal the water is much deeper, being in +places 15,000 feet on the east, while on the west there are depths +as great as from 17,000 to 21,000 feet. + +This sunken plateau, possibly including the shallower plateau on the +north, is believed by some to be the remains of the fabled continent +of _Atlantis_, to which we shall refer in another part of this book. + +The coast line of Iceland is unbroken on the southeast, but the +remainder of the coast is deeply indented with bays or fiords in which +are many excellent harbors. + +Iceland is liable to frequent earthquake shocks and volcanic +eruptions. From careful records that have been preserved in the +history of the island, we learn that since the beginning of the +twelfth century there have practically never been intervals longer +than forty years, and more generally not longer than twenty years, +in which there has not been a great earthquake or a great volcanic +eruption. These volcanic eruptions are often very protracted. For +example, one eruption of the volcano Hecla continued for six years +without ceasing. Sir Charles Lyell, the great English geologist, +writes as follows about Iceland: + + "Earthquakes have often shaken the whole island at once, + causing great changes in the interior, such as the sinking + down of hills, the rending of mountains, the desertion of + rivers by their channels, and the appearance of new lakes. + New islands have often been thrown up near the coast, some + of which still exist, while others have disappeared, either + by subsidences or the action of the waves. + + "In the interval between eruptions innumerable hot springs + afford vent to the subterranean heat, and solfataras + discharge copious streams of inflammable matter. The + volcanoes in different parts of the island are observed, + like those of the Phlegræan Fields, Italy, to be in + activity by turns, one vent often serving for a time as a + safety valve for the rest. Many cones are often thrown + up in one eruption and in this case they take a linear + direction, running generally from southeast to northwest." + +The volcanic eruptions of Iceland belong for the greater part to the +fissure type. During a volcanic eruption in Iceland the ground is +split in fissures or cracks, generally parallel to each other, and +varying in width from a few inches to several yards. These fissures +extend for great distances across the country. The lava quietly wells +out along the fissures not unlike the way quiet spring waters flow +from their reservoirs. + +According to Dr. Th. Thoroddsen, the Icelandic geologist, there are +two systems of fissures extending through Iceland, from southwest to +northeast in the southern part of the island, and from north to south +in the northern part. Where two lines of fissures cross each other the +points of intersection may be especially active. + +Dr. Th. Thoroddsen arranges the volcanoes of Iceland under three +heads, i. e., _cone-shaped volcanoes_; _lava cones_; and _chains of +craters_, the last being the commonest. Out of 107 volcanoes examined +by him in Iceland, eight were of the Vesuvian type, or were built up +of layers of lava and volcanic ashes; sixteen were of the lava-cone +type, similar to Mt. Loa, of the Hawaiian Islands, and the remaining +eighty-three were of the type of crater chains. + +The volcano of Snaefell Jökul, 4,710 feet above the level of the +ocean, is built up of alternate layers of lava and hardened volcanic +mud. It is not, however, a true cone-shaped mountain. + +The largest volcano in Iceland, the Dyngjufköll, with its immense +crater of Askja, has an area of some twenty-five square miles. In its +form it resembles Snaefell. + +Volcanoes of the lava-cone type have been built up entirely of lava +and have a slight angle of inclination. These volcanoes range in size +from small hillocks to the largest mountains on the island. Their +cones generally stand on a base of wide circumference and frequently +rise to great heights, the top being occupied by a caldera, or pit +crater like that on Mt. Loa or Kilauea. + +Volcanoes of the type of chain-craters follow the natural fissures in +the crust. These craters are generally low, seldom being more than 350 +feet high. + +There are also seen in Iceland caldron-shaped depressions that have +been formed by explosive eruptions. One of the best instances of such +craters is Viti, on the side of Mt. Krafla. This crater was formed by +the sudden eruption of May 17th, 1724. + +The lava sometimes quietly runs out of the entire length of the +fissure without forming any cone. This was the case of a great fissure +known as the Eldgja Chasm. Here three lava streams covered an area of +270 square miles. + +As the lava comes out of the fissures, it generally produces long +ramparts of slags, and blocks of lava that are piled up on either side +of the fissure. Sometimes a line of low cones is built up. These cones +consist of heaps of slag, cinders, and blocks of lava. Their craters +are not rounded as in the case of volcanoes of the Vesuvian type, but +are oblong, or have their greatest diameter extending in a direction +of the fissure. + +Icelandic lava as it escapes from the fissures is peculiar in that +it is very viscid or plastic and can be readily drawn out into long +threads that can be spun into ropes. When such lava runs down the +sides of a steep slope, it often splits on cooling into separate +blocks. Where it runs over flat, level ground, however, it spreads +uniformly on all sides, producing vast level lava deserts that are as +flat as the surface of a well built floor. + +There are many rivers in the north and the west of Iceland. Now, as +the lava streams flow out of the fissures they enter the channels of +the rivers so that the streams of water must find new paths to the +sea, and this operation may be repeated again and again. Often the +time between eruptions is long enough to give the rivers opportunity +to cut deep channels or gorges in their new channels; but on the next +escape of the lava these gorges and valleys are again filled with the +molten rock, and the rivers must begin their channel cutting all over. + +You will note the frequent use of the word Jökul, as Snaefell Jökul, +Skaptar Jökul, Orefa Jökul, etc. The name Jökul means a large mass of +ice, or a mountain that is continually covered with snow, for example, +Snaefell Jökul, is a beautifully shaped, snow-covered mountain +situated on a point of land on the western coast of the island, +extending out nearly fifty miles into the sea, between the Faxa Fiord +and the Briela Fiord. It is a very conspicuous object, being visible +to passing ships at considerable distances from the island. Orefa +Jökul is the highest mountain in Iceland. Skaptar Jökul is one of the +active volcanoes of Iceland. + +There can be no doubt that Iceland has been formed entirely by lava +thrown up from the bottom of a submarine plateau, until it extended +above the surface of the waters. To make an island entirely of lava +with an area of 40,000 square miles, must, of course, have required +many cones or craters that continued to pour forth lava for periods of +time much longer than those during which man has lived on the earth. + +The surface of Iceland is far from attractive. The interior is +practically a vast lava desert, covered with snow-clad mountains or +Jökuls. There is no plant life except in marshy lands near the coasts, +and even here scarcely enough grass is raised to feed the few cattle +and horses owned by the inhabitants. There is no agriculture, owing +to the very short summers, so that all grain is brought from Europe. +Every now and then the grass crop is destroyed by accumulation of +Polar ice on the northern and western coasts. Such failures are always +attended by great famines, when many of the people die. + +Should you ever visit Iceland you would probably be surprised to hear +the people speaking about their forests. You might go over all the +coasts of the island without seeing anything larger than a birch bush, +not much higher than six feet. These are what the Icelanders like to +speak of as their forest trees, and I suppose there is no harm done, +if one only understands just what they mean by "trees." + +While, however, Iceland has practically no trees, yet it has no +difficulty in obtaining a plentiful supply of timber, since in the +deep fiords or bays on the western and southern coasts there can +always be found much drift timber brought there by the ocean currents +from the forests of America. + +The principal town or settlement in Iceland is Reykjavik, the capital +of the island, on the southwestern coast; this is the chief trading +place on the island. Thingvalla is also an important town. + +The lavas that form the entire mass of Iceland were thrown out both +before and since the glacial age. It is the opinion of Geikie that +these outflows have continued uninterruptedly since that age to the +present time. It is known that the lavas of Iceland were thrown out +both before and after the glacial age, because during the glacial age, +deep cuttings or groovings were made on the surface of the earth by +the glaciers as they slowly moved over it. Now lava beds containing +the glacial scratches have been found and resting on them are other +lava streams. The scratched lavas must, therefore, have been thrown +out before the glacial age, and the second lavas after that age. + +Let us now examine some of the more active volcanoes of Iceland and +their eruptions. We will begin with the well-known volcano of Skaptar +Jökul. + +The following description of this volcano has been taken from a book +on Iceland by E. Henderson, published in Boston, 1831. Skaptar Jökul +lies in the south central part of Iceland about forty odd miles from +the coast. It takes its name from the Skaptar River, down whose +channel the lava flowed its entire distance of forty miles from the +ocean. Skaptar Jökul consists of about twenty conical hills lying +along one of the fissures that extends from northeast to southwest. + +It appears from Henderson's account that people living in the +neighborhood of Skaptar Jökul were greatly alarmed by repeated +earthquakes that were felt at different times from the first to the +eighth of June, 1783. These earthquake shocks increased in number and +violence, so that the people left their homes and awaited in terror +the coming catastrophe. On the morning of the eighth a prodigious +cloud of dense smoke darkened the air, and the surrounding land soon +became covered with ashes, pumice, and brimstone. As is common with +eruptions in Iceland, that have been preceded by long periods of rest, +the heat produced by the escaping lava and the sulphurous gases, +melted such quantities of ice that great floods were produced in the +rivers. + +On the 10th of June vast torrents of lava that had been escaping +from the craters entered the valley of the Skaptar River, and +commenced flowing through its channel. Immense quantities of steam +were produced, and, in less than twenty-four hours, the river was +completely dried up, for the lava had collected in the channel, +which in many places flows between high rocks from 400 to 600 feet +in height and nearly 200 feet in breadth, and had not only filled +the river to its brink, but had overflowed the adjacent fields to a +considerable extent, and flowing along the cultivated banks of the +river destroyed all the farms in its path. + +On gaining the outlet, where the channel of the Skaptar emerged +into the plain, it might have been supposed that the burning flood +would have at once spread over the low fields, which lay immediately +before it, but, contrary to all expectations, this flow was for a +time stopped by an immense unfathomed abyss in the river's bed, into +which it emptied itself with great noise. When this chasm was at +last filled, the lava increased by fresh flows, rose to a prodigious +height, and breaking over the cooled mass, proceeded south towards the +plain. + +In the meantime the thunder and lightning, together with subterranean +roars, continued with little or no intermission. + +On the 18th of June, 1783, another dreadful eruption of red hot lava +came from the volcano. This flowed with great velocity and force over +the surface of the cooling stream that had been thrown out principally +on the tenth of the month. Floating islands consisting of masses of +flaming rock were seen on the surface of the lava stream, and the +water that had been banked up on both sides of the stream was thrown +into violent boiling. + +In the meantime people living along the Hverfisfloit, the next largest +river to the east of the Skaptar, had not yet been visited by the +lava streams. It is true that their vegetation had been destroyed by +showers of red hot stone and ashes, and that both atmosphere and water +were filled with poisonous substances. The land had also been plunged +in utter darkness, so that it was scarcely possible at noonday to +distinguish a sheet of white paper held up at the window from the +blackness of the wall on either side. But the molten lava streams had +not yet reached the people of this valley and they hoped that the +eruption would soon be over, and that the lava flow would continue to +follow the Skaptar. On the 3d of August, however, they were alarmed by +seeing steam escaping from the River Hverfisfloit, and soon all its +water was dried up, and a fresh lava flow poured down upon them. As in +the case of the Skaptar, the melted rock completely filled the empty +channel to the brink, and then overflowing, covered the low grounds on +both sides, so that by the ninth of August it had reached the open and +level country near its mouth and in the course of a few hours spread +itself for a distance of nearly six miles across the plain. This flow +continued after the end of August, and, indeed, even as late as the +month of February, 1784, when a new eruption took place in this part +of the country. + +Hecla, another well-known volcano in Iceland, situated about thirty +miles from the southern coast, consists of three peaks, the central of +which is the highest. Its craters form vast hollows on the sides of +these peaks, and at the time of the eruption in 1766 were covered with +snow. Hecla is believed to have been an active volcano long before +Iceland was inhabited. No less than twenty-three eruptions have been +recorded between A. D. 1004 and the great eruption of 1766-68. + +Volcanic history frequently repeats itself. There had been no great +eruption of Hecla for a period of about twelve years, and the people +living in the neighborhood were congratulating themselves on the +belief that the mountain was becoming actually extinct, and that +therefore they need not trouble themselves about eruptions. Others, +however, more farseeing, pointed out the fact that the lakes and +rivers in the vicinity did not freeze, and that the amount of water +they contained was greatly decreased. + +The following description of the great eruption of Hecla that was +remarkable both for its violence, as well as for the time during which +it continued, is taken from Symington's "Sketches of Faroe Islands and +Iceland": + + "On the 4th of April, 1766, there were some slight shocks + of an earthquake, and early next morning a pillar of sand, + mingled with fire and red hot stones, burst with a loud + thundering noise from its summit. Masses of pumice, six + feet in circumference, were thrown to the distance of ten + or fifteen miles, together with heavy magnetic stones, + one of which, eight pounds weight, fell fourteen miles + off, and sank into ground still hardened by the frost. The + sand was carried towards the northwest, covering the land, + 150 miles round, four inches deep, impeding the fishing + boats along the coast, and darkening the air, so that at + Thingore, 140 miles distant, it was impossible to know + whether a sheet of paper was white or black. At Holum, 155 + miles to the north, some persons thought they saw the stars + shining through the sand-cloud. About mid-day, the wind + veering round to the southeast, conveyed the dust into the + central desert, and prevented it from totally destroying + the pastures. On the 9th of April, the lava first appeared, + spreading about five miles towards the southwest, and on + the 23d of May, a column of water was seen shooting up in + the midst of the sand. The last violent eruption was on the + 5th of July, the mountains, in the interval, often ceasing + to eject any matter; and the large stones thrown into the + air were compared to a swarm of bees clustering around the + mountain-top; the noise was heard like loud thunder forty + miles distant, and the accompanying earthquakes were more + severe at Krisuvik, eighty miles westward, than at half the + distance on the opposite side. The eruptions are said to + be in general more violent during a north or west wind than + when it blows from the south or east, and on this occasion + more matter was thrown out in mild than in stormy weather. + Where the ashes were not too thick, it was observed that + they increased the fertility of the grass fields, and + some of them were carried even to the Orkney Islands, the + inhabitants of which were at first terrified by what they + considered showers of black snow." + +The largest volcano in Iceland is Dyngjufjoll. This has on its summit +the gigantic crater of Askja, some twenty-five square miles in area. +This crater is of the intermediate form; the most general form of +volcanoes on the island consisting of a number of craters that closely +follow fissures. + +Professor Johnstrup, in a report to the Danish Government, on this +volcano, states that the valley of Askja has been gradually filled +by repeated flows of lava from enormous craters on the edge of the +mountain. In many places the surface of the earth is covered with +bright red pumice stone that was thrown out during an eruption March +29th, 1875. Some of these craters are filled with steam that escapes +with an almost deafening roar. The surprising feature of this eruption +was the immense quantity of pumice stone that escaped. + +The volcanoes in the Nyvatus Oraefi are entirely different. This +barren plain is thirty-five miles in length and thirteen miles in +breadth. Suddenly on the 18th of February, 1875, a volcano appeared in +the centre, and four other craters were formed at subsequent dates. +The mass of lava that was thrown out of these openings has been +estimated at 10,000,000,000,000 cubic feet, or eighteen times the +estimated mass of lava that has been emitted from Vesuvius between +1794 and 1855. This lava is basalt. + + + + +CHAPTER V + +VESUVIUS + + +The old Greeks and Romans had but little knowledge of volcanoes. They +only knew the volcanic mountains in the Mediterranean Sea. Here there +are three volcanic regions:--one in the neighborhood of Naples; one +including Sicily and the neighboring islands, and the other that of +the Grecian Archipelago. + +Some idea can be had of these three regions from a map of the +Mediterranean shown in Fig. 12. The principal volcanoes are Vesuvius, +Etna, Stromboli, and Vulcano, a mountain, by the way, that gave its +name to all volcanic mountains. In this chapter we will describe the +volcano of Vesuvius, the most active, though by no means the largest +of the volcanoes of the Mediterranean. + +But, before doing this, it will be well first to describe briefly the +volcanic districts surrounding Vesuvius. + +As shown in Fig. 13, this district includes Vesuvius, Procida, and +Ischia. + +[Illustration: FIG. 12. THE MEDITERRANEAN] + +Ischia is a small island measuring about five miles from east to west, +and three miles from north to south. There were such terrific volcanic +eruptions on this island long before the Christian Era, that several +Greek colonies were forced to abandon it. A colony established long +afterwards, about 380 B. C., by the king of Syracuse also +had to depart. Strabo, the Grecian geographer (born about 63 B. +C.), states that, according to tradition, terrific earthquakes +occurred on the island a little before his time, and its principal +mountain threw out large quantities of molten rock, which flowed into +the sea. At the time of this eruption there were earthquake waves in +the sea, the waters of which slowly receded, leaving large portions +of the bottom uncovered, and rushing, afterwards, violently over +the land, caused great destruction. It was during this disturbance, +so Strabo asserts, that the island of Procida was formed by being +violently torn from Ischia. + +[Illustration: FIG. 13. THE VOLCANIC DISTRICT AROUND VESUVIUS] + +The Phlegræan Fields was a name given by the ancients to some of the +lowlands in the neighborhood of Naples; they were believed to be under +the special protection of the Roman gods. When the frequent earthquake +shocks shook these fields, the Roman people believed that conflicts +were taking place between their gods and slumbering giants confined in +the regions below the surface. + +It is more than probable that Mt. Vesuvius has always been the centre +of these volcanic disturbances. Long before the Christian Era, +however, Vesuvius, or Somma, the name given to the old crater that +then occupied the summit of the mountain, had been an extinct crater. +Indeed, it had been so quiet that the people who lived on its slopes +did not appear to know they were living on the slopes of a slumbering +volcano. Their knowledge of volcanic mountains must have been very +limited, for this mountain with the huge pit at its summit had all +the appearance of a volcanic crater. When they climbed to the top of +the mountain, which, of course, they frequently did to look after the +vineyards they were cultivating on the slopes, and looked down into +the deep pit from the rocks on its edge, they could see at the bottom +of a great central pit three miles in diameter, a lake, with room here +and there to enable one to walk along its borders. The walls of the +precipice were covered with luxuriant vines. + +When we say that none of the people even suspected that Vesuvius had +ever been in a state of eruption, we must except some of their learned +men. For both Diodorus Siculus, a native of Sicily, who lived about +10 B. C., and wrote an Universal History, containing some +forty volumes, of which only about one-third remain, and Strabo, the +Geographer, pointed out in a general manner, that Vesuvius, and much +of the surrounding country, looked as if it had been eaten by fire. +Then, too, a Roman philosopher who lived between A. D. 1 and +A. D. 64, spoke of Vesuvius being "a channel for the eternal +fire!" + +Let us now endeavor to obtain some idea of the appearance of this +region a short time before A. D. 79, when Vesuvius burst +forth in a terrific eruption. The slopes of the mountain were covered +with the rich vegetation that characterizes this part of Italy. +When most volcanic ashes and lava have been exposed for some time to +the atmosphere they make a very fertile soil. Now, this soil on the +slopes of Vesuvius made the vineyards that covered the mountain slopes +and the fields for miles around its base, bear very plentifully, +so that the people lived very comfortably. Here and there on the +slopes of the mountain large towns like Herculaneum and Pompeii had +long been established, while, in the distance, was the large city of +Naples. Besides these there were numerous populous towns and villages +scattered here and there over the plain or on the lower mountain slope. + +You have all probably read of the Roman gladiator, Spartacus. +Spartacus was a Thracian by birth, and while a shepherd had been taken +prisoner by the Romans and sold to a trainer of gladiators at Capua. +Chaffing under the tyranny of the Romans, who forced him to fight in +the arena with men and beasts, he revolted against his masters, and +with a band of some seventy followers, fled to a mountain fastness in +the crater of Vesuvius. Proud Rome sent a few men to recapture him, +with scourges for his punishment, but they were beaten by Spartacus. +Every day dissatisfied men like himself escaped from the Romans and +joined his ranks. Rome sent a larger body of men against Spartacus, +but they also were beaten. At last, recognizing the gravity of the +position, the Roman Prætor, Clodius, was sent against Spartacus with +an army of some three thousand men. Clodius caught Spartacus in the +crater and guarded the only space by which it seemed possible for +Spartacus to escape. Using the vines that covered the precipitous +walls of the crater, Spartacus did escape, and falling unexpectedly +on the armies of Clodius, routed them. After this victory, Spartacus +with an army of over 100,000 men overran southern Italy, and sacked +many of the cities of the Roman Campania. During this time Spartacus +defeated one Roman army after another, until finally, in the year 71 +B. C., Crassus was sent against him and vainly endeavored +to conquer him. Being unsuccessful, Crassus urged the Roman Senate +to recall Lucullis from Asia and Pompey from Spain, and finally poor +Spartacus was cut down in a fight he made against Crassus and Lucullis. + +But let us come to the great eruption of Vesuvius in A. D. +79. The people living on the slopes of Vesuvius were not without +plenty of warnings of the dreadful catastrophe that was coming. As +early as A. D. 63 there was a great earthquake that shook the +country far beyond Naples. In Pompeii, then a flourishing city, the +Temple of Isis was so much damaged that it had to be rebuilt. + +Even if the earthquake shocks had not foretold the coming eruption, +there were other signs. The height of water in the wells decreased. +Springs that had never before been known to fail, dried up completely. +These changes, as we well know, were due to the red hot lava being +slowly forced up from great depths into the tube connected with the +crater. + +The earthquake shocks continued at irregular intervals for sixteen +years, until, on the 25th of August, A. D. 79, about one +o'clock in the afternoon, Vesuvius burst forth in the terrible +eruption that destroyed the towns of Pompeii and Herculaneum. Pompeii +was a seaport town situated near the mouth of the River Sarno, +about fifteen miles southeast of Naples. It was a beautiful place, +containing many splendid temples. Its people for the greater part +lived luxuriously, for Pompeii was the summer resort of the richer +people of Naples, some of whom lived there during the hottest months +of the year. + +Herculaneum, the other town, was nearer Naples, only five miles from +the city. It was also, like Pompeii, a beautiful town, and contained +many splendid buildings. In each town there were magnificent baths and +a large theatre. The inhabitants spent so much of their time in the +open air, or in the baths, that it was not necessary for them to build +very large houses. The houses, however, were well built, and though +generally consisting of practically a single story, were provided with +all the luxuries that great wealth could command. + +On August 25th, A. D. 79, severe earthquake shocks again +visited this part of the world and Vesuvius suddenly threw up from +its crater an immense column of black smoke, which, rising high in +the air, spread out in the form of a huge mushroom, or, perhaps, more +like the umbrella pine tree of the neighborhood. Rapidly spreading on +all sides, the smoke soon completely shut out the light of the sun, +and wrapped the earth in an inky darkness, except for a red glare from +columns of molten rock that rushed out of the crater. + +From the dark cloud immense quantities of red hot stones, pumice, and +volcanic ashes descended on the earth. At the same time there fell +a deluge of rain, caused by the sudden condensation of the enormous +amount of water vapor that was thrown out from the crater during the +eruption. Fortunately, very few of the people were killed in either of +the cities of Pompeii and Herculaneum, although some bodies were found +in the ruins. Most of the people escaped through the darkness and +gloom, continuing to flee from the city for at least three days. + +Both cities were covered so deep with ashes or mud that the tops of +the tallest buildings were no longer visible. Pompeii was buried by +showers of ashes or volcanic cinders, and Herculaneum mainly by vast +floods of aqueous lava. + +So completely were these cities covered that their very existence was +at last forgotten. It is true that Titus, who was then Emperor of +Rome, endeavored to clear away the ashes and rebuild Pompeii, but the +task was so great that he finally abandoned it. + +During the year 1592, the architect Fontana, while superintending the +building of an aqueduct, came across some ancient buildings. At a much +later date, in 1713, some workmen, while digging a well in the village +of Portici, uncovered three marvellously beautiful marble statues. In +the year 1738, the same well was dug deeper, when traces of the old +theatre of Herculaneum were discovered. Some effort was then made to +excavate the city and many of the public buildings and private houses +were uncovered, and statues, mosaics, wall paintings, and charred +manuscripts of papyrus were found. A few of these have been unrolled +and deciphered, but owing to the difficulty of doing this, without +destroying them, the greatest number still remain unread. + +In 1860, the Italian Government began a systematic excavation of the +buried cities, and now both Pompeii and Herculaneum are thrown open to +the sunlight so that one can walk through the old streets, and look +into the houses, in which, before A. D. 79, the people lived +so happily. + +Many interesting stories are told about the discoveries that were +made during the government excavations. The skeleton of one of the +inhabitants was found grasping a money bag. He might have escaped, +but had gone back to get his money. He got it, but remained with it. +In another place, the skeletons of a number of people were found in +an underground room or cellar of a house, where were also found some +mouldy bread and empty water flasks. Instead of leaving the city, +which they might have done, they had retreated to the underground +room for safety, but the fine volcanic dust drifted in and suffocated +them. + +The younger Pliny, the historian, has given an excellent account of +some features of this great eruption. It appears that his uncle was +stationed with the Roman fleet, in the Bay of Naples, at the time of +the eruption. He describes the dark cloud of ashes that was formed +over Vesuvius. He refers to the rapidity with which it spread, and +to the showers of ashes, cinders, and stones that it rained down on +the earth. His uncle, the elder Pliny, landed on the coast, and was +afterwards killed by a cloud of sulphurous vapor that swept down the +side of the mountain. + +The following letter from the younger Pliny, describing his flight +with his mother from Misenum, is quoted from Dana's "Characteristics +of Volcanoes." + + "It was now seven o'clock [on the morning of August 25th], + but the light was still faint and doubtful. The surrounding + buildings had been badly shaken, and although we were in + an open spot [a little yard between his uncle's house and + the sea], the space was so small that the danger of a + catastrophe from falling walls was great and certain. Not + till then did we make up our minds to go from the town.... + When we were free from the buildings we stopped. There we + saw many wonders and endured many terrors. The vehicles we + had ordered to be brought out kept running backward and + forward, though on level ground; and even when blocked + with stones they would not keep still. Besides this, we + saw the sea sucked down and, as it were, driven back by + the earthquake. There can be no doubt that the shore had + advanced on the sea, and many marine animals were left high + and dry. On the other side was a dark and dreadful cloud, + which was broken by zigzag and rapidly vibrating flashes of + fire, and yawning showed long shapes of flame. These were + like lightning, only of greater extent.... + + "Pretty soon the cloud began to descend over the earth + and cover the sea. It enfolded Capreæ and hid also the + promontory of Misenum." ... The flight was continued. + "Ashes now fell, yet still in small amount. I looked + back. A thick mist was close at our heels, which followed + us, spreading out over the country, like an inundation." + ... Turning from the roar in order to avoid the fleeing, + terror-stricken throng, they rested. "Hardly had we sat + down when night was over us--not such a night as when there + is no moon and clouds cover the sky, but such darkness as + one finds in close-shut rooms. One heard the screams of + women, the fretting cries of babes, and shouts of men.... + + "Little by little it grew light again. We did not think + it the light of day, but a proof that the fire was coming + nearer. It was indeed fire, but it stopped afar off; and + then there was darkness again, and again a rain of ashes, + abundant and heavy, and again we rose and shook them off, + else we had been covered and even crushed by the weight.... + At last the murky vapor rolled away, in disappearing smoke + or fog. Soon the real daylight appeared; the sun shone out, + of a lurid hue, to be sure, as in an eclipse. The whole + world which met our frightened eyes was transformed. It was + covered with ashes white as snow." + +Young Pliny and his mother returned to Misenum, and survived the +perils to which they were exposed. + +It was during this eruption that a large part of the old crater was +blown off the mountain by the tremendous force at work. + +There have been many eruptions of Vesuvius since the great eruption +of A. D. 79. One of these occurred during the reign of Severus, +A. D. 203. It was during this eruption that an additional part of the +old crater of Somma was blown away. + +Another great eruption occurred A. D. 472. Then great +quantities of volcanic dust were thrown up into the air, and falling, +covered practically all parts of Europe, producing darkening of the +sun and great fear as far as the city of Constantinople. + +But what was perhaps a still greater eruption occurred during December +of 1631. This eruption spread great quantities of ashes over the +country for hundreds of miles around, and great streams of mud rushed +down the slopes of the mountain. Buccini gives the following account +of this eruption: + + "The crater was five miles in circumference, and about + 1,000 paces deep. Its sides were covered with brushwood, + and at the bottom there was a plain on which cattle grazed. + In the woody parts wild boars frequently harbored. In one + part of the plain, covered with ashes, were three small + pools, one filled with hot but bitter water; another with + water saltier than the sea, and a third with water that + was hot but tasteless. But at length these forests and + grassy plains were consumed, being suddenly blown into the + air and their ashes scattered to the winds. In December, + 1631, seven streams of lava poured at once from the crater + and overflowed several villages, on its flanks, and at the + foot of the mountain. Reisna, partly built over the ancient + city of Herculaneum, was consumed by the fiery torrent. + Great floods of mud were as destructive as lava. This is + no unusual occurrence during these catastrophes for such + is the violence of the rains produced by the evolution of + aqueous vapors that torrents of water descend the cone and + become charged with impalpable volcanic dust, and rolling + among ashes, acquire sufficient consistency to deserve the + ordinary appellation of aqueous lava." + +Of course, you will understand that we have given only a few of +the most notable of the eruptions of Mt. Vesuvius. Since the yea +A. D. 1500 there have been no less than fifty-six recorded +eruptions, that of the year 1857 being especially violent. + +Omitting these eruptions we at last come to the great recent eruption +of 1872. + +Fortunately, the eruption of 1872, as well as still more recent +eruptions that have occurred, have been more accurately described than +have most volcanic eruptions, for the Italian Government, recognizing +the value to the natives of Italy of a knowledge of what was going on +at the crater of Vesuvius, has maintained for the past thirty years +an observatory on the western part of the mountain. This observatory +has been placed in charge of Prof. Luigi Palmieri, a well-known +student of volcanoes and earthquakes. At this place records are kept +of the behavior of the volcano, of all earthquake disturbances, as +well as other phenomena. At the same time, by the use of photography, +excellent pictures have been obtained showing the appearance of the +sky during an eruption. + +Vesuvius had been in a quiet state from November, 1848, to the year +1871, when small quantities of lava flowed continuously for several +months. Again, early in 1872, other quiet eruptions of lava continued +for weeks at a time. Finally, on April 26th, of that year, a violent +explosive eruption occurred. The following account has been taken from +Palmieri's report, entitled, "The Eruption of Vesuvius in 1872." + +On April 23d the recording earthquake instruments, the seismographs, +were greatly affected. On the evening of the 24th lava streams flowed +down the cone in various directions. These streams were continued +on the 25th and the 26th, so that on the night of the 26th the +observatory lay between two streams of molten lava that threw out so +much heat that the glass windows in the observatory were cracked, +and a scorching smell was quite perceptible in the rooms. The cone +of the mountain was deeply fissured, lava escaping freely from all +the fissures, so that the molten rock appeared to ooze from over its +entire surface, or as Palmieri expressed it, "Vesuvius sweated fire." + +This great cracking or fissuring of the cone was accompanied by the +opening of two large craters at the summit, that discharged, with a +great noise, immense clouds of steam, dust, lapilli, and volcanic +bombs. These latter are very curious and consist of masses of soft +lava that are thrown high into the air by the outrushing columns of +steam. Being rotated or spun, as they rise in the air, they assume a +spherical shape. Some of these volcanic bombs were thrown to a height +estimated by Palmieri to have been nearly 4,000 feet above the top of +the mountain. When the height of a projectile is known, the velocity +with which it left the opening from which it was projected or thrown +can be estimated, so that the volcanic bombs must have left the crater +at a velocity of about 600 feet per second. + +On the 27th, in the evening, the lava streams ceased flowing, but the +dust and lapilli continued to fall during the 28th and the 29th. On +the 30th the detonations decreased and by the 1st of May the eruption +was entirely over. + +Palmieri calculated that the quantity of molten rock thrown out during +this eruption was sufficient to cover an area of about 1.8 square +miles to an average depth of about thirteen feet. + +As we can see from the above descriptions, the volcanic activity of +Vesuvius is characterized by long periods of rest followed by periods +of activity. The periods of rest are measured by years, and often by +centuries; the periods of activity by days or hours. + +But Vesuvius was not to have a long period of rest after its eruption +of 1872. On the contrary, shortly after the great disaster of +Martinique in 1906, it again became active, and on the 5th of April, +1906, began throwing large blocks of lava out of its central cone, and +on the next day began to throw out large streams of lava, which, on +April 7th, destroyed a village in the neighborhood. At the same time +rumbling sounds were heard, and violent earthquake shocks shattered +the windows of the houses. + +Professor Matteucci, the present director of the Vesuvius Observatory, +made the following report on April the 8th. + + "The eruption of Vesuvius has assumed extraordinary + proportions. Yesterday and last night the activity of the + crater was terrific, and is increasing. The neighborhood + of the observatory is completely covered with lava. + Incandescent rocks are being thrown up by the thousands, to + a height of 2,400 feet or even 3,000 feet, and falling back + form a large cone. Another stream of lava has appeared.... + The noise of the explosion and of the rocks striking + together is deafening. The ground is shaken by strong and + continuous seismic movements, and the seismic instruments + [instruments employed to record the time, direction, and + intensity of earthquake movements] threaten to break. It + will probably be necessary to abandon the observatory, + which is very much exposed to the shocks. The telegraph is + interrupted, and it is believed the Funicular railroad has + been destroyed." + +On April 9th Matteucci made the following report: + + "The explosive activity of Vesuvius, which was so great + yesterday, and was accompanied by very powerful electric + discharges, diminished yesterday afternoon. During the + night the expulsion of rocks ceased, but the emission of + sand increased, completely enveloping me and forming a + red mass from six to ten centimeters deep, which carried + desolation into these elevated regions. Masses of sand + gliding along the earth, created complete darkness until + seven o'clock. Several blocks of stone broke windows in the + observatory. Last night the earthquake shocks were stronger + and more frequent than yesterday, and displaced the seismic + apparatus. Yesterday afternoon and this morning, torrents + of sand fell." + +On April 10th Matteucci sent the following report: + + "Last night was calm, except for a few explosions of + considerable force from time to time. At four o'clock this + morning the explosions became more violent. The seismic + instruments recorded strong disturbances." + +The eruption of Vesuvius of 1906 was especially noted for the great +quantities of sand and ashes thrown out of the crater. The amount +of sand that fell on the roof of the market house at Monti Olivetto +was so great that the roof fell in. In this eruption there were some +six lava streams that poured down the mountain. The most formidable +of these was that which descended towards Torre Annunziata. Here it +stopped just short of the wall of the cemetery outside of the town. + +During this eruption of Vesuvius, as in previous eruptions, clouds of +volcanic dust collected in the air, shutting off the light of the sun. +Naples was in a state of semi-darkness. The roofs of the houses were +covered to a depth of several inches with an exceedingly fine reddish +dust. In some places this dust had drifted into heaps fully a yard in +depth. + + + + +CHAPTER VI + +OTHER VOLCANOES OF THE MEDITERRANEAN + + +The relative positions of the other volcanic mountains of the +Mediterranean Sea; i. e., Etna, Stromboli, and the volcanoes of the +Santorin group of the Grecian Archipelago, are shown in the map, Fig. +12. + +We will begin with the volcanic mountain of Etna, under which, +according to mythology, the angry gods had buried the rebellious +Typhoon. + +Etna is situated on the island of Sicily, immediately southwest of +Italy. It is a much larger mountain than Vesuvius, rising, as it +does, from a circular base about eighty-seven miles around, to a +height of 10,840 feet above the level of the Mediterranean. It forms +a conspicuous object when seen either from the Mediterranean, or from +distant parts of Italy. + +The height of Etna is so great that its slopes can be divided into +three distinct climatic zones or belts. The lowest of these lies +between the sea and a height of 2,500 feet. In this zone the mountain +slopes are covered with cultivated fields, olive groves, orchards, +and vineyards. The middle zone lies between 2,500 feet and 6,270 +feet. This zone is covered with forests of chestnuts, oaks, beeches, +and cork trees. The third and highest zone includes the rest of the +mountain, and may be called the desert zone, since it is a sterile +region, covered with huge blocks of lava and scoriæ, and terminating, +in the higher portions, in a snow-covered plain, from which the +central cone rises. + +Etna is continually sending up columns of steam and sulphur vapor. +Every now and then it starts in eruption, throwing out large +quantities of lava either from the crater on its summit, or from +some of the 200 smaller cones or craters that occupy portions of its +slopes. On account, probably, of its height the eruptions are most +frequently on the sides. Etna affords a magnificent example of a huge +volcanic pile of the Vesuvian type, which has been slowly built up +by the gradual accumulation of materials that have escaped from its +craters. + +One of the most interesting features of the higher regions of Etna is +an immense chasm rent in a side of the cone near the summit, and known +as the Val del Bove. This chasm forms a vast amphitheater. + +The great force that removed such an immense mass of matter from +the cone could not have been the eroding power of water, since the +materials of the cone are too porous to permit streams of any size to +rush down the slopes. The force is most probably to be found in some +explosive eruption of the mountain, when a portion of the crater was +suddenly blown off, just as was done in Vesuvius when a large part of +the old crater of Somma was blown away. What is especially interesting +about the Val del Bove is the opportunity it affords for studying the +interior structure of the mountain, for it practically enables one to +enter to almost the heart of this great volcano. + +The Val del Bove has the shape of a great pit five miles in diameter. +It has almost vertical walls, the height of which varies with their +position. Those which reach highest up the mountain vary from 3,000 to +4,000 feet in height. + +Like Vesuvius, Etna has been split or fissured into great crevices +that have been filled with lava during the many eruptions of its +central crater. On hardening, these lava streams form what are known +as dikes. As the sides of the mountain are worn away by erosion, the +dikes, being harder than the rest of the cone, project from its sides +like huge walls. An excellent opportunity for seeing them is afforded +in the walls of the Val del Bove. + +Sir Charles Lyell, the English geologist, who has carefully studied +Mt. Etna, asserts that this mountain began to be formed during a +geological period known as the Tertiary Age, through a crater that +opened on the floor of the Mediterranean Sea. The material thus +thrown out, collected around the crater and produced a mountainous +pile that gradually emerged above the level of the sea, and on fresh +materials continuing to be thrown out, at length reached its present +height. It would appear that at some former time in its history, there +were two vents near the top of the mountain, the second crater being +formed immediately under the Val del Bove. Soon, however, the second +and lower crater was closed, the upper one alone remaining active. +The mountain, therefore, continued to be slowly raised in the air by +the materials brought out through this opening. Then came the great +explosive eruption during which the side of the mountain was blown off +to form the great chasm of the Val del Bove. + +Because of its almost constant activity, Mt. Etna must have been +well known to the ancients, who described some of its most violent +eruptions. The following brief notes concerning these eruptions have +been taken from Lyell. + +According to Diodorus Siculus, an eruption that occurred before the +Trojan war, caused the people living in districts near the mountain to +seek new homes. Thucididies, the Greek historian, states that in the +sixth year of the Peloponnesian war, which would be about the spring +of 425 B. C., a lava stream caused great destruction in the +neighborhood of Campania, this being the third eruption that had +occurred in Sicily since it had been settled by the Greeks. + +Seneca, during the first century of the Christian Era, calls the +attention of Lucullus to the fact that during his time Mt. Etna had +lost so much of its height that it could no longer be seen by boatmen +from points at which it had before been readily visible. + +But passing by these very early eruptions of Etna we come to the great +eruption of 1669. This eruption was preceded by an earthquake that +destroyed many houses in a town situated in the lower part of the +forest zone, about twenty-five miles below the summit of the mountain, +and ten miles from the sea at Catania. During this eruption two deep +fissures were opened near Catania. From these such quantities of sand +and scoriæ were thrown out, that, in the course of three or four +months, a double cone was formed 450 feet high, which is now known as +Monte Rosso. But what was most curious was the sudden opening, with +a loud crash, of a fissure six feet broad reaching down to unknown +depths that extended in a somewhat crooked course to within a mile +of the summit of Etna. This great fissure was twelve miles in length +and emitted a most vivid light. Five other parallel fissures of +considerable length opened, one after another, throwing out vapor, +and emitting bellowing sounds which were heard at a distance of forty +miles. These fissures were afterwards filled with molten rock, and in +this manner were formed the long dikes of porphyry and other rocks +that are seen to be passing through some of the older lavas of Mt. +Etna. + +[Illustration: FIG. 14. MT. ETNA _From Map of State and +Government_] + +The great lava streams which flowed down the side of the mountain +during this eruption, destroyed fourteen towns and villages, and +at length reached Catania. A great wall had been raised around this +city to prevent the lava from entering it. The molten rock, however, +accumulated, until it rose to the top of the wall, which was sixty +feet high, and then pouring over it in a fiery cascade, overwhelmed +part of the city. It is said that during the first part of its +journey, the lava streams moved over thirteen miles in twenty days, +or at the rate of 162 feet an hour. Beyond this, after the lava had +thickened by cooling, it had a velocity of only twenty-two feet per +hour. + +Fig. 14 represents a plan of Mt. Etna reduced from a map by the +Italian Government. During the eruption of 1865, a rent was made in +the mountain extending from Mount Frumento (B in the preceding map) +for one and one-half miles, and six cones from 300 to 350 feet in +height were formed along the fissure. + +During the eruption of 1874, great fissures three miles in length were +formed in the mountain. + +There exists on the slopes of Mt. Etna vast subterranean grottoes +formed by the sudden conversion into steam of great quantities of +water that were overwhelmed by the molten mass. These immense volumes +of steam produced enormous bubbles in the molten lava. When the lava +hardened irregular grottoes were left. Lyell describes one of these as +follows: + + "Near Nicolosi, not far from Monte Rosso, one of these + great openings may be seen, called the _Fossa della + Palomba_, 625 feet in circumference at its mouth and + seventy-eight deep. After reaching the bottom of this, we + enter another dark cavity, and then others in succession, + sometimes descending precipices by means of ladders. At + length, the vaults terminate in a great gallery ninety feet + long, and from fifteen to fifty broad, beyond which there + is still a passage, never yet explored, so that the extent + of these caverns remains unknown. The walls and roofs of + these great vaults are composed of rough bristling scoriæ + of the most fantastic forms." + +Besides the eruptions mentioned there have been many others, such as +those of 1811, 1819, and 1852. The last of these was greater than any +eruption except that of 1669. It began in August, 1852, and continued +until May, 1853, and was remarkable for the immense quantity of lava +thrown out. + +[Illustration: FIG. 15. STROMBOLI, VIEWED FROM THE NORTHWEST, +APRIL, 1874] + +We come now to the volcano of Stromboli. Stromboli, one of the Lipari +islands, is situated about sixteen miles west of the Straits of +Messina. Its general appearance is shown in Fig. 15. The form of the +mountain is that of an irregular four-sided pyramid, which rises about +3,090 feet above the level of the Mediterranean, and stands on the +bottom of the sea in water about 3,000 feet deep. + +If you carefully examine the appearance of Stromboli, as shown in the +preceding figure, you will notice that the flat cloud which hangs over +the island is made up of a number of globular masses of vapor, formed +during the peculiar action of the volcano. + +When examined by night Stromboli presents a still more curious +appearance. Since the mountain stands alone, its height permits it to +be seen readily at sea for distances of at least a hundred miles. At +night a curious glow of red light may be seen on the lower surfaces of +the cloud. This light is not continuous, but increases in intensity +from a faint glow to a fairly bright red light, then gradually +decreases, and finally dies away completely. After awhile the light +again appears, again gradually decreases, and disappears, and this +continues until the rising sun prevents the red glow from being any +longer visible. Stromboli, therefore, acts not unlike the flashing +lighthouses so common on the sea coasts of all parts of the world. +Indeed, it is actually used by sailors in the Mediterranean for the +purpose of showing them their direction. For this reason Stromboli is +commonly called "The Lighthouse of the Mediterranean." + +As Judd remarks, from whom much of the information concerning some of +the volcanic districts of the Mediterranean has been obtained, the +flashing light of Stromboli differs from that of the ordinary flashing +light in two important respects; viz., in the intervals that elapse +between the successive flashes, and in the intensity of the light +emitted. As you know, it is necessary that the different lighthouses +placed near one another on a coast must have their lights of such a +nature that they can be readily distinguished. In order to do this, +the flashing light has been devised. In flashing lighthouses, the +lights only appear at intervals, one lighthouse being distinguished +from another in its neighborhood by the intervals between successive +flashes, or, sometimes, indeed, by the color of some of the flashes. +Now, in the case of Stromboli, the intervals between the successive +glowings of the red lights are very irregular, varying between one and +twenty flashes per second. Moreover, the intensity of the light also +varies greatly from time to time. + +You naturally inquire as to the cause of these flashes of light that +are emitted by Stromboli. If, as Judd suggests, you should climb to +the summit of the mountain, during the daytime, and look down the +inside of the crater, you could see its black slag bottom crossed by +many cracks and fissures. From most of the smaller fissures the vapor +of water is quietly escaping. This vapor rises in the air in which it +soon disappears. There are, however, larger cracks on the bottom of +the crater from which, at more or less regular intervals, masses of +steam are emitted with loud snorting puffs not unlike those produced +by a locomotive. From some of the openings molten matter is seen +slowly oozing out, collecting in parts of the crater and moving up and +down in a heaving motion. Every now and then a bubble is formed on +the surface of this liquid. The bubble swells to a gigantic size, and +suddenly bursts. The steam it contained escapes, carrying fragments of +scum which are thrown high into the air. The masses of steam, formed +below the surface of the sticky, boiling, lava, in endeavoring to +escape, force their way through the mass, blow huge bubbles, which, +on bursting, produce the roaring sounds that are heard, and throwing +great columns of vapor in the air, produce the rounded masses of +clouds you can see floating high up in the air over the mountain. At +the same time the scum is partially removed from the red hot surface, +its light illumines the lower surface of the overhanging cloud, which +flings it back again to the earth. With the bursting of each bubble, +and the clearing of the scum from the surface of the red hot mass, +the light begins, increases in intensity, and then as the scum again +begins to collect on the surface, decreases, and finally disappears, +and not until the bursting of the next bubble is it again visible. + +But let us make a study of some of the peculiarities of Vulcano, +another of the Lipari islands, which lies north of Sicily. + +Vulcano affords a curious example of a volcano that has been harnessed +by man, or made to do work for him. All volcanoes bring from inside +of the earth different kinds of chemical substances, in the form of +vapors, gases, or molten materials. Now, these materials acting on +one another, produce chemical substances some of which, such as sal +ammoniac, sulphur, and boracic acid, possess commercial value. This is +especially true in the case of Vulcano, and since the eruptions are +not generally violent, a chemical works has actually been erected by +a Scotch firm on the side of the mountain, where the materials are +collected from the crevices. + +This effort to harness a volcano was for a time so successful that +the same people contemplated the building of great leaden chambers +over the principal fissure at the bottom of the crater, so that the +large volumes of ejected vapors might be condensed and collected. But +Vulcano, like all other volcanoes, could not be relied on continually +to keep the peace. One day it suddenly burst forth more fiercely than +usual, so that the workmen were compelled to abandon the factory and +fly down the mountain for their lives, but not, however, before some +of them were severely injured by the explosions. + +Vulcano is an instance of a volcano in an almost exhausted or dormant +condition. It has had, however, many eruptions during the past few +centuries, some of which have been very violent, for example, that of +1783, and that of 1786. + +There still remains to be considered the volcanic region of the +Santorin group of the Grecian Archipelago. The island of Santorin +or Thera, is the southernmost of the Cyclades. It is an exceedingly +curious island, being a submerged volcano, with most of the top of the +crater remaining above the waters, so that the entire island has the +shape of an irregular circle or crescent broken at several points. +Its formation is, probably, due to the gradual sinking of a volcanic +mountain until its crater has been almost completely submerged, only +the higher parts of the edges of the crater being left above the +surface of the waters. Suppose, for example, a mountain like Vesuvius +at the time the crater Somma existed, was sunk below the level of the +Mediterranean until only the highest parts of the crater remained +above the waters. If, now, one or more volcanic eruptions occurred, +producing craters or volcanic islands inside the submerged rim, you +would have a condition of affairs seen in the island of Santorin. + + + + +CHAPTER VII + +ORIZABA, POPOCATEPETL, IXTACCIHUATL, AND OTHER VOLCANOES OF MEXICO + + +While some of the volcanoes of Mexico are still in an active +condition, most of them are either only slightly active or are dormant +or extinct. Humboldt, the celebrated traveller and geographer, states +that there are only four active volcanic mountains in Mexico; namely, +Popocatepetl, Tuxtula, Colima, and Jorullo. But there are many others, +among which may be mentioned Orizaba, Ixtaccihuatl, Xinantecatl, +Tuxtula, Cofre de Perote, and Colima. + +Of course, you can understand that, since extinct volcanoes may at any +time become active, in parts of the world where communication with the +interior is not good, many volcanic mountains that have been regarded +as extinct may have broken out temporarily, during historical times, +without their eruptions having been recorded. + +It was at one time thought that Popocatepetl was the highest mountain +in North America. More recent measurements, however, have shown that +there are at least three other mountains in this part of the world, +that are much higher. One of these is the active volcano of Orizaba +that we will now briefly describe. + +[Illustration: FIG. 16. MEXICO AND CENTRAL AMERICA] + +Orizaba is situated in the north central part of Mexico, about +seventy-five miles west of Vera Cruz. Its ancient Aztec name was +Cittaltepetl, or _Star Mountain_. The height of the mountain is +18,200 feet. Like all high tropical mountains whose summits are +snow-clad, one would pass through the same changes in climate, in +going from its base to its summit, as in going along the earth's +surface from the equator to the poles. Near the base of the mountain +will be found a tropical climate, above that a temperate climate, +while in still higher regions, the climate of the Arctic region. + +According to Russell, from whose work on the volcanoes of North +America much of the information concerning the volcanoes of Mexico +and Central America has been condensed, Orizaba has three craters on +its summit. The last recorded eruption took place about the middle of +the Eighteenth Century. The mountain is now in a dormant or extinct +condition, as may be seen from the fact that its three craters are for +the greater part filled with snow. + +Orizaba, like Etna, and many other volcanoes, has deep fissures +extending through its sides. Through these, lava streams have flowed +during times when it was active. There are also found on the slopes +of this mountain many cones of a type known as _parasitic cones_. +These cones are not caused by materials that have been brought to the +surface during an eruption, but have been formed by the steam passing +through lava streams that have come out of the crater during other +eruptions. + +Popocatepetl, or, as the word means, _The Smoking Mountain_, is the +second highest mountain in Mexico. According to recent measurements +made by the Mexican Government, its height is 17,876 feet. +Popocatepetl is situated on the edge of the great plateau of Mexico, +forty miles southeast of the City of Mexico. It is a conical mountain, +and is a magnificent object when seen from the City of Mexico, rising, +as it does, fully 10,000 feet from the elevation of the city, while on +the east it towers for nearly 18,000 feet above the level of the sea. +This splendid mountain is poetically described by Russell: + + "Seen from the basal plains, it sweeps up in one grand + curve to nearly its full height,--a collossus of three and + a quarter miles in elevation, white with everlasting frost + on its summit, and bathed in the green of palms, bananas, + oranges, and mangoes, at its base. Evergreen oaks and + pines encircle its middle height, and above them, before + the ice itself is reached, occur broad areas of loose sand + into which the lavas have been changed by weathering. Soft + wreaths of sulphurous vapor may at times be seen curling + over the crest of the summit crater,--gentle reminders that + the days of volcanic activity are not yet necessarily over." + +Popocatepetl takes its name, _The Smoking Mountain_ from the fact that +gases and vapor are continually being emitted from its summit crater. +It has a conical peak with a depression or crater on its summit. +The bottom of the crater is crossed by fissures from which small +quantities of steam escape, not, however, sufficient to melt all the +snow which covers the slopes of the mountain to a depth of from eight +to ten feet. A small lake of hot water has collected in the crater +from the water derived from the melting snow. This water, sinking +through the porous materials in the cone, is the source of a great +number of large hot springs that occur around the base of the mountain. + +Reclus states that the first to climb to the top of Popocatepetl was +one of Cortez' officers, 1519. + +Another snow-capped volcano, which rising from the plain of Mexico is +in clear view of the city, is Ixtaccihuatl (Ets-tak'-se-wat-el), or as +the word means in the ancient Aztec, _The White Woman_. This mountain, +as measured by Heilprin, is 16,960 feet in height. Ixtaccihuatl is +now in so dormant a condition that many who have climbed to the top +assert that it is not a volcano at all, since they find no crater on +its summit. Nor are there any signs of volcanic heat, the summit being +snow clad during summer. The conical form of the mountain, however, +and the fact that the entire mountain is formed of volcanic rocks, +show beyond doubt that it is an extinct volcano, whose crater has most +probably been completely filled in by the washing away of its sides. + +Xinantecatl is another extinct volcanic mountain situated about forty +miles southwest of the City of Mexico. It is about 16,500 feet high. +Its name means in the ancient Aztec language, _The Naked Lord_. It is +also sometimes known as the Nevado de Toluca, or _The Snow of Toluca_. +On the top of the peak are two craters filled with lakes of fresh +water. Russell states that the larger of these lakes is about thirty +feet in depth and contain a peculiar species of fish. + +Tuxtula is another volcano of Mexico, situated on the western coast +of the Gulf of Mexico, about eighty miles southeast of Vera Cruz. It +was an active volcano in 1664, when it threw out molten lava. It then +became dormant until March, 1793, when its long rest was broken by one +of the grandest explosive eruptions of modern times. This eruption +rivalled in energy the great explosive eruption which blew off the +summit of Coseguina, in Central America, in 1835. As is common in the +case of explosive eruptions, volcanic dust and scoriæ were blown high +into the air, and, being carried by the winds, fell on the roofs of +houses and on the land at a distance of 150 miles. + +There have been a number of less violent eruptions of Tuxtula since +1835. Tuxtula is a comparatively low mountain, being only 4,960 feet +high, because much of the mountain was blown away by the eruption of +1793. + +As Russell points out, it is not safe to infer that because an eroded +mountain is not lofty it cannot be young or energetic, since the very +energy of some of its eruptions may, as in the case of Tuxtula, blow +away a large part of the mountain. A low mountain, with an unusually +large crater, generally means a mountain that has been visited by a +great explosive eruption. + +Another extinct volcano known as the Cofre de Perote is situated on +the eastern coast of Mexico, east of Ixtaccihuatl, about thirty miles +north of Orizaba. It takes its name Cofre de Perote which means the +Coffin of Perote, from its peculiar box-like shape. It was called in +the Aztec language "Nauhcampatepetl," or the _Four-Ridged Mountain_. +Cofre de Perote is in a dormant or extinct condition. + +We will conclude this brief description of the volcanoes of Mexico +with the volcano of Colima, a mountain about 5,500 feet high situated +on the western coast of Mexico. + +Colima has been active of recent years, eruptions having occurred in +1869, 1872, 1873, and 1885. During these eruptions lava escaped from +lateral openings in the sides of the mountain, these openings being +termed by the natives the _Sons of Colima_. + + + + +CHAPTER VIII + +COSEGUINA AND OTHER VOLCANOES OF CENTRAL AMERICA + + +Central America has a great number of volcanoes extending along nearly +all its western coast, or on the Pacific side of the country. + +Central America consists of a high plain or table-land sloping gently +towards the northeast, but terminating abruptly on the southwest. In +the opinion of geologists this table-land consists of the surface of a +huge tilted block of the earth's crust, or, perhaps, more probably, of +a series of such blocks, that are limited on the southwest by a narrow +belt of intersecting fractures. It is in these fractures that scores +of volcanoes are situated, together with active craters, solfataras, +and hot springs. The volcanoes are mainly of the Vesuvian type. There +are so many volcanoes in this part of the world that it will be +possible to describe but a few of them. + +We will begin with the volcano of Coseguina, situated on the Pacific +coast of Nicaragua. Its appearance is that of a conical mountain with +the top cut off, and suggests that it is most probably an explosive +volcano which has had the top blown away during some of its great +eruptions. + +Coseguina is celebrated by reason of its tremendous eruption of 1835. +Before the still more tremendous explosive eruption of Krakatoa in +1883, described in the first two chapters of this book, Coseguina +shared with Sombawa, on the island of Sumatra, as being the foremost +of explosive volcanoes. + +It had been estimated that before its eruption of 1835, Coseguina had +a height of perhaps 10,000 feet, but so much of it was blown away by +this eruption that it now is a little less than 4,000 feet. + +The following description of the great eruption of Coseguina in 1835 +has been condensed from an account prepared by Squier, published in +1850. + +You will note in reading this brief account how closely many of the +phenomena resemble those that occurred during the eruption of Krakatoa +in 1833. + +The eruption of Coseguina was heralded on the morning of January 20th, +1835, by several loud explosions that were heard for a distance of +some 300 miles around the crater of the volcano. Then followed an ink +black cloud formed directly over the mountain, which gradually spread +on all sides shutting off the light of the sun, except for a sickly +yellowish light. Fine sand was thrown from this cloud, which made it +both difficult and painful to breathe. For two whole days the cloud +continued to grow denser, the explosions louder and more frequent, +and the rain of sand thicker. On the third day the explosions were +strongest and the darkness greatest. + +The amount of sand that fell from the cloud was so great that people +left their houses, fearing the roofs would be crushed in by the great +weight. This sand fell in large quantities over an area more than +1,500 miles in diameter, or, quoting the language of Squier: + + "The noise of the explosions was heard nearly as far" + (1,500 miles). "And the Superintendent of Belize, eight + hundred miles distant, mustered his troops, under the + impression that there was a naval action off the harbor. + All nature seemed overawed; the birds deserted the + air, and the wild beasts their fastnesses, crouching, + terror-stricken and harmless, in the dwellings of men. + The people for a hundred leagues grouped, dumb with + terror, amidst the thick darkness, bearing crosses on + their shoulders and stones on their heads in penitential + abasement and dismay. Many believed that the day of doom + had come, and crowded in the tottering churches, where, in + the pauses of the explosions, the voices of the priests + were heard in solemn invocation to Heaven. The brightest + lights were invisible at the distance of a few feet; and + to heighten the terror of the scene, occasional lightnings + traversed the darkness, shedding a lurid glare over the + earth. This continued for forty-three hours, and then + gradually passed away." + +It appears that the eruption of Coseguina was followed by violent +earthquake shocks and other evidences of volcanic energy over extended +regions. For example, there were fearful earthquakes along the Andes, +the worst of which occurred on February 20th, and continued at the +rate of three or four a day up to March 6th, and, less frequently, +to March 17th. It was during one of these earthquakes that the city +of Concepcion, Chile, was so completely destroyed, that but a single +house remained. + +The same brilliant sunsets and sunrises occurred in different parts +of the world after the eruption of Coseguina, due to the presence of +large quantities of volcanic dust that followed the great eruption of +Krakatoa. + +The cause of this great explosive eruption of Coseguina was most +probably the same as that which is believed to have caused the +eruption of Krakatoa, namely, a large volume of water suddenly gaining +access to a mass of liquid lava. + +Volcán del Fuego is another of the many volcanoes of Central America. +It is situated as one of a group of volcanoes on the highest summit +of the Isthmus. This volcanic mountain has a regular cone with +regular slopes on all sides, except on the north, where a table-like +projection, about 1,000 feet below the summit, is all that remains of +a vast cone, the summit of which was blown away, according to Russell, +in prehistoric times, just as was the crater of Somma on Vesuvius. + +There have been in Central America, since the time of the Spanish +conquest, some fifty volcanic eruptions sufficiently great to have +been recorded. Some idea of the activity of Fuego during this time +may be had from the fact that of all these eruptions some twenty were +those of Fuego. At the present time, however, the volcano is dormant +and apparently almost extinct. + +The recorded eruptions of Fuego are nearly all of the explosive type. +Among the most violent were those that occurred during 1526, 1541, +and 1581. During 1582, 1585, and 1586, there were eruptions nearly +every month, the most terrible being near Christmas day in 1586. Other +memorable eruptions occurred in 1614, 1623, 1686, and 1705, and at +other dates down to August 17th, 1860, from which date to the present +time the volcano has been quiet. + +We will conclude this brief description of the volcanoes of Central +America with that of Volcán de Agua, or, as the word means, _The Water +Volcano_. It is situated in Guatemala near the coast, and is one of +the mountains that occupies the plateau on which Fuego is situated. + +The Volcán de Agua is one of the most remarkable volcanoes in Central +America, standing, as it does, nearly alone, and rising to an +elevation of 3,350 metres (10,988 ft.), above the level of the sea. It +has been extinct for a long time. + +It has been supposed by some, from its name, that this is a volcano +that throws out water. Others believe that the name comes from the +water produced by the melting of the snow that is collected on the +sides of the mountain. Now there almost always escapes from the +craters of volcanoes during violent eruptions immense quantities of +water vapor, which, condensing, fall as vast showers of rain that +often deluge the surrounding country. In snow-clad mountains, the +escape of lava is often attended by floods caused by the rapid melting +of the snow. The water volcano did not, however, take its name from +either of these facts, but rather because at the time of the Spanish +invasion, the crater of the mountain was occupied by a large lake, and +that during an earthquake in 1541 the wall of the crater was broken, +when the lake was poured as an immense stream of water down the side +of the mountain, overwhelming a village which was situated on this +slope. That this was the correct origin of the same may be seen from +the fact that the crater at the present time still shows the remains +of its former lake basin, and that on the sides of the broken rim an +immense ravine can be seen through which the water poured down on the +village below. + +Daubeny describes this volcano as follows: + + "The Volcán de Agua (Water-Volcano) is of enormous height, + being covered with eternal snow, in the latitude of 14°. + Captain Basil Hall estimates it at more than 14,000 feet, + but a recent traveller states it at 12,600. It has the form + of a blunted cone clothed with perpetual verdure to its + summit. The crater is from forty to sixty yards in depth, + and about 150 in diameter,--the sides and bottom strewed + with masses of rock, apparently showing the effects of + boiling water or of fire. + + "By a deluge of water from this volcano in 1527, the + original city of Guatemala was overwhelmed; and the next + built, called the Old City, _La Antiqua_, was ruined by an + earthquake in 1773. The present capital is situated at a + distance of eight leagues from the mountain." + +Another volcano in this part of the country is described by Daubeny as +follows: + + "Massaya, near the lake of that name, was one of the most + active vents at the time of the first discovery of the + country. Its flames were visible twenty-five miles off. Its + crater was only twenty or thirty paces in diameter; but + the melted lava 'seethed and rolled in waves as high as + towers.' A story is told of a Dominican who imagined the + fluid lava was melted gold, and descended into the crater + with an iron ladle to carry some away; but the ladle, it is + said, melted, and the monk escaped with difficulty." + + + + +CHAPTER IX + +THE VOLCANIC MOUNTAINS OF SOUTH AMERICA + + +The volcanoes of South America are limited to the Andes Mountain +System that stretches like a huge wall along the entire western side +of the continent. The names of the more important of these volcanoes +are marked on the map of South America, shown in Fig. 17. As will be +seen, this huge mountain wall reaches from Patagonia on the south to +the Isthmus of Panama on the north. The arrangement of the volcanoes +in South America is of the linear type. The craters follow one another +in more or less straight lines, or are situated along the lines of +great fissures that lie near the ocean. You must not, however, suppose +that there is a continuous chain of active volcanic mountains from the +Isthmus of Panama to the southern part of the continent. According to +Lyell, from lat. 2° N., or from the north of Quito, to lat. 43° S. or +south of Chile, a total distance including 45° of latitude, there is a +succession of districts with active and extinct volcanoes, or at least +with volcanoes that have been quiet during the last three centuries. + +[Illustration: FIG. 17. SOUTH AMERICA] + +Lyell traces the volcanoes of South America as follows: + + "The principal line of active vents which have been seen in + eruption in the Andes extends from lat. 43° 28' S., ... to + lat. 30° S.; to these thirteen degrees of latitude succeed + more than eight degrees, in which no recent volcanic + eruptions have been observed. We then come to the volcanoes + of Bolivia and Peru, extending six degrees from S. to N., + or from lat. 21° S. to lat. 15° S. Between the Peruvian + volcanoes and those of Quito another space intervenes of no + less than fourteen degrees of latitude, in which there is + said to be but few active volcanoes as far as is yet known. + The volcanoes of Quito then succeed, beginning about 100 + geographical miles south of the equator, and continuing + for about 150 miles north of it, when there occurs another + undisturbed region of more than six degrees of latitude, + after which we arrive at the volcanoes of Guatemala, or + Central America, north of the Isthmus of Panama." + +Of course, you must not understand that there are no extinct volcanoes +in these gaps. On the contrary, according to Daubeny, we find, +beginning on the north in the United States of Colombia, the lofty +volcano of Tolima. According to Daubeny's book published in 1848, +Tolima was then constantly emitting steam and sulphur gases from its +summit. Tolima is situated in the easternmost of the three mountain +ranges that extend through this section of the country. It is, +therefore, at a comparatively great distance from the ocean. Tolima +was in eruption in 1595. It again burst out in 1826. + +Coming now to Ecuador we find that this, the smallest of the South +American Republics, contains numerous great volcanic mountains. + +Some of the principal volcanic mountains are Chimborazo, 20,498 feet +above the sea; Antisana, 18,880 feet; Cotopaxi, 19,660 feet; Pichincha +(17,644 feet in 1848, Daubeny), El Altar, 16,383 feet. + +These all lie in South America on the plateau of Quito. As Baron +Alexander von Humboldt has pointed out, the volcanic mountains of +Quito are arranged in two parallel chains that extend side by side +for a distance of over 500 miles north into the State of Colombia, +including between them the high plateaus of Quito and Lacumbia. +According to Whymper, however, who has recently studied this part of +South America, there is a succession of basins between the mountains, +but there is no such thing as a single valley in the interior of +Ecuador. The extinct volcanoes of Cayamba, Antisana, and Chimborazo +are the most important. On all three mountains there are old lava +streams on their sides. Although no craters can be seen on their +summits, yet it is almost certain they once had craters. There is +plenty of room on the summit of Antisana for a cone as great as that +of Cotopaxi. Whymper is of the opinion that the snow domes that form +the summit of Chimborazo were at one time two of the highest points of +the rim of the old crater. + +Nearly due south of Quito is the great volcanic cone of El Altar. +Like all the peaks of this high plateau, El Altar rises to a great +height above the sea, being at the present time 16,383 feet above the +sea. This mountain has an enormous crater that appears to be dormant +or extinct, and is covered with snow. According to the traditions of +Indians, El Altar, or, as they call it, _Capac Urcu_ or _The Chief_, +was the highest mountain near the equator, being much higher than +Chimborazo. But during a prodigious eruption that occurred before the +discovery of America, and continued uninterruptedly for eight years, +the height of the mountain was considerably reduced. According to +Boussingault, the fragments of the cone of this celebrated mountain +are now spread for great distances around the mountain on the +surrounding lowlands. + +Pichincha in Ecuador, an extinct volcano, is situated almost +immediately on the equator. It has a height as measured by Whymper by +the barometer, of 15,918 feet above the Pacific. The summit is covered +by blocks of pumice. Several species of lichens are found at this +elevation. According to Daubeny, Pichincha was extinct prior to 1539, +when it became active. There were also eruptions in 1577, 1587, and +1668. It was also in activity during 1831. + +Cayamba, another volcanic mountain of Ecuador, lies to the east of +Pichincha, a short distance north of the equator. Its height is 19,186 +feet. It is nearly extinct. + +Cotopaxi, 19,680 feet, is another volcanic mountain of the high +plateau of Quito. Cotopaxi is still active. Its slopes are covered +with snow down to a height of about 14,800 feet. Between the lower +edge of this snow line and the lower slopes of the mountain, there +lies a zone of naked rock. + +According to Whymper, the eruption of Cotopaxi, in 1877, was preceded +by an unusual degree of activity in the earlier parts of the year. +This, however, did not cause any alarm until June 25th, 1877, when, +shortly after midday, an eruption, attended by tremendous subterranean +roars, began, and an immense black column shot up into the air for +about twice the height of the cone. This eruption was clearly visible +at Quito, for the wind blew the ashes towards the Pacific. At this +time the summit had not changed its appearance, but towards 6:30 +A. M., on the next day, another enormous column of ashes +rose from the crater. The ashes and cinders were first carried due +north by the winds, and then, spreading out in all directions, were +subsequently distributed through the air all over the country. At +Quito, as early as 8 A. M., the sky assumed the appearance it +generally has at twilight, and the darkness increased until midday, +when it became as dark as at midnight. Indeed, it was so dark that one +could not see his hand before his face. + +During this eruption, as is very common in the eruptions of the +snow-clad mountains of South America, a flood of water, due to the +rapid melting of the snow and ice on the summit, rushed down the +mountain slopes at 10 o'clock A. M., on the 26th of the +month, almost immediately after the appearance of a stream of lava +that began to flow down the mountain. In a few moments the mountain +was completely shut off from view by immense columns of steam and +smoke. At first, a low, moaning sound was heard, which rapidly +increased to a roar, when a deluge of mud, mingled with huge blocks of +ice and stones, swept down the mountain, leaving a desert in its path. +It is estimated that at some places this stream moved with a velocity +of fifty miles per hour. + +The general appearance of Cotopaxi is shown in the accompanying +reproduction from the painting by Frederick E. Church in the Lenox +Library, New York. + +According to Whymper, who made an ascent of Cotopaxi in 1880, the +crater on the summit has the form of an immense amphitheatre, 2,300 +feet across from north to south, and 1,650 feet from east to west. +Its crest is irregular and notched. The crater is surrounded by +perpendicular cliffs. The western side of the volcano is irregular. +Barometric measurements gave the height of this volcano at 19,498 +feet. Its height as taken by La Condamine, during the early parts of +the last century, was 19,605 feet, so that, according to Whymper, +assuming as would seem probable, that this difference in height has +not all been due to errors in measurements, the volcano has grown or +increased in height during the last century and a half. + +Chimborazo, 20,498 feet, is another lofty mountain on the plateau of +Quito. This volcano is situated in lat. 1° 30' S., and is not at the +present time in an active condition. It is, however, formed entirely +of volcanic material. Its upper portions are covered with a layer of +snow to a level of some 2,600 feet below the summit. + +[Illustration: COTOPAXI _From a Painting by Frederick E. +Church in the Lenox Collection of the New York Public Library. By +Permission_] + +Chimborazo has an enormous volcanic summit, which, when seen from the +Pacific, when the air is especially clear after the long rains of +winter, is a most splendid sight. Whymper, who ascended the mountain, +says: + + "When the transparency of the air is increased and its + enormous circular summit is seen projected upon the deep + azure of blue of the Equatorial sky, it represents a + magnificent sight. The great rarity of the air through + which the top of the Andes is seen adds much to the + splendor." + +Whymper says, that as far as records are concerned, there have been no +eruptions of Chimborazo, which has apparently been an extinct volcano +for many years. Its crater has been completely buried by a thick cap +of ice on its summit, while what lava streams exist on the mountain +are either covered by large glaciers, or have been removed by erosion, +or hidden by vegetation. + +Chimborazo possesses less of the conical outline than Cotopaxi. There +are steep cliffs towards the summit that have been named by Whymper +"the northern and southern walls." They seem to him to have been +formed by the violent upheavals of the explosive eruptions that have +blown away portions of the cone. + +There are other volcanoes in this district, but the above are all we +have space for describing. + +According to Lyell, the volcano of Rancagua, in Chile, lat. 34° 15' +S., is continually throwing up ashes and vapors like Stromboli. +Indeed, a year seldom passes in Chile without some earthquake shocks. +Of these shocks those which came from the side nearest the sea are +most violent. The town of Copiapo was laid waste by these shocks +during the years 1773, 1796, and 1819, in both instances after +intervals of twenty-three years. + +Since the volcanic mountains of South America are snow-covered the +occurrences of volcanic eruptions are apt to be attended by great +floods caused by the rapid melting of the snow, as well as sometimes +by the breaking of huge subterranean cavities that are filled with +water. + +According to Lyell, the volcanoes of Peru rise from a plateau from +17,000 to 20,000 feet above the sea. One of the principal volcanoes +of Peru is Arequipa, whose summit is 18,877 feet above the level of +the sea. The mountain takes its name from the city of Arequipa, which +is situated not far from its base. It is an active volcano. Another +volcano, Viejo, is found in lat. 16° 55' S. + +According to Lyell, there are active vents extending through Chile to +the island of Chiloe to lat. 30° N. + +Aconcagua, west of Valparaiso, in lat. 32° 39' S., 23,000 feet in +height, the highest mountain in South America, is still in an active +condition. According to Scrope, when the city of Mendoza was destroyed +by an earthquake, that killed 10,000 people, in March, 1861, it is +probable that Aconcagua was in eruption. + +There are many other active volcanoes in Chile, extending as far south +as the volcanoes of Patagonia, north of the Straits of Magellan as +well as others of Tierra del Fuego. + + + + +CHAPTER X + +VOLCANOES OF THE UNITED STATES + + +For some readers this may be a surprising chapter heading, for it is a +general impression that there are no volcanoes in the United States. +It is true that practically all of the volcanoes of this country are +dormant or extinct. They have, however, at one time been exceedingly +active, and, if reports are correct, some of them were active during +comparatively recent times. + +Nearly all of the volcanoes of the United States lie west of the +meridian of Denver. These volcanoes belong to two distinct types, +either the Vesuvian type with built up cones, or the plateau or +fissure type already referred to. + +The following brief description of the volcanoes of the United States +has been collated, for the greater part, from Wallace's excellent book +on the volcanoes of North America. + +Crossing the United States on the Southern Pacific Railroad one's +attention is caught, in Arizona, by a magnificent group of mountains +known as the San Francisco Mountains. The highest peak of these +mountains reaches 12,562 feet above the level of the sea, and 5,700 +feet above the surface of the plateau on which the mountains stand. + +[Illustration: FIG. 18. THE UNITED STATES] + +According to G. K. Gilbert, the San Francisco Mountain group is formed +of a variety of lava known as trachyte, that is of comparatively +recent ejection, possibly of a geological age called the Tertiary. The +lava forming the mountains escaped through a number of crater cones, +some of which can still be seen in the neighborhood. Some of these +craters are now in almost as perfect a condition as the day they were +formed. Indeed, to one looking at them from a neighboring elevation, +they appear so fresh, and so little affected by the climate, that one +might almost believe that the lava had just flowed out of the craters, +and has not yet hardened. Nevertheless, geologists are sure they have +been formed long before man appeared on the earth. In one of these +craters a lake of fresh water has collected. + +Another extinct volcano of the United States is Mt. Taylor in New +Mexico, nearly east of the San Francisco Mountains. This mountain +rises from the surface of a high table-land, or, as it is called +in this part of the world, a _mesa_. The surface of the plateau is +covered with a thick lava stream from which Mt. Taylor rises to +a height of 11,390 feet above the level of the ocean. This mesa, +or table-land, is forty-seven miles in length from northwest to +southeast, and about twenty-three miles in breadth. Its general +elevation is about 8,200 feet. The plateau rises about 2,000 feet +above the surface of the level land that surrounds it. All these +2,000 feet have been removed by erosion. The table-land from which +Mt. Taylor rises has not been eroded by the action of the rain, +rivers, and other weathering agencies like the surface of the country +surrounding it, because of a covering of lava that has been spread +over its surface to a depth of about 300 feet. + +Mt. Taylor is formed almost entirely of lava that has escaped through +a single opening and has built up a high cone around it. The volcano +is now quite extinct, so that the original form of the mountain has +been greatly changed by erosion. + +You will remember, when we were discussing the general subject of +volcanoes, in the beginning of this book, that we spoke of volcanic +mountains being bottled up after an eruption, by the hardening of +the lava which remained in the crater and the tube that connects the +crater with the place from which the lava had been derived. We then +spoke of this hardened mass being known as a _volcanic plug_, or +stopper, explaining how the volcano could never again erupt through +its old crater unless it could develop sufficient force to blow out or +remove this stopper. + +Now besides the crater at the top of Mt. Taylor there were several +others in the eroded region surrounding the mesa, or high table-land, +from which Mt. Taylor rises. When, therefore, the erosion which +removed the 2,000 feet of rocks on all portions of the old mesa that +were not protected by the coating of lava, these old mountain plugs +were too hard to be worn away or eroded, and were, therefore, left +projecting into the air like vast pyramids. + +If you should ever visit Mt. Taylor and should go to the eastern +border of this mesa, and look over the eroded plain, you would see in +the lowlands a part of the places from which the 2,000 feet of matter +have been slowly eroded. Dutton describes the beautiful panorama that +is to be seen as follows: + + "The edge of the mesa suddenly descends by a succession of + ledges and slopes, nearly 2,000 feet into the rugged and + highly diversified valley-plain below. The country beneath + is a medley of low cliffs and bluffs, showing the browns + and pale yellows of the Cretaceous sandstones and shales. + Out of this confused patchwork of bright colors rise + several objects of remarkable aspect. They are apparently + inaccessible eyries of black rock, and at a rough guess, by + comparison with the known altitudes of surrounding objects, + their heights above the mean level of the adjoining plain + may range from 800 to 1,500 feet. The blackness of their + shade may be exaggerated by contrast with the brilliant + colors of the rocks and soil out of which they rise, but + their forms are even more striking." + +These black piles are the _necks_ or lava plugs of extinct volcanoes. +They rise above the level of the plain because, being harder than +the surrounding rocks, they have resisted erosion. In some cases +these necks or plugs have been converted by shrinkage, on cooling, +into beautiful columns, somewhat of the type of the basaltic columns +of the Giant's Causeway. It would be difficult to count the number +of volcanic necks that can be seen near the edge of the mesa. One's +attention is at once attracted to some dozen of these piles, which are +especially striking on account of their great size, and ominous black +color, but the number is by no means limited to this dozen. There are +hundreds of them. + +Fig. 19 gives some idea of a part of the view from the edge of the +mesa, and Fig. 20 the appearance of two of these volcanic necks. + +But besides high volcanic mountains such as the San Francisco +Mountains and Mt. Taylor, there are, in different parts of the United +States, to be found fragments of huge craters from which, in the +geological past, immense quantities of lava have escaped. In some +instances these craters are but fragments of huge craters, that, like +the crater of Mt. Somma, in Vesuvius, have been nearly completely +blown away by some unrecorded explosion during the far past. + +[Illustration: FIG. 19. PANORAMA FROM THE MESA AT THE EDGE OF MT. +TAYLOR _From U. S. Geological Survey_] + +A crater of this type, known as Ice Springs Crater, is situated in the +desert valley west of the Wahsatch Mountains, some 125 miles south +of Salt Lake City, Utah. This crater is especially interesting from +the fact that it occupies a position on a plain that was formed by +the deposition of sediment in an immense lake that covered this part +of the United States very long before man lived on the earth. We +are alluding to Lake Bonneville, a lake that existed in a geological +time known as the Glacial Epoch. This lake occupied the territory now +filled by the Great Salt Lake of Utah, but towards the close of the +Glacial Epoch it was immensely larger than it is now. This can be +shown not only by the presence of shore lines, that are clearly marked +on the sides of the surrounding mountains, but also by the ancient +lake beaches, and deltas, that are common in the district, so that +instead of there being the comparatively limited area of Great Salt +Lake as marked on the maps of to-day there was a lake that had an area +of 19,750 square miles, that covered an area on which at least 200,000 +people dwell. + +[Illustration: FIG. 20. VOLCANIC NECKS, EDGE OF MESA AT MT. +TAYLOR _From U. S. Geological Survey_] + +A similar lake, known as Lake Lehontan, existed at the same time, +covering large areas in the western parts of Nevada. + +Coming now to Ice Springs Craters in Utah, we find here three small +craters formed of scoriæ and lapilli (volcanic ashes consisting of +small angular stony fragments). Near them lies a fragment of a much +larger crater known as the Crescent. In some respects this crater was +not unlike the crater of Somma that surrounded Mt. Vesuvius. It was +not, however, as large, having a diameter of only 2,200 feet. From +these craters streams of basalt flowed until they covered considerable +areas. + +A still more recent crater known as Tabernacle Crater is situated +four miles south of the Ice Springs Crater. Tabernacle Crater takes +its name from the building known in Salt Lake City as the Tabernacle. +According to Gilbert, this crater was formed at a time when Lake +Bonneville stood at a comparatively low level, or when the water was +only from fifty to seventy-five feet above the bottom of the valley +on which the crater now stands. At that time an explosive volcanic +eruption occurred on the bottom of the lake, and the rim of the +crater, built up by this explosion, was gradually pushed above the +surface of the lake, so as to shut out its waters. + +Extinct volcanic craters, not unlike those of Utah, occur also near +Ragtown, in Nevada, in a district known as the Carson Valley Desert, +in one of the broadest areas of what was once Lake Lahontan. Ragtown +is twenty-two miles southwest of Wadsworth on the Central Pacific +Railroad. At the present time there are two circular depressions or +volcanic craters filled with pools of strongly alkaline water known +as the Ragtown Pond, or Soda Lake. The large lake covers an area of +268-1/2 acres. Its greatest diameter is over 4,000 feet. Without going +into a detailed description it will suffice to say that the larger +crater probably was destroyed by an explosive volcanic eruption. + +Another intensely alkaline lake that fills an extinct volcanic crater +is the Mono Lake, situated in Mono Valley in California at the eastern +base of the Sierra Nevadas. It has an area of about 200 square miles. +The centre of the lake has two small islands named Pacha and Negit. +Immediately south of Mono Lake are a number of craters that occupy +portions of what was once apparently a fissure extending in a general +north and south direction. The highest of these craters are in the +neighborhood of 2,500 feet. + +But leaving these inconspicuous craters, let us briefly examine some +of the higher mountain peaks of the United States that are of volcanic +origin. One of the most conspicuous of these is Mt. Shasta. This +mountain is situated in California, at the northern end of the Sierra +Nevadas. It has a height of 14,350 feet. It is a snow-clad mountain of +a conical form, and is a conspicuous object in the landscape, because +it stands alone. + +Mt. Shasta is a double-coned mountain. Besides the cone on its summit +there is a well-developed cone known as Shastina on the western side +of the mountain, 2,000 feet lower than the main summit. + +There are well-defined lava streams on the slopes of Mt. Shasta. One +of these, which issued from the southern side of the mountain at +an elevation of 5,500 feet, divided into two streams. One of these +streams is twelve miles in length. The other entered the canyon of the +Sacramento River, thus displacing the water. + +Coming now to the Cascade Mountains, in Oregon and Washington, we +will find in them a number of giant peaks of volcanic origin. The +most important of these are in regular order from south to north, as +follows: Mt. Pitt, 9,760 feet; Mt. Mazana, 8,223; Mt. Union, 7,881; +Mt. Scott, 7,123; Three Sisters, Mt. Jefferson, 10,200, and Mt. Hood, +11,225, in Oregon; Mt. Adams, 9,570; Mt. St. Helen's, 9,750; Mt. +Rainier, 14,525, and Mt. Baker in Washington, 10,877. + +Nearly all these mountains have craters either on their summits or on +their sides. They are extinct volcanic mountains, that were, for the +most part, thrown up during the Tertiary Geological Period, so that +they have all been greatly affected by erosion. + +One of the most remarkable of the above volcanic mountains is Mt. +Mazana, in Oregon. This mountain has on its summit an approximately +circular cavity from five to six miles in diameter, that is occupied +by a lake of water known as Crater Lake. This lake is 6,239 feet above +the level of the sea, and has a depth of 1,975 feet. It is surrounded +by nearly vertical walls ranging from 900 to 2,200 feet deep, so that +the vast caldera of which this great depression consists has a depth +of at least 4,000 feet. + +Mt. Pitt, situated about sixty miles north of Mt. Shasta, in southern +Oregon, has a regularly shaped volcanic cone, and the remnant of a +crater at its summit. The Three Sisters and Mt. Jefferson lie to +the north of Mt. Pitt. Like the others they are ancient volcanic +mountains. But little is accurately known concerning them. + +Mt. Hood, 11,225 feet high, rises from the crest of the Cascade +range in Northwest Oregon, about twenty-five miles south of the +Columbia River. Mt. Hood is an exceedingly majestic mountain. At its +summit there are only portions of the walls of the original crater. +When ascended in 1888, streams of sulphur vapor were escaping from +fumaroles on its northeastern slopes, at an elevation of 8,500 feet +above the sea. + +Mt. Adams and Mt. St. Helen's lie to the north of Mt. Hood. Mt. Adams +about sixty miles to the north, and beyond this, Mt. St. Helen's. +Accurate information concerning the summit of Mt. Adams is still +lacking. Mt. St. Helen's in Washington has more of a conical summit. +Russell states that according to frontiersmen, St. Helen's has been +in a state of activity within the past fifty years. A French-Canadian +asserts that the mountain was in actual eruption during the winter of +1841-43, that at this date the light from the volcano was sufficiently +bright to enable one to see and pick up a pin in the grass at midnight +near his cabin some twenty miles distant. Mt. St. Helen's was ascended +in 1889, when fumaroles were found on the northeast side. + +Mt. Rainier in Washington is plainly visible from Puget Sound. It is +a most magnificent mountain. The summit has a bowl-shaped crater, of +an almost perfectly circular form. The inside of the crater, when +last ascended, was filled to within thirty or thirty-five feet of its +rim with ice and snow. There was, however, evidences of heat, since +numerous jets of steam were seen issuing from its interior rim. + +Mt. Baker, Washington, is the northernmost of the volcanoes of the +Cascade Mountains, south of the boundary line between the United +States and Canada. But little is known of this mountain. The summit +appears as a conical peak from Puget Sound, so that its form would +seem to show that it is of volcanic origin. According to Gibbs, +officers of the Hudson Bay Company, as well as the Indians, declared +that Mt. Baker was in eruption in 1843, when it broke out at the same +time as Mt. St. Helen's, covering the country with ashes. + +There are but few volcanoes in the Rocky Mountains which extend from +north to south through the United States at a considerable distance to +the east of the Sierra Nevadas and Cascade Ranges. The Spanish Peaks, +situated in the southeastern part of Colorado about sixty miles south +of Pueblo, are the remains of ancient volcanoes. Two of the most +prominent of these peaks rise from 12,720 to 13,620 feet above the sea. + +We shall make no effort to attempt to describe the volcanic mountains +that may exist in those portions of the Rocky Mountain Ranges or the +Cascade Range lying in Canada. Comparatively little is known of them, +but inasmuch as volcanic activity has been manifested in Alaska, it +would seem highly improbable, as Russell remarks, that volcanoes +should suddenly cease at the northern boundaries of the United States +and then begin again at the most southern part of Alaska. It will be +sufficient to say that Mt. Edgecome, situated on an island in the +neighborhood of Sitka, is of volcanic origin, and that the Aleutian +Islands, beginning at Alaska on the east at the head of Cook's Inlet, +extend westward through the Peninsula of Alaska to the Peninsula of +Kamtschatka for a distance of nearly 1,600 miles. This belt, which +is called by Russell "the Aleutian Volcanic Belt," contains numerous +volcanoes that are known to have been active in historical times. + +Mt. Wrangell, on the Copper River, 200 miles northeast of the head +of Cook's Inlet, is a lofty volcanic mountain that is said to have +been in eruption in 1819, and at the time of last report was still +throwing out columns of steam. While much remains to be ascertained +about the volcanoes of the Aleutian Islands, it would appear that +there are active volcanoes on twenty-five of these islands, on which +some forty-eight craters have been found. Eruptions are common in the +district. + + + + +CHAPTER XI + +THE CATASTROPHE OF MARTINIQUE AND THE VOLCANIC ISLANDS OF THE LESSER +ANTILLES + + +The West Indies Island chain consists of two groups of islands; i. e., +the Greater Antilles, including Cuba, Jamaica, Hayti, and Porto Rico, +on the west, and the chain of the Lesser Antilles on the east. + +The Lesser Antilles consists of two parallel chains, the westernmost +of which is for the greater part mountainous with peaks several +thousand feet in height. All these islands are volcanic. The chain +on the east consists of low, calcareous rocks, or rocks consisting +largely of lime. + +In the western chain the islands beginning on the south are, Grenada, +St. Vincent, St. Lucia, Martinique, Dominica, Guadeloupe, Montserrat, +Nevis, and St. Eustace, while in the calcareous chain are found the +Tobago, Barbadoes, and others. + +Prior to 1902, the greatest volcanic eruption in this part of the +world occurred on the island of St. Vincent, with the volcano of +Soufrière. Although the forces displayed were exceedingly great, yet +they become insignificant when compared with the appalling eruption +that took place in Martinique only a short time ago; namely, May the +8th, 1902, when the volcano of Mt. Pelée, situated on the northwestern +part of the island, burst into an eruption so terrible that in +destruction of life it far exceeded the eruption of Krakatoa, although +the amount of energy causing the eruption was much smaller. + +[Illustration: FIG. 21. THE LESSER ANTILLES] + +Heilprin, in a book called "Mt. Pelée and the Tragedy of Martinique," +from whom most of the information of this chapter has been obtained, +calls attention to the fact that before the eruption of Pelée there +were plenty of warnings for those intelligent enough to note them. For +two or three weeks prior to May 8th, 1902, the volcanic activity of +Pelée had been rapidly increasing, the mountain throwing out clouds +of ashes and sulphurous vapors from its crater. By April 25th the +sulphurous vapors had so increased in quantity as to make breathing +difficult in St. Pierre. The ashes fell on the surrounding country and +by the 2d of May had so covered the streets of St. Pierre as to stop +traffic. + +Three days later, May 6th, shortly before noon, an avalanche of mud +poured down the slopes of the mountain with the rapidity of an express +train. These torrents of mud and water deluged the towns and villages +in the neighborhood. The activity of Mt. Pelée increased until the +morning of May 8th, 1902, when, almost at exactly 8 A. M., an +eruption occurred, so terrible in its effects that in two minutes the +city of St. Pierre was almost completely destroyed. + +St. Pierre, the principal town of Martinique, is situated on the +island of Martinique, on the northwestern coast, about ten miles +southwest of Mt. Pelée. St. Pierre was settled as far back as 1635. It +is situated on an open roadstead without any harbor. + +That there were many points of resemblance between the position of St. +Pierre and the destroyed city of Pompeii will be recognized as the +description of the catastrophe is given. + +St. Pierre was a beautiful city, and formed the natural outlet to one +of the richest districts in Martinique for the production of sugar +cane and cocoa. It contained many fine houses, the homes of planters, +wealthy bankers, merchants, and shippers, who, besides their regular +houses in the city, had constructed handsome villas on heights on the +outskirts of the city. The houses were to a great extent one or two +stories in height, and were in many cases surrounded by fine gardens. +The city extended along the coast for about two miles. The streets +were well lighted. + +The eruption of Mt. Pelée on May 8th, 1902, was of a very unusual +character, containing a feature that--with the exception of a volcanic +eruption of Soufrière, a volcanic mountain on the neighboring island +of St. Vincent, and an eruption of Kilauea in Hawaii--so far as I am +aware, never before occurred. This was a blast of highly heated air, +mingled with white hot or incandescent dust, that swept down the side +of the mountain with a velocity of one or two miles per minute, or +possibly more. + +Nearly all of the people in St. Pierre were killed. From the +appearance of the bodies it seemed that death was practically +instantaneous, and was due either to scorching or burning, or +asphyxiation by the breathing of highly heated air. The number of +people so killed, including almost the entire population of St. +Pierre, as well as a number of adjoining settlements, was not less +than 30,000. + +The zone of absolute destruction was limited to an area the extent +of which did not greatly exceed eight or nine square miles. On the +outskirts of this zone the destruction, though considerable, was less +complete. + +There was almost an entire absence of great earthquake shocks during +the eruption. + +Following the terrible eruption of May 8th were a number of less +violent eruptions on May 20th, 26th, June 6th, July 9th, and August +31st. According to Heilprin these eruptions were of the same character +as that of May 8th. + +There has been considerable discussion as to the exact causes of the +tornadic incandescent blast that caused the awful destruction of life. +Without entering this discussion it is sufficient to say that it is +now generally considered that the blast consisted of highly heated +air, and super-heated steam loaded with great quantities of finely +divided red hot or even white hot dust particles. + +While, perhaps, the force producing the awful eruption of Mt. Pelée +was greatly excelled in the case of many other volcanic eruptions; +such as Papandayang, in 1772; Asamayama, in 1783; Skaptar Jökul, in +1783; Tomboro, in 1815; Coseguina, in 1835; and Krakatoa, in 1883; +yet, in the words of Heilprin, "in intensity and swiftness of its +death-dealing blast ... the eruption of May 8th, and of later dates, +stands unique in records of volcanic manifestations." + +While the amount of ashes that accompanied the blast of white hot +steam and air was comparatively small, yet during the time between +this and the subsequent eruptions, the amount of ashes that were +thrown from the surface of Mt. Pelée was exceedingly great. + +According to Russell, in a paper on the volcanic eruptions of +Martinique and St. Vincent, in 1902, the amount of ashes and solid +matter generally thrown out from the crater of Mt. Pelée would be +equal to 40,000,000 cubic feet every minute, or one and a half times +the sediments discharged by the Mississippi in the course of a whole +year. + +According to Heilprin, however, the actual amount of dust thrown from +the crater of Mt. Pelée was, probably, 500 times greater than the +amount discharged by the Mississippi River in the course of a year, +and, consequently, considerably greater than that of all the rivers of +the world combined, or, as he says: + + "Mont Pelée has now been in a condition of forceful + activity for upwards of two hundred days; can we assume + that during this time it may have thrown out a mass of + material whose cubical contents are hardly less than + a quarter of the area of Martinique as it now appears + above the waters? One is, indeed, almost appalled by the + magnitude of this work, and yet the work may even be very + much greater than is here stated. We ask ourselves the + questions, what becomes of the void that is being formed in + the interior? What form of new catastrophe does it invite? + There can be no answer to a question of this kind--except + in the future happening that may be associated with this + special condition. But geologists must take count of the + force as being one of greatest potential energy, whose + relation to the modelling and the shaping of the destinies + of the globe is of far greater significance than has + generally been conceived." + +A curious circumstance connected with the eruption of Mt. Pelée was +the most pronounced electric and magnetic disturbances. Moreover, as +in the case of the eruption of Krakatoa, there were the same after +glows or red sunsets and sunrises due to the presence of fine volcanic +dust in the higher regions of the air. These phenomena were observed +over widely separated areas. + +It appears that this great eruption in Martinique was preceded by +severe earthquakes in the northern part of South America, especially +in Colombia and Venezuela. The most marked was the great earthquake +which on April 18th destroyed the city of Guatamaula; this was, +perhaps, the most destructive earthquake that has occurred in the +Western Hemisphere since the great earthquake of 1812, that destroyed +the city of Caracas. Indeed, Professor Milne suggests that it was this +earthquake that brought about the eruption of Mt. Pelée. + +Soufrière, on the island of St. Vincent, had a great eruption on May +7th, 1902, one day before the awful eruption of Mt. Pelée. No lava +flowed during this eruption. There were, however, great discharges +of mud, due to a lake that before the eruption filled the top of +a depression known as the old crater which lay southwest of a new +crater, or the crater that was formed during the eruption of 1812. The +old crater was nine-tenths of a mile across from east to west, and +eight-tenths of a mile from north to south. The depth to the crater +floor was from 1,000 to 2,400 feet. The surface of the new and shallow +boiling lake which occupied the deepest part of the floor during the +latter part of May, and from June to August, was estimated to be +only 1,200 feet above the level of the sea. The sheet of water that +occupied it before the eruption being several hundred feet higher. + +Soufrière did not fail to give warnings of its coming eruption. +Rumblings were heard two days before the explosion. On May 5th, 1902, +fishermen who crossed the lake noticed that the water was disturbed +and agitated. On the Tuesday following, May 6th, great clouds were +thrown out during the afternoon, and the volcano was illumined by a +reddish glare of fire. The first explosion was heard shortly before +two o'clock on the following day and the volcano burst into activity. +The explosions, together with great discharges of pumice, ashes, and +boulders, followed one another rapidly. A column of steam was shot up +into the air for a height of 30,000 feet. The severest paroxysm came +shortly after ten A. M., and was succeeded by others nearly +as violent during the next few hours. By this time a reddish curtain +of clouds nearly shut out the island from view, and rapidly advanced +over the land and descended on the sea. This eruption caused a loss of +life of about 1,350. + +This eruption of Mt. Soufrière was accompanied by the same tornadic +blast of glowing air. There was not, however, any single blast quite +as severe as that which attended the eruption of Pelée on May 8th, +1902. + + + + +CHAPTER XII + +SOME OTHER NOTED VOLCANIC MOUNTAINS + + +Since the limits of our book will prevent any further description +of volcanic districts or regions, we must content ourselves with +descriptions of some of the noted of the remaining volcanoes, although +many we will thus omit contain great wonders. + +As we have already seen from the description of Krakatoa, the island +of Java near which Krakatoa is situated is especially noted not only +for the great number of its volcanic mountains, but also for the +frequency and severity of their eruptions. + +Perhaps the most destructive eruption of any of the volcanic mountains +of Java was of a volcanic mountain called Papandayang. This volcano, +situated on the southern coast of the island, is 7,034 feet in +height, and was in eruption in 1772. According to Scrope, from whom +the details of this eruption have been obtained, two others of the +many volcanoes on Java, situated at 184 and 352 geographical miles +respectively from Papandayang, broke out at the same time into active +eruption, although several intervening cones were undisturbed. + +The eruption of Papandayang was of the explosive type, a large part +of the mountain being broken off by the great force of the eruption, +and its materials scattered far and wide over the surrounding country. +During this eruption forty villages with their inhabitants were +buried by great showers of ashes. An area of fifteen by six miles was +left in the shape of a huge pit by the great eruption. It was at +first believed by some that this pit was due to the actual sinking +in of the ground, but a more careful study has shown that it was in +reality caused by the great force of the eruption, being, in point +of fact, a vast explosive crater that was formed by the expulsion of +the materials that formerly filled it. Some idea of the great extent +of this eruption of Papandayang may be had by the size of this huge +crater that was six by fifteen miles in diameter. + +Another great volcanic mountain in Java that had a terrific eruption +was Galungoon, or Galung Gung. According to Lyell, from whom the facts +of this eruption have been obtained, prior to this eruption the slopes +of the mountain were highly cultivated and densely populated. There +was a circular pit or crater on the summit of the mountain, but there +had been no traditions of any eruptions prior to 1822. + +In July, 1822, the waters of the Kunir River, one of the small rivers +that flow down the slopes of the mountain, were observed to become +hot and turbid. On the 8th of October, 1822, a terrific explosion was +suddenly heard, accompanied by great earthquake shocks, when immense +columns of hot water and boiling mud, mixed with burning brimstone, +ashes, and lapilli, were thrown violently like a great waterspout from +the opening in the mountain, with such enormous violence that great +quantities fell across the River Tandoi, forty miles distant, while +the valleys in the neighborhood were filled with a burning torrent. +The rivers overflowed their banks and produced great destruction by +floods of burning and boiling materials that washed away all the +villages and cultivated fields in their path. During this eruption an +extended area was covered with boiling mud in which were completely +buried the bodies of many of those who perished. + +So great was the violence with which the boiling mud, cinders, etc., +were thrown out of the mountain that they entirely failed to fall on +many of the villages in the immediate neighborhood, while the more +remote villages were completely destroyed and buried out of sight +under the mud. + +The first eruption continued for nearly five hours. During several +days following the eruption, torrents of rain fell, which produced +floods in the rivers that covered the country far and wide with thick +layers of mud. + +Four days after the great eruption, that is, on the 12th of October, +1822, a second and still more violent eruption occurred, when immense +quantities of hot mud were again thrown out of the crater. Great +blocks of hardened lava called basalt were thrown a distance of seven +miles from the volcano. This eruption was accompanied by a violent +earthquake. It was during this eruption that a huge piece of the side +of the cone was blown out, not unlike the case of the Val del Bove on +Mt. Etna. The surrounding country was covered with mud. The immense +quantity of materials thus thrown out of the side of the mountain +produced changes in the courses of several rivers, thus causing great +floods which in the single night of October 12th drowned 2,000 people. +During these eruptions there were 114 villages destroyed, with a total +loss of life of about 4,000. + +There is a volcanic mountain on the island of Sumbawa that is noted +for the very destructive eruption that occurred on it in April, 1815. +If you examine the map of the Sunda Islands chain, you will see that +the island of Sumbawa lies immediately east of a little island called +Lombock, about 200 miles east of Java. + +This eruption of Sumbawa was of the most frightful violence, and, +indeed, with the exception of Krakatoa and Pelée, was one of the +greatest eruptions in historic times. + +Like all great eruptions, that of Sumbawa gave plenty of signs of +its coming. During April, 1814, the volcano manifested considerable +increase in its activity, and ashes fell on the decks of vessels +sailing past the island. + +The eruption began on April 5th, 1815, but reached its greatest +violence on the 11th and 12th of April. According to Lyell, the sound +of the explosion was heard at the island of Sumatra at a distance of +970 geographical miles towards the west, and in the opposite direction +it was heard for a distance of 720 miles. The destruction of life was +terrible. Out of a population of 12,000 in the province of Tomboro, +only twenty-six people escaped with their lives. + +Like many other great eruptions the shooting upwards of the great +column of matter from the crater produced a violent whirlwind that +carried people, horses, cattle, and almost every movable object high +into the air, and tore up huge trees by their roots. + +Immense quantities of ashes fell over the surrounding country, or were +carried towards Java to the west a distance of 300 miles, while on the +north they were carried towards Celebes for a distance of 217 miles. +Cinders covered the ocean towards the west two feet thick and several +miles in length, so that ships could hardly make their way through +them. + +The darkness in Java produced by the dense ash cloud was greater than +had ever before been experienced with the single exception of the +great eruption of Krakatoa. A considerable quantity of this volcanic +dust was carried to the islands of Amboyna and Banda, the last named +island being at a distance of 800 miles east of the volcano. + +This eruption of Sumbawa was attended by great lava streams that +covered vast areas of the land and afterwards poured into the sea. + +As in the case of the explosive eruption of Krakatoa great waves were +produced in the ocean all along the coasts of Sumbawa, and surrounding +islands. The sea suddenly rose from two to twelve feet. A great wave +rushed up the mouths of the rivers, and at the town of Tomboro, on +the west side of Sumbawa, an area of land was sunk in the waters and +remained permanently covered by eighteen feet of water. + +The most important of the still active volcanoes of Japan is +Assamayna. This mountain was in terrible eruption during the autumn of +1783, when dense showers of ashes thrown out of the crater darkened +the sky, turning the day into night, and, falling on the cultivated +fields around the mountain, changed them into deserts. During the +eruption some forty-eight villages were destroyed by showers of ashes +and red hot stones and thousands of the inhabitants were either killed +directly by the stones and ashes, or died from starvation, since their +fields were covered with ashes for miles around to a depth of from two +and a half to five feet. + +Another terrible eruption in Japan was in the volcanic mountain of +Wunzen, or Onzen-Gatake. This occurred during 1791-93. During the last +eruption of this volcano, 53,000 people lost their lives, either by +reason of the eruption of the volcano, or by huge waves set up in the +ocean by an earthquake. + + + + +CHAPTER XIII + +JORULLO, A YOUNG VOLCANIC MOUNTAIN + + +You must not suppose that when we speak of Jorullo as a young volcanic +mountain that we mean young in the sense that you or I might be called +young, but young as regards mountains; for Jorullo, now a great +mountain range, had no existence before the year 1759, and that would +make the mountain a little less than 150 years old, which so far as +mountains are concerned may properly be regarded as quite young. + +The story of Jorullo is very interesting, and affords an excellent +example of the great scale on which modern volcanic eruptions take +place during historical times. + +If you examine the map of Mexico on page 86 you will see that Jorullo +lies 170 miles southwest of the city of Mexico, and 108 miles from the +Pacific Ocean, which is the nearest large body of water. This mountain +is of especial interest because, if old traditions are to be believed, +it was thrown up during practically a single night. This wonderful +event took place on an elevated plain or plateau, called the Plain of +Malpais, that lies between 2,000 and 3,000 feet above the level of the +ocean. The plain was situated in a part of Mexico that was celebrated +for the growth of the finest cotton and indigo in the world. It +formed the large estate of a wealthy planter, Señor Pedro de Jorullo, +who lived at his ease as a wealthy planter is apt to do in tropical +countries like Mexico. + +Jorullo's plantation was covered by an especially fertile soil, since +it was formed by the deposits of volcanic ashes, dust, tufa, etc., +produced, most probably, by neighboring volcanoes long before man +appeared on the earth, for the plain of Malpais was bounded by hills +that were composed of volcanic materials. There had, however, been no +signs of volcanic activity in the neighborhood. It had indeed been +quiet, so far as volcanic eruptions were concerned, since the time of +the discovery of America by Columbus, until the middle of the last +century. The fertile fields of the Jorullo plantation were watered by +two rivers, or as we would probably call them, brooks, the Cuitamba +and the San Pedro. + +Signs were not wanting of the coming calamity. During June, 1759, +subterranean sounds were heard of a low rumbling character, which +every now and then increased until they resembled in intensity the +sounds produced by the firing of large guns. These sounds were +accompanied by earthquake shocks that greatly terrified the people +and caused them to flee from their homes. Nothing, however, occurred, +so, becoming accustomed to the noises, the people returned to their +houses. The noises and tremblings ceased for over two months, until, +on the 29th of September, 1759, they were again heard, and a terrible +eruption began. A long fissure opened in the earth, extending +generally from northeast to southwest. From this fissure flames +burst out, fragments of burning rock and stone, together with large +quantities of ashes were thrown to great heights in the air, and were +followed by streams of molten rock. Six volcanic cones were formed +along the fissure. The highest of these cones is what now constitutes +the volcanic mountain of Jorullo, which then reached a height of at +least 1,600 feet above the level of the plain. From its cone were +thrown out great quantities of lava of the same type as that which +escaped from the craters of many volcanic islands such as Hawaii and +Iceland, namely, basaltic lavas. This eruption, which began on the +29th of September, 1759, continued until the month of February, 1760. + +The account as above given was obtained by Humboldt, who visited the +country some fifty-six years after the eruption. This story was told +him by the Indians, but was also recorded in verse by a Jesuit priest, +Raphael Landiva, a native of Guatemala. According to the account given +Humboldt by the Indians, it appears that when a long time after the +eruptions had quieted down, they had returned to their old homes with +the hope of cultivating part of the grounds, they found the plains +still too hot to permit their living on them. + +According to Lyell, there was around the base of the cone, spreading +from them as a centre over an area of some four square miles, a convex +mass, about 550 feet in height, most of the surface of which was +covered with thousands of small flattish conical mounds from six to +nine feet in height. These, together with numerous large fissures that +crossed the plain in different directions, served as points for the +escape of sulphur vapors, as well as for the vapors of hot water. + +During the escape of lava from the craters in 1759, the molten rock, +spreading over the plain, ran into the channels of the river or brooks +before named, driving out the water. This water reappeared at the base +of the mountain in numerous hot springs. + +Humboldt thought that the conical mountains had been lifted or raised +by the formation of huge bubbles formed under the lava, thus causing +it to assume a shape not unlike that of a huge bladder. This opinion, +however, has not been accepted by geologists at the present time. +Scrope points out that this was probably the origin of the little +conical mounds that covered the surface of the principal conical +mounds but was not, in all probability, the cause of the mound itself. +He says: + + "With regard to the disputed question as to the origin + of the raised plain of the Malpais, M. de Saussure, the + last and most trustworthy visitor, entirely confirms the + opinion which I ventured to proclaim in 1825, that Humboldt + was mistaken in supposing it to have been 'blown up from + beneath like a bladder,' and that it is merely an ordinary + current of lava, which, owing to its very imperfect + liquidity at the time of its issue from the volcanic vent, + as well as to the overflow of one sheet or stream upon + another, had acquired great thickness about its source, + gradually thinning off towards the outer limit of the + elliptical area it covered." + +If you have been able to follow the above you will see that Mr. Scrope +means that in his opinion the cone of Jorullo is a lava cone like +that we have already studied on Mt. Loa or Mt. Kilauea, or, in other +words, that the lava as it came out from the opening on the top of +Jorullo, flowed in all directions around the opening, thus building up +a mountain in the form of a flat lava cone. + +Perhaps one of the reasons Humboldt had for believing the entire +elevation of Jorullo to be due to the formation of a huge bladder was +the fact that the plain on which the cone is situated, when struck, +gave out a sound as though there was a vast hollow space below it. +This was especially the case when the hoofs of the horses driven over +its surface produced sounds as though they were moving over the summit +of a hollow dome-like space below. But, as Lyell points out, this was +probably only due to the fact that the materials forming the cone were +very light and porous. + +According to Burkhardt, a German mining engineer who visited Jorullo +in 1827, there appears to have been no other eruptions of the volcano +since the time of Humboldt's visit. Mr. Burkhardt descended to the +bottom of the crater and observed that small quantities of sulphurous +vapors were still escaping. The small cones or _hornitos_, however, on +the slopes had entirely ceased emitting steam. It appeared, too, that +the twenty-four years that had passed since the time of Humboldt's +visit, the rich soil of the surrounding country had permitted the +successful cultivation of some crops of sugar cane and indigo. + +Russell appears to doubt the reliability of the information obtained +by Humboldt concerning Jorullo. He suggests that a poetical account +by the Jesuit missionary from whom Humboldt obtained much of his +information was not apt to possess marked scientific accuracy. While, +however, this may be true, yet to a certain extent it seems entirely +probable that the principal facts were as above given. The following +account as given by Humboldt, is taken from a translation made in the +early part of 1800: + + "The affrighted inhabitants fled to the mountains of + Aguasarco. A tract of ground from three to four square + miles in extent, which goes by the name of Malpays, rose up + in the shape of a bladder. The bounds of this convulsion + are still distinguishable in the fractural strata. The + Malpays, near its edge, is only twelve metres above the + old level of the plain called the Playas de Jorullo; but + the convexity of the ground thus thrown up increases + progressively towards the centre, to an elevation of 160 + metres (524.8 ft.). + + "Those who witnessed this catastrophe from the top of + Aguasarco assert that flames were seen to issue forth + for an extent of more than half a square league, that + fragments of burning rocks were thrown up to prodigious + heights, and that through a thick cloud of ashes, + illuminated by the volcanic fire, the softened surface + of the earth was seen to swell up like an agitated + sea. The rivers of Cuitamba and San Pedro precipitated + themselves into the burning chasms. The decomposition of + the water contributed to invigorate the flames, which were + distinguishable at the city of Pascuaro, though situated on + very extensive table-land 1,400 metres (4,592 ft.) elevated + above the plains of Las Playas de Jorullo. Eruptions of + mud, and especially of strata of clay enveloping balls + of decomposed basalt in concentrical layers, appeared to + indicate that subterranean water had no small share in + producing this extraordinary revolution. Thousands of small + cones, from two to three metres in height, called by the + indigenes ovens, issued forth from the Malpays.... + + "In the midst of the ovens, six large masses, elevated from + 400 to 500 metres each above the old level of the plain, + sprung up from a chasm, of which the direction is from + N. N. E. to the S. S. E. This is the phenomenon of the + Montenovo of Naples, several times repeated in a range of + volcanic hills. The most elevated of these enormous masses, + which bears some resemblance to the puys de l'Auvergne, is + the great Volcan de Jorullo. It is continually burning, + and has thrown up from the north side an immense quantity + of scorified and basaltic lavas containing fragments of + primitive rocks. These great eruptions of the central + volcano continued till the month of February, 1760. In the + following years they became gradually less frequent.... The + roofs of the houses of Queretaro were then covered with + ashes at a distance of more than forty-eight leagues in a + straight line from the scene of the explosion. Although + the subterranean fire now appears far from violent, and + the Malpays and the great volcano begin to be covered with + vegetation, we nevertheless found the ambient air heated to + such a degree by the action of the small ovens, that the + thermometer at a great distance from the surface and in the + shade rose as high as 43° C." (109° 4' F.). + + + + +CHAPTER XIV + +MID-OCEAN VOLCANIC ISLANDS + + +Besides the volcanoes we have already described, there are many others +situated in mid-ocean far from any continent. A brief description will +be given of a few of these. + +All the three great central oceans, the Pacific, the Atlantic, and the +Indian, contain numerous volcanic islands, some of which rise many +thousands of feet above the general level. + +We will begin with a description of some of the more important +volcanic islands of the Pacific. It was first pointed out by Kotzebue, +and afterwards by Darwin, that all the islands of the Pacific Ocean +can be divided into two great classes, the _high islands_ and the +_low islands_. All the high islands are of volcanic origin, while +the low islands are of coral formation. It is the opinion of Dana, +who has made a careful study of coral formations, especially in the +Pacific, that in all probability even the low islands of the Pacific +were originally volcanic, and that the deposits of coral had been made +along their shores after their volcanoes had become extinct. + +The islands of the Pacific, like the shores of the continents and +most of their mountain ranges, extend in two great lines of trend, or +general direction, which intersect each other nearly at right angles. +These lines extend from the southeast to the northwest, and from the +northeast to the southwest respectively, those extending in a general +direction from southeast to northwest being the most common in the +Pacific. + +Now, perhaps, the greatest number of the earth's volcanoes are +arranged along fissures, or cracks in the earth's crust. The craters +are situated along the cracks, the openings being kept clear at the +crater, and gradually closing elsewhere, probably by pressure. In +other words, most of the volcanoes follow one another along more or +less straight lines. For example, in the western part of South America +they follow the Andes Mountains. A similar arrangement exists in the +volcanoes of Central America, Mexico, and the United States. Now, this +is especially true of mid-ocean volcanoes of the Pacific which lie +along lines extending from southeast to northwest, or from northeast +to southwest, though mainly along the former. + +Some of the volcanic islands of the Pacific have already been +described or referred to, as, for example, the Aleutian Islands, +which stretch in a curved line from the southwestern extremity of +the peninsula of Alaska to Kamtschatka on the coast of Asia. We have +already described the island of Hawaii, the great volcanoes of the +Sandwich Islands chain, and besides these there are in the North +Pacific the Ladrone Islands, lying east of the Philippines. + +Some of the principal remaining islands are: the Fejee Islands, which +are volcanic, with numerous hot springs and craters. The Friendly +Islands, with the peak of Tafua, 2,138 feet high, an active volcano +with a large crater always burning, and two other volcanoes, Apia, +and Upala. Tahiti, to the east, is at present extinct. One of its +mountains, Orobena, said to be 10,000 feet high, has a crater on its +summit. The Marquesas, still further to the east, are also volcanic. +All of these islands lie generally in the lines of the northeast +trend. + +The Tongan or New Zealand Island chain extends in the direction of +the northeast trend. This, as you will see, is the direction in which +the two islands of New Zealand extend. The Tongan Island chain is +continued to the south through Auckland and the Macquaire Islands to +58° S. Towards the north, in almost the same line, are the Kermadec +Islands near 30° S. + +There are several active volcanoes in New Zealand. An explosive +eruption of Tarawera, in New Zealand, in 1883, continued for several +days, and was followed, three days afterwards, by an outburst in an +active volcano in the Bay of Plenty, and two months afterwards, by a +violent outburst in a volcano on the island of Ninafou in the Tongan +Islands. + +Coming now to the Atlantic Ocean we find a number of volcanic +mountains in the deep waters near mid-ocean. The principal of these, +besides Iceland, are the Azores, the Canaries, Cape Verde Islands, +Ascension Island, St. Helena Island, and Tristan d'Acunha. The Peak +of Pico, in the Azores, rises to a height of 7,016 feet. The Peak +of Teneriffe, in the Canaries, reaches the height of 12,225 feet. +Teneriffe is a snow-capped mountain. It has a cone on its summit with +precipitous walls like Vesuvius. Sulphurous vapors are continually +formed at its summit, but no flames can be seen. + +In the Cape Verde Islands is to be found the active volcanic mountain +of Fuego, rising 7,000 feet above the sea. It has a central cone that +has been broken down on one side like that of Somma on Vesuvius. Fuego +was in eruption in 1785, and also in 1799. + +Ascension Island, south of the equator, is formed entirely of volcanic +materials. This island rises from an apparently granite floor on the +bed of the ocean, in water 12,000 feet deep. + +St. Helena lies further to the south. It is an extinct volcano, and +has the remains of a crater on its summit with lava dikes in various +parts of the island. + +Tristan d'Acunha is an isolated mountain that lies in the South +Atlantic, south of St. Helena, 1,500 miles from Africa, the nearest +land. It is an extinct volcano that rises from a depth of 12,150 feet +to a height of 7,000 feet above the sea. It has a truncated cone on +its summit and a lake of pure water in its old crater. + +There are only a few volcanic islands in the Indian Ocean. Kerguelen +Island lies in the southern waters. St. Paul and Amsterdam to the +north, lying near 40° S. lat., as well as the Crozet Islands, are +extinct volcanoes. + +In the Arctic Ocean is the volcanic island of Jan Mayen. In the +Antarctic Ocean, as far as is known, there are only two volcanoes, +Mt. Erebus and Mt. Terror. Mt. Erebus, 12,400 feet high, is an active +volcano. Mt. Terror, 10,990 feet high, is an extinct volcano. + + + + +CHAPTER XV + +SUBMARINE VOLCANOES + + +A submarine volcano is a volcano that erupts on the bed of the ocean +with its crater covered by the waters. Many of the great volcanic +mountains of the world began as submarine volcanoes. A crater first +opened on the floor of the ocean, and lava escaping, was heaped up +around the opening, until it emerged above the surface as an island. +As we have seen, the island of Iceland is believed to have begun in +this way. Such, too, in all probability, was the origin of Hawaii, +Vesuvius, Etna, and Santorin. + +But besides the volcanic mountains that were thrown up during the +geological past, there are others that have been called into existence +while man has been living on the earth. We will now describe a few +islands that have been formed in this manner by submarine volcanic +eruptions. + +That volcanic eruptions, or at least something that greatly resembles +eruptions, occur on the bed of the ocean too far below the surface to +permit them to be directly seen from above, has been shown in a number +of cases where the captains of vessels have reported that in certain +parts of the ocean, jets of water, or steam, and pillars of flame have +been seen rising to great heights from the surface of the water, and +that in certain regions sulphurous smoke has also been seen. During +such occurrences, the water is agitated, as if it were being violently +boiled. Moreover, these parts of the ocean are shaken by severe +earthquake shocks. + +Another evidence of submarine volcanic eruptions is to be found in +great quantities of ashes, scoriæ, or pumice stone, that are seen +spread out over the surface of the ocean after the commotions referred +to in the preceding paragraph. Still another proof is that parts of +the ocean whose waters were previously very deep are found to have +suddenly shoaled. + +Of course, the best proof is the appearance of rocky reefs or small +islands thrown up above the surface of the water, especially where +volcanic cones appear. While in many cases the new islands thus thrown +up are subsequently washed away by the waves, yet some have continued +above the water. + +One of the most noted instances of the formation of an island by a +submarine volcano was Sabrina, which was thrown up in 1811, in the +Atlantic Ocean, off the shores of St. Michael in the Azores Islands. +Sabrina had a cone that was 300 feet in height. It did not long remain +above the waters, however, being soon washed away by the waves. It is +interesting to note that in the same part of the ocean where Sabrina +appeared, other islands have appeared and disappeared, at times long +before 1811; that is, during the year 1691, as well as during 1720. + +Another instance of a submarine island is Graham's Island, that was +thrown up in 1831, in the Mediterranean Sea, between the west coast +of Sicily and the nearest part of Africa, on which ancient Carthage +was situated. The part of the sea where the island was thrown up had +previously a depth of 600 feet. + +The general appearance of Graham's Island is represented in Fig. 22. + +Graham's Island was formed by accumulations of loose scoria and +cinders, together with blocks of lava and fragments of limestone. It +reached a height of 200 feet above the water, but only remained above +the surface for a few months, when it was washed away, leaving a +submarine bank some twelve miles in width, that was covered by water +of about 150 feet, but which, however, increased rapidly in depth +towards the edge until depths of from 1,200 to 2,000 feet were reached. + +[Illustration: FIG. 22. GRAHAM'S ISLAND--A RECENT VOLCANIC +ISLAND] + +According to Lyell, on the 28th of June, 1831, before Graham's Island +appeared, a ship passing over this portion of the sea felt severe +earthquake shocks. On July 10th of the same year, the captain of a +vessel from Sicily reported that as he passed near this part of the +Mediterranean, a column of water, 800 yards in circumference, was seen +to rise from the sea to a height of sixty feet, and that afterwards a +column of steam rising to a height of 1,800 feet was seen in the same +place. On again passing the same region on July 18th, this captain +found a small island about twelve feet in height, with a crater in +its centre, that was throwing out volcanic materials, together with +immense masses of vapor. + +The island thus formed grew rapidly, both in size and height. When +visited at the end of July, it had attained a height of from fifty to +ninety feet, and was three-quarters of a mile in circumference. By +August 4th, it had reached a height of 200 feet, and was then some +three miles in circumference. From this time, however, the island +began to decrease in size, as the waves began to wash it away. By +August 25th, it was only two miles in circumference. On September +3d, it had decreased to three-fifths of a mile in circumference, and +continued to decrease until it entirely disappeared, so that in the +year 1832, there were, according to measurements, some 150 feet of +water over its former site. + +The Mediterranean Sea between Sicily and Greece is also especially +liable to submarine activity. New islands appear and disappear so +frequently that in this region they are almost regarded as common +phenomena. + +There are many other parts of the ocean where submarine volcanic +eruptions are common. This is especially the case in the narrowest +part of the Atlantic Ocean between Africa and South America. Here +there is a region situated partly above the equator, though for the +greater part south of the equator, frequently visited by submarine +eruptions, that are accompanied by earthquakes, by the agitation of +the water, by the appearance of floating masses of ashes and scoriæ, +as well as by columns of steam or smoke. Floating masses of ashes and +scoriæ sometimes occur so thick as to retard the progress of vessels. + +But what forms, perhaps, one of the best instances of a large island +formed by submarine eruptions during historical times, is Bogosloff +Island in Behring Sea, some forty miles west of Unalaska Island. This +island, the position of which is seen on the accompanying map, is +known to the Russians as Ioanna Bogoslova, or St. John the Theologian. +It is situated in lat. 53° 58' N., long. 168° west. It is said that +during the year 1795, some of the natives of Unalaska Island saw what +they thought was a fog in the neighborhood of a small rock, which they +had known for a long time to project above the sea in these waters. +This rock was marked on some Russian chart dated 1768-69. It was seen +by Captain Cooke, in 1778, and was named by him Ship Rock. + +But it was not a fog that the Unalaskans had seen in the neighborhood +of Ship Rock; for, to their great surprise, the fog continued in sight +although everywhere else the air was quite clear. Of course, this +was a great mystery to the people. During the spring of 1796, one of +them, who possessed either greater curiosity than the rest, or greater +courage, or both, visited the rock. He returned, telling the strange +story that all the ocean around the rock was boiling, and that the +mist or fog was caused by the rising steam. What was taking place was +a submarine eruption. During May, 1796, sufficient matter had been +brought up from below to increase greatly the area of the small rock. + +[Illustration: FIG. 23. ALEUTIAN ISLANDS] + +During later years several attempts have been made to visit Bogosloff +Island. For example, the island was visited during 1872 and 1873, +when it was found to have increased in height to 850 feet. But no +appearance of any volcanic crater was to be seen. + +During October, 1883, a great volcanic eruption occurred there. +Considerable changes were produced in its shape, as well as in the +depth of the surrounding water. During this eruption, clouds of steam +completely hid the island. Great quantities of ashes obscured the +light of the sun. After the eruption, a new island was thrown up near +the old one, in a place where the water had previously been deep +enough for the ready passage of ships. The new island was about half a +mile from the old one. It was conical in form, from 500 to 800 feet in +height, and about three-quarters of a mile in diameter. + +The new island was visited in 1884 by the U. S. Revenue Marine Steamer +_Corwin_. Lieutenant Cartwell, who visited the island at this time, +described it as follows: + + "The sides of New Bogosloff rise with a gentle slope to the + crater. The ascent at first appears easy, but a thin layer + of ashes, formed into a crust by the action of rain and + moisture, is not strong enough to sustain a man's weight. + At every step my feet crushed through the outer covering + and I sank at first ankle-deep and later on knee-deep into + a soft, almost impalpable dust which arose in clouds and + nearly suffocated me. As the summit was reached, the heat + of the ashes become almost unbearable, and I was forced + to continue the ascent by picking my way over rocks whose + surfaces being exposed to the air, were somewhat cooled and + afforded a more secure foothold. + + "On all sides of the cone there are openings through + which steam escaped with more or less energy. I observed + from some vents the steam was emitted at regular + intervals, while from others it issued with no perceptible + intermission. Around each vent there was a thick deposit of + sulphur, which gave off suffocating vapors." + + + + +CHAPTER XVI + +DISTRIBUTION OF THE EARTH'S VOLCANOES + + +Having now considered at some length the principal volcanoes of the +earth, and endeavored to obtain some idea of the many wonders they +exhibit, especially as regards the vast quantities of material they +bring from the inside of the earth, as well as the great force with +which they sometimes throw these materials out of their craters, it +will be well to point out where such volcanoes are to be found. + +It may have seemed to you, when you have carefully followed what has +been said about the earth's volcanoes, that they are to be found +pretty nearly everywhere, at least so far as latitude is concerned; +and in this supposition you are correct; for there are volcanoes in +the Arctic Ocean, as in the volcanic island of Jan Mayen between +Iceland and Spitzbergen, there are Mt. Erebus and Mt. Terror in the +Antarctic Ocean, besides very numerous volcanoes in the Atlantic, +Pacific, and Indian Oceans, and their shores in both the temperate and +the torrid zones. + +There is, however, one thing that you have probably especially +noticed and that is that volcanoes are seldom found at very great +distances from the ocean, except on some of its arms or seas, such +as the Mediterranean Sea. I do not mean by this that all the earth's +volcanoes are either situated directly on the coast of the continents +or on islands, since, in such a large body as the earth, a distance of +a few hundred miles from the ocean is hardly to be regarded as being +very far from it. But it is true that all the earth's volcanoes are +either situated on the coasts of the continents, or on islands, and, +moreover, they are situated to a greater or less extent along lines, +which, as we have already pointed out, are believed to mark weak +portions of the earth's crust that have been fissured or fractured. + +In order that you may have some idea of this distribution, I think it +will be well to give you a number of interesting facts that have been +pointed out by Dana. According to this authority, there are something +in the neighborhood of 300 active volcanoes on the earth. Of these, +no less than five-sixths, or 250, lie either on the borders of the +Pacific Ocean, or on some of its many islands. Thirty-nine either +lie within or on the borders of the Atlantic, of which thirteen are +in Iceland, or near the Arctic Circle, three in the Canaries, seven +in the Mediterranean Sea, six in the Lesser Antilles, and ten in +the Atlantic Oceanic Islands. The Indian Ocean contains only a few +active volcanoes. There are, however, a much greater number of extinct +volcanoes, which may at any time again become active. + +The following is the distribution of the earth's volcanoes as given +by Dana. As you will see, from an inspection of Fig. 24, all of the +regions of volcanoes lie either on the borders of the continents, or +on islands in the oceans. The districts are as follows: + +1. _Scattered Over the Pacific Ocean._--This district includes the +following active volcanoes; i. e., the Hawaiian Islands, nearly in +mid-ocean, almost directly below the Tropic of Cancer; in the west +central parts of the South Pacific; in the New Hebrides; in the +Friendly Islands, the Tongan or New Zealand Islands, in the Santa Cruz +Islands, and in the Ladrones. + +[Illustration: FIG. 24. MAP OF THE WORLD, SHOWING LOCATION OF +ACTIVE AND RECENTLY EXTINCT VOLCANOES] + +2. _On the Borders of the Pacific._--This district includes the +volcanoes that extend from the southern part of South America +at intervals along the Andes Mountain range. Of these there are +thirty-two in Chile, seven or eight in Bolivia and Southern Peru; +about twenty in the neighborhood of Quito. Further north there are +thirty-nine in Central America, and seven in Mexico. Proceeding +northwards through the United States, there are a number of volcanic +mountains, generally extinct, in portions of the Sierra Nevadas +and Cascade Ranges. Probably a number of volcanic mountains exist +in portions of Canada lying between the northern boundaries of the +United States and Alaska, and a number in Alaska; some twenty-one +volcanic mountains in the Aleutian Islands; some fifteen or twenty +in Kamtschatka; thirteen in the Kuriles; some twenty-five or thirty +in Japan and the neighboring islands; some fifteen or twenty in the +Philippines; several along the northern coasts of New Guinea; a number +in New Zealand and south of Cape Horn; the volcanoes of the Deception +Island with its hot springs, and also in the South Shetlands 62° 30' S. + +3. _In the Indian Ocean._--On the western border of the Indian Ocean +there are a few volcanoes in Madagascar; in the Island of Bourbon; +Mauritius; the Comoro Islands; and in Kerguelen Land on the south. +There are also volcanoes on the western border of the Indian Ocean +where the lofty peak of Kilima Ndjro, 18,000 feet, is volcanic. + +4. _Over the Seas that Separate the Northern and the Southern +Continents and in their Vicinity._--This is an especially active +region of volcanoes. For the sake of convenience the continents of the +world are sometimes divided into three pairs or double continents; +namely, North and South America, connected by the Isthmus of Panama; +Europe and Africa, connected by the Isthmus of Suez; and Australia and +Asia, completely separated by a sunken isthmus, the summits of which +form the Sunda Island chain. In the first of these regions we have the +very active group of the West Indies, where there are ten volcanic +islands. In the second pair of double continents we have the volcanoes +of the Mediterranean and Red Seas, and their borders, such as Sicily, +Vesuvius, and other parts of Italy, Spain, Germany, the Grecian +Archipelago, Asia Minor, and extending eastward through the Caspian, +Mt. Ararat, Demavend, on the south shores of the Caspian, Mt. Ararat, +and some few others along the borders of the Red Sea. + +In the East Indies we find the most intense centre of volcanic +activity in the world. Here there are some 200 volcanoes of which +there are nearly fifty in Java alone, more than half of which are +still active. There are nearly as many volcanoes in Sumatra, and many +in the small islands near Borneo, the Philippines, etc. + +5. _On the Borders of the Atlantic and Elsewhere._--It is an +interesting fact that there are no volcanoes on the eastern borders +of the Atlantic north of the West Indies Island chain. In the South +Atlantic the only volcano on the borders is one of the Cameroons +Mountains. In the Atlantic Ocean we have Iceland, the Azores, the +Canaries, Cape Verde, Ascension, St. Helena, and Tristan d'Acunha. + +This curious distribution of the volcanoes of the world near the +oceanic waters appears to be dependent rather on the very early shapes +of the continents and the ocean beds than on their present shapes. + + + + +CHAPTER XVII + +VOLCANOES OF THE GEOLOGICAL PAST + + +The question is often asked whether the volcanic eruptions of the +geological past were not much more violent and destructive than the +volcanoes of the present time. Now, while this is a matter that +properly belongs to the subject of geology, and will be treated at +greater length in the Wonder Book on Geology, yet a short mention +should be made of it here. + +It is the opinion of Dana that while there have been volcanoes during +the different geological ages, yet volcanic activity has increased +through the geological past until the age that immediately preceded +the appearance of man on the earth. He thinks there is no reason for +believing that there were any very great volcanic eruptions during the +earliest geological time known as the Archæic. Dana speaks as follows +concerning this: + + "In this connection it is an instructive fact that in + eastern North America, at epochs when there was the + greatest amount of friction and crushing ... those of the + making of the Green Mountains and the Appalachians ... no + volcanoes were made, and little took place in the way of + eruptions through fissures." + +On the other hand, Prestwich seems inclined to think that the absence +of well-marked cones of volcanic material in the rock of the older +geological ages is not to be regarded as proof that no eruptions then +took place, since the very great amount of erosion that occurred +between that time and the Tertiary Age before the appearance of man, +would, probably, have completely obliterated any cones, and even the +volcanic materials would have undergone such changes as completely to +alter their general character. He agrees, however, with Dana that, +probably, the most violent and explosive volcanoes of the geological +ages have been those of the Tertiary Age. + +Without, however, attempting anything more than a brief reference to +the volcanoes of the geological past, it may be said that many of the +more important of the active volcanoes of the earth's present time +were begun in the Tertiary Age. Mt. Etna, Vesuvius, and Mt. Hecla are +believed to have commenced at this time. + +There is an interesting region of geological volcanoes in the +neighborhood of Auvergne in Central France. Here they occur in three +separate groups that extend over a high granite platform from north +to south for a distance of about 100 miles, and from twenty to eighty +miles from east to west. The eruptions began in the earlier portions +of the Tertiary Age, and continued down to the latter periods of +prehistoric times. Some of these volcanic craters remain to-day almost +as unaffected by erosion as if they had been formed but recently. + +Other regions of geological volcanoes are to be found in parts of +Spain near the foot of the Pyrenees Mountains, in parts of Italy and +Germany, as well as in regions in the Caucasus Mountains. + +In Asia Minor there exists a group of almost thirty extinct volcanoes +in the neighborhood of the Gulf of Smyrna. Both Little and Great +Ararat contain volcanic cones: that in the latter mountain was active +during historical times. There are also extensive volcanic districts +in the Taurus Mountains. In addition to these there are groups of +extinct volcanoes in portions of Central Asia. + +Aden, on the Red Sea, is the centre of an extensive volcanic district. +Indeed, on both shores of the Red Sea there are a few volcanoes that +are still active, while in Sinai, and in the districts of the south, +there are several extinct craters. + +But it is in the New World, especially on the Pacific coast of +North America, that volcanic activity was especially great during +the geological past. There is a district containing volcanic rocks +that extends through various parts of western North America, from +New Mexico and North California, to Oregon and British Columbia. +This district has a width of from eighty to 200 miles, and a length +of not quite 800 miles. This great area of nearly 150,000 square +miles is covered with great sheets of volcanic rocks except where +mountain ranges rise from them, or where the rivers have cut deep +valleys through them. In portions of California and New Mexico these +plateaus rise to heights of from 8,000 to 10,000 feet, while in parts +of Colorado, where they form huge dome-like mountains, they reach a +thickness of 14,000 feet. In Oregon the sheet of lava is 2,000 feet +thick, and, indeed, in some places, is estimated to have a depth of +7,000 feet. + +In the opinion of nearly all American geologists these great lava +flows in western North America were not of the type known as crater +eruptions, but were what are called fissure eruptions. Some of them +are believed to have occurred during geological times as early as the +Eocene. Prestwich, however, is of the opinion that the eruptions of +the past in these portions of the world were not confined to fissure +eruptions, but that crater eruptions also occurred; and that it was +towards the close of the Tertiary Age that crater eruptions occurred +with great lava flows. Indeed, as we have seen, in portions of Utah +and the neighborhood the remains of true craters can be found. + +Besides the above there are evidences of geological volcanoes of still +older times. In portions of Deccan, in southern Hindostan, there is an +immense plateau formed of trap rock, that extends from east to west +for a distance of 400 miles, and from north to south through from 700 +to 800 miles. This district, with an area of almost 200,000 square +miles, is covered with a vast lava sheet. It was, in the opinion of +Prestwich, from whom many of the facts of the geological volcanic +eruptions have been obtained, probably still more extensive. The +plateau of Deccan rises gradually from the east to the west, where, in +some parts of the Ghauts Mountains, it reaches a height of from 4,000 +to 5,000 feet. + +One of the greatest of these prehistoric volcanoes of Scotland was a +volcano in the Isle of Mull in the Hebrides. This volcano was probably +nearly thirty miles across at its base, and was from 10,000 to 12,000 +feet high. It is now only 3,172 feet in height. + +According to Judd the Island of Skye in Inverness-shire is the remains +of a volcano that was active in Tertiary times, probably many millions +of years ago. This volcano was very large, probably about thirty miles +across at its base, with a height of perhaps as great as 12,000 or +15,000 feet. Now there are only left some granite and other similar +rocks that form the Red Mountains and Coolim Hills of Skye that reach +about 3,000 feet above the sea level. + +There are many other parts of the world containing volcanoes that were +active during the geological past. The above, however, is as far as we +can describe such volcanoes in this book. + + + + +CHAPTER XVIII + +LAPLACE'S NEBULAR HYPOTHESIS + + +LaPlace's nebular hypothesis is the name given to an ingenious +hypothesis proposed by LaPlace, a celebrated French astronomer, in an +endeavor to explain how the solar system has been evolved. + +You will notice that this is called a hypothesis and not a theory. +The word hypothesis is properly applied to a more or less intelligent +guess or assumption, that has been made for the purpose of trying +to find out in the cause of any natural phenomenon. A theory is an +expression of a physical truth based on natural laws and principles +that have been independently established. A theory, therefore, is much +more complete than a hypothesis. A hypothesis, as Silliman remarks, +bears the same relation to a theory or law, that a scaffolding does to +a completed building, since it forms a convenient means for erecting +the building. LaPlace's work is properly called a hypothesis, because +it is not to be considered as any more than a means for enabling one +intelligently to inquire into the probable manner in which the solar +system has reached its present condition, by gradual steps or stages +during the almost inconceivable length of time since its creation. + +Before describing LaPlace's hypothesis it will be necessary to give +you some ideas concerning what is known by astronomers as the solar +system. + +The solar system consists of the sun, and the eight large bodies +called planets that revolve around the sun. It also includes a number +of moons or satellites revolving around the planets, a number of small +bodies, called planetoids or asteroids, together with numerous comets +and meteorites. Besides these there is probably a system of meteoric +bodies that are believed to revolve around the sun, and to produce, by +the reflection of the light from their surfaces, what is known as the +_zodiacal light_. + +The principal bodies of the solar system are the planets. These +constitute eight large bodies named in their order from the sun, +beginning with the nearest: Mercury, Venus, Earth, Mars, Jupiter, +Saturn, Uranus, and Neptune. The last four planets, Jupiter, Saturn, +Uranus, and Neptune are much larger than the others, and are therefore +known as the _major planets_ in order to distinguish them from +Mercury, Venus, Earth, and Mars, which are called the _minor planets_. +You can remember the order in which the last three planets come by +their initial letter, S-aturn, U-ranus, and N-eptune, spelling the +word SUN, around which they all revolve. + +It may be interesting to state here that the ancients knew of seven +only of these planets. Since, as they asserted, there were only seven +days in the week, and seven openings into the head; i. e., two for the +eyes, two for the nostrils, two for the ears, and one for the mouth, +it was natural that there should be but seven planets. During later +years, however, an eighth planet was discovered and named Neptune. It +would be interesting to explain to you how the position of this planet +was reasoned out by mathematical calculations, that is, in other +words, how, as a result of such calculations, an astronomer was told +that if he would point his telescope to a certain part of the heavens +he would discover a new planet. He did this and located the planet +Neptune. However interesting this story may be it belongs properly +to astronomy, and will be described in full in the Wonder Book of +Astronomy. + +In the opinion of some astronomers it is quite probable that a ninth +planet will be found far beyond the orbit of Neptune. There may also +be some additional planets discovered between Mercury and the Sun. + +Besides the eight known planets there exist, somewhere between the +orbits of Mars and Jupiter, many smaller planets called _asteroids_, +or _minor planets_. A long time ago it was pointed out by Bode that +a curious relation exists between the distances of the planets from +the sun. This relation or law is generally known, after the name of +the astronomer who first called attention to it, as _Bode's Law_. +No reason has been discovered for this arrangement of the planets, +so that Bode's Law may be regarded as empirical. It may, however, +be mentioned here that the distances of all the planets from the +sun agrees with the law very closely, with the single exception of +Neptune, which is quite at variance with the law. + +It was noticed at an early date, that a gap existed between Mars +and Jupiter, so that astronomers began to believe that there was +probably a missing planet in that space, and this belief was greatly +strengthened when Neptune was discovered in 1781. Without going any +further into this story in this book, it may be said that it is the +general opinion of astronomers that the planetoids or asteroids were +formed possibly from the fragments of the missing planet, or, more +probably, from the breaking up of some of the outer rings on the +planet Mars. + +The distances of the planets from the central sun vary from the +nearest planet, Mercury, which is about 36,000,000 miles from the sun, +to the furthest, or Neptune, which is 2,766,000,000 miles from the sun. + +All the major planets have a single moon, or more, revolving around +them. For example, Jupiter has four moons; Uranus, six; Saturn, eight; +Neptune, one. As to the minor planets, Mars has two moons; and, as far +as is known, neither Mercury or Venus has a moon. Our earth has one +moon, but, as we shall afterwards see, this is not to be regarded as +a moon or satellite of the earth, but rather as a twin planet to the +earth. + +LaPlace's nebular hypothesis was proposed by LaPlace during the year +1796. While there are many objections that can be brought against +it, since it fails to account for all of the phenomena of the solar +system, yet it is a significant fact now, in the year 1907, nearly a +century and a quarter after the hypothesis was first announced, that +although modified in many respects, there has not been any hypothesis +proposed to entirely replace it. + +While the nebular hypothesis of LaPlace is necessarily a matter that +belongs to astronomy, yet it will be advisable to consider it here, +since it explains the source of the original heat of both the earth +and the moon, which we believe is the true cause of volcanoes. + +In his nebular hypothesis, LaPlace assumes that all the materials of +which the solar system is formed, were originally scattered throughout +space in the shape of an exceedingly rare form of matter known as +nebulous matter. He points out that if it be granted that this medium +began to accumulate around a common centre, so as to form a huge globe +or sphere, and if a motion of rotation on its axis from west to east +were given to this sphere that, on strictly mechanical principles, a +system of heavenly bodies corresponding to the solar system might have +been evolved. Let us, therefore, try to understand how this might have +been brought about. + +The nebulous matter that LaPlace assumed originally constituted all +the matter in the solar system, was highly heated gaseous matter. In +other words, it consisted of ordinary matter raised to a very high +temperature; LaPlace thought at a temperature very much hotter than +that of the sun. + +As this great mass of matter commenced to cool, it began to collect +around a centre and slowly rotate. Its contraction or shrinkage, while +cooling, must have caused an increase in the speed with which it spun +around or rotated on its axis. At first it spun but sluggishly, but as +it cooled and began to shrink this rate of rotation began slowly to +increase. + +Now you must bear in mind that the huge rotating mass, as imagined +by LaPlace, was very many times larger than the size of our present +sun. Indeed, instead of having a diameter of only 866,500 miles, its +temperature was so high that the nebulous matter of which it was +composed had expanded it so much that it extended far beyond the orbit +of Neptune, or had a diameter twice as great as 2,766,000,000 miles. + +As the huge mass continued to shrink or contract, its rotation +began to gradually increase until at last its centrifugal force was +sufficiently great to cause it to bulge out at the equator, so as +at last to separate a ring of gaseous matter. This ring was left +behind by the sun, as it continued cooling, and formed the first +planet that was born into the solar system. The ring might have +continued to revolve around the sun for a time, and would, of course, +revolve in the same direction as that in which the sun was rotating, +that is, from west to east. Eventually, however, it broke up into +smaller fragments, that afterwards collected in a single body, and, +assuming a globe-like shape of the planet, formed the planet Neptune. +Necessarily, too, the planet so formed not only would revolve in its +orbit from west to east in the same direction in which the sun was +revolving on its axis, but would also rotate or spin on its axis in +the same direction. + +After, in this way, throwing off the first planet, the central sun +continued to cool and grow smaller, until the increase in the rate +of its rotation was again such as to permit its centrifugal force to +form a second ring around its equator, which being left as the sun +continued to contract, gave rise to another planet, or to Uranus, and +so on until the four major planets and the four minor planets were +born. + +According to this hypothesis, the planet that was first born was the +planet that is farthest from the sun, that is, Neptune, and the planet +last born must have been the nearest planet, Mercury. + +But while all this planet forming was going on, the separate planets +also continued to shrink, and, therefore, began to rotate more rapidly +on their axes. Under the influence of the centrifugal force, ring-like +masses began to form around their equators, and these masses left by +the planet constituted their moons or satellites. As you can see, +according to this hypothesis, just as the planets would all revolve in +their orbits from west to east, and rotate on their axes in the same +direction as the sun, so, too, the moons or satellites of the planets +would also rotate on their axes, from east to west, and revolve in +their orbits in the same direction. + +In order to show the extent to which LaPlace's nebular hypothesis +explains the peculiarities of the solar system, we must inquire what +are the most important of these peculiarities. We will take these from +Young's general book on Astronomy, from which most of the facts in +this chapter have been condensed. They are as follows: + +The orbits of nearly all the planets and their satellites are nearly +circular; they are all in the same plane; and all revolve in the same +direction. They are, moreover, with the single exception of Neptune, +arranged at distances from the sun in accordance with Bode's Law. + +All the planets increase in both directions, towards and from the sun, +in density from Saturn, the least dense. + +All the planets, with the exception probably of Uranus, rotate in a +plane that is nearly the same as the plane of the orbit in which they +revolve. Moreover, with the exception of probably both Uranus and +Neptune, all the planets rotate in the same direction as that in which +they revolve. + +The satellites revolve in orbits whose planes nearly coincide with the +plane of the planets' rotation, while the direction of the revolution +of the satellites is the same as that in which their planets revolve. + +Finally, the largest planets rotate most swiftly. + +Now, LaPlace's nebular hypothesis explains nearly all of the above +facts. The following modifications of the hypothesis, however, are +necessary. Let us briefly examine some of these modifications. + +In the first place it can be shown that the original nebulous mass +instead of being at a higher temperature than that of the sun was +probably at a much lower temperature, since the condensation of +the gaseous matter must have increased the temperature. Instead, +therefore, of the original nebulous mass being purely gaseous it was, +as Young expressed it: "Rather a cloud of ice cold meteoric dust than +an incandescent gas or a fire mist." Or in other words, the original +nebulous mass from which the solar system was evolved, consisted of +finely divided particles of solid or liquid matter surrounded by an +envelope of permanent gaseous matter. + +A doubt, too, has been raised as regards the manner in which the +planets were liberated from the central sun. Instead of separating in +the form of a regular ring, it has been thought that probably in most +cases this separation assumed the shape of a lump. It might, however, +have occurred at times in the ring-like form as may be seen in the +case of the planet Saturn. + +Again, instead of the outer rings being separated first, and the +others in regular order, so that the outer planets are much the older, +it would seem possible, or, as Young states, even probable, that +several of the planets may be of the same or nearly the same age, as +they would be if more than one ring had been separated at one time, +or, indeed, several planets may have been formed from different zones +of a single ring. + +As you will see, LaPlace's nebular hypothesis assumes that both +sun and moon were in a highly heated condition when they were +separated from the nebulous sun, so that we can understand that the +former molten condition of their interiors was due to the heat they +originally possessed. + + + + +CHAPTER XIX + +THE EARTH'S HEATED INTERIOR, THE CAUSE OF VOLCANOES + + +As we have already seen, the nebular hypothesis of LaPlace would seem +to make it more than probable that the earth was originally in a +highly heated condition, and only reached its present state after long +cooling. While this cooling has gone on for probably millions upon +millions of years both before and during the geological past, yet in +the opinion of perhaps the best geologists the interior of the earth +is still very hot, only the outer portions or crust having hardened by +loss of heat. + +That there is a very hot region somewhere inside the earth is evident, +since from some place or places below the surface there come out +the immense streams of lava that, continuing to flow at irregular +intervals, have at last built up such great masses of land as the +island of Hawaii, the still greater island of Iceland, the even +greater lava fields of the western United States, and the great +plateau of the Deccan in southern Hindustan. + +It certainly must have required a great quantity of lava to build up +an island like Hawaii with its area of fully 40,000 square miles, for +the highest point on the summit of Mt. Kea reaches 13,805 feet above +the level of the sea, and, moreover, stands on the bed of the Pacific +Ocean in water fully 12,000 feet deep. + +But Iceland is only one of many similar cases. Volcanoes are to +be found in practically all parts of the earth, not only in the +equatorial regions, where they are especially numerous, but also in +the frigid and temperate zones. We must also remember the immense lava +streams that are known to have come from the interior during the great +fissure eruptions of the geological past. When all these facts are +taken into consideration, it would certainly seem that there is only +one source sufficiently great to supply this wonderful demand, and +that is the entire inside of the earth. + +But entirely apart from volcanic phenomena there are other proofs that +the entire interior of the earth is in a highly heated condition. The +differences of temperature caused by the sun during day and night +do not affect the earth much below a depth of three feet, while the +differences of temperature between summer and winter do not extend +much further below the surface than forty feet. Below these depths, in +all parts of the earth, the temperature of the crust rises at a rate, +which, although not uniform, yet is not far from an increase of one +degree of the Fahrenheit thermometer scale for every fifty or sixty +feet of descent. + +If the above rate of increase continues uniform the temperature of +the crust would be sufficiently hot to boil water at a distance of +about 8,000 feet below the surface, while at a depth of about thirty +miles the temperature would be sufficiently high to melt all known +substances at ordinary conditions of atmospheric pressure; that is, to +melt all known substances if they were subjected to such a temperature +at the level of the sea. + +In considering the above we must not lose sight of the fact that this +increase in temperature with descent below the surface of the earth's +crust occurs, not only in places where there are volcanoes, but over +all parts of the earth, thus seeming to point out that there is +something hot below the surface which fills the entire inside of the +earth. + +It is true the greatest distance to which man has actually gone down +through the earth's crust is but a few miles. We do not, therefore, +know by actual experience that the interior is anywhere in a fused +condition, yet the escape of lava or molten rocks in all latitudes, +and in the enormous quantities referred to above, seems to show that +the entire inside of the earth is at a temperature sufficiently high +to melt all known substances under ordinary conditions. + +It may be interesting in this connection to examine some of the proofs +of this increase in temperature with descent below the surface. The +following figures are given by Dana: + +Borings to great depths have been made in various parts of the earth, +both for artesian wells as well as for the shafts of mines. After +passing the line of invariable temperature, the rate of increase for a +total distance of 4,000 feet below the surface is in the neighborhood +of from one degree for fifty-five to sixty feet, or an average of +fifty-seven and a half feet for each degree of heat. In the case of +the deep artesian well bored at Grenelle, Paris, where a temperature +of eighty-five degrees Fahrenheit was reached at a distance of 2,000 +feet, the rate of increase was somewhat more rapid, being one degree +Fahrenheit for every sixty feet. + +In a deep well bored in a salt mine at Neusalzwerk, Prussia, a depth +of 2,200 feet showed a temperature of ninety-one degrees Fahrenheit at +the bottom. This was at the rate of one degree for every fifty feet of +descent. At Schladenbach, in Prussia, a well has been dug to the depth +of 5,735 feet with a temperature of 134° F. A boring at Wheeling, in +West Virginia, reached a depth of 4,500 feet, 3,700 feet below the +level of the sea. Here the rate of increase of temperature in the +upper half was one degree Fahrenheit for every eighty feet, and in +the lower half of one degree for every sixty feet. + +It must not be supposed because the rate of increase of temperature is +not uniform that the argument of a highly heated interior is weakened. +On the contrary, it would be very surprising if the rate continued +uniform; for it is evident that the conducting power of different +materials in the earth's crust for heat must necessarily make a great +difference in the rate at which heat should increase, as we go farther +down into the earth. This is so important a matter that I will explain +it at somewhat greater length. + +Let us suppose that instead of the highly heated interior of the +earth, we consider the simple case of a hot stove, the doors or other +openings into which are closed so that it is impossible to see the +red hot coals inside. Now, suppose holes were bored in the sides of +this stove not deep enough to reach the red hot mass within, and that +tightly fitting rods or plugs all of the same length and thickness, +but of different kinds of materials such as wood, earthenware, glass, +iron, copper, silver, and gold, etc., were so placed in the holes as +to tightly fit them. Now, under these circumstances the end of all +the plugs would be at the same distance from the heated inside. They +would not, however, by any means show the same temperatures, the +metallic rods would be too hot to touch, while the end of the piece +of wood would hardly be hot enough to burn the hand when held against +it. The piece of glass and earthenware though less cool would be much +less hot than the different rods of metals. Their temperatures would +be necessarily affected by their conducting power for heat. The wood, +the glass, and the earthenware being poorer conductors than the metals +would show much lower temperatures. + +Now, the same thing is true with the different materials that +constitute the rocks of the earth's crust. Some of these are much +better conductors of heat than others, so that the rate of increase of +temperature with descent below the surface must necessarily vary with +the kind of materials that form the crust of different parts of the +earth. + +You may, therefore, safely conclude that the entire interior of the +earth is in a highly heated condition, and that the source of this +heat is to be traced to the heat the earth originally possessed when, +in accordance to the nebular hypothesis of LaPlace, it was separated +from the sun which gave birth to it, that the present crust of the +earth has been formed on the outside by the loss of a portion of this +heat. + +The rapidity with which a body cools, depends, among other things, +on the difference between its temperature and that of the medium in +which it is placed. The greater this difference of temperature the +greater the rapidity of cooling. Careful measurements made by Tait, +the English physicist, show that our earth loses every year from each +square foot of surface, an amount of heat that would be able to raise +the temperature of one pound of water from the melting point of ice to +the boiling point of water, or from 32° F. to 212° F. The rate of loss +of heat, must, therefore, have been much greater when the earth was +more highly heated than it is now, and will be much smaller than now +many years from the present. + +Now, let us suppose, what nearly everyone acknowledges to be true, +that the earth was originally so hot as to be a molten globe, and that +while in this molten condition, it began to revolve or move around the +sun. Since the empty space through which the earth moves is very cold, +something in the neighborhood of 45° below the zero of the Fahrenheit +thermometer scale, the loss of heat would take place very rapidly and +a thin crust of hardened materials would be formed on the outside. Now +all the time the earth is cooling, it is shrinking or growing smaller. + +A very little thought will convince you that this cooling or shrinkage +could not go on uninterruptedly; for, while the earth was cooling it +was contracting, or growing smaller, and in this way a great pressure, +or as it is generally called in science, a great stress was being +produced. Every now and then this stress became so great that the +crust of the earth was fractured or broken. + +At first these fractures would not require a very great amount of +stress or force, since the crust of lava was then very thin. After +great periods of time, however, the crust grew thicker and thicker, +and the amount of force required to break it continually increased, so +that the fractures of the crust produced a greater disturbance. + +Whenever the earth's crust was fractured in this way the earth was +shaken by what are called earthquakes, while a part of the molten +interior would run out or escape, making volcanoes. In the very early +times neither the earthquakes or the volcanoes were as energetic as +they were at later periods when the thickness of the earth's crust +increased. + +Now, having as we believe correctly come to the conclusion that the +entire interior of the earth is in a highly heated condition, the +next question that arises is as to the present condition of this +interior. A long time ago it was believed that the interior of the +earth is still melted, and that a cooled portion or crust surrounds +a great molten mass that fills all the inside; that it is this mass +which supplies the immense quantities of molten rock or lava that +escape through the craters of volcanoes or through the fissures in +the crust. Without going into this question thoroughly, since it is a +very difficult question to understand, it will be sufficient to say +that there are many reasons why it is impossible to believe that the +interior is still melted. + +You will understand that if the interior of the earth were melted like +a huge central sea of fire that each volcano would necessarily affect +all the others. Now, as we have seen, this is never the case, so that +this is one reason we cannot believe in the existence of a melted +interior. + +Another reason we cannot believe in a molten interior is an +astronomical consideration. It can be shown that under the attraction +of the sun and moon the earth could not possibly behave as it does +if it were still liquid in the interior. That, on the contrary, the +behavior of the earth to the attraction of the sun and moon is such as +to make it necessary for us to believe that it is as rigid throughout +as would be a globe of steel of the same size. + +I can easily understand that you find it very difficult to see how it +can be believed that the interior of the earth is solid and yet at the +same time be sufficiently hot to melt. I can imagine hearing you ask +if it is hot enough in the inside to melt any known materials, why it +is not melted. The reason, however, is very simple when you come to +think it over. For a solid to fuse or become melted, it is not only +necessary for it to be heated to a temperature which is different for +different substances, but that at the same time it is heated it shall +have plenty of room in which to expand or grow bigger. In other words, +the temperature required to fuse any substance increases very rapidly +with the pressure to which that substance is exposed. + +Now, try to think of the pressure to which the materials that fill +the inside of the earth are subjected at great distances below the +surface. This pressure is enormous, not only by reason of the weight +of the many miles of rocks that are pressing down, but also by reason +of the enormous stress or pressure caused by contraction or shrinkage. +When we say that the interior of the earth is hot enough to melt all +known substances we mean hot enough to melt them if they could be +brought from great depths to the level of the sea, but not hot enough +to melt them when subjected to the great pressure that exists in +regions far below the surface of the earth. + +Briefly, the condition of things is believed to be as follows: The +entire interior is filled with rock hot enough to melt at the level +of the sea, but under too great pressure to melt. If this be granted, +as it is by perhaps the greatest number of men who are competent to +judge, the phenomena of earthquakes can be readily explained, as can, +indeed, the phenomena of those great movements whereby great changes +of level take place in different parts of the earth. + +Now let us see how volcanoes can be explained on the assumption that +the interior of the earth is hot enough to melt, but remains solid +only because there is no room for the heated mass to expand in. Such +a heated interior as we have imagined, must be constantly losing its +heat and, therefore, shrinking. Every now and then this shrinkage must +produce great fissures or cracks in the solid crust of the earth. +Now should such cracks or fissures extend downwards to the heated +interior, there must result a decrease in the pressure. The rocks +would, therefore, begin to expand and would be forced by the great +pressure to rise slowly in such cracks or fissures. The further they +rise the greater the relief of pressure, until they at last assume a +molten condition in which they are forced out through the craters of +volcanoes as molten rocks or lava. + +But it is not only volcanoes that seem to indicate a highly heated +plastic condition as existing in the earth's interior. As geologists +well know, there are to be found in the various strata of the earth +places where great fissures have been made at various times during the +geological past. These fissures vary in width from a few inches to +many hundreds of feet, and are frequently scores of miles in length. +Lava either flows out of them, and covers adjoining sections of the +country, or simply rises in them and, afterwards cooling, forms dikes. +In many instances, however, the lava is forced in between more or less +horizontal layers and in some cases has caused these layers to assume +the shape of what geologists know as _subtruderant mountains_. Some +of the eastern ranges of the Rocky Mountains have been formed in this +manner. + +We can, therefore, picture to ourselves the following as the manner +of formation of an ordinary volcano. A fissure is first formed in the +solid crust of the earth, extending downwards to the regions of great +heat. There is thus produced a relief of pressure, so that at this +point the highly heated rocks begin to be slowly forced up through the +fissure. As they rise higher and higher they become less solid and +finally expand into fused masses that can flow out of the crater or +opening in the earth's surface. In this way a volcano is started. + +But for this volcano to continue in eruption, it is necessary that +the conditions shall continue that force the molten rock upwards from +great depths. It is not enough for the lava to fill the crevice that +exists upwards to the surface, it must continue to be forced upwards +until it escapes. If it is permitted to remain in the fissure for any +time, it hardens, and only great dikes are formed. It would seem, +therefore, that some other force must be called into action to keep +the fissure open or, in other words, to prevent the chilling of the +lava. Now, this force is generally believed to be the expansive force +of steam or the vapor of water. + +As Dana points out, by far the greater part of the vapor which escapes +from the craters of volcanoes consists of steam or the vapor of water. +Indeed, it can be shown that for every hundred parts of different +vapors, at least ninety-nine of such parts consist of water vapor. It +is for the greater part, to the pressure of steam or water vapor that +the escape of lava from the tube near the top of the crater is due. + +Of course, the question arises as to where the water comes from that +produces this steam. There are three possible sources. From the rains; +from leakage at the bed of the ocean; and from vapors existing at +great depths below the surface. + +It is not probable that either rain water, or water from the ocean, +penetrates through the earth's crust for distances much greater than a +few thousand feet. It is, however, very well known that in all parts +of the earth, except in desert regions, whether they are near or far +from the ocean, the rocks are always found fully charged with water. +When, therefore, the slowly rising lava passes through the moist rocks +that everywhere form the crust of the earth, there must be formed in +them great quantities of steam under very high pressure. Moreover, +many substances, especially those forming lava, possess the power of +absorbing large quantities of steam and other gases. Therefore, as +the molten material reaches the moist rocks in the earth's crust, it +becomes highly charged with steam, and as the lava rises towards the +surface this steam expands. + +Where the lava is in a very fluid condition the steam quietly escapes, +as does the steam from the surface of boiling water. But where the +lava is viscous, like tar or pitch, great bubbles are formed, which, +on their explosion, throw the lava upwards for great distances into +the air. + +We can, therefore, account in this manner for both the non-explosive +as well as the explosive type of volcanoes. + +It must not be supposed, however, that it is the explosive power of +steam which is the principal cause of the lava rising upwards from +great depths. This is caused by the great pressure or stress set up +by the contraction of a cooling crust. The pressure of this steam is +added to this pressure which keeps the lava flowing upwards from great +depths below. + +The objection has sometimes been urged that it is impossible to +believe the lava comes from a highly heated interior, because, as is +well known, lavas are of different types even when coming from the +same volcano at different times of eruption. While such an objection +would have weight were it believed that the interior of the earth is +still in a molten condition, it loses its weight when one believes +that the interior is solid. It must, however, be acknowledged that +the largest part of the interior of the earth would probably have the +same chemical composition if it had ever been in a completely melted +condition throughout. + +I do not doubt you have already concluded that the reason the earth's +volcanoes are practically limited to the borders of continents, +or to the shores of islands, is the leakage of the ocean waters +into the crust at these parts. This was at one time believed by +most geologists. That sea water has much to do with such volcanoes +as Vesuvius there is no doubt, but it is now generally recognized +that it is not so much the present outlines of the earth, or the +present arrangement of its land and water areas, that determines the +distribution of the world's volcanoes. It is rather believed that the +location of the lines of fractures along which the earth's volcanoes +are found were determined by conditions that occurred long before the +earth assumed its present outlines. + +But there is another explanation that has been suggested as regards +the condition of the interior of the earth. Judd refers to this +explanation as follows: + + "Some physicists have asserted that a globe of liquid + matter radiating its heat into space, would tend to + solidify both at the surface and the centre at the + same time. The consequence of this action would be the + production of a sphere with a solid external shell and a + solid central nucleus, but with an interposed layer in a + fluid or semi-fluid condition. It has been pointed out that + if we suppose the solidification to have gone so far as + to have caused the partial union of the interior nucleus + and the external shell, we may conceive a condition of + things in which the stability and rigidity is sufficient to + satisfy both geologists and astronomers, but that in still + unsolidified pockets or reservoirs, filled with liquefied + rock, between the nucleus and the shell, we should have + a competent cause for the production of the volcanic + phenomena of the globe. In this hypothesis, however, it is + assumed that the cooling at the centre and the surface of + the globe would go on at such rate that the reservoirs of + liquid material would be left at a moderate depth from the + surface, so that easy communication could be opened between + them and volcanic vents." + +I must caution you, however, not to think that the above theory of +volcanoes is accepted by all scientific men. On the contrary, there +are many who believe that the earth is solid throughout because it +has completely lost its original heat; that it is only comparatively +small areas that are to be found filled with molten or at least highly +heated material. But these opinions are held largely by those who have +given their attention almost entirely to the phenomena of earthquakes, +or who base their reasonings on mathematical grounds only and have not +sufficiently considered the phenomena of volcanoes. Since, however, +they can be better understood after we have explained the phenomena of +earthquakes, we will defer their discussion to the last chapters of +this book. + + + + +CHAPTER XX + +SOME FORMS OF LAVA + + +In describing the wonders of volcanoes, we must not fail to say +something of the many remarkable forms that lava is capable of +assuming. + +All volcanic lavas contain large quantities of an acid substance known +as _silica_, or what is known better as _quartz sand_. This material +exists in lava combined chemically with various substances called +bases, the principal of which are alumina, magnesia, lime, iron, +potash, and soda. + +Although there are many kinds of lava, yet all lavas can be arranged +under three great classes according to the quantity of silica they +contain. + +_Acid lavas_ are those in which the quantity of silica is greatest. +In these lavas the silica, which varies from 66 to 80%, is combined +with small quantities of lime or magnesia, and comparatively large +quantities of potash or soda. Some of the most important varieties of +acid lavas are known as _trachytes_, _andesites_, _rhyolites_, and +_obsidians_. + +_Basic lavas_ are those containing from 45 to 55% of silica. They +are rich in lime and magnesia, but poor in soda or potash. Some of +the most important of basic lavas are the _dolerites_ and _basalts_. +Generally speaking, basic lavas are of a darker color than acid lavas, +and fuse at much lower temperatures. + +_Intermediate lavas_ are those containing silica in the proportion of +from 55 to 66%. + +While the temperature of liquid lava has not been very accurately +determined, yet, since we know that molten lava is able to melt silver +or copper, its temperature must be somewhere between 2,500° F. and +3,000° F., the melting point varying with the chemical composition. + +According to Dana lavas can be divided into the following classes +according to their fusibility; i. e., _lavas of easy fusibility_, such +as _basalts_; these lavas fuse at about 2,250° F.; _lavas of medium +fusibility_, including andesites; these lavas fuse at about 2,520° F.; +_lavas of difficult fusibility_, such as trachytes; these lavas fuse +at about 2,700° F. + +But what is, perhaps, most curious about lavas is that when the +surface of a freshly broken piece of cold lava is carefully examined, +it is found to contain a number of small crystals of such mineral +substances as quartz, feldspar, hornblende, mica, magnetite, etc. + +The best way to study the different forms of lava crystals is to +prepare a thin transparent slice of hardened lava and then examine it +with a good magnifying glass. It will be found that the slice consists +of a mass of a glass-like material through which the crystals are +irregularly distributed, not unlike the raisins and currants in a +slice of not over rich plumcake. + +When examined by a more powerful glass, such as a microscope, cloudy +patches can be seen distributed irregularly through the glass-like +mass. When these patches are examined by a higher power of the +microscope they are seen to consist of small solid particles of +definite forms known as _microliths_ and _crystallites_. It has been +shown by a careful study of these minute objects that they form the +exceedingly small particles of which crystals are built up. + +If we fuse a small quantity of lava and then let it slowly cool, the +glassy mass will be found to contain numerous crystallites. On the +other hand, when fused lava is permitted to cool quickly, it takes on +the form of a black, glass-like mass known as _obsidian_ or _volcanic_ +glass, a very common form of lava in some parts of the world. + +In some lavas there are found larger crystals that appear to have been +separated from the glassy mass, under the great pressure that exists +in the subterranean reservoirs at great depths below the volcanic +crater, and then floated to the surface surrounded by the glass-like +material. Now when we examine these crystals with a higher power of +the microscope, we frequently find in them minute cavities containing +a small quantity of liquid and a bubble of gas, thus causing them to +resemble small spirit levels. The liquid in such cavities has been +examined chemically and in most cases has been found to consist of +water containing several salts in solution. Sometimes, however, the +liquid consists of liquefied carbonic acid gas. These wonderful things +will be discussed at greater length in the Wonder Book of Light. + +When the mass of molten rock or lava that comes out of the crater +of a volcano is thrown upwards in the air the condition it assumes +by the time it falls back again to the earth depends on the height +it reaches. If this height is great the lava chills or hardens +before reaching the earth, and assumes various forms according to +the size of the fragments. The largest of these fragments are called +_cinders_; the finer particles _volcanic dust_; while most of those +of intermediate particles are known among other things as _volcanic +ashes_. + +We have already seen that when an explosive volcanic eruption occurs +there is suddenly thrown out of the crater of the volcano a huge +column of various substances that rises sometimes as high as 30,000 +feet or even more. The smaller fragments of lava are quickly cooled +and form volcanic ashes, sand, cinders, or dust. These are rapidly +spread out by the wind in the form of a black cloud, that not only +covers the mountain but reaches out over the surrounding country, +completely shutting off the light of the sun. From this cloud +particles of red hot ashes, cinders, sand, etc., begin to fall, the +largest particles near the crater of the volcano, and the smaller +particles at much greater distances. In very powerful explosive +volcanic eruptions such as Krakatoa, the finer dust may be carried to +practically all parts of the world. + +Volcanic ashes consist of a fine, light, gray powder. These particles +take the name ashes from their resemblance to the ashes left after the +burning of pieces of wood or coal in an open fire. The name, however, +as Geicke points out, is unfortunate, since it is apt to lead one to +suppose that volcanic ashes consist of some burned material. Such an +idea is erroneous, however, since ashes do not consist of anything +that is left after burning, but merely of fine particles of molten +rock that have hardened by cooling. When in the shape of what is known +as volcanic dust these particles are so exceedingly small that they +can readily make their way through the smallest openings in a closed +room just as does the finest dust in the rooms of our houses when +they are shut up. There are cases on record where people have been +suffocated by the entrance of volcanic dust in closed rooms to which +they have fled for safety during volcanic eruptions. + +_Volcanic sand_ consists of the coarser particles of chilled lava that +are partly round and partly angular. They are of various sizes up to +that of an ordinary pea. Volcanic sand is formed by the breaking up of +the lava by the explosion of the vapors as they escape from the lava +on relief from pressure. Volcanic dust when examined by the microscope +is found to consist of very small particles that are more or less +crystalline. + +But besides the above there are larger fragments known as _lapilli_, +consisting of rounded or angular bits of lava varying in size from +that of a pea to an ordinary black walnut. These sometimes consist of +solid fragments, but are usually porous, sometimes so much so that +they readily float on water. + +A curious form sometimes assumed by lava consists of what are called +_volcanic bombs_. These are formed during explosive eruptions, +when masses of liquid lava are hurled high up into the air. During +their flight they take on a rotary motion, which tends to make them +globular, so that cooling, while still revolving, they assume the +form of a more or less spherical mass. At times, however, they are +still sufficiently soft when they strike the earth to be flattened out +in the form of flat cakes. When of a spherical form these are very +properly called volcanic bombs. + +That volcanic bombs have actually been subjected to a spinning motion +while in the air can sometimes be shown by the fact that masses of +scoriæ are frequently found in the interior with air cells largest at +the centre of the bomb. + +Volcanic bombs are sometimes thrown from the crater to great +distances. During one of its recent eruptions, Cotopaxi threw out +bombs that fell at a distance of nine miles from the crater. + +According to Dana another form of lava bombs is sometimes found on the +slopes of the active volcanoes of Hawaii, where masses of lava acquire +a ball-like shape while rolling down an inclination. + +What are sometimes called volcanic bombs, but which are more properly +_volcanic vesicles_, are produced by small fragments of lava which +are thrown up in the air for only a moderate height and, on cooling, +assume pear-like forms. Fig. 25 represents the appearance of volcanic +vesicles. The direction in which these vesicles moved through the air +while in a molten state is indicated by their shape, the blunt end +being the end towards which the particles were projected. + +[Illustration: FIG. 25. VOLCANIC VESICLES _From Dana's Manual +of Geology_] + +But by far the greater portion of the hardened lava; i. e., the +coarser, heavier particles, fall back on the mountain, and collecting +around the crater build up volcanic cones, as already described in the +case of mountains of the Vesuvian type. + +There are two different ways in which the melted lava is broken up +into fine particles when it is thrown upwards from the crater of the +volcano. Nearly all lava contains large quantities of steam that are +shut up, or occluded in the mass, being prevented from escaping by +reason of the pressure to which the lava is subjected. The lava is +released from this pressure as it is thrown out of the crater. The +steam or gases escape explosively and thus break the lava into fine +liquid spray, which rapidly hardens. + +There is another way in which small particles of lava are formed. +Sometimes large pieces of hardened lava are shot upwards into the air +with a velocity as great as that with which a heavy projectile leaves +the muzzle of a large gun. These heavy particles striking against +one another, either while rising or falling, are broken into smaller +fragments. Sometimes, indeed, these fragments fall back again into +the crater from which they are again violently thrown out, and are +again broken into smaller fragments either while rising or falling. + +You will, probably, remember several instances of volcanic eruptions +where masses of rock were thrown violently up into the air out of +the crater. These larger masses are known as _volcanic blocks_. They +probably consist of masses of hardened lava that have collected in +the tube of the volcano during some of its periods of inactivity. +Sometimes, however, they consist of fragments of rocks that are not +of volcanic origin. Cases are on record where volcanic blocks have +been thrown out of the craters in so great quantities as to cover the +surface of many square miles of land with fragments hundreds of feet +deep. + +There is sometimes formed on the surface of a pool of lava as it +collects in the craters of such volcanoes as Mt. Loa or Kilauea, when +the volcanoes are not in eruption, a material resembling froth or +scum. The same thing sometimes occurs on the surface of some kinds +of lava as it runs down the side of the mountain. In this way a very +light variety of highly cellular lava known as _pumice stone_ is +produced. The action which thus takes place is not unlike that which +occurs during the raising of a lot of the dough from which bread is +made, where the carbonic acid gas which is formed during the raising +of the dough expands, and produces the well-known open cellular +structure of well-raised bread. In the case of pumice stone, however, +this raising goes on to such an extent that the mass consists often of +less than 2% of solid matter, the remainder being a tangled mass of +air. + +[Illustration: THE LAVA FLOW OF THE CRATER OF KILAUEA, HAWAIIAN +ISLANDS _From a Stereograph, Copyright, by Underwood & Underwood_] + +Fragments of lava that possess a cellular structure form what are +known as _scoriæ_. The lightest of all kinds of scoriæ is what is +known as _thread-lace scoriæ_. Here the thin walls consist of mere +threads. Figs. 26 and 27 represent the appearance of thread-lace +scoriæ from Kilauea. The separate threads are very fine, being only +from one-thirtieth to one-fortieth of an inch in thickness. As can be +seen, this form of scoriæ have six-sided or hexagonal shapes. You can +form some idea of the great lightness of such scoriæ when you learn +that they contain only 1.7% of rocky material. Indeed, they contain +so little solid material that a layer of volcanic glass only one inch +thick, if blown out into scoriæ, would be able to produce a layer +sixty inches thick. + +[Illustration: FIG. 26. THREAD-LACE SCORIÆ FROM KILAUEA _From +Dana's Manual of Geology_] + +Another curious form sometimes assumed by lava, especially in the +case of Kilauea, is where the lava is spun out in the form of long +silk-like hairs. This is called by the natives _Pele's hair_, after +the name of their goddess. Inasmuch as the origin of this form of lava +was at one time generally attributed to the action of the wind in +drawing out thread-like pieces from the jets of lava thrown upwards +from the pool, it will be interesting if its true cause is explained. + +[Illustration: FIG. 27. THREAD-LACE SCORIÆ FROM KILAUEA _From +Dana's Manual of Geology_] + +Dutton, in his report on the Hawaiian volcanoes, refers to the +formation of Pele's hair as follows: + + "The phenomenon of Pele's hair is often spoken of in the + school books, and receives its name from this locality. + It has generally been explained as the result of the + action of the wind upon minute threads of lava drawn out + by the spurting up of boiling lava. Nothing of the sort + was seen here, and yet Pele's hair was seen forming in + great abundance. Whenever the surface of the liquid lava + was exposed during the break-up the air above the lake was + filled with these cobwebs, but there was no spurting or + apparent boiling on the exposed surface. The explanation of + the phenomenon which I would offer is as follows: Liquid + lava coming up from the depths always contains more or + less water, which it gives off slowly and by degrees, in + much the same way as champagne gives off carbonic acid + when the bottle is uncorked. Water-vapor is held in the + liquid lava by some affinity similar to chemical affinity, + and though it escapes ultimately, yet it is surrendered + by the lava with reluctance so long as the lava remains + liquid. But when the lava solidifies the water is expelled + much more energetically, and the water-vapor separates + in the form of minute vesicles. Since the congelation of + all siliceous compounds is a passage free from a liquid + condition through an intermediate state of viscosity to + final solidity, the walls of these vesicles are capable of + being drawn out as in the case of glass. The commotion set + up by the descending crust produces eddies and numberless + currents in the surface of the lava. These vesicles are + drawn out on the surface of the current with exceeding + tenuity, producing myriads of minute filaments, and the + air, agitated by the intense heat at the surface of the + pool, readily lifts them and wafts them away. It forms + almost wholly at the time of the break-up. The air is then + full of it. Yet I saw no spouting or sputtering, but only + the eddying of the lava like water in the wake of a ship. + The country to the leeward of Kilauea shows an abundance + of Pele's hair, and it may be gathered by the barrelful. A + bunch of it is much like finely shredded asbestos." + +You have probably often seen the beautiful frost pictures that collect +on the panes of glass in a room where the ventilation has been +neglected. These pictures consist of groupings of ice crystals that +collect on the surface of the windows, when the moist vapor-laden +air in the room is chilled by contact with their cold surfaces. Now +the crystals formed in cooling lavas are sometimes grouped in forms +closely resembling frost pictures. A few of such forms are represented +in Figs. 28 and 29 in lava from Mt. Loa and Mt. Kea. + +[Illustration: FIG. 28. FROST-LIKE LAVA CRYSTALS _From Dana's +Manual of Geology_] + +[Illustration: FIG. 29. FROST-LIKE LAVA CRYSTALS _From Dana's +Manual of Geology_] + +Certain varieties of lava, especially that which is found in dikes, +form cool, beautiful columns called basaltic columns. They are due to +the contraction that occurs on the cooling of the material. Instances +of basaltic columns are seen in the Giant's Causeway, on the northern +coast of Ireland, as well as in the Isle of Cyclops on the coast of +Italy. The general appearance of the latter is represented in Fig. 30. + +[Illustration: FIG. 30. BASALTIC COLUMNS, ISLE OF CYCLOPS, +ITALY] + +It is a curious fact that the entire mass of basalt does not generally +take the columnous form but only certain layers which terminate +suddenly above and below at structureless masses of basalt, as shown +in Fig. 31. These columns, however, are always found at right angles +to the cooling surfaces as seen in the figures. They may, therefore, +be inclined at all angles to the horizon. + +[Illustration: FIG. 31. COLUMNAR AND NON-COLUMNAR BASALT] + +When molten lava is only thrown up a short distance into the air +from a crater it is still partially molten when on falling it again +reaches the earth, and therefore clings to any surface on which it +falls. There are thus built up curious cones known as _driblet cones_, +in which the separate drops covering the sides of the cone can be +distinctly traced. Driblet cones are represented in Figs. 32 and 33. +Here, as can be seen, the separate drops can be readily traced as they +run down a short distance before cooling. + +[Illustration: FIGS. 32, 33. DRIBLET CONES _From Dana's +Manual of Geology_] + +We have already referred briefly to the _lava caves_ or _grottoes_, +that are formed in some of the lava streams issuing from Vesuvius, +Etna, or Hawaii. These caves consist either of a number of +communicating huge bubbles, or of the tunnels that are formed in the +lava by the hardening of the outside of the lava streams as they flow +down the sides of the mountain, and towards the close of the eruption +are afterwards emptied by the molten lava within continuing to flow to +a lower level before solidifying. Now, in the interior of these caves, +there are often found on the walls, as well as on the portions of the +floors of the caves, immediately below them, curious pendants, like +icicles, or, more correctly, like the _stalactites of limestone_ that +are seen hanging to the walls of caves in limestone districts, where +they are formed as follows: as the rain water sinks through limestone +strata it dissolves some of the lime, when, slowly falling, drop after +drop, from the roofs of the caverns, small particles of lime are +deposited on the roof, and in this manner a pendant of limestone is +formed. The water that falls to the floor of the causeway immediately +below, also builds up a dome-like hillock called a stalagmite. In due +time the pillar reaches downwards, and the opposite hillock upwards +until the two meet, thus forming great natural pillars that appear +to hold up the roof of the vast cave in which they have been slowly +formed. A number of _lava stalactites_ are represented in Fig. 34. + +[Illustration: FIG. 34. LAVA STALACTITES _From Dana's Manual +of Geology_] + +Now, in a similar manner these lava stalactites, formed in the lava +caves or grottoes, are caused by the stream as it escapes from the +walls of the caves depositing on them stalactites of various lava +minerals it has dissolved as it slowly passed through them. + +But the most important of all volcanic products is _volcanic dust_. +This, as we have seen, is so light that it remains longest in the air, +and is often carried by the winds to great distances from the volcano +from which it escaped. It may interest you to know that some of the +most fruitful of the great wheat fields of the western parts of the +United States owe their extraordinary fertility to immense deposits +of volcanic dust that have been thrown out from some of the great +volcanoes of the geological past, now found in an extinct condition in +these parts of the United States. + +According to Russell, immense deposits of volcanic dust are spread +over vast areas in Montana, Southern Dakota, Nebraska, and Kansas, as +well as over parts of Oregon, and Washington, and, indeed, over large +areas of southwestern Canada and Alaska. + +It is practically certain that many of the eruptions producing this +dust occurred within historic times. There must, therefore, have been +many times in these parts of our country when the dense ash clouds +hiding the sun turned the day into night and destroyed the forests and +other vegetation by showers of red hot ashes. There were produced, +too, the same great dread, and possibly loss of life as common during +historical eruptions. It is pleasing, however, to think that while +these great catastrophes brought suffering and dread to the people who +then lived on the earth, they were, nevertheless, but the forerunners +of those fruitful fields that at a much later age were to bless the +people who afterwards lived on them. + + + + +CHAPTER XXI + +MUD VOLCANOES AND HOT SPRINGS + + +Mud volcanoes are the more or less conical hillocks from which, under +certain conditions, mud is thrown out through the crust of the earth. + +Geikie defines mud volcanoes as follows: + + "Conical hills formed by the accumulation of fine and + usually saline (salty) mud, which, with various gases, is + continuously or intermittently given out from the orifice + or crater in the centre. They occur in groups, each hillock + being sometimes less than a yard in height, but ranging up + to elevations of 100 feet or more. Like true volcanoes, + they have their periods of repose, when either no discharge + takes place at all, or mud oozes out tranquilly from the + crater, and their periods of activity, when large volumes + of gas, and sometimes columns of flame, rush out with + considerable violence and explosion, and throw up mud and + stones to a height of several hundred feet." + +There are two kinds of mud volcanoes: those in which the mud is thrown +out by the action of different kinds of gases, and those in which the +mud is thrown out by the action of steam. + +Mud volcanoes may or not be volcanic phenomena. Those which occur in +the neighborhood of volcanoes whether active, dormant, or extinct, are +probably of volcanic origin. There are others, however, which occur +in regions far removed from volcanoes. These are probably due not to +volcanoes, but to chemical action and the eruptions are caused by the +action of gases. + +The gases producing these eruptions are either carbonic acid gas +(the gas that is given off from soda water); carburetted hydrogen +(the gas that is sometimes seen escaping from the bottom of marshy +ground); sulphuretted hydrogen (a gas that is given off from rotten or +decomposing eggs, and possessing the characteristic odor of decayed +eggs) and nitrogen gas derived from the atmosphere. In mud volcanoes +of the gaseous type the mud is generally cold, and the water salty. In +this latter case the mud volcanoes are also called _salses_. Daubeny +has pointed out that the mud volcanoes of this class that occur in the +neighborhood of Sicily are due to the slow burning or oxidation of +beds of sulphur. + +Mud volcanoes which eject hot mud by the force of eruption of steam, +which occur in volcanic districts, are of volcanic origin. They are +caused by the passage of hot water and steam through beds of volcanic +rock such as tufa, or hardened volcanic mud and other volcanic +products. The hot water or steam raises the temperature of the mud +through which it passes to the boiling point. As Dana remarks, the mud +varies in consistency from very liquid muddy water to a thick mass +like boiling soap, or in some cases like masses of mud or paint, and, +in still other cases, to material like soft mortar, the consistency of +the mud varying with the dryness of the season. + +There are three regions where mud volcanoes are especially common. +One of the best known is in the Yellowstone National Park, four miles +north of Yellowstone Lake, and six miles from Crater Hill. Some of +these mud volcanoes have circular craters about ten feet in depth +around which they have built mounds, the rims of which are several +feet above the general level. + +There are well-known regions of mud volcanoes in different parts of +Iceland. Here, according to Lyell, they occur in many of the valleys +where sulphur vapor and steam bursts from fissures in the ground with +a loud hissing noise. In these regions there are pools of boiling +water filled with a bluish black clay-like paste, that is kept +violently boiling. Huge bubbles, fifteen feet or more in diameter, +rise from the surface of the boiling mass. The volcanoes pile up the +mud around the sides of their craters or basins. + +Another part of the world where mud volcanoes are especially numerous +is on the western shores of the Caspian Sea at a place called Baku. +These are of the gaseous type and are attended by flames that blaze +up to great heights often for several hours. These flames are due to +the presence of natural gas and petroleum vapor that pass out through +the water. Large quantities of mud are thrown out from the craters of +these mud volcanoes. + +There are also many mud volcanoes in a district in India about 120 +miles northwest of Cutch near the mouth of the Indus. In this region +the cone built up around the crater is sometimes as high as 400 feet. + +The following description of mud volcanoes on Java is quoted from +Daubeny's book on volcanoes. + + "It would appear likewise from Dr. Horsfield's description, + that Java exhibits phenomena of a similar kind to those + noticed in Sicily and at the foot of the Apennines, and + there known under the name of 'Salses.' In the calcareous + district (which I suspect to belong to the same class + of formations as the blue clay and tertiary limestone + of Sicily) occur a number of hot springs, containing in + solution a large quantity of calcareous earth, which + incrusts the surface of the ground near it. Of these, some + are much mixed with petroleum, and others highly saline. + + "The latter are dispersed through a district of country + consisting of limestone, several miles in circumference. + They are of considerable number, and force themselves + upwards through apertures in the rocks with some violence + and ebullition. The waters are strongly impregnated with + muriate of soda, and yield upon evaporation very good salt + for culinary purposes (not less than 200 tons in the year). + + "About the centre of this limestone district is found an + extraordinary volcanic phenomenon. On approaching the + spot from a distance, it is first discovered by a large + volume of smoke rising and disappearing at intervals of a + few seconds, resembling the vapors arising from a violent + surf, whilst a dull noise is heard like that of distant + thunder. Having advanced so near that the vision was no + longer impeded by the smoke, a large hemispherical mass was + observed, consisting of black earth mixed with water, about + sixteen feet in diameter, rising to the height of twenty or + thirty feet in a perfectly regular manner, and, as it were, + pushed up by a force beneath, which suddenly exploded with + a dull noise, and scattered about a volume of black mud + in every direction. After an interval of two or three, or + sometimes four or five seconds, the hemispherical body of + mud or earth rose and exploded again. + + "In the same manner this volcanic ebullition goes on + without interruption, throwing up a globular mass of mud, + and dispersing it with violence through the neighboring + places. The spot where the ebullition occurs is nearly + circular and perfectly level; it is covered with only the + earthy particles impregnated with salt water, which are + thrown up from below; its circumference may be estimated + at about half an English mile. In order to conduct the + salt water to the circumference, small passages or gutters + are made in the loose muddy earth, which lead it to the + borders, where it is collected in holes dug in the ground + for the purpose of evaporation. + + "A strong, pungent, sulphurous smell, somewhat resembling + that of earth-oil (naphtha), is perceived on standing near + the site of the explosion, and the mud recently thrown + up possesses a degree of heat greater than that of the + surrounding atmosphere. During the rainy season these + explosions are more violent, the mud is thrown up much + higher, and the noise is heard at a greater distance. + + "This volcanic phenomenon is situated near the centre of + the large plain, which interrupts the great series of + volcanoes, and owes its origin to the same general cause as + that of the numerous eruptions met with in this island." + +There are, in many parts of the world, springs, whose waters issue +from their reservoirs at temperatures either at or near the boiling +point of water. These are called _hot_ or _thermal springs_. Hot +springs are found both in volcanic regions, as well as in regions +where there are no volcanoes, but where there are lines of deep +fissures or faults. According to Dana, in both of these classes, the +cause is to be traced to heat of volcanic or deep subterranean origin. +Hot springs are also found in regions where there are no volcanoes. +In these cases the heat is due to the gradual oxidation of various +sulphide ores, or to some other chemical action. + +The waters of hot or thermal springs almost always contain various +mineral substances in solution. All spring water contains some little +dissolved mineral matter, but in hot springs the quantity of this +matter is greater than in cold springs, because hot water can dissolve +mineral substances much better than can cold water. + +It might surprise you to hear that one of the commonest substances +that is found in solution in the waters of many hot springs is silica; +for silica is practically sand, and sand does not easily dissolve in +water as does sugar. The very hot water, however, which comes from +the hot spring, whose temperature below the earth's surface is very +much higher than it is when it comes out of the spring, possesses +the power of readily dissolving silica from the rocks over which it +flows. When the waters of such springs reach the surface the silica +is deposited in a solid condition around the outlets of the springs. +In this way there are built up craters or mounds, or, more correctly, +crater-shaped basins. + +Sometimes the hot water contains calcareous substances dissolved in +it, the solution being caused not only by reason of the hot water, but +also by means of the carbonic gas it contains. When this water flows +from the springs, it builds up the same crater-shaped mounds, only in +this case the mounds are of lime instead of silica. + +There are peculiar kinds of hot springs called _geysers_, that possess +the power of throwing huge streams of water up into the air at more or +less regular intervals. The word geyser is an Icelandic word meaning +to rage, or snort, or gush, the name being given by reason of the +manner in which the waters rush violently out during an eruption. + +As Dana points out, when the water in a basin of a hot spring merely +boils, whether this boiling is nearly continuous, or the water is +alternately boiling and quiet, the spring is called a hot or thermal +spring, but where the water is thrown violently out at more or less +regular intervals, it is called a geyser. + +The cause of the eruption of a geyser was discovered by Professor +Bunsen, the celebrated German chemist, after a careful study of +the geyser regions in Iceland. The waters of geysers contain large +quantities of either silica or lime in solution. Bunsen traced the +cause of these curious eruptions to be the manner in which the hot +springs pile up cones of silica or limestone around their mouths. + +The water of a geyser generally issues from the top of a more or less +conical hillock, reaching the surface through a funnel-shaped tube. +Both the tube and the basin are covered with a smooth coating of +silica or limestone. In the case of the Great Geyser in Iceland, the +basin is over fifty feet high and seventy-five feet deep. Both the +tube and the basin have been slowly deposited by the hot water of the +geyser. + +It is only when the tube of a geyser has reached a certain depth that +the geyser is able to erupt. Moreover, as soon as this tube passes a +certain depth the geyser can no longer erupt and forever afterwards +becomes an ordinary hot spring. There are, therefore, to be found in +most geyser regions, a number of what might be called young geysers or +merely hot springs, that are not yet deep enough to erupt; others that +have just commenced eruption, others that have reached their prime, +while others that, old and decrepit, have again merely become hot +springs. + +Let us now try to understand the cause of the eruption of a geyser. +Bunsen's explanation, which is now generally accepted, is as follows: + +The heat of the volcanic strata through which the tube of the geyser +extends, gradually raises the temperature of the water that fills +the geyser tube. Since the boiling point of a liquid increases with +the pressure to which it is subjected, far down in the tube of a +geyser, the pressure arising from the weight of the water above it is +sufficiently great to prevent the water from beginning to boil until +it reaches a temperature far higher than that at which it would boil +in the upper parts of the tube. Suppose now, when the water in the +funnel-shaped tube is nearly filled to the top, the water at last +grows hot enough to begin boiling at some point near the middle of +the tube. The pressure of the steam driven off from this portion of +the water raises the column of water above it in the tube and begins +to empty it out of the top of the geyser. All the water below this +point being thus suddenly relieved of its pressure, and being now much +hotter than is necessary to boil the water at that decreased pressure, +suddenly flashes into steam, and violently shoots out all the water +above it to a height that in some cases may be as great as 100 to 200 +feet. The steam causes this eruption, then rushes out with a roar, and +the geyser eruption is over. + +Professor Tyndall in his charming book entitled "Heat as a Mode of +Motion" speaks as follows concerning Professor Bunsen's discovery: + + "Previous to an eruption, both the tube and basin are + filled with hot water; detonations which shake the ground, + are heard at intervals, and each is succeeded by a violent + agitation of the water in the basin. The water in the + pipe is lifted up so as to form an eminence in the middle + of the basin, and an overflow is the consequence. These + detonations are evidently due to the production of steam in + the ducts which feed the geyser tube, which steam escaping + into the cooler water of the tube is there suddenly + condensed, and produces the explosions. Professor Bunsen + succeeded in determining the temperature of the geyser + tube, from top to bottom, a few minutes before a great + eruption; and these observations revealed the extraordinary + fact that at no part of the tube did the water reach its + boiling point. In the sketch [not reproduced] I have given + on one side the temperatures actually observed, and on + the other side the temperatures at which water would boil, + taking into account both the pressure of the atmosphere and + the pressure of the superincumbent column of water. The + nearest approach to the boiling point is at A, a height of + 30 feet from the bottom; but even here the water is 2° C., + or more than 3-1/2° F., below the temperature at which it + could boil. How then is it possible that an eruption could + occur under such circumstances? + + "Fix your attention upon the water at the point A, where + the temperature is within 2° C. of the boiling point. Call + to mind the lifting of the column when the detonations + are heard. Let us suppose that by the entrance of steam + from the ducts near the bottom of the tube, the geyser + column is elevated six feet, a height quite within the + limits of actual observation; the water at A is thereby + transferred to B. Its boiling point at A is 123.8°, and + its actual temperature 121.8°; but at B its boiling point + is only 120.8°, hence, when transferred from A to B the + heat which it possesses is in excess of that necessary to + make it boil. This excess of heat is instantly applied to + the generation of steam: the column is thus lifted higher, + and the water below is further relieved. More steam is + generated; from the middle downwards the mass suddenly + bursts into ebullition, the water above, mixed with steam + clouds, is projected into the atmosphere, and we have the + geyser eruption in all its grandeur. + + "By its contact with the air the water is cooled, falls + back into the basin, partially refills the tube, in which + it gradually rises, and finally fills the basin as before. + Detonations are heard at intervals, and risings of the + water in the basin. These are so many futile attempts at + an eruption, for not until the water in the tube comes + sufficiently near its boiling temperature, to make the + lifting of the column effective, can we have a true + eruption." + +The principal geyser regions of the world are in Iceland, in New +Zealand, and in the Yellowstone National Park in the United States. + +There are several geyser regions in Iceland. The best known lies in +the neighborhood of Mt. Hecla. Here is a great geyser that shoots up +a column of water to a height of about 100 feet every thirty hours. +Fig. 35 represents the appearance of the crater of the great geyser in +Iceland. + +[Illustration: FIG. 35. CRATER OF THE GREAT GEYSER OF ICELAND] + +It is a well-known fact that in geyser regions generally, the throwing +of stones or other materials into the tube will frequently hasten an +eruption. This is probably due to the fact that the throwing in of +these things results in the raising of the water in the tube, thus +hastening the eruption. + +The New Zealand region is in the neighborhood of Lake Rotomahama in +the northern island. + +The geyser region in the Yellowstone Park is by far the most +interesting of all geyser regions. This region is situated principally +around Fire-Hole Fork of the Madison, and near Shoshone Lake at the +head of Lake Fork of the Snake River. There are many geysers in this +region, as well as simple hot springs. The temperature of their +waters varies from between 160° and 200° F. to the boiling point of +water at this elevation. As you are probably aware, water boils at +the temperature of 212° F. only under the condition of the ordinary +atmospheric pressure that exists at the level of the sea. At higher +elevations, such as on the slopes of mountains, or on high plateaus, +water boils at a lower temperature. The height of the country in which +the Yellowstone Park is situated is so great that the water boils at +temperatures of from 198° to 199° F. + +The conical hillock of geyser cones from which the waters flow assume +various shapes, two of which are shown in Figs. 36 and 37. + +[Illustration: FIG. 36. GIANT GEYSER _From Dana's Manual of +Geology_] + + +[Illustration: FIG. 37. BEE HIVE _From Dana's Manual of +Geology_] + +That shown in Fig. 36 represents the shape of the cone of the giant +geyser in the upper geyser basin of the Fire-Hole, Yellowstone +National Park. This cone is about ten feet in height, and twenty-four +feet in diameter. As shown in the figure it is broken on one of its +sides. It throws out, at long intervals, a column of water the height +of which varies from ninety to 200 feet. + +Fig. 38 represents the crater of a cone known as the Bee Hive in +eruption. + +Besides the above named geyser regions there is another region on the +shores of Celebes, and a small region on San Miguel, in the Azores +Islands, in the Atlantic Ocean. + +Besides hot springs and mud volcanoes there are two other phenomena +connected with volcanic action that we will now briefly describe. + +When eruptions take place and the lava begins to flow down the side +of a mountain, the different vapors and gases with which the lava is +charged begin to escape or pass out from the boiling or fused mass. +When these substances are of such a character that they produce fumes, +or the vapors of various chemical substances, that become solid on +cooling, they form what are called _fumaroles_, a word derived from +a Latin word meaning "to smoke." For the greater part, fumaroles are +found on the edge of craters, but sometimes are found in cavernous +places either in the crater or in the lava streams. + +There is, still, another class of openings through which only +sulphurous vapors escape. These are called _solfataras_, a word +derived from the Italian word _solfo_, or sulphur. Solfataras are +generally found in regions distant from volcanic action. In the +materials that escape from recently ejected lava, or molten lava, +the temperature is high enough to volatilize many of the solid +ingredients. But where the temperature is low, only sulphur vapors are +driven off. It is for this reason that fumaroles are only found around +the craters of active volcanoes, or on the lines of cracks or crevices +of the lava stream where the temperature is very high. + +[Illustration: FIG. 38. BEE HIVE GEYSER OF ICELAND _From +Dana's Manual of Geology_] + +Besides water vapor and sulphurous vapors there are other substances +that escape from the earth in volcanic districts. Sulphurous acid, +together with hydrogen and nitrogen escape from nearly all lava. At +Vesuvius chlorine gas is given off. This, however, as soon as it +passes into the atmosphere becomes changed into hydrochloric acid. +Sulphurous acid is frequently changed into sulphuric acid, which, +combining with various substances, forms such materials as _gypsum_, +or sulphate of lime, the chemical name for plaster of Paris; sulphate +of soda or _Glauber's salt_; sodium chloride or _common table salt_; +and _sal ammoniac_. You will remember in reading the description of +Vulcano, in the Grecian Archipelago, that some of these products were +collected at the chemical works that had been established on the +volcano. + +When a volcanic mountain is for the time being passing from an active +to an extinct condition, it is sometimes said to be in the _fumarole +stage_, since the presence of the fumaroles are the only indication +of its activity. The volcanic heat is still great. When it reaches a +still greater decline, the fumaroles disappear, and only solfataras +are left. The amount of heat is now only sufficient to produce sulphur +vapors and the vapor of water. This is called the _solfatara stage_. + +Of course, as we have already pointed out, fumaroles and solfataras +may occur in the neighborhood of a volcano at different distances from +its crater. + + + + +CHAPTER XXII + +THE VOLCANOES OF THE MOON + + +There can be no doubt that the moon was once the seat of very great +volcanic activity. It was formerly believed that the very many +volcanic craters which can be seen on its surface when it is examined +by a comparatively small telescope, were all extinct. While this +is nearly true, yet recent investigations have shown that in all +probability a feeble volcanic activity still exists in a few of these +craters. + +The distinctness with which the surface of the moon is seen does not +depend so much on the size of the telescope employed, as it does +on the steadiness of the atmosphere when the telescope is being +used. When one wishes to examine a very distant body like a star, +it is necessary to use a powerful telescope, but in the case of a +comparatively near body, like one of the planets or the moon, a big +telescope is not necessary. It is, however, necessary to make the +observations at some time of the year, or in some part of the world, +when the air is apt to be free from winds. + +A person on the earth's surface looking at the heavenly bodies through +a telescope is practically in the position in which he would be were +he at the bottom of the water in a large lake looking up through the +water at some body in the heavens. He would have no difficulty in +seeing such a body distinctly as long as the upper surface of the +water remained quiet, and unruffled by waves. As soon, however, as +waves were set up, the images seen in the telescope are so distorted +as to become practically worthless. It is for this reason that it is +customary to build great astronomical observatories in parts of the +world where there are apt to be many days in the year when the air is +almost entirely free from wind. + +Since the atmosphere is apt to be disturbed by winds in both the +temperate and the polar latitudes, these parts of the world are +not very satisfactory as sites for astronomical observatories. The +conditions are more favorable near the equator, since, although at +certain seasons of the year there are very severe storms in these +regions, yet there are quite long periods when the air is almost +entirely free from winds. + +It is for this reason that Harvard University has erected an +astronomical observatory at Arequipa, Peru, at an elevation of 8,000 +feet above the level of the Pacific Ocean. Here, with a comparatively +small object glass, of about twelve inches aperture, magnificent +photographs have been obtained not only of the moon but also of the +planet Mars. + +According to Professor Pickering, from whose magnificent work, +entitled, "The Moon," much of the information in this chapter has been +obtained, the moon, which is generally spoken of as a satellite of the +earth, ought rather to be called the earth's twin planet. Although the +moon appears to revolve in a small elliptical orbit around the earth +it should properly be said to revolve around the sun; for, together +with the earth, it revolves around the sun once every year. As seen +from any of the planets that lie near the earth the earth and moon +would appear as a very beautiful double star. + +In order the more readily to understand what will be said shortly +concerning the origin of the moon, it may be mentioned that the +moon's diameter is 2,163 miles, or a little more than one-fourth the +diameter of our earth. + +You will, most probably, be surprised to learn that the origin of the +moon is believed to be very different from the origin of the moons +or satellites of Jupiter, Saturn, and the other planets. As we have +already seen, according to the nebular hypothesis, all the planets +except the earth probably had their moons formed from the rings that +were left surrounding them when they shrunk on cooling to their +present dimensions. Such a ring is still to be seen surrounding Saturn. + +Now it is believed that our moon was formed in a different manner. +It was not thrown off from the earth while the latter was in a +highly fluid or gaseous condition, but after the earth had shrunken +to nearly its present size and, most probably, after a solid crust +had been formed on its surface. In order that our earth should be +able to violently throw off a large portion of its mass, it is only +necessary that at the time this separation occurred, its motion of +rotation on its axis was sufficiently great to enable it to make one +complete revolution in rather less than three hours instead of in +the twenty-four hours it now requires. At this velocity of rotation, +objects would fly off the earth in the neighborhood of the equator, +under the influence of the high centrifugal force. Let us, then, +endeavor to see if it was at all probable that the earth ever did turn +so rapidly on its axis. + +You all probably know that it is principally the attraction of the +moon that produces the earth's tides. Of course, the sun also produces +tides on the earth, but it is so far off from the earth that not +withstanding its greater mass the tides it forms are much smaller +than those produced by the moon. You also know that the moon produces +at the same time two tides in every twenty-four hours, on directly +opposite sides of the earth; one on the side immediately under the +moon, and the other on the side furthest from the moon. As the earth +rotates between these two tides, they act as a break which serves to +impede its motion. Every high tide, therefore, tends to make the earth +rotate more slowly, and thus to slowly increase the length of the day. +For this reason to-day is a trifle longer than yesterday, and still +longer than a day a hundred years ago. + +You must not suppose for a moment that this increase in the length of +the day is large. On the contrary, it is so small that since the year +A. D. 1, up to the present time, the day is only a very small +fraction of a second longer. + +But it was very different in the earth's geological past, when the +inside of the earth was in a molten condition; for then great tides +were set up in the melted interior of the earth that not only greatly +changed the shape of the earth, but decreased the rate of rotation +much more rapidly than it does when the earth's tides are limited as +they are now to the waters on the earth's surfaces. + +There was, however, at the same time, something going on that tended +greatly to make the earth turn more rapidly on its axis. While the +originally melted earth was cooling and shrinking, the rate of +its rotation was necessarily increasing. As you know, the time of +vibration of a pendulum, that is, the time it requires to make one +complete to-and-fro motion, is shorter the shorter the length of the +pendulum. A pendulum two feet long moves to and fro more slowly than +a pendulum one foot in length. In the same way a rotating sphere will +make one complete rotation in a shorter time when its radius, which +corresponds to the length of a pendulum, is shorter. Therefore, as the +earth shrunk, it rotated more and more rapidly, and at last reached a +rapidity of motion at which an immense quantity of matter flew off +its surface nearest the equator and went out into space, never again +to return. It was this mass that constituted the earth's moon. + +Necessarily such a tremendous catastrophe was attended by an +earthquake as well as by the most fearful volcanic phenomena that +the earth has ever witnessed. The terrible catastrophe produced by +the explosive eruption of Krakatoa was but as a small drop of rain +falling on the earth, when compared with the catastrophe produced when +the "five thousand million cubic miles of material left the earth's +surface, never again to return to it." + +It is not known whether this matter was torn off the earth at a single +time or during successive times, but quoting the beautiful language of +Professor Pickering: + + "We may try in vain to imagine the awful uproar and fearful + volcanic phenomena exhibited when a planet was cleft in + twain, and a new planet was born into the solar system." + +This terrible catastrophe took place at a time not when the earth was +a gaseous mass, but when it had condensed into a comparatively small +mass not much larger than it is at its present time, and possibly +even after it had hardened sufficiently to form a solid crust on its +outside. + +If you look at a map of the earth on a Mercator's projection, such, +for example, as that employed in illustrating the distribution of the +world's volcanoes in Fig. 24, you can see, even without any very close +examination, that the great water area of the Atlantic Ocean has its +eastern and western shores almost parallel to each other, so that +if you conceive the Eastern and Western Continents as being pushed +together, they would, except at the south, almost completely fit +together, and the same thing is true, if Greenland is pushed towards +the northeastern coast of North America. Of course, some portions of +the coast would not fit exactly, but then these portions might either +have been worn away, or, as is more probable, have been changed in +shape by the deposit of immense beds of sedimentary rocks spread over +the borders of the Atlantic by the great rivers that empty into it. +This is so remarkable a fact that it will be well worth your while to +turn to the map mentioned and convince yourself of the proof of what +I have just said. As you will see, Europe and Africa would almost +exactly fit against South America and North America, while Greenland +would even more closely fit against the northeastern coast of North +America. + +Now, while we do not say that it was so, it has been suggested as just +possible that the great depression of the Pacific Ocean represents the +spot that was once filled by the moon. That the Eastern and Western +Continents, then torn asunder by the great force of the convulsion, +were left floating on the surface of a sea of molten matter, a greatly +widened crack marking positions they assumed at the end of this +cataclysm. + +Of course, you must understand that all this is a mere supposition, +and that we do not know whether the earth was actually cooled on the +outside when this occurred, since it might have still been in a liquid +condition throughout. It would seem, however, to have occurred rather +recently, since it could not have occurred until the earth shrunk so +much that it became so small in radius as to acquire a very rapid rate +of motion on its axis. + +It is an interesting fact that we are, perhaps, better acquainted with +that side of the moon which is turned towards us than we are with the +surface of the earth on which we live. Of course, I do not mean in the +small details of the moon's surface, but with such portions as can be +seen through a good telescope when the air is quiet. While there are +no parts of the moon's surface that have not been carefully examined +in detail probably thousands of times by acute astronomers, there are +still comparatively large areas of the earth that have never been once +trodden by civilized man. + +When I speak of all parts of the moon's surface, I only mean those +parts that are turned towards us. You may possibly be ignorant of the +fact that the moon always turns exactly the same face towards the +earth. Not only has no man ever seen the opposite side of the moon, +but he never can hope to see it while he remains on the earth. This is +because the moon turns or rotates on its axis in exactly the same time +that it revolves in its orbit. + +When I say that the time of rotation is the same as the time of +revolution of the moon, I do not mean that it is almost the same, but +that it is exactly the same. If it differed even but a small fraction +of a second, a time would come when we would be able to see the other +side of the moon. Now, since astronomers have made careful pictures +of the moon, many, many years ago, we can see by comparing them +with photographs taken at the present time there has been no change +whatever in that face of the moon which is turned towards us, and +this, of course, proves beyond question, that the time of the moon's +rotation during this great period has remained exactly the same as the +time of its revolution. + +It may possibly seem to you that it cannot be a matter of great +importance in a book like this on the Wonders of Volcanoes and +Earthquakes, whether or not the moon always turns its face towards +the earth; on the contrary, it is a matter of the greatest importance +since by it we can prove positively that the moon was at one time at +least in a partly fluid condition. It was the presence of this partly +fluid interior that resulted in the time of the moon's rotation +agreeing exactly with the time of its revolution. The tides of the +earth set up in the moon's molten interior, tides, that instead of +reaching twice every day the height of a few feet only, were set up +in the molten mass in the moon's interior, probably reaching miles in +height, rapidly decreased the time of the moon's rotation until the +moon rotated once only during every complete revolution. + +Even now that the moon is probably solid throughout, the time of its +rotation and revolution exactly agree because, while in a molten +condition, the action of the earth changed its shape from that of an +exact sphere to a spheroid, with its longest axis in the direction of +the earth. Even, therefore, if the moon at any time began to rotate +faster than the earth, the earth acting on its projecting surface +retarded it until the time of its rotation agreed exactly with the +time of its revolution. + +It was at one time believed that the moon had no atmosphere. It is +now known, however, that it has an atmosphere. It is true this is a +rare atmosphere, probably not greater in density than the one-ten +thousandth of the earth's atmosphere. This important question was +settled once for all on August 12th, 1892, at the Harvard Observatory +at Arequipa, Peru, when a photograph was taken of an object on the +moon. It could be readily seen on examining this photograph that the +light coming from the moon experienced a bending, known as refraction, +in passing from the space outside the moon to its atmosphere on to its +surface. + +Of course, when the moon was thrown off from the earth by reason of +its great centrifugal force, it carried along with it a portion of the +earth's atmosphere. But since the quantity of matter in the moon is +only about one-eightieth of that of the earth, the force of gravity +on the moon is much smaller than that on the earth, being almost +exactly one-sixth that of the earth's gravity. In other words, if you +could succeed in reaching the moon's surface, you would only weigh +one-sixth of what you weigh on the earth, but then you could carry a +weight six times heavier with no greater effort, and, as for running, +jumping, and other athletic exercises, the surface of the moon would, +indeed, be a great place on which to break records, since one could +readily jump six times higher, put the shot six times further, than +on the earth, or go through most other athletic exercises with a +corresponding increase. + +Without going any further into this question it will be sufficient +to say that the moon's present atmosphere is believed to consist of +carbonic acid gas, and that while on the general surface of the moon +this atmosphere must be very rare, yet, at the bottom of the great +fissures that cross the moon's surface, it may possess a fairly great +density, especially if the moon still possesses feeble volcanic +activity; that carbonic acid gas is still being given off from the +inside of the moon as we know it is being given off from inside the +earth. + +Under the best conditions of atmosphere and telescope, we can see the +moon's surface as it would appear at a distance varying from 800 miles +to 300 miles from the earth. With a fifteen-inch telescope, under +perfect conditions of vision, objects can be seen as if they were at +a distance of 800 miles from the earth, and with the most powerful +glasses, and the best conditions of atmosphere this distance can be +reduced to about 300 miles. This would enable us to clearly see large +objects like rivers, lakes, seas, or forests, if they existed, but +would not be sufficient to enable us to see houses, buildings, or +roads. + +When we come to examine the surface of the moon under the most +favorable conditions, we find that it is extremely irregular. There +are plenty of high mountains. These mountains are not collected +in ranges as they are on the earth's surface, but are completely +separated from each other, and are scattered in great numbers over the +moon's surface. + +You may form some idea of the number of volcanoes that have been +observed on the moon when I tell you that as many as 32,000 have been +seen on that side of the moon that is turned towards the earth. + +Now it is an interesting fact that almost all these mountains possess +great craters that are not unlike some of the volcanic craters we see +on the earth. The volcanic craters of the moon, however, are of very +much greater size than those on the earth, many being from fifty to +sixty miles in diameter, while some of them are more than 100 miles +in diameter. Smaller craters, say from twenty to twenty-five miles in +diameter, can be counted by the hundreds. + +Like most of the moon's craters, the largest crater more closely +resembles one of the pit-craters or calderas on the island of Hawaii. +This volcanic crater consists of a huge circular ring with a small +irregular peak that rises inside the ring. This peak, by the way, +might at first appear to resemble the crater of Vesuvius, which after +a long period of inactivity of the mountain during the eruption that +destroyed Pompeii and Herculaneum was thrown up inside of what had +been left standing of the old crater of Somma. But it has no crater +at its summit, and, therefore, resembles rather the irregular pile or +rock that rises from the surface of a lava lake in the craters of Mt. +Loa or Mt. Kilauea in Hawaii. + +Besides the numerous craters to be seen on the moon's surface there +are many lines of deep, crooked valleys, known as _rills_, that may +at one time have been the beds of rivers. Besides the rills, there are +many straight clefts about half a mile in width, that extend down into +the surface of the moon for unknown depths. These clefts can be seen +passing directly through mountains and valleys. They are believed to +be cracks or fissures in the moon's surface. + +On the moon is a great crater called Tycho. It is situated near the +moon's south pole. The great crater of Tycho is by far the most +prominent object on the moon's surface. It has a system of rays that +extend for great distances around its craters. + +You will also see if you examine the moon's surface by a powerful +glass that there are immense plains called _oceans_ or _seas_. By an +appropriate custom the names of the different craters on the moon are +the same as the names of the great astronomers and philosophers that +have long since passed from their labors, such as Tycho, Copernicus, +Kepler, Plato, etc. + +Various explanations have been given as to the origin of the craters +on the moon's surface, but without going into a discussion it may be +said that they are now generally regarded as having been formed in the +main just as were the craters of the earth's volcanoes. + +The tremendous size of the moon's craters is of course due to the +great decrease in the force of gravity. This would make the craters, +approximately, six times as great as the craters on the earth. +Professor Pickering points out that while the moon's craters resemble +more closely those of Hawaii than those of any other of the earth's +volcanoes, yet there is this difference in them: that while the +earth's crater floors are generally considerably higher than the level +of the sea, the moon's crater floors are generally below the level of +the surrounding country. Still, taking them all in all, the craters +of the moon's volcanoes resemble those of the island of Hawaii, or +again quoting from Pickering:-- + + "There seems, indeed, to be no feature found upon the moon + which is not presented by these Hawaiian volcanoes, there + is no feature of the volcanoes that does not also have its + counterpart in the moon." + + + + +CHAPTER XXIII + +EARTHQUAKES + + +An _earthquake_ is a shaking of the earth. It may vary in intensity +from a shaking so feeble that it requires the use of a delicate +instrument to detect it, to a shaking violent enough to overthrow +heavy buildings, and even to make great rents or fissures in the crust. + +An earthquake then is an _earth-shake_. It may be caused by anything +capable of shaking the earth; for example, as the falling of a heavy +weight on its surface. Now, a shaking so caused is only felt in the +immediate neighborhood of the place the weight strikes the earth. On +the contrary, in an earthquake, the shaking spreads in all directions +through the earth's crust, until, in the case of very violent +earthquakes, it reaches portions that may be situated many thousands +of miles away from where the shock started. This spreading of the +earthquake waves through the solid earth is not unlike the spreading +of the circular waves that are set up in a still water surface when a +stone is tossed in. + +Any shaking of the earth's crust produces what may be called an +earth-shake or earthquake. The mere falling of a raindrop on the earth +produces a slight shaking. The falling of a heavy stone produces a +stronger shaking, and sets up a series of minute waves, generally +called vibrations, that spread around the place in all directions from +where the stone struck. These movements, however, while they spread +in all directions, just as they do in a surface of a lake, when a +stone is thrown into it, are of course much more quickly stopped by +the solid earth than similar movements are by the more readily movable +water. + +But, while any shaking of the earth's crust constitutes an earthquake, +yet, strictly speaking, an earthquake is produced only by some force +that acts suddenly on the earth, _at a point below its surface_, and, +therefore, out of sight. This, of course, would rule out all such +shakings as are caused by bodies striking the outer surface of the +earth. + +Earthquakes may occur in any part of the world, and at any time of the +day or year. They do occur, however, most frequently in certain parts +of the world, at certain seasons of the year and at certain hours of +the day. + +Earthquakes are far from being unusual occurrences. In some parts of +the world, such as the island of Java, they are very common, and in +Japan, under certain circumstances, scarcely a day passes without one +or more shocks in some part of that little empire. + +Professor Mallet, who has made a very extensive study of earthquakes, +published in 1850 to 1858, in the Philosophical Transactions, brief +abstracts or descriptions of all the more important earthquakes he +could find records of during the past 3,456 years. The number of +earthquakes thus recorded during this period reached 6,830. Of this +great number nearly one-half occurred during the last fifty years. + +It should not be inferred from the above figures that the number of +earthquakes has really increased so greatly in the past half-century. +The explanation of the apparent increase is that greater care has +been taken recently in recording earthquakes, and that an apparatus +called a _seismometer_, or _earthquake-recorder_, has been invented +which automatically produces a record of the smallest shocks; so that +a great many have been recorded that would otherwise have passed +undetected. + +It is the opinion of Le Conte that if the records of all the +earthquakes of 3,456 years had been thus made there would have been +found during the entire time of Mallet's researches to have occurred +no less than 200,000, while during the last four years of Mallet's +records, the number would have probably reached two earthquakes per +week. + +Since Mallet's time, Prof. Alexis Perry published (1876) a much larger +list of earthquakes. Perry finds that from 1843 to 1872 there have +been 17,249 earthquakes, or 575 every year. Perry's list, however, +is incomplete, since it fails to record earthquakes that occurred in +mid-ocean, and in the unexplored and uncivilized parts of the world. +So it seems likely that earthquakes are so common that our earth, at +some part or other of its surface, is continually shaking or quaking. + +Earthquakes are such tremendous phenomena that they were necessarily +observed by the ancients. We find more or less complete accounts of +them in various writings. Lucretius (Titus Carus Lucretius, a great +Roman poet) speaks as follows, in his De Rerum Natura (On the Nature +of Things). We use Munro's translation here: + + "Now mark and learn what the law of earthquakes is. And + first of all take for granted that the earth below us as + well as above is filled in all parts with windy caverns, + and bears within its bosom many lakes and many chasms, + cliffs and craggy rocks; and you must suppose that many + rivers hidden beneath the crust of the earth roll on with + violent waves and submerged stones; for the very nature + of the case requires it to be throughout like to itself. + With such things then attached and placed below, the + earth quakes above from the shock of great falling masses, + when underneath, time has undermined vast caverns. Whole + mountains, indeed, fall in, and in an instant from the + mighty shock tremblings spread themselves far and wide from + that centre. And with good cause, since buildings beside + a road tremble throughout, when shaken by a wagon of not + such very great weight; and they rock no less, where any + sharp pebble on the road jolts up the iron tires of the + wheels on both sides. Sometimes, too, when an enormous mass + of soil through age rolls down from the land into great + and extensive pools of water, the earth rocks and sways + with the undulation of the water just as a vessel at times + cannot rest, until the liquid within has ceased to sway + about in unsteady undulations.... + + "The same great quaking likewise arises from this cause, + when on a sudden the wind and some enormous force of air + gathering either from without or within the earth have + flung themselves into the hollow of the earth and there + chafe at first with much uproar among the great caverns + and are carried on with a whirling motion, and when their + force, afterwards stirred and lashed into fury, bursts + abroad and at the same moment cleaves the deep earth and + opens up a great yawning chasm. This fell out in Syrian + Sidon and took place at Ægium in the Peloponnese, two towns + which an outbreak of wind of this sort and the ensuing + earthquake threw down. And many walled places besides fell + down by great commotions on land and many towns sank down + engulfed in the sea together with their burghers. And if + they do not break out, still the impetuous fury of the + air and the fierce violence of the wind spread over the + numerous passages of the earth like a shivering-fit and + thereby cause a trembling." + +Of course, no one at the present time believes this ridiculous +explanation as to the cause of earthquakes. + +Aristotle, a Greek philosopher, speaks thus concerning earthquakes. We +quote the translation employed by Mallet: + + "Three theories on the subject have been handed down to + us by three different persons; namely, Anaxagoras of + Klazomene, before him Anaximenes the Milesian, and later + than these Democritus of Abdera. + + "Anaxagoras says that the ether of nature rises upward, but + that when it falls into hollow places in the lower parts + of the earth it moves it (the earth); because the parts + above are cemented or closed up by rain, all parts being by + nature equally spongy or full of cavities, both those which + are above (where we live) and those which are below. Of + this opinion it may perhaps be unnecessary to say anything, + as being foolish, for it is absurd to suppose that things + would thus exist above and beneath, and that the parts of + bodies which have weight would not on every side be borne + to the earth, and those which are light, and fiery, rise; + especially since we see the surface of the earth to be + convex and spherical, the horizon constantly changing as + we change our place, at least as far as we know. And it is + also foolish to assert on the one hand that it remains in + the air on account of its great size, and on the other to + say that it is shaken, when struck from beneath upwards. + And besides these objections, it is to be remarked that + he has not treated of the attendant circumstances of + earthquakes, for neither every time nor place is subject to + these convulsions. + + "But Democritus says, that the earth being full of water, + and receiving much also by means of rain, is moved by + this. For when the water increases in bulk, because the + cavities cannot contain it, in its struggles it causes an + earthquake. And when the earth becomes partially dried up, + the water being drawn from the full reservoirs into those + which are empty, in passing from one to the other, by its + movements it causes an earthquake also. + + "Anaximenes, however, says that the earth, when parched up + and again moistened, cracks, and by the masses thus broken + off falling on it, is shaken; wherefore earthquakes occur + in drouths and again in times of rain; in drouths, because, + as we have said, it cracks, when highly dried, and then, + when moistened over again, it cracks and falls to pieces. + Were this the case, however, the earth ought to appear + in many places subsiding. Why then is it that hitherto + many places have been very subject to these convulsions + which do not present any such remarkable differences from + others? Yet such ought to be the case. And, moreover, those + who think thus must assert that earthquakes constantly + become less and less, and at last cease altogether. For + the continual condensation of the earth would cause this. + Wherefore, if this be not the fact, it is plain that this + is not the correct explanation." + +Besides the above, there are numerous references to earthquakes in the +works of other writers. Thales, Seneca, and Pliny all speak of these +phenomena and appear to describe correctly the movement of the earth +in waves both in the solid land, as well as on the sea. + +Coming down to less ancient writers, Mallet refers to a book by +Fromondi, published in Antwerp, in 1527, that contains much valuable +and interesting information. Among other things Fromondi declares +that in the year 369, in the reign of Valentinian, there was a great +earthquake that shook nearly the entire world and that another +earthquake of almost equal severity occurred in 1116. He also states +that in 1601 an earthquake continued for nearly forty days; that a +great earthquake in Italy, in 1538, lasted fifteen days, and that +another, in Spain, lasted for nearly three years. + +This does not mean that these earthquakes actually continued to shake +the earth violently for the times mentioned. These are only the times +during which, at intervals of greater or less length, successive +shocks were felt in these localities. + +Another of the less ancient writers referred to by Mallet is +Travagini, who published a book in Venice in 1683. This book contains +a description of a terrible earthquake occurring in Italy on the 6th +of April, 1667, which affected large portions of the country adjacent +to Ragusa. + +Without attempting at present to discuss the various theories of +earthquakes, it will suffice to say that earthquakes can be divided, +according to their origin, into two classes: _volcanic earthquakes_, +or earthquakes that are caused by practically the same forces that +cause volcanoes, and _tectonic[3] earthquakes_, or those produced by +the slipping of a large mass of rock lying along the lines of old or +new fractures. + +Earthquakes of the first class are found especially in volcanic +districts, while those of the second class are found in all parts +of the world, whether in volcanic districts or elsewhere. According +to Dana, earthquakes of the second class generally start in the +neighborhood of mountains, where old lines of fractures are especially +abundant. + +As regards the direction of the shaking movements of the earth, +earthquakes can be divided into three different classes: _explosive +earthquakes_, or those in which the force acts vertically upwards; +_horizontal earthquakes_, or those in which the force moves in a more +or less horizontal direction, or parallel to the general surface +of the earth, and _rotary earthquakes_, or those in which the earth +rotates or moves in great eddies or whirls. + +When the earthquake wave is started below the earth's surface, it +spreads through the crust in all directions. The direction these waves +will have on emerging, or coming out of the surface, will depend on +the distance of this point from the place the waves started. When a +place is situated directly over where the wave started, the waves will +emerge so as to move vertically upwards, so that the earth at this +point will be shaken by an explosive earthquake. As the point where +the waves pass out is situated further and further from the place +where the waves start, the waves will emerge more nearly horizontally, +the greater the distance from the source. + +In explosive earthquakes, which, as just explained, occur at areas +almost immediately above the point where the disturbance starts, +the force is, generally speaking, the greatest. In earthquakes of +this character the force is sometimes sufficiently great to throw +large bodies high up into the air. In the case of the great Riobamba +earthquake of 1797, the force was not only sufficiently great to +fracture the earth in various places, but also to throw bodies lying +on the surface great distances into the air. Bodies of men were thrown +several hundred feet into the air and were afterwards found on the +other side of a broad river or high up on the side of a hill. + +It is possible that Humboldt did not inquire with as much care as +he should have done into these reports. They were probably greatly +exaggerated, since it is difficult to understand how a force great as +this would have failed to detach the soil at these places, and hurl it +after the people. This much, however, can be accepted, that the upward +force was very great. + +In the great Calabria earthquake of March, 1783, Dolomieu states that +the tops of the granite hills of Calabria were distinctly seen to rise +and fall. In some cases houses were suddenly raised a great distance +in the air, and were afterwards brought down again to a position of +rest, at a higher level without any damage occurring to them. In a +similar manner during the Caracas earthquake of March, 1812, the +ground was seen to rise and fall in a nearly vertical direction. But, +perhaps, one of the most terrible earthquakes of this character was +the earthquake that destroyed the greater part of Jamaica in June, +1793. During this earthquake the entire surface of the ground at Port +Royal assumed the appearance of a rolling sea. Houses were shifted +from their old sites. Many of the inhabitants who had succeeded in +escaping from the city to the neighboring country were thrown great +distances into the air. Some of these, by good fortune, fell into the +harbor, from which, in some cases, they escaped with their lives. Here +again the projectile force was probably greatly exaggerated. + +Vertical movements characterized the great earthquake of Lisbon, on +November 1st, 1755, the city appearing to have been not far from the +point of origin. + +The commonest type of earthquakes is the horizontal, where the waves +emerge at the surface in a direction either horizontal or parallel +to the general surface, or at least inclined to it at a very small +angle. Where the materials of the earth's crust, through which the +waves spread, are of the same kind and of the same density in all +directions, the area shaken is approximately circular, but where the +materials of the crust are more or less dense in some directions than +in others, the area of disturbance is of course oblong or elliptical. + +In some cases earthquakes of the horizontal type are limited almost +entirely to a single direction. This is especially the case with +earthquakes that occur in mountainous districts. These earthquakes are +known as _linear earthquakes_, since they spread almost in a single +line. + +When earthquake waves pass from one medium to another, that is, from +one kind of rock to another, the greater portion of the waves is +refracted or bent out of their straight direction as they pass into +the new medium; a part of the waves, however, are reflected. It is +these reflected waves that probably cause rotary earthquakes. + +The speed with which the surface waves move outwards in all +directions, varies not only with the force of the wave, but also with +the kind of material through which they pass. This velocity may be +in the neighborhood of twenty miles per second, while in others the +velocity is as great as 140 miles per second. + +Naturally, one would suppose that the most severe earthquakes are +those in which the waves move the most rapidly. On the contrary, +however, the comparatively feeble shocks are sent through the earth +with greater velocity. + +In rotary earthquakes, as the name indicates, the ground is whirled +or twisted in the manner of a violent eddy, and is often left in +this twisted condition. In the great Calabria earthquake, huge +blocks of stone forming obelisks were twisted on one another in a +manner represented in Fig. 39. In this case the pedestals remained +unaffected, but the separate blocks of stone were partially turned +around, as shown. During this earthquake the earth was so twisted that +trees, which had been planted in straight lines before the earthquake, +were left standing in zigzags. During the great Charleston earthquake, +South Carolina, the chimney-tops of the houses were separated at +places where they joined the roof and were twisted around these places +without being overthrown. In some of the houses wardrobes or bureaus +were turned at right angles to their former positions, and in some +cases were even found with their faces turned towards the wall. + +[Illustration: FIG. 39. HEAVY STONE OBELISKS TWISTED BY CALABRIAN +EARTHQUAKE OF 1783] + +Mallet suggests that in some cases the rotary motion is more apparent +than real, being due only to a to-and-fro motion without any twisting, +the apparent turning being due to the greater freedom of motion of the +object in one direction than in another. A twisting motion, however, +has actually taken place in some earthquakes. + +While separate shocks, in a given locality, may follow one another +at intervals for fairly long times, yet the principal shock or shake +that produces the greatest damage is generally of exceedingly short +duration. In the Caracas earthquake the greatest destruction was +accomplished in about one minute. There were three distinct shocks, +each of which lasted but three or four seconds. The great Calabria +earthquake, of 1783, lasted but two minutes. The earthquake of Lisbon, +in 1755, lasted five minutes, but the first, and worst, shock, was +only from five to six seconds. + + + + +CHAPTER XXIV + +SOME OF THE PHENOMENA OF EARTHQUAKES + + +The nature of an earthquake and the movements of its waves from +their starting place having now been briefly described, it remains +to explain some of the strange phenomena that precede, accompany, or +follow one. + +Next to the violent shaking of the earth's crust, perhaps the most +wonderful and impressive thing is the great variety of sounds and +noises. These occur not only while the earth-waves are passing through +the crust at any place, but also long before the principal shocks +reach the place, as well as long after they have passed. + +Earthquake sounds vary almost infinitely, both in intensity and +character. Some are like the gentle sighings of the wind, or resemble +faint mysterious whisperings; some are not unlike the confused +murmurings of a crowded room; some resemble the sounds of a busy +street. Some sounds are full and strong, like the deep bass notes +of a large organ. Others resemble the din of a great battle with +the reports of the large guns. Still others reach the intensity of +continuous peals of thunder. But we can better understand the nature +of earthquake sounds from an actual description of them in a number of +great earthquakes, and by inquiring at the same time into any of the +peculiar facts connected. + +Humboldt in his great work, "Cosmos," thus describes the varied voice +of the earthquake: + + "It is either rolling or rustling, or clanking, like + chains being moved, or like near thunder, or clear and + ringing, as if obsidian or some other vitrified masses were + struck in subterranean cavities." + +That the sounds produced during earthquakes are carried through the +ground faster than through the air appears clear from the fact that +such sounds are sometimes heard in deep mines when they are not at all +heard on the earth's surface. + +In describing the earthquake that occurred in Kamtschatka, in 1759, +Krashenikoff of St. Petersburg states that noises were heard like the +rushing of a strong underground wind, accompanied by a hissing sound, +which resembled the sizzlings heard when red hot coals are thrown in +water. + +In an earthquake that occurred in Lincolnshire, England, February +6th, 1817, a noise was heard closely resembling the sounds of wagons +running away on a road. So complete and convincing was the resemblance +that several wagoners on one of the roads drew their teams to one side +so as to permit the runaway to pass safely. + +Another kind of noise heard during earthquakes is a loud hollow +bellowing. Sometimes, however, the sounds are more musical in their +nature, being not unlike those produced by a very large organ pipe. At +other times they resemble the noises produced when steam is blown into +cold water. + +The following account of earthquake sounds is given by Daubeny, +in his book on volcanoes. It appears that during March, 1822, the +people living on the island of Melida, opposite Ragusa, in Dalmatia, +were greatly alarmed by sounds that at first they believed due to +cannonading either at sea or on the neighboring coast. They afterwards +found that these sounds were due to something that was taking place +under the ground. The noises continued at intervals until August +23d, 1823, when a great earthquake occurred, during which one of the +highest mountains on the island was cleft or split in one place. The +underground noises continued from time to time and so frightened +the people that they were about to leave the island permanently and +emigrate to the mainland of Dalmatia. They were dissuaded from doing +so by the government, and while the noises continued at intervals it +so happened that no damage came to them. It is said, however, that +twenty years after an active volcano broke out on the island. + +There are various causes that produce earthquake sounds. A very slight +rubbing or grinding together of rock surfaces may produce fairly +loud noises, the volume of the sound being increased by transmission +through the rock masses that lie in the path of the waves. An example +of such an increase in the loudness of sounds is seen in the case of +several of the large blocks of stone used for some of the piers of +Kingston Harbor, in Ireland. When these rocks are moved together by +blows of the waves they produce loud and appalling sounds, as if the +whole island were being washed away. The same rocks, however, when +left high and dry on the falling of the tide, can be caused to rub +together, when moved by the hand. Under these circumstances, they +produce but feeble sounds that can only be heard in their immediate +neighborhood. + +No doubt, some find it difficult to understand how it is possible for +comparatively feeble sound-waves to be strengthened by their passage +through large masses of solids. This is important and should be made +clear. As everyone well knows, the ticking of a watch can only be +heard at a short distance when the watch is held in the hand, because +the sound-waves cannot readily pass through the body of the person +holding the watch to the earth, the materials of the body not being +sufficiently elastic. If, however, the watch be placed on the bare +surface of a large wooden table from which the tablecloth has been +removed, so that the watch can come directly in contact with the wood, +and nothing else is placed on the table but the watch, the sound-waves +are transmitted to the mass of the table and its entire surface sends +them out into the air. The ticking of the watch can then be heard +distinctly in almost any part of a large room. + +Mallet states that in nearly all great earthquakes sounds are heard +before the principal shock, and in his description of the Calabrian +earthquake Hamilton says: + + "All agreed that every shock seemed to come with a rumbling + noise from the westward, beginning with the horizontal and + ending with the vorticose (rotary) motion." + +According to Dolomieu, during the Lisbon earthquake, the shocks were +preceded "by a loud subterranean noise like thunder, which was renewed +for every shock.... This great shock," he says, referring to one of +the great upward shocks, "occurred without the prelude of any slight +shocks, without any notice whatever as suddenly as the blowing up of +a mine.... Some, however, pretend that a muffled interior noise was +heard almost at the same moment." + +The noises do not generally continue long after the earthquake shocks. +In some cases, however, a very loud noise is heard at intervals for a +considerable length of time after the principal shock. This was the +case at Quito and Ibarra, in which a great noise was heard for from +eighteen to twenty minutes after the principal shock. In a similar +manner during the earthquake of October, 1746, at Lima, and Callao, +South America, peals of underground thunder were heard at Truxillo +for fifteen minutes after the principal shock. In such cases it +seems probable that the noises were not caused by the same impulses +that caused the original shock, but by the forces that caused the +subsequent shock. + +Humboldt relates that in 1784 there were noises heard at Guanajuato, +from the 9th to the 12th of February. They were not, however, followed +by an earthquake. + +Humboldt also states that in an earthquake which occurred on the 30th +of April, 1812, on the banks of the Orinoco River, in South America, +a loud thundering noise was heard, without, however, any shock, but +at this time a volcano on the island of St. Vincent, in the Lesser +Antilles, although some 632 miles to the northeast, was pouring out +streams of lava. Again in the great eruption of Cotopaxi, in 1734, +underground noises were heard as if cannon were being fired. These +sounds were distinctly heard at as great a distance as Honda on the +banks of the Magdalena River. Now, bearing in mind that the crater of +Cotopaxi is situated on the high plateau of Quito, in a region full +of valleys and fissures, it would seem that for the sounds to have +been sent through the 436 miles between the mountains and the valley +of the Magdalena River, the waves must, for the greater part, have +been transmitted through the solid earth at some considerable distance +below the surface. + +Mallet states that the underground noises which continued for more +than a month from the midnight of January 9th, 1784, at Guanajuato, +were not followed by any earthquake shocks, that it was if as thunder +clouds occupied the space below the surface at that part of the earth +and from these clouds there came the slow rolling sounds like short, +quick, snaps of thunder. + +Major Dutton in his book entitled "Earthquakes in the Light of the +New Seismology" gives the following as the principal signs that herald +the coming earthquake in the open country. + + "The first sensation is the sound. It is wholly unlike + anything we have ever heard before, unless we have already + had a similar experience. It is a strange murmur. Some + liken it to the sighing of pine-trees in the wind, or to + falling rain; others to the distant roar of the surf; + others to the far-off rumble of the railway train; others + to distant thunder. It grows louder. The earth begins to + quiver, then to shake rudely. Soon the ground begins to + heave. Then it is actually seen to be traversed by visible + waves somewhat likes waves at sea, but of less height and + moving much more swiftly. The sound becomes a roar. It is + difficult to stand, and at length it becomes impossible to + do so. The victim flings himself to the ground to avoid + being dashed to it, or he clings to a convenient sapling, + or fence-post, to avoid being overthrown. The trees are + seen to sway sometimes through large arcs, and are said, + doubtless with exaggeration, to touch the ground with + their branches, first on one side, then on the other. As + the waves rush past, the ground on the crests opens in + cracks which close again in the troughs. As they close, the + squeezed-out air blows forth sand and gravel, and sometimes + sand and water are spurted high in air. The roar becomes + appalling. Through its din are heard loud, deep, solemn + booms that seem like the voice of the Eternal One, speaking + out of the depths of the universe. Suddenly this storm + subsides, the earth comes speedily to rest and all is over." + +There are many other curious phenomena besides earthquake sounds or +noises. Among some of the more interesting are the fire and smoke that +are seen to come out of fissures that have been rent in the ground. + +It is possible that in many cases these flashes of fire are in reality +produced by electric discharges that momentarily light the clouds of +dust thrown up out of the fissure. But sometimes true flames are seen +escaping from the fissures. This was the case during the earthquake of +Lisbon, in 1755, when fire burst through fissures at several places, +burning with a lambent flame for some hours. + +The clouds of dust that follow the rending of mountain masses by +earthquakes are probably to be traced to the fracture of the rock +masses, the dust so formed being violently thrown forth by the air +squeezed out of the fissures, when they are suddenly closed. The +violent compression of this air may raise this dust to incandescence. + +Mallet asserts that in many cases the clouds of smoke observed do +not consist of true smoke like that produced when wood or vegetable +matters are incompletely burned, but is only ordinary air mixed with +sulphurous acid gas, and various other gases. + +But not only fire and smoke are seen at times coming out of fissures +in the earth. A thing still more frequently thrown out is water, which +often spouts forth along with great quantities of mud, sand, and the +finely ground fragments of earthy materials generally. Among many +other instances where the emission of water from the crevices was +particularly noticeable, may be mentioned the earthquakes at Jamaica +in 1687 and 1692. Here the water, in some places, was thrown out of +the ground to considerable heights in the air. + +Mallet calls attention to the fact that the waters of springs collect +in reservoirs consisting either of fissures or crevices of the rocks, +of small width but great depth, which are vertical or inclined to the +horizon, or in reservoirs that are formed of extended beds of sand or +gravel. + +Now, when the earthquake waves moving horizontally over the surface +produce movements that squeeze these fissures together, the water in +the fissures is spurted out in high jets, and carries with it the +finely divided rock or sand formed by the rubbing together of the rock +surfaces. In the case of the reservoirs consisting of beds of sand +or gravel, lying between impervious layers, if, during an earthquake +motion, the land areas are suddenly lowered, the water rushing into +the cavity thus left will afterwards be shot out with considerable +force, when the land is suddenly raised again. + +Where there are no direct openings in the ground the water will burst +through the crust in the shape of great vertical jets, thus forming a +circular hole, broken or fractured at its edges. Water jets of this +character were especially numerous during the earthquake of Calabria +in 1783. In a swampy plain, known as Rosarno, many of these circular +wells or openings about the size of an ordinary carriage wheel, though +in some cases much larger, were to be seen crowded together. The +appearance of the openings are represented in Fig. 40. + +Some of these were filled with water, but the greater number were dry +and filled with loose sand. These latter, when examined by digging, +were shown to be funnel-shaped, as seen in Fig. 41. As seen, the +margins of the wells exhibit a series of cracks or crevices extending +radially outward from the centre. Their origin is evident. As the +water was violently expelled by the squeezing motion of the upper +and lower impervious strata, it shot upwards, thus producing the +funnel-shaped tube. At the same time the force of the eruption was +sufficiently great to produce the radial fissures or fractures at the +sides. + +[Illustration: FIG. 40. CIRCULAR HOLLOW FORMED BY CALABRIAN +EARTHQUAKE] + +[Illustration: FIG. 41. SECTION OF CIRCULAR HOLLOW FORMED BY +CALABRIAN EARTHQUAKE] + +But greater fissures than these have been formed by earthquakes, +especially those of the class created by a slipping of the earth's +strata. In the case of an earthquake on the South Island of New +Zealand, in 1848, a fissure having an average width of eighteen +inches could be clearly seen extending in a direction parallel to +the mountain chain for a distance of sixty miles, and during a later +earthquake in the same region, in 1855, a fracture was formed that +could be clearly traced for a distance of nearly ninety miles. + +In some cases these fissures or fractured parts of the crust are left +with one of their sides at a higher level than the opposite side. This +was the case of the great Japanese earthquake of October 28th, 1891. + +There are three kinds of waves produced by earthquakes; namely, the +earthquake waves proper through the earth; the sound waves in the air, +and great forced waves in the sea. + +The sound waves of course reach the air from the point of origin below +the earth's surface through the solid materials of the crust, and take +on the curious varieties already described in connection with the +sounds accompanying earthquakes. + +We have already briefly described the manner in which the earthquake +waves travel through the materials of the earth's crust. There remain +to be discussed the great waves that are rolled up in the ocean +during an earthquake shock. These waves are, perhaps, among the most +destructive phenomena of great earthquakes. The following are only +some of the more remarkable of such waves, and have been taken from +Mallet's collection of earthquake data. + +During some of the great earthquakes on the coasts of Chile and Peru, +huge waves from the ocean did great damage when they reached the land. +In the earthquake of 1590, ocean waves rushed for several leagues +inland over the coast of Chile, carrying with them ships that were +left high and dry as the wave receded. In the earthquake of 1687, +Callao was inundated by a great wave from the Pacific Ocean, and ships +were carried a full league into the country. During the earthquake of +1746, Callao was again swept away by a huge ocean wave. At later times +earthquake waves have caused great damage to several other parts of +the coast of South America. + +Ocean waves of this character are formed by successive upward and +downward movements at the bottom of the ocean, following each other at +very brief intervals. Le Conte points out that the sudden upheaval of +the bed of the ocean forms a huge mound in the surface of the water +which results in a large wave that spreads rapidly in all directions. +Waves produced in this manner sometimes reach a height of fifty to +sixty feet. They are not readily observed in the deep ocean, but +as soon as they reach the shallow waters near the shore they rush +forward, forming waves from fifty to sixty feet in height and, rushing +over the land, sweep everything before them. + +During the great Lisbon earthquake of 1755 a huge wave started at a +point fifty miles off the coast of Portugal. Half an hour after the +earthquake was over several waves, the largest of which was sixty +feet in height, rushed over a part of the city and greatly increased +the ruin already wrought by the earthquake. According to Le Conte the +great waves so formed moved in all directions across the Atlantic +Ocean. They were thirty feet high when they reached Cadiz, eighteen +feet in height at Madeira, and five feet on the coast of Ireland. They +even crossed the Atlantic, being observed on the coasts of the West +Indies. + +A great ocean wave accompanied the Japanese earthquake in 1854. As in +the case of the Lisbon earthquake this wave started in the bed of the +ocean off the coast of Japan and only reached the island half an hour +afterwards. It was thirty feet in height, and completely swept away +the town of Simoda. + +Owing to water's greater freedom of motion earthquake waves travel +greater distances through the water than they do on land. + +Of course, great earthquake shocks as a rule cause a very large loss +of life. The following figures from Mallet give some idea of the +extent of this loss, which is generally a matter of a few moments. + +In the Lisbon earthquake, where the worst shock lasted a few seconds, +60,000 people were killed. During other earthquakes the losses have +been as follows: 10,000 at Morocco; 40,000 in Calabria; 50,000 in +Syria, and probably 120,000 in earthquakes that occurred in Syria in +A. D. 19 and in A. D. 526. + +But even these figures give only a meagre idea of the vast loss of +life that has occurred during the past. It is said that during the +reign of Justinian, earthquakes repeatedly shook the whole Roman +world. The city of Constantinople was visited by earthquake shocks +that continued at intervals for forty days. Deep chasms were opened in +the earth and huge masses were thrown into the air. Enormous sea-waves +were formed. At Antioch, during the earthquake of May 20th, A. +D. 526, 250,000 people are believed to have been killed. + +On the 31st of July, A. D. 365, in the second year of +Valentinian, a dreadful earthquake shook the Roman world, and a great +wave rolled in from the Mediterranean and swept two miles inland, +carrying ships over the tops of houses. During this earthquake 50,000 +people lost their lives at Alexandria. + +In the earthquake of Messina in 1692, 74,000 people are said to have +been killed; and, according to other accounts, 100,000. In the year +A. D. 602, another earthquake at Antioch killed 60,000 people. + +During the earthquake of Quito, in 1797, Humboldt estimates that +40,000 natives were either buried in crevices in the earth, under +the ruins of buildings, or were drowned in lakes and ponds that were +temporarily formed. + +In this connection Mallet writes as follows: + + "Such are the numbers to be met with in narratives, and + if we suppose that there occurs one great earthquake in + three years over the whole earth and that this involves the + entombment of only 10,000 human beings, and that such has + been the economy of our system for the last 4,000 years, we + shall have a number representing above 13,000,000 men thus + suddenly swallowed up, with countless bodies of animals of + every lower class. Sir Charles Lyell then with good reason + suggests that even in our own time we may yet find the + remains of men and of their habitations and implements thus + buried deep and embalmed, as it were, by earthquakes that + occurred in the days of Moses and the Ptolemies." + +Necessarily the progress of a great earthquake wave will produce great +changes in the earth's surface features; for example, landslides, +where immense layers of clay or other material slip or slide to a +lower level and are thrown across the course of a river, causing its +waters to be dammed up and then by spreading to form great lakes. + +Sometimes, after vast bodies of water have been collected in this +manner, disastrous floods result later from a sudden giving way of the +barrier, and the loss thus caused is occasionally far greater than +that directly due to the earthquake. + +Permanent changes of level are frequently caused by earthquakes, as, +for example, the coast of Chile during the earthquake of November +19th, 1822, where the coast for many miles was raised from three to +four feet above its former plane. + +In other cases the level of the ground is permanently lowered. This +occurred in the Bengal earthquake in 1762, when an area of some sixty +square miles suddenly sank, leaving only the tops of the higher points +above water. + +In some cases of changes in the level of the ground, large areas being +raised in one place and lowered in another, rivers take new courses, +and their old courses are completely obliterated. + + + + +CHAPTER XXV + +THE EARTHQUAKE OF CALABRIA IN 1783 + + +All students of elementary geography are quick to notice that the +extreme southeastern part of Italy is shaped something like a boot, +which appears to be kicking at the island of Sicily. This part of the +Mediterranean Sea has for very many years been the arena or storm +centre of more or less intense volcanic activity. To the northwest is +the active volcano of Vesuvius, as well as the volcanic regions of the +Phlegræan Fields. Immediately opposite the point of Italy, near the +toe of the foot, is the active volcanic mountain, Etna, while not far +from this point is the volcano of Stromboli. + +In 1783 this part of the world was visited by a very severe +earthquake. Since at that time the country was divided into two +parts, known as Upper Calabria and Lower Calabria, this earthquake is +sometimes spoken of as the earthquake of the Calabrias, or more simply +as the Calabrian earthquake. + +The great mountain range of the Apennines, mainly of granite +formation, extends through the central part of Italy. The lands +adjoining the mountains on each side are flat and marshy, and +consequently unhealthy. + +Numerous observers have compiled excellent accounts of the Calabrian +earthquake. These, having been made by educated persons, are, to a +large extent free from the inconsistencies and exaggerations apt to +characterize descriptions by ignorant persons, especially when in +a condition of excitement or alarm. Among reliable writers was Sir +William Hamilton, who made a personal examination of the region, soon +after the first severe shock, and collected much valuable information +for a paper which was afterwards published in the Philosophical +Transactions of the Royal Society. Then, too, Dolomieu, another +scientific man of high ability, made a careful study of the effects +produced by the earthquake. + +[Illustration: FIG. 42. MAP OF THE CALABRIAN EARTHQUAKE OF +1783] + +As can be seen by an examination of the map presented in Fig. 42, the +part of Italy included in the Calabrias covers an area from north to +south almost equal to two degrees of latitude. Although the shock +extended beyond the limits of Calabria, since it reached as far north +as Naples, as well as over a great part of the Island of Sicily, the +territory in which the greatest damage was done did not exceed in area +about 500 square miles. + +The southern part of Italy is subject to frequent earthquake shocks. +Pignatari, an Italian physician, asserts that this region was visited +during 1783 by no less than 949 earthquakes, of which 501 were of the +first class, or degree of intensity, while in 1784, there were 151 +earthquakes, of which ninety-eight were of the first class. + +It seems that the city of Oppido, marked on the above map as midway +between the two coasts, was the point from which the severe earthquake +of 1783 started. If one draws a circle, with a radius of twenty-two +miles, around Oppido as a centre, the portions of the Calabrias that +were the most affected will all lie within this circle. + +The great Calabrian earthquake was attended by numerous shocks. The +first and the most severe shock, that of February 5th, 1783, was only +two minutes in destroying most of the houses in all cities, towns, and +villages on the western side of the Apennines in this part of Italy. + +Another severe shock occurred on the 28th of March. This shock was +almost as severe as that of February 5th. + +In order to understand many of the effects produced by this +earthquake, inquiry must be made into the geological character of the +region. According to Dolomieu, the flat country at the slopes of the +Apennines, known as the Plain of Calabria, is covered with sand and +clay mixed with sea shells. These strata have been deposited by the +sea from materials that have been obtained by the decomposition of the +granite mountain ranges in the Apennines. The plain is quite level +except where it is crossed by deep valleys or ravines, which have +been eroded or cut by the swift mountain torrents. In many cases, +these ravines or valleys have depths as great as 600 feet. Their sides +are generally almost perpendicular. Consequently, as Lyell remarks, +throughout the length of the mountain chain, the soil, which adheres +but loosely to the granite base of the mountain chain, could therefore +be easily separated from the mountain, and sliding over the solid +steeps of the mountain could readily move, especially through the +ravines or gorges, to distances in some cases as great as from nine to +ten miles. + +This peculiarity of the country must be thoroughly understood, since, +otherwise, it would seem impossible that lands could be carried +several miles from their former position, and often bear along +with them almost undisturbed houses, olive groves, vineyards, and +cultivated fields. + +The heaving of the surface of the earth like the waters of the sea, +so common in severe earthquakes, occurred during the Calabrian +earthquake. In some places this heaving so shook the trees that they +bent until their tops touched the ground near their base. + +Parts of the ground were violently thrown upwards into the air as in +the explosive type of earthquakes. In many instances the large paving +stones were thrown into the air and afterwards found with their lower +portions upwards. + +During the earthquake deep fissures were made in the earth at various +localities and there were, moreover, marked changes of level. At +Messina in Sicily the shore was fissured and rent and while before the +convulsion the surface had been level, it was afterwards found to be +inclined toward the sea. + +According to Dolomieu the following curious incident occurred during +the passage of the earthquake waves. A well in the ground of one of +the convents of the Augustines, lined on the inside with stones, was +so affected by the upward thrust given to the land that its stone +lining was left projecting above the level of the earth in the form of +a small tower some eight or nine feet in height. + +Frequent instances occurred of deep fissures in the surface of the +earth. Many of these remained open after the earthquake, although in +other cases they were firmly closed together before the earthquake +shocks ceased. + +[Illustration: FIG. 43. FISSURES CAUSED BY THE CALABRIAN +EARTHQUAKE] + +Fig. 43 represents the appearance of certain fissures in a part of +Calabria during this earthquake. These cracks, it will be noticed, +radiate or pass outward in all directions from a central point, just +like the cracks that are formed in a glass window pane when it is +fractured by a stone thrown against it. + +Of course, the most violent effects were near the origin of the +earthquake at Oppido. Here the formation of deep fissures was common. +In another part of the country a number of buildings were suddenly +swallowed up in a central chasm, which almost immediately closed, +thus permanently burying all these objects. + +Some idea of the force with which the fissures were afterwards closed +can be formed by reflecting on a case where, in order to recover some +of the buried articles, the ground was dug up at these points, and it +was found that the materials, human bodies and other objects, were so +jammed together as to make one compact mass. + +To Sir William Hamilton a place was shown where the fissures, though, +when he saw them, they were not more than a foot in width, had opened +sufficiently wide during the shock to swallow up a hundred goats as +well as an ox. + +An earthquake that caused such marked changes in the appearance of the +earth's surface, naturally made great changes in the direction of the +rivers. In one case the end of a small valley was so completely filled +with stones and dirt that the water was dammed up, producing a lake +two miles in length and one mile in breadth. In a similar manner no +less than 215 lakes were formed in different portions of Calabria. + +Of course, in the flat country at the base of the Apennines, +frequent landslides occurred, the land sliding into great chasms and +continuing to move down them for considerable distances, so that in +many places pieces of land containing olive trees, vineyards, and +green fields, were bodily transported for distances of several miles. +This, moreover, was done so quietly as to leave the houses entirely +uninjured, and the trees and other vegetation continuing to grow up +with apparently no marked decrease in vitality. + +As is usual in such cases, the sudden and strong blows acting on the +waters of the sea, killed great numbers of fish just as does the +explosion of dynamite at a point below the surface of the water; and +in a similar way the fish that usually live at the bottom of the sea +in the soft mud, being disturbed by the earthquake shocks, came near +the surface where they were caught in vast numbers. + +It is an interesting fact that during this earthquake the volcano of +Stromboli showed a marked decrease in the volume of smoke it gave out. +Etna, however, was observed to emit large quantities of vapor during +the convulsion. + +Lyell tells the following story of the Prince of Scilla, who with +many of his vassals sought safety in their fishing boats. Suddenly, +on the night of February 5th, while some of the people were sleeping +in the boat, and others were resting on a low plain near the sea, +in the neighborhood, another shock occurred, a great mass was torn +from a neighboring mountain and hurled with a crash on the plain, and +immediately afterwards a wave, twenty feet or more in height, rolled +over the level plain, sweeping away the people. It then retreated, but +soon rushed back again, bringing with it many of the bodies of the +people who had perished. At the same time all the boats were either +sunk or dashed against the beach, and the Prince with 1,430 of his +people was destroyed. + +The total number of deaths caused by this earthquake in the Calabrias +and Sicily were estimated by Hamilton at 40,000. Besides these about +20,000 more perished in epidemics that followed the earthquake, or +died for lack of proper food. + + + + +CHAPTER XXVI + +THE GREAT LISBON EARTHQUAKE OF 1755 + + +Lisbon, the capital of Portugal, on the Tagus River, is built along +both banks for five miles, and on several small neighboring hills. It +is supplied with water by means of an aqueduct, called the Alcantara, +which brings the water from springs about nine miles to the northwest. +For portions of its length the aqueduct is placed underground, but +where it crosses the deep valley of the Alcantara it is supported, +for a distance of 2,400 feet, by a number of marble arches, which +in one place are 260 feet in height. This fact is put forward not +merely for the sake of its artistic interest, but because, strange to +relate, this part of the aqueduct remained uninjured during that great +earthquake, the greatest of modern times. + +On the 1st of November, 1755, this frightful catastrophe, according to +Lyell, from whose excellent account much of the information contained +in this chapter has been obtained, struck the beautiful city almost +without any warning. Terrible sounds came suddenly from underground; +almost instantly afterward a violent shock threw down the greater +portion of the city; in less than six minutes 60,000 people were +killed. + +The place from which this earthquake started must have been situated +on the bed of the ocean at some distance from the coast; for the great +wave thus raised in the Atlantic Ocean did not reach the mouth of the +Tagus River until about half an hour after the most severe shocks +were over. The arrival of this wave at the mouth of the Tagus was +announced by the sea retiring to such an extent as to leave the bar +dry. Then a huge wave, sixty feet in height, rolled in from the ocean +and completed the work of destruction that had been commenced by the +earthquake. + +So great was the shock that the mountains in the neighborhood were +violently shaken and some of them split or fractured in a most +wonderful manner. + +Particularly large was the loss of life in the churches whither +hundreds hastened for refuge when the shakings of the earth began, +for most of these buildings fell and buried the worshippers. Another +immense loss of life was caused by the destruction of a large marble +quay or wharf that was suddenly swallowed up by the sea. While the +buildings in the city were being overthrown by the violent shakings +of the earth, a multitude sought the quay as a flat place where they +could not be injured by the falling buildings. Suddenly, however, +this structure sank into the water and not only were all the people +drowned, but none of the bodies was ever afterwards found. + +Failure to find any remnants of the pier or any of the people who +perished on it has been attributed to the formation of eddies or +whirls that were sufficiently strong to carry down vessels by suction +similar to that of the famous maelstrom off the coast of Norway. Of +course, in a time of boundless excitement like that of the Lisbon +earthquake, accounts are apt to be highly exaggerated. For example, +assertions are made in many books that the water left in the harbor +after the sinking of the quay was unfathomable. Now, in point of fact, +the depth of this place has been measured and found to be less than +100 fathoms. + +When it is remembered that not one of the bodies of the people on that +quay was ever again seen, it is possible, as Lyell suggests, that a +deep fissure or chasm opened immediately on the ground on which the +quay stood, so that it, together with all on it, were dropped into the +chasm, which, closing, buried them deep in the earth. + +The Lisbon earthquake was especially noted for the extent of country +affected by it. Humboldt estimated this area as being more than four +times the size of Europe. In parts of this area immense mountain +ranges, such as the Pyrenees, Alps, etc., were violently shaken. When +the size of these mountains is considered one realizes that it must +have required a mighty force to shake them. These shakings were so +severe that they produced a deep fissure in the ground in France. +Continuing towards the north the solid earth was shaken as far as +the shores of the Baltic and Norway and Sweden, generally. This, of +course, included the flat country of Northern Germany. The hot springs +of Toplitz disappeared for a time, but, breaking out afterwards, +discharged such quantities of muddy water that the surrounding country +was inundated. + +The waves crossed the Atlantic, causing high tides on the island of +Antigua, Barbadoes, and Martinique, of the Lesser Antilles, where, +instead of the usual tides of two feet, tides of twenty feet high were +observed. Further to the north the waves reached the eastern shores of +North America, and shook the continent as far west as the Great Lakes, +and spread in the North Atlantic as far as Iceland. + +Toward the south the waves affected parts of northwestern Africa, +where much loss of life occurred in the villages some eight leagues +distant from the city of Morocco. Here from 8,000 to 10,000 people +were killed, being swallowed up by deep fissures in the earth, which +afterwards closed on their bodies. + +Severe shocks were in many cases felt on vessels at sea. In one +instance, although the vessels were at considerable distances from +where the waves started, the captains reported that the shocks were so +great that on several occasions it was believed the vessel had struck +a rock, till, on heaving the lead, they found that they were in very +deep water. In another instance, such was the shock to the vessel that +the planks on the deck had their seams opened. In still another case +several of the sailors were thrown into the air for a distance of +about one and a half feet. + +It has been frequently observed that when great earthquakes happen, +curious changes take place in the level of the waters of lakes +entirely disconnected with the ocean; for example, mountain lakes, +far above the level of the sea, the water suddenly rising and then +resuming its original level. Sometimes the waters of such lakes have +suddenly disappeared, probably being drained off through a fissure +formed in the bed of the lake. In such event the lake generally +remains dry after the passage of the earthquake. + +At the time of the Lisbon earthquake it was observed that the water of +Loch Lomond in Scotland first rose above its ordinary, then sank again +to its usual level. This difference of level is explained by Lyell as +follows: when the earthquake waves reached the lake, the water being +unable to take the sudden shove given to it by the earthquake waves, +dashed over that side of the basin which first received the shock. +Assuming this to be the case, since the rise of the level in the water +of Loch Lomond was two feet and four inches, it is comparatively easy +to calculate the speed of movement that the earthquake waves had, +when they reached this body of water. Calculated in this way it would +seem that the waves had a speed of about twenty miles a minute. + +But what especially characterized the Lisbon earthquake were the great +waves that were produced in the ocean. Besides the huge wave that +entered the Tagus, a wave of the same height swept eastward along the +southern coast of Spain, and the northwestern coast of Africa. At +Tangier in Africa it swept the coast as a very high wave no less than +eighteen times, or, in other words, eighteen huge waves rolled in from +the ocean. At Funchal, on the Madeira Islands, this wave rose fifteen +feet above the high water mark. + +Many attempts have been made to explain the manner in which the great +sea waves are started in earthquake movements. Some believe that they +are due to the sudden raising or heaving up of the water, far above +ordinary level. But, as Lyell points out, this explanation would not +be satisfactory for the waves produced in the case of the Lisbon +earthquake, since it would fail to account for the fact that both on +the coasts of Portugal as well as on the island of Madeira the high +wave was preceded by a movement of the water toward the point of +origin; that is, the waters moved away from Lisbon and the Madeira +Islands, so as to leave the water very low at those points, when +shortly afterwards a huge wave rushed in from the sea and swept over +the land. + +Earthquake waves move much more rapidly through the solid rocks of +the earth's crust than through the waters of the ocean. The shock +transmitted through the solid earth from Lisbon to the Madeira Islands +took only twenty-five minutes to reach the islands, while the waves in +the ocean took about two and a half hours to cover the same distance. + + + + +CHAPTER XXVII + +THE EARTHQUAKE OF CUTCH, INDIA, IN 1819 + + +Cutch is one of the Provinces of India lying on the western coast of +Hindostan, east of the delta of the Indus River. + +A great earthquake occurred in this region on June 16th, 1819. As +indicated by the map presented in Fig. 44, by Lyell, the district +of Cutch lies on the coast of the Arabian Sea. Cutch is at times a +peninsula, being washed on the south and east by the Arabian Sea and +the Gulf of Cutch, and on the north by a depression known as the Runn +of Cutch which, during unusual tides, is overflowed by the waters of +the sea, but for the rest of the year is dry. + +The earthquake of Cutch was apparently central at the town of Bhooj, +where the destruction was extreme, hardly a house being left standing. +The shock extended over a radius of about 1,000 miles from Bhooj, +reaching to Khatmandoo, Calcutta, and Pondicherry. + +At Anjar the fort, together with its tower and guns, were completely +ruined. The shocks continued at intervals after the principal shock +until June 20th, when the volcano of Denodur is said by some to have +emitted flames, although this is denied by others. + +Great changes were produced in the eastern channel of the Indus, +which forms the western boundary of the Province of Cutch. The water +in this inlet had become so low that it was readily fordable at low +tide at Luckput, and was only covered with six feet of water at high +tide. After the earthquake it deepened at the port of Luckput to over +eighteen feet at low tide, while in other parts of the channel the +water had deepened from four to ten feet at high tide, where before +the earthquake shock it had never been deeper than from one to two +feet. Indeed, after these changes the inland navigation of the country +again became possible after having been closed for many centuries. + +[Illustration: FIG. 44. MAP SHOWING DISTRICT VISITED BY THE +EARTHQUAKE OF CUTCH OF 1819] + +The Cutch earthquake resulted in a marked depression of the country, +especially north of Luckput, where the fort and village of Sindree +were so quietly sunk that the fort, with its tower and walls, was left +projecting slightly above a body of water that not only completely +covered the old site but also formed a large lake marked on the +preceding map, at Sindree, by the dark shading. It was this change of +level that deepened the eastern channel of the Indus, just mentioned. + +[Illustration: FIG 45.. SINDREE BEFORE THE EARTHQUAKE OF +1819] + +Fig. 45, from Lyell, gives an idea of the appearance of the fort at +Sindree before the earthquake. The appearance of the fort after its +submergence is represented in Fig. 46, where, as will be noticed, only +the top of the tower and the walls remain above the surface of the +water. That the masonry was not affected either by the earthquake, or +by the inrush of waters, is evident from the fact that the ruins were +still standing in March, 1838, as represented in the figure. + +In heavy shading on the map in Fig. 44 is a large area lying in the +northern part of the province known as the Runn of Cutch. This is a +flat region of about 7,000 square miles. It owes its level surface to +its being the deserted or dried-up bed of a sea. For the greater part +of the year its bottom is dry and hard, and is covered with a crust of +salt half an inch or so in thickness. + +[Illustration: FIG. 46. SINDREE AFTER THE EARTHQUAKE OF 1819] + +According to Lyell, from whom most of the facts concerning this +earthquake have been obtained, the Runn of Cutch is connected with +a vast inland sea, not only by the water driven into it through the +Gulf of Cutch, but also through the eastern channel of the Indus at +Luckput. These changes occur especially during the monsoon, when the +seas are high, and especially after the heavy rains that come with +these winds, when the wet condition of the soil permits the sea water +to spread rapidly. + +Traditions of the natives tend to confirm belief that Cutch a long +time ago was a true peninsula, and that the Runn of Cutch was then an +arm of the sea. + +That a change of this character did occur in the Runn of Cutch seems +to be proved by the ruins of old towns now far inland that are said to +have been ancient seaports, and as apparent evidences of this many +pieces of wrought iron and ships' nails have been found in parts of +the Runn. + +At the same time that the sinking of the land around the fort and +village of Sindree took place a considerable elevation occurred in the +neighborhood. Immediately after the earthquake, the people in Sindree +saw that a low hill or mound had been thrown up in a place that before +had been a low and perfectly level plain. They named this elevation +the Ullah Bund, or _the Mound of God_, in order to distinguish it +from several embankments that had been built directly across the +eastern mouth of the Indus; for the Ullah Bund had been raised by the +earthquake across the same branch of the Indus. + +For several years after the earthquake of 1819 marked changes kept +developing in the channels of the Indus. During 1826 a large body of +water entered into the eastern branch of the Indus above the Ullah +Bund and finally forced its way through the mound, thus establishing +a direct course to the sea. The Ullah Bund, being thus cut in two, +an opportunity was afforded of seeing the materials of which it was +composed. These were found to consist principally of clay filled with +shells. + +The opening of the river resulted in throwing such large quantities of +fresh water into Lake Sindree that its waters were rendered fresh for +several months, but at last regained their saltiness. + +Dana states that in 1845 another earthquake occurred in this district +which converted Sindree Lake into a salt marsh. + + + + +CHAPTER XXVIII + +THE SAN FRANCISCO EARTHQUAKE OF APRIL 18, 1906 + + +About twelve minutes past five o'clock on the morning of the 18th of +April, 1906, the inhabitants of San Francisco were rudely awakened by +a few frightful earthquake shocks. Their houses were violently shaken +to and fro, and on all sides were heard the awful crashings of falling +walls, chimneys, and buildings, together with the death-shrieks of +those caught in the ruins. Rushing madly into the streets they could +see on every side evidences of destruction; for, in almost every +direction, were heaps of fallen buildings, still being violently +shaken by the earthquake waves that rapidly passed through the solid +earth. Huge cracks or crevices had been formed in the streets, while +the heavy rails of the trolley tracks had been bent and twisted by the +mighty forces. + +Before describing in detail the great San Francisco earthquake, the +location of the city and its surroundings demand consideration. + +As can be seen from the map, Fig. 47, San Francisco is situated on the +western coast of California, at the northern end of a peninsula, some +twenty miles in length and about six miles in width. This peninsula +is formed by the magnificent Bay of San Francisco on the east, a +navigable strait called the Golden Gate on the north, and the Pacific +Ocean on the west. + +[Illustration: FIG. 47. MAP OF WESTERN COAST OF CALIFORNIA SHOWING +POSITION OF SAN FRANCISCO] + +San Francisco Bay, accessible by the Golden Gate, is the principal +harbor on the Pacific Coast, and is, indeed, one of the most +magnificent harbors in the world. It is land-locked, that is, +surrounded by a continuous land border except at its entrance through +the Golden Gate. Including San Pablo Bay, it has a length of about +fifty-five miles, and varies in breadth from three to twelve miles. +The entrance to the harbor, however, is impeded by a bar across the +mouth of the Golden Gate, over which there is a depth of but thirty +feet of water at low tide. + +San Francisco has over 750 miles of streets, 200 miles of which are +paved. The city is lighted by both electricity and gas, and has an +extensive system of water-works, the water being brought from the +Pilarcitos and Calaveras Creeks, situated from twenty to forty miles +respectively from the city. + +San Francisco is in a region where earthquakes are common. It might, +therefore, be visited at any time by a great catastrophe. There have +occurred between 1850 and 1888, no less than 254 earthquake shocks in +the State of California, these shocks having been especially frequent +in the country surrounding San Francisco Bay. The most severe were +the earthquake of 1868, which injured San Francisco; the Owens Valley +earthquake of 1872; the Vacaville earthquake of 1892; the Mare Island +earthquake of 1898; and a smaller earthquake in 1900. Since 1900 there +was a period of rest until the 18th of April, 1906. + +As in the case of practically all severe earthquakes, that which +destroyed San Francisco consisted of a few momentary shocks: then all +was over. According to a preliminary report of the State Earthquake +Commission, appointed by the Governor of California, April 21st, 1906, +these shocks, as recorded in the observatory at Berkeley, began at +twelve minutes and six seconds after five A. M., Pacific +Standard Time. Their entire duration was only one minute and fifty +seconds, but, as frequently happens, there were a number of minor +shocks, following at regular intervals during the next few hours as +well as the next few days. + +While the most severe shocks were in the neighborhood of the Peninsula +of San Francisco, yet minor disturbances were felt as far north +as Coos Bay, Oregon, and as far south as Los Angeles, California. +As shown by recording instruments at the seismograph station at +Washington, D. C., Sitka, Alaska; Potsdam, Germany; and Tokio, Japan, +a series of waves were propagated through the earth, as well as over +its periphery. + +The damage done within the city limits was wide-reaching. Among the +buildings almost completely destroyed were the City Hall, on which +about $7,000,000 had been expended, the United States Post Office, +besides many business blocks, hotels, department stores, theatres, +banks, churches, and dwelling houses. + +Amid the terrors of such a calamity it is difficult to obtain +observations possessing any scientific value. Fortunately, however, +there was in the city a physicist trained to observe phenomena of this +character, Professor George Davidson of the University of California. +Like others, he had been awakened by the first severe shock. At once +recognizing the nature of the phenomenon, and desirous of obtaining +the exact time of its occurrence, he counted seconds while he ran +towards the table on which he had placed his watch, and in this way +estimated that the shock occurred at twelve minutes past five in +the morning. The closeness of this observation is emphasized by the +fact that it differed from the recorded time by only six seconds. He +states that the motion, at the time of its greatest intensity, closely +resembled that of a rat vigorously shaken by a terrier. + +The destruction caused by the earthquake was, however, but a small +part of the total loss to the city. Fires were almost immediately +started in the ruined houses by the fires in the kitchens and other +parts of the houses, by the ignited jets of the illuminating gas, +and, perhaps, especially, by the crossing of numerous electric light +wires. + +The manner in which the woodwork and other combustible materials of +the buildings were loosely tossed together by the shocks helped the +quick spread of the fires, and this, too, was probably greatly aided +by the illuminating gas from the broken gas pipes and mains. Eight +severe conflagrations were, therefore, soon raging in different parts +of the doomed city. What made these fires especially dangerous was the +fact that the earthquake shocks had destroyed the water pipes. Thus +the firemen were handicapped in their heroic endeavors to extinguish +the flames. + +At the time of the fire a strong wind was blowing from the northeast. +Since the firemen were unable to check the flames, the fire line +rapidly advanced. Its path led towards the best residential parts of +the city through portions of the mission section containing a dense +population of poor people. The dwellings in this latter section +consisted of frame houses, through which the flames rapidly spread. + +There was but one way to save the city from total destruction--a free +use of dynamite! This was intelligently employed until the supply gave +out, when it seemed that the city was doomed to utter destruction. +But at the last moment, as it were, came a lucky change in the +direction of the wind. Instead of blowing from the northeast, the +steady southwest winds set in, and beat back the fire on itself, so by +Friday, the 18th being Wednesday, it was under complete control and +the rest of the city was saved. + +[Illustration: A SAN FRANCISCO PAVEMENT TORN BY THE +EARTHQUAKE _From a Stereograph, Copyright, 1906, by Underwood & +Underwood_] + +The extent of the fire is thus described in an article in the +"Outlook," for Saturday, April 28th, 1906, as follows: + + "The turn in the direction of the fire endangered for a + time the great Ferry House, at the foot of Market Street. + While the section actually destroyed is not, geographically + speaking, much more than one-third of the city limits, + yet it is in the heart of San Francisco, and includes the + chief business streets and the Mission District, inhabited + by poor people, and a large part of the so-called Nob Hill + Quarter, where were the finest and costliest residences of + the city. Another fine residence section, Civic Heights, + escaped, together with that known as the Western District. + + "The unburned district, though large in extent, was in + the nature of suburbs, and was not closely built up, so + that estimates made, as late as Saturday, declared that + three-fourths of San Francisco's improvements in real + estate had been destroyed." + +The burnt district was about two miles from east to west and from two +to four miles from north to south, with, of course, very irregular +outlines. + +Naturally, the great destruction wrought by the earthquake of April +18th, 1906, attracted the almost universal attention of scientific men +especially interested in earthquake phenomena. We are, therefore, able +to speak authoritatively about the probable causes. + +The great San Francisco earthquake of April 18th, 1906, appears to +have been a _tectonic_ quake. Ransome, in an article entitled, "The +Probable Cause of the San Francisco Earthquake," says: + + "The region thus amply fulfils the conditions under which + tectonic earthquakes arise. It is in unstable equilibrium, + and it is cut by long northwest faults into narrow blocks + which are in turn traversed by many minor dislocations. + Under the operation of the unknown forces of elevation and + subsidence, stresses are set up which finally overcome the + adhesion of the opposing walls of one or more of the fault + fissures; an abrupt slip of a few inches, or a few feet, + takes place and an earthquake results. The region extending + for some hundreds of miles north and south of the Bay of + San Francisco may be considered as particularly susceptible + to shocks on account of the number and magnitude of the + faults and the evidences that these furnish of very recent + slippings and the marked subsidence in the vicinity of the + Golden Gate." + + + + +CHAPTER XXIX + +SOME OTHER NOTABLE EARTHQUAKES + + +It would, of course, be impossible within the limits of this book to +attempt a description of all the remarkable earthquakes in the annals +of science; but before leaving this part of the theme a brief account +of a few more among the many may be worth while. + +Jamaica, one of the West Indian Islands, about ninety miles south of +Cuba, suffered a very destructive earthquake in 1692. During this +earthquake the ground was agitated like the waves of the sea. These +movements were so violent that numerous fissures were made in the +ground, as many as 300 being formed at the same time, rapidly opening +and closing. Many of the inhabitants were swallowed up in these +fissures. In some cases, however, their bodies were afterward thrown +out of the fissures, along with quantities of water. + +The Jamaican earthquake was characterized by marked sinkings of the +ground. At the city of Port Royal, which was then the capital, many +houses on the harbor side sank in from twenty-four to forty-eight +feet of water. As in the case of the earthquake at Cutch, many of +these houses were left standing, the chimney tops of some being seen +above the water, with their foundations and other parts apparently +uninjured, and some of them were standing at a date as late as 1780. +At a little later date, 1793, they were mostly ruins. + +During the Jamaican quake a tract of land containing at least 1,000 +acres near the town was sunk, and a wave of the sea rolled over it. +This wave is said by Lyell to have carried a frigate over the roofs of +the houses and left it stranded on one roof. When the wave rolled back +to the sea, the weight of the frigate made it fall through the roof. + +Perhaps one of the most remarkable things about the Jamaican +earthquake was the swallowing up of several plantations, which +disappeared, together with all their inhabitants, their former place +becoming a lake. But the lake soon disappeared, leaving a mass of sand +and gravel which obliterated any least sign that dwellings and trees +had once adorned the spot. + +The forces developed during this earthquake were sufficiently powerful +to make several rents in the Blue Mountains, and the shock of blows on +the waters of the sea killed fish by the hundred thousands so that the +silver shine of their dead bodies stretched for miles and was beheld +for days "on the face of the deep." + +Portions of the world that have been frequently visited by mighty +earthquakes, are the coasts of Chile. On the 24th of May, 1751, a part +of the Chilian coast near the ancient town of Concepcion, sometimes +called Penco, was destroyed by an earthquake, and the powerful +earthquake waves that afterwards rushed in from the sea. So complete +was this destruction that the ancient harbor was rendered useless and +the people had to build another town about ten miles from the coast, +so as to be beyond the reach of earthquake waves from the sea. + +Another great earthquake occurred on the coast of Chile on the +19th of November, 1822. This shock was felt simultaneously over a +distance of 1,200 miles from north to south. It reached its greatest +intensity about 100 miles north of Valparaiso. This earthquake caused +a rising of the coast to a height of from three to five feet. From +careful examinations it appears that the area over which a permanent +elevation of the country took place must have been equal to 100,000 +square miles, an area equal to about half of the area of France, and +five-sixths that of Great Britain and Ireland. + + "If we suppose," says Dana, "the elevation to have been + only three feet on an average, it will be seen that the + mass of rock added to the continent of America by the + movement, or, in other words, the mass previously below the + level of the sea, and after the shock, permanently above + it, must have contained fifty-seven cubic miles in bulk; + which would be sufficient to form a conical mountain two + miles high (or about as high as Etna) with a circumference + at the base of nearly thirty-three miles.... Assuming the + Great Pyramid of Egypt, if solid, to weigh in accordance + with the estimate before given 6,000,000 tons, we may + state that the rock added to the continent by the Chilian + earthquake would have equalled more than 100,000 pyramids. + + "But it must always be borne in mind that the weight of + rock here alluded to constituted but an insignificant + part of the whole amount which the volcanic forces had to + overcome. The thickness of rock between the surface of + Chile and the subterranean foci of volcanic action may be + many miles or leagues deep. Say that the thickness was only + two miles, even then the mass which changed place and rose + three feet, being 200,000 cubic miles in volume, must have + exceeded in weight 363,000,000 pyramids." + +The shocks of this earthquake continued from the time of its +occurrence, on November 19th, 1822, to the end of September, 1823, and +even then there were scarcely two days that passed without a shock. + +On the 20th of February, 1835, the same part of the world was in the +throes of an earthquake that was felt nearly 1,000 miles from north to +south, or from near the town of Concepcion to the Isle of Chiloe, and +from east to west a distance of about 500 miles, from Mendoza to the +island of Juan Fernandez, which you probably know better as Robinson +Crusoe's Island. By this earthquake the new town of Concepcion and +several other towns were partly destroyed. + +There were the same phenomena connected with great sea waves that are +common in earthquakes of this character. Both this and the preceding +earthquakes probably began on the bed of the ocean at some distance +from the coast; for, in the last earthquake, the sea retired from the +Bay of Concepcion and vessels were grounded that had been anchored +in seven fathoms of water. Shortly afterwards waves from sixteen to +twenty feet in height rushed in from the ocean and swept over the land. + +It is interesting in this connection to note that the volcanoes of the +Chilian Andes were in an unusual state of activity before, during, and +after the earthquake. + +Another characteristic of this quake was the great number of severe +shocks. Between the day of the first great shock; i. e., on February +20th, 1835, and March 4th, there were more than 300 severe shocks. + +In this as in the preceding quake a notable elevation of the land near +the coast occurred, amounting to from four to five feet, and a part of +the bed of the ocean near the coast was raised permanently above the +level of the sea. + +In the description of the explosive eruption of Krakatoa in 1883, the +fact was noted that the island of Java is very frequently visited by +earthquakes. Here a terribly severe earthquake occurred on the 5th of +January, 1699. There were no less than 208 shocks of great intensity. +Considerable property in the city of Batavia was destroyed, and a +neighboring river, that has its head waters by a volcano near the +city, ran high and muddy and brought down multitudes of fishes that +had been killed, together with many buffaloes, tigers, rhinoceroses, +deer, and other wild beasts. Seven hills bordering on the river sank +down, damming up the streams of the region and thereby causing wide +destruction from floods. + +During portions of the years 1811 and 1812 an earthquake occurred +in the United States, in the Mississippi Valley near the town of +New Madrid, Missouri, at the mouth of the Ohio River. These shocks +continued almost incessantly for several months, and were accompanied +by a sinking of the ground over large areas. This depressed area, +known in the neighborhood as _The Sunk Country_, extended along the +course of the White Water River and its tributaries for a distance of +about eighty miles from north to south, and several miles from east +to west. Most of it was converted into a marshy lake characterized by +thousands of submerged trees. The area was covered for the greater +part with water to a depth of about three to four feet. + +As the earthquake shocks continued at intervals for several months +there was an ample opportunity for studying the peculiarities of the +earth waves. The ground rose and fell like large waves in the sea, and +after the crest of the waves had reached great heights, the ground +burst, and threw large quantities of water, sand, and earth into the +air. + +[Illustration: FIG. 48. NEW ZEALAND] + +Throughout the disturbed district there were numerous depressions +known as _sink-holes_, or irregularly shaped pits, varying from ten to +thirty yards across, and having a depth of about twenty feet. These +were formed by the forcible ejection of large quantities of water +mixed with sand. + +New Zealand has been subject to earthquake shocks for a long time, the +years 1826, 1841, 1843, 1848, and 1855 being especially marked by such +visitations. It is a characteristic of the New Zealand earthquakes +that they have produced a marked change in the coast line. This was +particularly the case with those of 1848 and 1855. + +The 23d of January, 1855, an earthquake occurred that was most violent +in the narrowest part of Cook's Strait, a body of water separating +the two principal islands that constitute New Zealand; or, as they +are called, the North Island and the South Island. These shocks were +felt at sea by ships 150 miles from the coast. The entire area shaken, +including the water, has been estimated at three times the area of +the British Isles. In the vicinity of the southern shores of the +North Island a tract of land having an area of 4,600 square miles is +believed to have been permanently raised from one to nine feet. + +The earthquakes in New Zealand are evidently of the tectonic type. +During that of 1848 a rent or fissure was formed, which, though but +eighteen inches in average width, yet extended for a distance of sixty +miles in a direction parallel to one of the mountain chains. + +On the 31st of August, 1886, an earthquake of considerable intensity +occurred in the United States in the neighborhood of the city of +Charleston, South Carolina. The details of this earthquake were +carefully studied by Major Dutton of the U. S. A., and published in +the Ninth Annual Report of the United States Geological Survey of 1888. + +Charleston is situated on a narrow tongue of land between the Ashley +and the Cooper Rivers, about seven miles from the Atlantic Ocean. +There are in this area numerous creeks connected with the drainage of +these rivers. As the city limits extended, the creeks were filled in, +forming "made land," all buildings or structures erected on this land +being supported by pilings. + +It appears that the point at which the earthquakes started was +situated sixteen or seventeen miles from Charleston. + +The earthquake shock affected a large area of the United States. Fig. +49 shows curved lines called isoseismal connecting places, having the +same degree of seismic intensity. This map shows that these isoseimals +are marked by figures or numbers from two to ten. These numbers are +the numbers of the Rossi-Forel earthquake scale. They indicate varying +degrees of intensity, beginning from the least intense shock which +is marked as two and ending with the severest shock marked as ten. +There is one degree not marked on this map, the least, called the +micro-seismic shock. + +The shocks then increase in intensity as follows: II. Extremely +feeble shocks; III. Very feeble shocks; IV. Feeble shocks; V. Shocks +of moderate intensity; VI. Fairly strong shocks; VII. Strong shocks; +VIII. Very strong shocks; IX. Extremely strong shocks; X. Shocks of +extreme intensity. + +The meaning of the map presented in the accompanying figure will now +become more apparent in several ways. That portion numbered ten, +denoting where shocks of greatest intensity have been experienced, +clearly indicates the region just above the point where the earthquake +originated. + +Beyond this is a region marked nine where the earthquake shock has +decreased in intensity to the next figure on the Rossi-Forel scale, +and then to eight and a half, seven, six, five, four, three, and two. + +[Illustration: FIG. 49. MAP SHOWING REGION AFFECTED BY THE +CHARLESTON EARTHQUAKE OF 1886] + +The Charleston earthquake damaged property to a considerable extent; +for, although comparatively few buildings were completely destroyed, a +considerable number were partially injured, and many, not thrown down +by the shock, had to be torn down in order to insure public safety. +The loss of life, fortunately, was comparatively small. During this +earthquake a number of openings called _craterlets_ were made in the +ground by the forcible ejection of large quantities of water and sand. + +The empire of Japan is another part of the world particularly subject +to great as well as frequent earthquake shocks. Although Japan is also +especially noted for its volcanic activity, its earthquakes are almost +entirely of the tectonic type, or are due to the slipping of the land +at faults in the earth's crust. Most of these quakes occur on the bed +of the ocean on the sides of a steep slope that extends down to a very +deep part of the Pacific known as the _Tuscarora Deep_. + +On the 28th of October, 1891, Japan was visited by a great quake, +generally known as the Mino-Owaro earthquake, from the name of the two +provinces of Mino and Owaro in which it occurred. + +This earthquake is correctly regarded as one of the most severe in +Japanese records. Originating, as it did, in a densely populated +section, it caused a great loss of life and property. The deaths +reached about 7,000, while the number of houses entirely destroyed +reached about 80,000 and those partly destroyed nearly 200,000. The +total area markedly affected reached 250,000 square kilometres, while +the area sensibly affected reached 900,000 square kilometres, or a +little more than one-half the Empire. + +The place at which this earthquake started was situated, not as usual +on the bed of the ocean, but on the surface of the land. The first +shock was the strongest and wrought the greatest havoc. Besides the +loss of life and property, the damage to the system of dikes or levees +on the river where it passed through the delta plain near the river's +mouth was heavy, and singular in some of its features. In one case, +near the city of Nagoya, on the Bay near the southern coast of Niphon, +one of these levees was lifted and shifted bodily more than sixty feet +from its original position. + +That this quake was of the tectonic type was evident from the great +fault that was formed. According to Davison this fault was seventy +miles in length and in places had a breadth of from two to five feet. +It extended from east to west, crossing the entire width of the island. + +Another great earthquake was that which hit northeastern Bengal and +Assam in India on the 12th of June, 1897. According to the India +Geological Survey, by whom a careful examination of the effects +produced by this quake was made, it was, perhaps, the greatest quake +that ever happened, not even excepting the Lisbon earthquake. + +The place where the quake started appears to have been of unusual size +and irregularity of outline. Its southern boundary was almost in the +shape of a straight line extending from east to west about 200 miles, +and covering a total area of nearly 6,000 square miles. Over all this +vast area the intensity of the shock was exceedingly severe. The total +area perceptibly shaken by the quake was about equal to 1,750,000 +square miles. + +That this quake was of the tectonic type became evident, when several +faults were found in the ground afterwards. Some of these extended +twelve miles, with a breadth at places as great as thirty feet. + +Valparaiso, or, as the name means, Vale of Paradise, the second +largest city of Chile and its chief seaport, lies about ninety +miles east of Santiago, the capital, with which it is connected by a +railroad. + +This beautiful sea city is built at the base of a cluster of hills +about 1,600 feet above sea level. On August 16th, 1906, it was visited +by an earthquake. There were two distinct shocks. Contrary to general +rule it was not the first, but the second shock that did the most +damage, coming about ten minutes after the first. As you will see from +the above date the earthquake of Valparaiso occurred shortly after +the catastrophe of San Francisco. In a general way, its coming was +predicted by Dr. G. F. Becker of the United States Geological Survey, +on April 19th, 1906, one day after the San Francisco disaster. Becker +published an article in the "New York Tribune," in which he argued +that the severe shock at San Francisco, having occurred on one part +of the earthquake region extending around the Pacific, would probably +soon affect other portions of this region along the Pacific coast line +of this hemisphere. + +As at San Francisco fierce fires immediately started in the ruins of +the houses, but the Valparaisans were more fortunate in having a water +supply available. + +There were very many shocks following the first two of this +earthquake. Indeed, during August 16th, 17th, 18th, and 19th, no less +than 380 were noted. + +Santiago, situated at the foot of the Andes, was also considerably +damaged by the same earthquake. Estimates, probably conservative, put +the total of dead in both cities at 1,000 and the number of people +rendered homeless temporarily, at 100,000. + + + + +CHAPTER XXX + +SODOM AND GOMORRAH AND THE CITIES OF THE PLAIN + + +The eastern border of the Mediterranean Sea or Syria, with that part +of Arabia forming the Sinai Peninsula and which lies between the two +northern arms of the Red Sea, is a region formerly characterized by +extreme volcanic activity. This region includes the greater part of +the land promised, according to the Old Testament, to the Children +of Israel. Through a large part of this region flows that historic +river, the Jordan, until it empties into the Dead Sea, also called the +Salt Sea, the Sea of the Plain, and by some Lake Asphaltites because +of asphalt or bitumen so abundant on its shores. This river has its +source in the Mountains of Lebanon, some distance north of the Sea of +Chinnerth, Tiberius, or the Sea of Galilee, which empties into the +River Jordan. + +As the map in Fig. 50 shows, this famous, though small river, flows +between ranges of high hills, or low mountains, that lie on both its +eastern and western boundaries; and these parallel ranges extend +down to the Gulf of Akaba, which forms the eastern boundary of the +Sinai Peninsula. The Sea of Galilee, the valley of the Jordan and the +country between the Dead Sea and the Gulf of Akaba, are all, for the +most part, considerably below the level of the Mediterranean or the +Red Sea; the Sea of Galilee being about 626 feet and the Dead Sea 1312 +feet below that line. + +[Illustration: FIG. 50. SYRIA] + +That this country has been the scene of great volcanic activities is +evident from the volcanic rocks found over different portions of its +surface. Moreover, the remains of several craters are still visible. +On the western banks of the Jordan numerous dikes and streaks of +basalt occur in the limestone that covers parts of the region. Besides +there are thermal springs whose waters are at a temperature, according +to Daubeny, of 114° F. Then, too, in the neighborhood of the Dead +Sea, as well as in the neighborhood of the adjoining mountain ranges, +there are quantities of sulphur and asphaltum or bitumen, while on the +Dead Sea asphaltum is found floating in sufficient quantity to be a +source of considerable revenue to the boatmen who collect it. It was +in this region that Sodom, Gomorrah, and other cities of the plain +were situated; cities so wicked that God utterly destroyed them by +volcanoes and earthquakes. + +Volcanic activity was evidently common in this land of the Bible +during the times of the prophets of Israel; for in their poetic +writings are frequent references to such phenomena--beautiful and +majestic similes and metaphors derived from contemplation of live +volcanoes. + +Jeremiah says: + + "Behold, I am against thee, O devouring mountain, saith the + Lord, which destroyeth all the earth; and I will stretch + out mine hand upon thee, and roll thee down from the rocks, + and will make thee a burnt[4] mountain. + + "And they shall not take of thee a stone for a corner, + nor a stone for foundations; but thou shalt be desolate + forever, saith the Lord." (Jer. li, 25-26.) + +So, too, the prophet Isaiah says: + + "Oh that thou wouldst rend the heavens, that thou wouldst + come down, that the mountains might flow down at thy + presence! + + "As when the melting fire burneth, the fire causeth the + water to boil, to make thy name known to thine adversaries, + that the nations may tremble at thy presence! + + "When thou didst terrible things which we look not for, + thou cameth down, the mountains flowed down at thy + presence." (Is. lxiv, 1-2.) + +So, too, the prophet Nahum says: + + "The mountains quake at him, and the hills melt, and the + earth is burned at his presence, yea, the world, and all + that dwell therein. + + "Who can stand before his indignation? And who can abide in + the fierceness of his anger? His fury is poured down like + fire, and the rocks are thrown down by him." (Nahum, i, + 5-6.) + +Let us now examine briefly the description Moses gives of the +destruction of Sodom, Gomorrah, and other cities of the plain. This +destruction occurred during the life time of Abraham and his nephew +Lot. The record says that God told Abraham He intended to destroy +them because of their wickedness. Then follows in the 18th chapter +of Genesis the eloquent pleading of Abraham for one of the doomed +cities. At Abraham's earnest plea God promises to spare Sodom if +fifty righteous men can be found therein. Obtaining this respite, +Abraham repeatedly asks further mercy for the city, and at last +receives the sacred promise that the city shall not be destroyed, if +but ten righteous people can be found there. An evidence of the great +wickedness of the city is seen in the fact that not even ten could be +found. Whereupon the Lord gives notice to Lot that the cities were +doomed and commands Lot to leave at once with his family. + + "Escape for thy life; look not behind thee, neither stay + thou in all the plain; escape to the mountain, lest thou be + consumed!" + +Moses describes what happened as follows: + + "The sun was risen upon the earth, when Lot entered into + Zoar. + + "Then the Lord rained upon Sodom and upon Gomorrah + brimstone and fire from the Lord out of heaven; + + "And he overthrew those cities and all the plain, and all + the inhabitants of the cities, and that which grew upon the + ground. + + "But his wife looked back from behind him, and she became a + pillar of salt. + + "And Abraham gat up early in the morning to the place where + he stood before the Lord: + + "And he looked toward Sodom and Gomorrah, and toward all + the land of the plain, and beheld, and lo, the smoke of + the country went up as the smoke of a furnace." (Gen. xix, + 23-28). + +This is clearly the description of a volcanic eruption, for throughout +the Bible things are described as they appear to be. When Moses speaks +of brimstone and fire being rained upon Sodom and Gomorrah out of +heaven, he is describing the phenomenon as it would appear to one +looking at it. Of course, we know that in volcanic eruptions such +things come to the earth through the crater of the volcano. The lava +is thrown high into the air, and the hardening, but still red hot, +ashes, rain down on the earth from the ash cloud that forms over the +mountain. But, looked at from a distance they appear to fall or be +rained down from the skies. In exactly the same way, Livy, the Roman +historian, tells about showers of stones that fell from heaven on +Mt. Albano near Rome for two whole days during the second Punic War. +So, too, even Pliny, who had some pretensions to be considered a +naturalist, in describing the appearance of Mt. Vesuvius during the +terrible eruption of A. D. 79, when Herculaneum and Pompeii +were destroyed, speaks of the red hot stones and ashes as falling +from above. So, in reality, they did, although, as in the case of the +cities of the plain, the materials forming the cloud came from the +crater of the volcano below. + +As to brimstone falling from the sky, this is by no means an unusual +occurrence during many volcanic eruptions, since sulphur is a common +material, often thrown out of the craters of some volcanoes. + +Note also the statement that, when Abraham rose early in the morning +and looked toward the place where Sodom and Gomorrah stood, he saw +the smoke of the country go up like the smoke of a furnace. This was, +probably, the smoke caused by the burning of the city, or even by the +destruction of the crops in their fields, when ignited by the falling +red hot ashes. It might also have been partly due to the burning of +asphalt thrown out from the fissures in the ground, or to the showers +of volcanic ashes that fell from the cloud formed during the eruption. + +That the cities there were destroyed by a volcano far in the past +appears from things outside of the Bible proper; for Strabo, +the Greek geographer, refers to Jewish traditions that thirteen +flourishing cities were swallowed up by a volcano, and this finds fair +corroboration in the ruins along the western borders of the Dead Sea. + +A writer referring to these eruptions says: + + "The eruptions themselves have ceased long since, but the + effects, which usually succeed them, still continue to be + felt at intervals in this country. The coast in general is + subject to earthquakes, and history notes several which + have changed the face of Antioch, Laodicea, Tripoli, + Berytus, Tyre, and Sidon. In 1793 there happened one which + spread the greatest ravages. It is said to have destroyed + in the valley of Balbec upwards of 20,000 persons." + +Attention has already been called to the fact that the valley of the +Jordan occupies a depressed or sunken region far below the level +of the Mediterranean and the Red Seas. It is the belief of some +geologists that this depression was caused by an earthquake which +accompanied the volcanic eruption that destroyed Sodom and Gomorrah +and the cities of the plain. Indeed, some contend that the present +site of the valley of the Jordan, including the Sea of Tiberius and +the Dead Sea, is a great fissure that was made in the limestone of the +valley during the time of that earthquake. + +It would appear from the peculiar geography of this section of country +that the Jordan River has not always emptied into the Dead Sea, but +that before the time of the destruction of the Cities of the Plain the +greater part of the country now occupied by the Dead Sea was a fertile +valley, and the Jordan emptied directly into the Red Sea at the Gulf +of Akaba; that during the disturbance through changes in the valley, +or possibly by a lava stream flowing across a portion of the bed of +the lower Jordan, or even by a huge accumulation of stones or ashes +thrown out from a neighboring volcano, the discharge of the river into +the Red Sea was cut off, and that in this way the waters of the rivers +began to accumulate and to flow over the plain, thus forming the basin +of the Dead Sea. + +There is no difficulty in accounting for the saltness of the Dead +Sea. There are large quantities of salt, and salty matters generally, +in the volcanic rocks of the region, but, even if this were not so, +when a river empties into a lake with no outlet to the sea, and +which therefore loses its water by evaporation only, the water will +gradually become very salt, since the remaining waters of such a lake +contain more or less salt, while the water they lose by evaporation +contains none. + +The waters of the Dead Sea are very salt, but not the saltest in +the world. In every 100 pounds of Dead Sea water twenty-four pounds +consist of salty matters. The waters of the Great Salt Lake, in Utah, +contain eighteen per cent of salty matters. Lake Van, in eastern +Turkey, is, perhaps, the saltest lake on earth, it containing no less +than thirty-three pounds of salty substances in every 100 pounds of +water. + +Daubeny, an authority on volcanoes, and quite competent to give an +opinion concerning what is possible in this line, describes what he +believes took place, as follows: + + "Briefly then to recapitulate the train of phenomena by + which the destruction of the cities might have been brought + about, I would suppose that the River Jordan, prior to + that event, continued its course tranquilly through the + great longitudinal valley, called El Arabah, into the + Gulf of Akaba; that a shower of stones and sand from some + neighboring volcano first overwhelmed these places; and + that its eruption was followed by a depression of the whole + of the region, from some point apparently intermediate + between the lake of Tiberius and the mountains of Lebanon, + to the watershed in the parallel of 30°, which occurs in + the valley of El Arabah above-mentioned. I would thence + infer that the waters of the Jordan, pent-up within the + valley by a range of mountains to the east and west, and a + barrier of elevated table-land to the south, could find no + outlet, and consequently by degrees formed a lake in its + most depressed portion, which, however, did not occur at + once, and therefore is not recorded by Scripture as a part + of the catastrophe, though reference is made in another + passage of its existence _in what was before the valley of + Siddim_." + +As regards the turning of Lot's wife into a pillar of salt, Henderson, +who has carefully studied this part of the country, remarks: "How +natural is the incrustation of his wife on this hypothesis! Remaining +in a lower part of the valley, and looking with a wistful eye towards +Sodom, she was surrounded, ere she was aware, by the lava, which +rising and swelling, at length reached her, and (whilst the volcanic +effluvia deprived her of life) incrusted her where she stood, so that +being, as it were, embalmed by the salso-bituminous mass, she became a +conspicuous beacon and admonitory example of future generations." + + + + +CHAPTER XXXI + +INSTRUMENTS FOR RECORDING AND MEASURING EARTHQUAKE SHOCKS + + +To attempt by the unaided senses a determination of the direction in +which earthquake shocks reach any certain spot, the velocity with +which they are travelling, their degree of intensity, their general +character, whether horizontal or vertical, or any peculiarities which +might show them to be exceptional would be futile for more reasons +than one. Even a skilled scientific observer, familiar with what has +already been discovered and eager to discover more, might in the +excitement of an earthquake become so excited himself as to make him +unable to take reliable observations. + +But human ingenuity has succeeded in devising delicate instruments +capable of recording not only the exact time of the arrival of an +earthquake shock, but also of measuring the different parts of what +may seem to be a single shock, the direction in which the shocks reach +the place, as well as the variations of intensity in all the shocks. + +Crude instruments to do some of these things have been in use from +very early times. According to Mallet among the more important +of these early instruments was the following: the instrument of +Cacciatore of Palmero. This consisted of a circular wooden dish, about +ten inches in diameter, placed horizontally, and filled with mercury +to the brim of eight notches at equal distances apart. Beneath each +notch was placed a small cup. On the passage of the earthquake waves +the vessel, being tilted in a direction dependent on the direction in +which the waves were travelling, would cause some of the mercury to +spill over into one or more of the cups, thus indicating by its amount +the intensity of the wave, and by the particular cup or cups that were +filled, the direction in which the waves reached the place. + +Somewhat similar contrivances were of a vessel partly filled with +molasses, or other sticky liquid; or a cylindrical tub, the sides of +which were chalked or whitewashed and filled with some colored liquid. +In either of these cases, on the passage of the earthquake waves, +the vessels were tilted and showed by the height of the marks the +intensity of the waves, and by the position of the marks the direction +in which the waves first reached the instrument. + +These instruments, though satisfactory for the study of earthquake +shocks a long time ago, when an earthquake was regarded as practically +consisting of but a single shock, or, at the most, of a very few +shocks, would be worthless for the study of earthquakes now, for it is +finally known that an earthquake consists of a series of many hundreds +of vibrations, differing greatly in their rapidity and intensity, and +following one another in a definite order. + +The old forms of earthquake instruments were known as _seismoscopes_. +The word seismoscope is a compound word from Greek consisting of +the two words, seism and scope. It means literally any instrument +capable of seeing, or calling attention to, a seism, or _earth-shake_. +In other words, a seismoscope is any instrument capable of calling +attention only to an earth-shake. + +Of course, neither of the rude seismoscopes just mentioned would be +able to give any valuable indications of the successive shakings to +which the vessel containing the viscid liquid had been subjected, +since the liquid would simply be splashed a number of times over the +same parts of the vessel. In order to get a record of the successive +shocks another form of apparatus must be employed, a form known as a +_seismograph_. + +Concerning the complex character of the apparently single earthquake +shock, Professor Milne makes this highly interesting and picturesque +statement: + + "An earthquake disturbance at a station far removed from + its origin shows that the main movement has two attendants, + one which precedes and the other which follows. The first + of these by its characteristics indicates what is to + follow, whilst the latter, in a very much more pronounced + manner, will often repeat at definite intervals, but with + decreasing intensity, the prominent features of what + has passed. Inasmuch as these latter rhythmical, but + decreasing, impulses of the dying earthquake are more + likely to result from reflection than from interference, I + have provisionally called them Echoes." + +There are many different forms of instruments known as seismographs +that are capable of recording all of these vibrations, but there is +this objection to their use: that the records appear in so tangled a +form that it is practically impossible to decipher or untangle them. +This fact can be grasped by examining Fig. 51, which represents a +record of this kind. + +[Illustration: FIG. 51. COMPLEX RECORD OF SEISMOGRAPH] + +It is necessary, therefore, to employ a modified form of instrument +called a _seismometer_, able not only to record all the different +vibrations, but to record them in such a manner that they can be +easily recognized. Fig. 52, for example, shows results obtained by the +use of a seismometer, in which the different vibrations are separated, +and so recorded on a sheet of paper, as to be readily understood. Such +a record is called a _seismogram_, and represents a _long distance +seismogram_. Here the large arrow indicates the beginning of the +record. And herein, as can be clearly seen, what would appear to an +observer without an instrument only a single shock, lasting but the +fraction of a minute, in reality consists of the _preliminary shake_ +as represented in ab and bc, the _principal shake_, as represented +at c, d1, d2, and d3, and the _final portions of the shake_ or the +"echoes" of Professor Milne, as represented from d3 to e. + +[Illustration: FIG. 52. LONG DISTANCE SEISMOGRAM] + +Except in a very general way there is for present purposes no need +of explaining the construction and operation of the seismometer +and seismograph. Suffice it to say, there are many forms of these +instruments, any of which are capable of recording the details of a +passing shock. The most important thing in either a seismograph or a +seismometer is to obtain what is known as a _steady point_; that is, a +point consisting of some object or mass that will remain practically +at rest, while everything around it, even the support which holds it, +is affected by the earthquake. + +It is, of course, not very easy to obtain a steady point, but it can +be done; and it will be at once comprehended that if a plate or piece +of paper were attached to such a steady point or mass, and a pencil +or tracer had one of its ends resting on the plate, and its other end +attached to the support that vibrates with the earth, a tracing or +record would be drawn on the plate from which the character of the +motion of the end of the tracer, and, therefore, of the earth, would +be marked on the plate. + +[Illustration: FIG. 53. VICENTINI VERTICAL PENDULUM] + +Various devices have been employed for the steady points. The most +successful consists of a heavy mass of lead. + +Fig. 53 represents a form of instrument invented by Professor +Vicentini of Italy. Here the steady point consists of a heavy leaden +bob, of 200, 400, or even 500 kilograms, suspended by three metallic +rods united above by a brass cap, hung on a steel wire to a bracket +fixed on the wall. This wire may have a length as great as fifty feet. + +[Illustration: FIG. 54. VICENTINI PENDULUM AND RECORDER] + +Fig. 54 represents the recording instrument. Here a tracer is provided +that is capable of multiplying the motion fifty times, or even eighty +times. A record is traced on a sheet of paper passing over a roller +which imparts a rapid motion to a sheet so as to make sure that the +different parts of the shock or vibration will be recorded on separate +portions of the paper. + + + + +CHAPTER XXXII + +SEAQUAKES + + +As earthquakes are shakings of the earth's crust in places where it is +uncovered by the waters of the ocean, so _seaquakes_ are the shakings +of those portions that lie on the bed of the ocean. + +Mallet points out that the earthquake wave may start either in the +interior of the continent, or on the bed of the ocean; that the latter +place is the more common, since on the land vents--rude safety-valves, +as it were,--are provided by the craters of the volcanoes; that, when +earthquakes start on the ocean bed, the impulses are conveyed in +different forms of waves, i. e., those through the solid earth, those +through the water, and those through the air, with varying sounds like +bellowings and explosions, or like the rolling of wagons over rough +roads. + +To learn when quakes occur on the sea is a much harder task, since on +the land we can use seismoscopes, seismographs, or seismometers to +indicate, record, or measure the shakings of the crust, while on the +sea, where the water is always in more or less motion and the surface +so far from the ocean's bed this is impossible, or, rather shall it +be said, has hitherto been found so; for that the mind of man may +surmount this obstacle is not impossible to conceive. + +To detect the wave produced by the quaking of the bed of the ocean +is exceedingly difficult, since those in very deep water are flat or +possess but a small height. Indeed, in the deepest parts of the ocean +this height is probably to be measured only by inches instead of feet. +When, however, the waves advance towards the shore they increase in +height, and when they reach the shallows near the coast, they begin +to curl over and break, thus creating the enormous waves mentioned so +often as attending great earthquakes in the ocean. + +During the great earthquake of Simoda in Japan, 1854, the waters of +the bay were first greatly agitated, and then retreated, leaving the +bottom bare in places where the water was formerly thirty feet deep. A +wave, thirty feet high, then rushed in from the bay and, climbing the +land, swept away everything in its path, covering the town with water +to the tops of the houses. This monster wave then receded, but rushed +back five times. + +In 1751, an earthquake wave suddenly entered Callao, the port of Lima, +Peru, sinking twenty-three vessels and driving a frigate inland, where +it was left high and dry. This wave extended across the Pacific to the +Hawaiian Islands, a distance of 6,000 miles. + +On the 13th of August, 1866, an earthquake wave, that started a short +distance from shore, produced a number of earthquake waves sixty feet +high that reached the coast of Peru half an hour after the principal +earthquake shock. These waves reached Coquimbo, 800 miles distant, +in about three hours, and Honolulu, on the Sandwich Islands, 5,520 +miles distant, in twelve hours, and the coast of Japan, more than +10,000 miles distant, on the next day. Le Conte remarks that these +waves would have encircled the earth, had it not been for the barrier +interposed by the Andes. + +Another great seaquake, known as the Iquiqui seaquake, during 1868 in +the same neighborhood damaged severely the towns of north Chile and +southern Peru. + +While, however, there is difficulty in readily observing the +earthquake waves that form in the deep ocean, yet such is at times the +violence of an earthquake that there is no difficulty in detecting its +presence, even in deep water. Dr. Rudolph has made a careful study of +the evidences of earthquakes produced in the deep sea, from a careful +examination of a great number of the logs of ships. Logs, as everybody +knows, are books in which the captain or commanding officer makes +careful entries of all important happenings to the vessel, conditions +of the weather and of the sea. From this source Dr. Rudolph obtained +considerable information of much value concerning these phenomena. + +I have already called your attention to portion of the Atlantic Ocean +lying near the Equator, in the warmest part of the ocean, between +Africa and South America, as being a region especially liable to +submarine volcanic showers. While, generally speaking, there is +nothing in this region to indicate the probability of submarine +disturbance, yet suddenly, if a vessel happens to pass directly over +the point of origin of the quake, there ensues a great quaking or +quivering. Loose objects on the ship begin to shake and clatter. +Noises arise from some invisible point deep down in the ocean. The +disturbance grows, the noises begin to resemble distant thunder, the +ship trembles and staggers as though it had struck rocks, and many +believe she is about to go down; when, as suddenly as it began, the +commotion ceases, the noises stop, and the ship shapes her course as +calmly, and as gallantly, as before. + +Rudolph gives two excellent examples of seaquakes in this region, both +of which were, doubtless, due to submarine eruptions. + +On the 25th of January, 1859, as the ship _Florence_ was in lat. +0° 48' N., long. 29° 16' W., about ten miles N. W. by N. from St. +Paul's Rock, the people on board felt a sudden shock that began with a +rumbling sound like distant thunder. This lasted only forty seconds. +The glass and dishes of the vessel rattled so violently that it was +feared they would be broken. The shakings were so strong that several +objects on the vessel were thrown down. Everyone believed the ship +had struck on rocks. The captain leaned over the taffrail in order to +see the position of the reef, but soon saw that the vessel had struck +nothing, and informed his crew "it was only an earthquake shock." + +Another of the log books examined by Rudolph was that of a ship in the +same part of the Atlantic Ocean. This record showed that suddenly on +a morning, in 1883, strange noises were heard that soon increased and +became not unlike the firing of great guns or the peals of distant +thunder. The ship vibrated as if its anchor had been suddenly let go, +and at the same time a feeling came over all the crew, as if they had +been electrified. + +In some cases the vibrations were sufficiently severe to throw heavy +objects from the deck, as appears in an account given by a French +geologist of a quake in the Mediterranean off the shores of Asia Minor. + +"Our ship was over the epicentre,"[5] he says, "and was so severely +shaken that at first the Admiral feared the complete destruction of +the corvette." He then makes the statement that the shocks which were +directly upwards were so strong as to throw heavy objects in the air; +for example, a heavy gun and its carriage. While it is possible, as +Dutton remarks, that this incident of the heavy gun and carriage was +grossly exaggerated, yet it should not be forgotten that in the case +of submarine eruptions such as that which resulted in the production +of the island of Sabrina, an immense column of water, weighing +probably many times more than a gun and its carriage, was observed to +be shot high into the air. + +Where the seaquake is produced by a strong submarine volcanic +eruption, there is a violent commotion of the water itself, so that a +vessel passing over such a point may be greatly injured, and, indeed, +even destroyed. Such disasters, however, are fortunately exceedingly +rare. + +Among other common effects of seaquakes is the destruction of fish +already mentioned by the sudden blow to the water stunning and killing +them, just as the explosion of dynamite or other high explosives does +in a lake or pond. + +The most marked effect, however, of seaquakes is the starting of the +great wave on the coasts of continents and islands. + +There are certain parts of the ocean that are especially liable to +seaquakes. Some of the more important of these, as shown by Rudolph's +researches, are: + +The region already referred to in the narrowest parts of the Atlantic +Ocean between Africa and South America almost immediately under the +equator. Here there are two well marked regions. One is in lat. 1° +N., long. 30° W., where there is a submarine ridge, the tops of which +form what are known as St. Paul's Rock. The ocean here is very deep, +the slopes of the ridge descending rapidly. It is on these slopes +that earthquakes are very apt to occur just as they do on the steep +slopes of mountain ranges. The other region, called by Rudolph the +_Equatorial District_, lies a little further to the east on both sides +of the equator in long. 20° W. + +It appears from Rudolph's researches that between 1845 and 1893 no +less than thirty-seven seaquakes were reported in the logs of ships +in the neighborhood of St. Paul's Rock, and between 1747 and 1890, in +the equatorial district, there were forty-nine seaquakes. It must not +be supposed, however, that these were all the quakes in the regions +during these times, since, of course, many shocks must have happened +that were not felt even by vessels in the neighborhood and many more, +when this portion of the ocean was free from any craft. + +In the North Atlantic there is a portion of the ocean's bed known as +the _West Indies Deep_. Here the bed is marked by great depths and by +many irregularities and is, therefore, a region where seaquakes are +common. + +Still another district is found in the North Atlantic in the +neighborhood of the Azores. This is the region in which the Lisbon +earthquake is believed to have started. + +Another region where seaquakes are common is in the Pacific along the +coast of South America from the equator to 45° S. lat. "Here," says +Dutton, "especially in the vicinity of the angle where the Peruvian +and Chilian coasts meet have they been most numerous and formidable. +The harbors of Pisco, Arica, Tacua, Iquiqui, and Pisago have been +repeatedly subject to these destructive invasions." + +There has been considerable discussion as to the exact manner in which +the earthquake waves are set up. Whatever be the cause or causes, +the action must be sudden, such as an upheaval of the bottom, or a +collapse of a large section of the ocean's bed, with a dropping of a +vast body of water. Or, possibly, a submarine volcanic eruption causes +the water to lift suddenly under pressure of steam generated by escape +of the lava and other hot volcanic products. + +Dr. Rudolph attributes earthquake waves to submarine volcanic +eruptions alone. It would seem, however, as if each one of the other +things above referred to might at times be the direct cause. + + + + +CHAPTER XXXIII + +THE DISTRIBUTION OF EARTHQUAKES + + +Earthquakes may occur at any part of the earth's surface, at any time +of the day, or at any season of the year, yet they are more frequent +at certain parts, certain hours, certain seasons. + +Since some earthquakes are unquestionably connected with volcanic +eruptions, a map or chart of the volcanoes of the earth would also, +to a certain extent, show the parts of the earth that are likely to +be visited by earthquakes. Since, however, by far the most severe +earthquakes are not directly connected with volcanoes, but are due to +sudden slips of faulted strata, a volcanic chart would necessarily +fail to indicate accurately the principal earthquake regions. + +In the preparation of a map showing the distribution of earthquakes +over the earth's surface, Mallet adopted the plan of colorings or +tintings in such a manner that the depth of the colors would represent +not only the parts shaken, but also the relative number of times +shaken, as well as the intensity of the shocks. In order to determine +the depth of tint to be employed, Mallet divided earthquakes into the +following classes according to their intensity: + +_Great earthquakes_, or earthquakes of the first class; or those in +which the area affected is of great size, in which many cities have +been overthrown, and many people killed, and parts of the surface +greatly altered. + +_Intermediate earthquakes_, or those in which, although the area +affected is great, yet the destruction of buildings, or loss of life, +has been comparatively small. + +_Minor earthquakes_, or those which, although capable of producing +small fissures in the crust, generally leave but few or no traces of +their occurrence. + +The greatest distance to which earthquake waves of the first class +extend is taken by Mallet as being over a diameter of 1,080 miles; +those of the second class over a diameter of about 360 miles, and +those of the third class over a diameter of about 120 miles. + +According to the Rossi Forel scale already given, earthquake shocks +are divided according to their relative intensity into ten separate +classes, viz.: I. The micro-seismic; II. The extremely feeble; III. +The very feeble; IV. The feeble; V. The moderately intense; VI. +The fairly strong; VII. The strong; VIII. The very strong; IX. The +extremely strong; X. Shocks of extreme intensity. + +An earthquake map prepared according to Mallet's scale would show a +greater depth of color or tint in the neighborhood of the volcanic +districts of the earth and especially in the neighborhood of the +mountain regions, where tectonic quakes are most frequent. Oceanic +areas would be left almost untinted, not because earthquakes do not +occur on the bed of the ocean, but because of the difficulty of +observing such earthquakes at great distances from the land. So far +from earthquakes being absent on the bed of the ocean it is most +probable that they are more frequent there than elsewhere. + +Prepared in this way, Mallet's map would show a preponderance of +earthquakes along the borders of the continents, especially along the +"Great Circle of Fire" on the borders of the Pacific Ocean. + +Dutton as well as some others assert that the "Great Circle of Fire" +on the shores of the Pacific has in reality no existence; that, +instead of there being a continuous region of volcanoes, there is in +reality nothing more than a considerable number of volcanoes arranged +in groups along the borders of this ocean, but separated by spaces +containing no marked volcanic activity. We do not think this a tenable +position, since it is well known that volcanoes lie along great lines +of fissures at different points or openings which are kept open +by subsequent volcanic activity, while the remaining portions are +closed soon afterwards; and, moreover, in parts of these so-called +non-volcanic regions, there are probably extended regions of extinct +volcanoes. + +Since the time of Mallet many maps have been made to show the +distribution of earthquakes. Among the best of such is that by M. de +Montessus de Ballore. + +Some idea of the great amount of work required for the preparation of +Montessus' map may be formed when one learns that the catalogue of +earthquakes collected by him for this purpose included for the years +1880 to 1900, 131,292 quakes. + +De Montessus' earthquake map divides the grand divisions of the earth +into numerous sub-divisions, too numerous, indeed, for even brief +description in a work of this kind. From the map he thus laboriously +prepared De Montessus drew the following general conclusions: + +1. The parts of the earth that are most apt to be shaken by +earthquakes are those which possess the greatest differences of relief +between their highlands and lowlands, and that in such regions the +most pronounced earthquakes are found on the steepest slopes. + +2. Earthquakes are most common along those parts of the crust that are +thrown up in huge wrinkles, or mountain ranges, whether these masses +be above the level of the sea or are covered by it. + +[Illustration: FIG. 55. DAVISON'S EARTHQUAKE MAP OF JAPAN] + +3. Earthquakes are more common in mountainous districts than in +plains. But not all mountains are characterized by earthquakes nor +are all plains free from them. Sometimes the plain at the base of +the mountain appears to be especially liable to shocks, probably by +reason of slips along faults at these points. + +The great mountain ranges of the world are generally characterized +by unequal slopes, the long gentle slope facing the interior of the +continents, and the short, abrupt slopes being turned towards the +coast. Now, Montessus points out that volcanoes are the most frequent +on the short, abrupt slopes. In some cases, however, where the long +slopes are the roughest, it is these slopes that are most frequently +shaken. + +The beds of the ocean that lie along rapidly descending lines, +especially when they lie on the borders of large mountain ranges, are +especially liable to earthquakes. + +Dr. Charles Davison has made a map of the earthquakes of Japan in +which he had adopted the plan of representing the origin or centres +of earthquakes by a series of contour lines like those employed on +topographical maps. The advantage of this type of map over that +employed by Mallet is just this: Davison's earthquake map of Japan in +which the active volcanoes are marked by dots, and the earthquakes +by contour lines surrounding the points of origin, discloses the +interesting fact that here the positions of the volcanoes and the +earthquake centres coincide, since the mountainous districts where the +active volcanoes are numerous are singularly free from earthquakes. +This can be seen from an inspection of Fig. 55. + + + + +CHAPTER XXXIV + +THE CAUSES OF EARTHQUAKES + + +Earthquakes occurred long before man appeared on earth. It is natural, +therefore, that our early ancestors, experiencing these unwelcome +phenomena, vaguely endeavored to explain their causes. These early +attempts at explanation have in many cases been of an exceedingly +fanciful character. + +The ancient Mongolians and Hindoos declared that earthquakes are due +to our earth resting on a huge frog and that they occur whenever the +frog scratches its head. + +In Japan, where earthquakes are very common, the ignorant people even +at a much later day declared that there exists in the depth of the sea +an immense fish which, when angry, dashes its head violently against +the coast of the island, thus making the earth tremble. This is, +doubtless, the biggest fish-story extant. + +Another folk-lore explanation in Japan attributes the cause of the +tremblings of the earth to a subterranean monster whose head lies in +the north of the island of Hondo, while his tail lies between the two +principal cities. The shaking of his tail causes earthquakes. + +Fantastic and foolish as these explanations are, it is worthy of +note that the first of the Japanese explanations shows no little +observation on the part of the people, since it locates the +starting-points of earthquakes as being not on the land, but on the +bottom of the sea. In point of fact, nearly all the great earthquakes +in Japan seem to start somewhere between the coasts of the islands +on the sea-bottom that leads down to a very deep part of the Pacific +known as the Tuscarora Deep. + +Many years ago nearly everyone believed that earthquakes were caused +solely by the forces that produce volcanic eruptions; that all +earthquakes, whether in the neighborhood of active volcanoes, or at +great distances therefrom, were to be regarded solely as volcanic in +their origin. + +It is now recognized that the most severe and far-reaching earthquakes +have no immediate connection with volcanic explosions, but are due to +the sudden slippings of the earth's strata over lines of faults; or, +in other words, earthquakes are most frequently of the tectonic type. + +At the present time there is unfortunately much difference in +opinion as to the exact cause of earthquakes. By this is not meant +the immediate cause, but the ultimate cause. As to the immediate +cause, practically all are agreed that quakes of volcanic origin are +to be traced to the same forces that produce volcanic eruptions, +while quakes of tectonic origin are due directly to the slipping of +the strata along the faults. But when inquiry is instituted as to +the nature of the forces that cause the volcanic eruptions, or that +produce such an alteration of the strata as permits them afterwards to +slip and thus jar the earth, there is much difference of opinion. + +As can be seen from a few quotations of well-known authorities, only +two kinds of earthquakes exist; namely, volcanic earthquakes and +tectonic earthquakes. + +Dana, for example, while acknowledging that small earthquakes may be +caused by the sudden falling of large rock masses into cavities in the +crust of the earth, says: + + "But true earthquakes come, for the most part at least, + from one or the other of the following sources of + disturbance. + + "1. Vapors suddenly produced, causing ruptures and friction. + + "2. Sudden movements or slips along old or new fractures. + + "Earthquakes due to the former of these methods are common + about volcanoes, and at the Hawaiian islands shakings that + are destructive over the island of Hawaii at the moment of + some of the more violent eruptions, do not often affect the + island of Oahu, a depth of 500 fathoms of water, the least + depth between the two islands, being sufficient to stop off + the vibrations.... + + "Earthquakes of the second mode of origin may occur in all + regions, volcanic or not. They have their origin mostly in + the vicinity of mountain regions, where old fractures most + abound. The vibrations may begin in a slip of a few inches, + in fact; but where there has been a succession of slips, + up and up from 10,000 feet or more, as in the Appalachian, + earthquakes of inconceivable volcanic activity must have + resulted." + +Dana points out that volcanoes stand on lines of fractures in the +openings of which their existence began and that, during geological +time, slips up or down these fractures have occurred, producing +earthquakes and possibly starting eruptions. + +Prestwich, a well-known English geologist, speaks very decidedly +concerning the causes of earthquakes: + + "For my own part, I am disposed to share the belief + expressed by Dana that the tension or pressure, by which + the great oscillations or plications of the earth's crust + have been produced, have not entirely ceased; and that + this is generally the most probable cause of earthquakes. + The uplifting of the great continental tracts and mountain + ranges must have always left the interior of the crust in + a state of unstable equilibrium, and any slight slide or + settling along an old fracture, or in highly disturbed and + distorted strata, would be attended by an earthquake shock. + + "In volcanic areas the removal of the large volumes of + molten rock from the interior to the surface must produce + settlements and strains which might also result in some of + these minor earthquakes to which volcanic districts are + so subject. Where we have the two conditions combined, as + they are in the Andes in South America, these earthquake + phenomena are, as we should expect, developed on the + grandest and widest scale." + +Geikie, the Scotch geologist, says: + + "Various conceivable causes may, at different times + and under different conditions, communicate a shock to + the subterranean regions. Such as the sudden flashing + into steam of water in the spherodial state, the sudden + condensation of steam, the explosion of a volcanic outpour, + the falling in of the roof of a subterranean cavity, or the + sudden snap of deep-seated rocks subjected to prolonged and + intense stress." + +Sir Charles Lyell, the great English geologist, holds the following +views concerning the origin of earthquakes. He speaks as follows in +his "Principles of Geology": + + "1. The primary cause of the volcanoes and the earthquakes + are to a great extent the same, and connected with the + development of heat and chemical action at various depths + in the interior of the globe. + + "2. Volcanic heat has been supposed by many to be the + result of the high temperature which belonged to the + whole planet when it was in a state of igneous fusion, + a temperature which they suppose to have been always + diminishing and still to continue to diminish by radiation + into space.... + + "The powerful agency of steam or aqueous vapor in volcanic + eruptions leads us to compare its power of propelling lava + to the surface with that which it exerts in driving up + water in the pipe of an Icelandic geyser. Various gases + also, rendered liquid by pressure at great depths, may + aid in causing volcanic outbursts and in fissuring and + convulsing the rocks during earthquakes." + +Major Clarence Edward Dutton, U. S. A., an acknowledged authority on +seismology, speaks as follows: + + "Thus far, then, we have two causes of earthquakes which + are apparently well sustained: (1) the downthrows, which + have often been observed to be accompanied by earthquakes, + and (2) volcanic action. But neither of them have been + shown to be connected with more than a comparatively small + number. Much the greater part of the earthquakes still + require explanation, and the indications are manifold that + some of them are produced by some cause yet to be stated." + +He acknowledges, however, this unknown cause may be traceable to +volcanic agency. To quote him in full: + + "It remains now to refer to the possibility that many + quakes whose origin is unknown, or extremely doubtful, may, + after all, be volcanic. This must be fully admitted, and, + indeed, it is in many cases highly probable. Evidences + that volcanic action has taken place in the depths of the + earth without visible, permanent results on the surface + abound in ancient rock exposures. Formations of great + geological age, once deeply buried and brought to daylight + by secular denudations, show that lavas have penetrated + surrounding rock-masses in many astonishing ways. Sometimes + they have intruded between strata, lifting or floating up + the overlying beds without any indication of escaping to + the surface. Sometimes the lava breaks across a series of + strata and finds its way into the partings between higher + beds. Or it forces its way into a fissure to form a dike + which may never reach the surface. In one place a long arm + or sheet of lava has in a most surprising and inexplicable + manner thrust itself into the enveloping rock-mass, and in + the older or metamorphic rocks these offshoots or apophyses + cross each other in great numbers and form a tangled + network of intrusive dikes. In other places the intruded + lava has formed immense lenticular (lense shaped) masses + (laccolites), which have domed up the overlying strata + into mountain masses. These intrusions, almost infinitely + varied in form and condition, are often, in fact usually, + inexplicable as mechanical problems, but their reality is + vouched for by the evidence of our senses. What concerns + us here is the great energy which they suggest and their + adequacy to generate in the rocks those sudden, elastic + displacements which are the real initiatory impulses of an + earthquake. They assure us that a great deal of volcanic + action has transpired in past ages far under ground, which + makes no other sign at the surface than those vibrations + which we call an earthquake." + +Koto, the celebrated Japanese student of earthquakes, and a member +of the Earthquake Investigation Committee appointed by the Japanese +Government for studying the great Mino-Owaro earthquake, in Japan, +1891, is properly regarded as an authority on earthquakes. Living, as +he does, in a country where earthquakes and volcanic eruptions are of +almost daily occurrence, he has had abundant opportunity for studying +these phenomena, especially in connection with the Seismological +Institute of Japan. He speaks as follows: + + "To make clear once for all my own standpoint, I may say + plainly that the chain of volcanoes and the system of + mountains of the non-volcanic earthquake, appear to me + to have very intimate and fundamental relations with the + so-called tectonic line." + +Mallet regards earthquakes that can be directly traceable to volcanic +origin as unsuccessful efforts on the part of nature to establish +volcanoes. He speaks concerning this matter as follows: + + "An earthquake in a non-volcanic region may, in fact, be + viewed as an uncompleted effort to establish a volcano. + The forces of explosion and impulse are the same in both; + they differ only in degree of energy, or in the varying + sorts and degrees of resistance opposed to them. There is + more than a mere vaguely admitted connection between them, + as heretofore commonly acknowledged--one so vague that the + earthquake has been often stated to be the cause of the + volcano (Johnson, 'Phy. Atlas,' Geology, page 21), and more + commonly the volcano the cause of the earthquake, neither + view being the expression of the truth of nature. They are + not in the relation to each other of cause and effect, but + are both unequal manifestations of a common force under + different conditions." + +Before closing this chapter on the causes of earthquakes it may be +well to state briefly the explanations that have been suggested by +those who hold that the earth is solid and cold throughout its entire +mass, except that in the neighborhood of volcanic districts there +are limited areas situated only a comparatively few miles below the +surface where the rocks are highly heated. + +Professor Mallet suggested that the source of heat for these local +areas of melted rocks was to be found in the enormous mechanical force +that is developed by the crushing of the strata in the earth's crust. +The principal objection to Mallet's theory is to be found in the +fact that, for this heat to be available for the melting of rocks, +it must be produced rapidly, and not spread out over long periods of +time. Moreover, there would appear to be no other way to account for +the production of the great force required to effect the crushing of +the earth's strata save on the assumption of a highly heated interior +still cooling and contracting. + +In his "Aspects of the Earth" Shaler has suggested an hypothesis +that may be regarded to a certain extent as explaining how heat, +slowly generated, might be blanketed, or prevented from escaping and +so possibly reaching a temperature sufficiently high to melt the +materials in portions of the interior not far below the surface of the +earth. + + "We thus see that in the water imprisoned in the deposits + of the early geological ages and brought to a high + temperature by the blanketing action of the more recently + deposited beds, we have a sufficient cause for the great + generation of steam at high temperatures, and this is the + sole essential phenomenon of volcanic eruptions. We see + also by this hypothesis why volcanoes do not occur at + points remote from the sea, and why they cease to be in + action soon after the sea leaves their neighborhood.... + + "The foregoing considerations make it tolerably clear that + volcanoes are fed from deposits of water contained in + ancient rocks which have become greatly heated through the + blanketing effects of the strata which have been laid down + upon them. The gas which is the only invariable element + of volcanic eruptions is steam; moreover, it is the steam + of sea-water, as is proven by analysis of the ejections. + It breaks its way to the surface only on those parts of + the earth which are near to where the deposition of strata + is lifting the temperature of water contained in rocks by + preventing, in fact, the escape of the earth's heat." + +Another very common theory is that of chemical action, or the heat +produced by the oxidation of various substances inside the earth, +such, for example, as iron pyrites, a compound of iron and sulphur. + +When Sir Humphrey Davy discovered metallic sodium and it was found +that this material, when thrown on water, possessed the power of +liberating intense heat, the discovery was welcomed by geologists +as affording a possible explanation of the cause of volcanoes and +earthquakes. + +It may be said generally concerning chemical action as the source +of the earth's interior heat, that the chief objection against it +is the fact that such heat is liberated too slowly to result in the +production of a very high temperature. This objection does not exist +in the case of such substances as metallic sodium, since here the +heat is rapidly developed and is sufficient in amount to fuse the +substances produced. But in the lava produced in such great quantities +as it is in volcanic districts there must be liberated at the same +time large quantities of gaseous hydrogen. Now, although hydrogen +is, as we have already seen, sometimes given off with the gases that +escape from volcanic craters, yet the quantity which escapes is so +small that this theory of volcanic activity has been practically +abandoned. + +Quite recently, however, among the various chemical substances that +are produced under the extremely high temperatures of the electric +furnace have been found, or formed, a number of curious substances +such as _calcium carbide_, _calcium silicide_, _barium silicide_, +etc., that possess the property of becoming highly heated on coming in +contact with water. + +Now it is an interesting fact that the hydrogen and other gases +which are given off by the action of water on these substances are +absorbed in large quantities by the materials themselves, so that the +objection of the absence of hydrogen and similar gases in the craters +of the volcanoes would not be quite as objectionable as in the case of +such substances. + +Of course, it is impossible to say whether such substances as calcium +carbide, etc., actually exist inside the earth's crust, yet, as +has been pointed out, the principal condition necessary for their +formation, i. e., a high temperature, existed at times long after +the earth, assuming the correctness of the nebular hypothesis, was +separated from the nebulous sun. + +There still remains to be discussed the most curious of all possible +causes that have been suggested for the presence of the local heated +areas at comparatively short distances below the earth's crust; +namely, radio-activity. + +In 1896, Henri Becquerel, a Frenchman, while investigating the power +of the X-rays, when passing through certain substances, to produce +phosphorescence, or causing the substances to shine in the dark, +made the extraordinary discovery that some of the salts of uranium +possess the power of emitting a peculiar radiation closely resembling +the X-rays, that is able to pass through substances opaque to +ordinary light as well as to affect photographic plates. But the most +extraordinary part of this discovery was that the salts of uranium +apparently possess the power of giving out this radiation continuously +without being exposed to the sun's rays. + +This peculiar property was called _radio-activity_, and was shortly +afterwards found to be present in many other substances besides +uranium, and notably so in two newly discovered elements known as +polonium and radium. + +Now it has been suggested that if there existed somewhere beneath the +earth's crust in these locally heated areas, large quantities of +radio-active substances, these regions would at last become highly +heated, and in this way likely to produce volcanoes and earthquakes. +It would not, however, seem that this is probably their true cause. + +From what has just been said it is clear how exceedingly difficult it +has become to explain the source of the earth's interior heat when +the fact of the earth's original highly heated condition is denied. +We are, therefore, disposed with Russell to believe, as stated in the +first part of this volume, that the ultimate cause of both volcanoes +and earthquakes is to be found in the gradual cooling of an originally +highly heated globe, and that the greater part of the interior is +still in a highly heated condition, hot enough to be melted but yet +in a solid condition by reason of the great pressure to which it is +subjected. + + + + +CHAPTER XXXV + +EARTHQUAKES OF THE GEOLOGICAL PAST--CATACLYSMS + + +There were numerous volcanoes in the geological past; therefore, since +volcanic eruptions are generally attended by earthquake shocks, it +follows that during that remote past the earth has been violently +shaken by earthquakes. Indeed, if we assume, as we believe to be the +case, that the cause of earthquakes is correctly to be traced to an +originally heated globe which is gradually cooling, it follows that +the earth was necessarily subject to great earthquakes almost from the +time when it began to cool. + +But to establish as a fact the occurrence of an earthquake at so +remote a time in the earth's history is far more difficult than to +detect the occurrence of a volcano at that time. While the earthquake +shocks may produce fissures in the earth's crust, and may be +accompanied by great changes of level, yet the great time that has +elapsed between such occurrences and the present would permit the +various geological agencies that are at work either to cover these +fissures completely, or completely to remove by erosion, or in other +similar ways, the rocks in which they occurred. It is different in +the case of a volcano; for the volcanic craters are in many cases +still left standing, and then there are the voluminous sheets of lava +that have spread over great areas of the earth, as well as numerous +volcanic cones. Besides, there are thousands of square miles of +surface that have been covered, often to great depths, by deposits of +volcanic dust thrown out at one time or another from the craters of +the then active volcanoes. + +I am sure you will acknowledge that any force capable of causing great +cracks or fissures in the earth's crust, must, while doing this, have +produced violent shakings of the earth. Great cracks or fissures are +to be found in the rocks of all the geological formations. These are a +record of the earthquakes that must have attended these convulsions. +And there is plenty of evidence to show that the earth's crust has +been torn into these fissures in places deep down below the present +surface; for, by the action of water, many of these portions have +been uncovered so that these great cracks or fissures which have been +afterwards filled with a molten rock that has hardened can be seen in +the great dikes that still remain. + +But there are still other evidences of the existence of earthquakes +during the geological past. There are found in the different strata +of the earth's crust fossil remains of the plants and animals that +lived on the earth long before the creation of man. By a careful study +of these fossils we know positively the kinds of animals and plants +that lived on the earth, in its waters, or in its atmosphere, when +these strata were being deposited. It is in this way possible for a +geologist to trace the life of the earth and its development as it +is written on the great book of which the earth's different strata +form the separate pages. Now, a careful study of the earth's fauna +and flora during the geological past, shows, beyond any question, +that occasionally great changes have occurred in the earth; for, here +and there, during different times, we find that certain species of +animals and plants have completely disappeared, to be followed, after +certain intervals, by entirely different species. It is evident, +therefore, that changes have occurred that have made it impossible for +the animals and plants that formerly lived on the earth to exist under +the changed conditions. These occurrences are known to geologists +as _exterminations_, _catastrophes_, or _cataclysms_. They are also +sometimes called _revolutions_, for they mark a more or less complete +wiping-out of the animals living at the time they occurred. + +If you will try to think you will readily understand how great a +catastrophe must be, that would be able to wipe out or completely +destroy an entire race of animals. + +You have doubtless read with astonishment the terrible catastrophe +that accompanied the eruption of Krakatoa, especially at the loss of +life and property caused by the great waves that were set up in the +ocean, but far reaching as these losses were they have nevertheless +affected but a limited portion of the earth. The plain truth is even +more stupendous, for catastrophes of the geological past appear to +have been so far-reaching and powerful as to affect the whole surface +of the earth, and to have annihilated entire races of animals and +plants as if they had never existed. + +Geologists are all practically agreed that there are only two ways in +which such exterminations of the earth's life could have been caused, +and these are changes in the earth's climate, or the starting of waves +in the sea by great earthquakes. In the sea; for it must be borne +in mind that in the geological past the greater part of the earth's +surface was covered by water, and the land areas were comparatively +small and low, so that waves created by earthquakes might easily have +overwhelmed the entire land surface. + +Of course, it is fair to suppose that in many cases these +exterminations may have been caused by sudden changes of climate, such +as would naturally have resulted from any change in the direction +of hot ocean currents which formerly flowed from the equator to the +poles. The appearance of a fairly large mass of land in the central +parts of the ocean might readily have turned aside the hot ocean +currents that formerly swept over the polar regions, thus greatly +lowering the earth's average temperature in these regions. + +But it seems probable that the principal cause of the destruction of +life in the geological past was produced by earthquake waves in the +sea, sweeping over the continents. Let us, therefore, examine two of +the earth's principal geological revolutions or cataclysms; namely, +that which occurred at the close of an early geological time known as +the Palaeozoic, and that which occurred at the end of a geological +time intermediate between the Palaeozoic time or the time of ancient +life, called the Mesozoic time, and the Cenozoic time, or the time +immediately preceding the present time. These two revolutions are +called by Dana, _the Post-Palaeozoic_, or _Appalachian Revolution_, +and the _Post-Mesozoic Revolution_. Both were characterized by the +making of great mountain systems, and were, therefore, especially +liable to repetitions of tremendous earthquakes that must have +produced enormous waves in the ocean. + +"Palaeozoic time," says Dana, "closed with the making of one of the +great mountain ranges of North America--the Appalachian, besides +ranges in other lands, and in producing one of the most universal and +abrupt disappearances of life in geological history. So great an event +is properly styled a revolution." + +Towards the close of the Palaeozoic time immense disturbances of +the earth's crust occurred during the uplifting of the Appalachian +Mountain System. One may, perhaps, form some faint idea of the +immensity of the forces at work, from the fact that there were +great faults produced by the uplifting of the lands attended with +displacement amounting to 10,000 or 20,000 feet or more; that in parts +of southwestern Virginia there were flexure faults 100 miles in length. + +As to the probability of the extensive exterminations that have +occurred during these times being produced by earthquake waves, Dana +speaks thus: + + "The causes of the extermination are two.... (1) a colder + climate.... (2) earthquake waves produced by orogenic + movements (movements producing mountain ranges). If North + America from the west of the Carolinas to the Mississippi + Valley can be shaken in consequence of a little slip along + a fracture in times of perfect quiet (the allusion here + to the Charleston earthquake, in 1886), and ruin mark its + movements, incalculable violence and great surgings of + the ocean should have occurred and been often repeated + during the progress of flexures, miles in height and + space, and slips along newly opened fractures that kept up + their interrupted progress through thousands of feet of + displacements.... + + "Under such circumstances the devastation of the sea-border + and the low-lying land of the period, the destruction of + their animals and plants, would have been a sure result. + The survivors within a long distance of the coastline + would have been few. The same waves would have swept over + European land and seas, and there found coadjutors for new + strife in earthquake waves of European origin. These times + of catastrophe may have continued in America through half + of the following Triassic period; for fully two thirds of + the Triassic period are unrepresented by rocks and fossils + on the Atlantic border." + +Coming now to the Post-Mesozoic revolution this period was marked by +the making of the greatest of the North American mountain systems. + +Dana points out that this revolution affected the summit region of the +Rocky Mountains over a broad belt probably as long as the western side +of the continent. + +This great belt of mountain-making extended from the Arctic regions +through North America, probably paralleled by like work, of equal +extent, in South America, but on a more eastern line. + +"The disappearance of species," says Dana, "at the close of Mesozoic +time was one of the two most noted in all geological history. Probably +not a tenth part of the animal species of the world disappeared +at the time, and far less of the vegetable life and terrestrial +Invertebrates; yet the change was so comprehensive that no Cretaceous +species of Vertebrate is yet known to occur in the rocks of the +American Tertiary, and not even a marine Invertebrate." + +In tracing the causes of these disappearances, Dana points out that, +perhaps, the principal cause was a decrease in the temperature of the +ocean, since the destructions were limited in large measure to marine +life. He regards, however, the other most probable cause as traceable +to earthquake waves; for the making of a great mountain range along +the entire length of the continent resulted in displacements of +the rock formations along lines hundreds of miles in length. Such +displacements must have been attended by a succession of earthquakes +of unusual violence, causing the destruction by sudden shocks beneath, +and resulting, directly and indirectly, in waves sweeping over the +continent. Since at this time the land was still low for the greater +part, the huge waves must have repeatedly swept over the greater part +of the land, leaving only the smaller species of animals and the +vegetation. + +It is evident, therefore, that during the geological past earthquakes +occurred that were probably vastly greater than any that have occurred +on the earth during more recent times. + + + + +CHAPTER XXXVI + +THE KIMBERLY DIAMOND FIELDS AND THEIR VOLCANIC ORIGIN + + +The elementary substance carbon occurs in three forms, i. e., +_charcoal_, _graphite_, and the _diamond_. The commonest form of +carbon is to be found in charcoal, as well as in bituminous coal, +anthracite coal, and _lignite_. Graphite, also known as _plumbago_, +or _black lead_, is the substance you have seen so often in the lead +of pencils. The diamond, as every one knows, is the highly prized +precious stone that sparkles so brightly in the light, and is so hard +that it is capable of scratching almost any other substance. + +Diamonds are found in various parts of the world. We are now +interested in them, however, only as they occur in certain parts of +the world, as in the great Kimberly diamond fields in Southern Africa. + +Dr. Max Bauer in his book on precious stones says that the discovery +of diamonds in South Africa was made by a traveller named O'Reilly, +who, in 1867, saw a child sitting in the house of a Boer named Jacobs, +playing with a shining stone. Jacob's farm was a short distance south +of the Orange River near Hopetown. This stone proved to be a diamond +weighing some twenty-one and three-tenths carats and was afterwards +sold for $2,500. The incident led to the discovery and consequent +development of the Kimberly diamond fields. + +Without going into a description of the different deposits in which +diamonds are found, it will suffice to say that in the Kimberly +district the diamonds occur distributed through the materials that +fill peculiar funnel-shaped depressions called _pipes_ which extend +vertically downward to unknown depths. The rock that fills a pipe +consists of an entirely different material from that in which the pipe +occurs. The upper extremity of the pipe is generally slightly elevated +above the general surface for a few yards. The pipes vary in diameter +from twenty to 750 yards, diameters of from 200 to 300 yards being +quiet common. + +In 1892, the diamond-bearing material found in the pipes of the +Kimberly mines had been excavated vertically downwards a distance of +1,261 feet, without any signs of its being exhausted. + +Now, the materials which fill the pipe of the great Kimberly mine are +practically the same in all the mines in the neighborhood. At the +upper part of the pipe the materials show the action of weathering by +exposure to the air. Here the ground is of a yellowish color. Below, +the materials have a blue color. + +According to Bauer the diamond-bearing material that fills the upper +part of the pipe consists of a soft, sandy material of a light yellow +color, known to diamond miners as _yellow ground_, or _yellow stuff_. + +In the case of the Kimberly mine, the yellow ground has a thickness of +about sixty feet. Below it the material has a blue color and is known +as the _blue ground_. This latter material possesses the character +of a volcanic _tuff_, which is a hardened clay. It is of a green or +bluish green color and has the appearance of dried mud that holds +or binds together numerous irregular, tough, and sometimes rounded +fragments of a green or bluish black serpentine. + +The diamonds are found near the surface in the yellow ground, as +well as downwards through the blue ground. It was at one time thought +that most of the diamonds existed in the yellow ground, and that they +would soon disappear entirely at short distances below where the blue +ground began. Under this belief some of the most valuable claims +changed hands at prices far below their true value. It was soon found, +however, that large and valuable stones existed in the blue ground, +and, indeed, this ground has never been mined to a depth below where +valuable diamonds appear. + +The diamonds occur in very small quantities spread through the yellow +and blue grounds. The following statement by Bauer will show this: + + "A striking illustration of their sparing occurrence is + furnished by the fact that in the richest part of the + richest mine, namely, in the Kimberly mine, they constitute + only one part in 2,000,000, or 0.00005% of the blue ground. + In other mines the proportion is still lower, namely, one + part in 40,000,000, a yield which corresponds to five + carats per cubic yard of rock." + +Of course, you will desire by this time to know the manner in which +the pipes of the diamond mines of South Africa have become filled with +the diamond-bearing rocks, and particularly what diamonds have to do +with a book on volcanoes and earthquakes. + +Dr. Emil Cohen, who has made a study of these regions, regards the +pipes as volcanic vents or chimneys, and that the materials filling +the pipes have been brought up from below by volcanic forces. He says: + + "I consider that the diamantiferous ground is a product + of volcanic action, and was probably erupted at a + comparatively low temperature in the form of an ash + saturated with water and comparable to the materials + ejected by a mud volcano. Subsequently new minerals were + formed in the mass, consequent on alterations induced in + the upper part by exposure to atmospheric agencies, and in + the lower by the presence of water. Each of the crater-like + basins, or, perhaps, more correctly, funnels, in which + alone diamonds are now found, was at one time the outlet + of an active volcano which became filled up, partly with + the products of eruption and partly with ejected material + which fell back from the sides of the crater intermingled + with various foreign substances, such as small pebbles, + or organic remains of local origin, all of which became + imbedded in the volcanic tuff. The substance of the tuff + was probably mainly derived from deep-seated crystalline + rocks, of which isolated remains are now to be found, + and which are similar to those which now crop out at the + surface, only at a considerable distance from the diamond + fields. These crystalline rocks from which the diamonds + probably took their origin, were pulverized and forced + up into the pipes by the action of volcanic forces, and + imbedded in this eruptive material, these diamonds either + in perfect crystals or in fragments are now found." + +So far as the volcanic origin of the diamonds of the Kimberly diamond +fields is concerned, Cohen's theory has been generally accepted with +the following modifications: that the pipes were not filled by a +single volcanic eruption, but by successive eruptions, and that in +the case of the Kimberly mine, the pipes contain the results of as +many as fifteen successive eruptions. There has, however, been another +and more important modification proposed to Cohen's theory, which is +far more probable. It will be noticed that Cohen's theory regards the +action of the volcanic eruption as only serving to bring fragments +of a deep-seated mother rock that contained the diamonds up from +below with the material that fills the pipe. Now, Prof. Carvill Lewis +proposes the following very important change in Cohen's theory: that +the blue ground does not consist of fragmentary material or tuff, but +was forced up from below in the pipe in a molten mass and consolidated +on cooling. In other words, the blue ground is filled with an ordinary +igneous rock that was solidified in place in the vent or pipe. + +In the great Kimberly mines the surface of the pipe is divided into +numerous separate claims, each consisting of a small square lot. There +are so many of these claims in the Kimberly mine that its surface is +honey-combed by numerous square pits. The work is done largely by +native Kaffirs employed there since the '70's. As the material was +removed from the pit, the adjoining claims were separated from each +other by high vertical walls. + +At a later date, in order to remove the material and separate the +lots, high staging provided with ropes and hauling machinery was +erected. The number of these ropes is now so great that the mine has +the appearance of a huge cobweb. + +A very extensive series of investigations has been made at a +comparatively recent date by Prof. Henri Moissan of France on various +chemical products that are obtained under the influence of the high +temperatures of the electric furnace. When a powerful electric current +is caused to pass through a highly refractory material, that is to +say, a material difficult to fuse, such as carbon, it raises it to an +extremely high temperature. A still higher temperature can be obtained +by causing a powerful current to flow between two carbon rods that +are first brought into contact, and then gradually separated from +each other, just as they are in the ordinary arc lights employed for +lighting the streets of our cities. In the latter way a temperature +that is estimated as high as 3,500° C. (6,332° F.), can be readily +obtained. Under these very high temperatures some very curious +chemical products have been obtained in electric furnaces. These +furnaces consist of small chambers made of highly refractory materials +closely surrounding the incandescent carbon, or the carbon voltaic +arc. Among some of the most curious of these products are artificially +produced diamonds. + +Moissan, however, was not the first to produce diamonds artificially. +As soon as Lavoisier had experimentally shown that the chemical +composition of the diamond and carbon are the same, efforts were made +to convert charcoal into diamonds, and Despretz, as early as 1849, +by means of the combined influence of a powerful burning glass, the +oxyhydrogen blowpipe, and the carbon voltaic arc obtained a very high +temperature. He claims by this temperature to have been able to change +carbon into a few microscopic diamonds. It is quite possible, in the +light of later investigations, that Despretz may have been mistaken +in his belief that he had actually produced diamonds; but whether +this be so or not, he was certainly one of the pioneers in this early +transformation of charcoal. + +Theoretically, all that would be required in order to change the +non-crystalline form of carbon into the diamond, would be to +subject the carbon to a temperature sufficiently high to fuse it +and then permit it slowly to crystallize. Could this be done, there +should be no trouble in transforming any amount of coal into any +equal amount of diamonds. But the transformation is by no means as +simple as might be supposed. It is not that the temperature of the +carbon cannot be raised to its point of fusion, but that as soon +as a certain temperature has been reached, the carbon, instead of +fusing or melting, is suddenly volatilized or turned into vapor. +There is no doubt that this is done. Thousands of feet of carbon +rods are volatilized every night in the arc lamps of our cities, +but the trouble is that this carbon vapor so formed, when cooled, +or condensed, is not converted into the exceedingly hard, clear, +crystalline diamond, but into the soft, dull black graphite or +plumbago. + +Now the process adopted by Moissan in order to cause volatilized +carbon, or carbon vapor, to condense in the form of crystalline +diamonds was practically as follows: he placed pieces of pure carbon +inside a very strong steel tube, such, for example, as would be formed +by boring a short cylindrical hole in a piece of strong thick steel, +and placing a small quantity of carbon inside the tube so formed. +Closing the open end of the tube by means of a tightly fitting screw +plug, he volatilized the carbon inside the tube. The steel, tube, and +plug formed an electric furnace, for, as soon as he passed an electric +current through it, the temperature at once became high enough to +volatilize the carbon. + +Under these circumstances the carbon vapor was subjected to great +pressure owing to the limited space in which it was liberated. As soon +as this mass of dense vapor had been formed, he seized the steel tube +with a pair of furnace tongs, and plunged it below the surface of cold +water in a bucket. + +Of course, as the hot tube suddenly chilled, there was a great +shrinking in the walls of the furnace, so that the already compressed +carbon vapor was subjected to a still greater pressure which possibly +liquified it. Of that, however, we cannot speak definitely. This, +however, can safely be asserted, that when the tube was broken open +a confused mass of small crystals was found inside, some of which, +on examination with the microscope, were found to consist of small +crystals of two forms of diamonds, namely, the black diamond, or +carbonado, and the regular crystallized diamond. + +Moissan made a great number of experiments for producing diamonds +in this way, and succeeded in forming some very beautiful, though +microscopic, diamonds. + +What may be said to characterize especially Moissan's experiments was +the comparatively great number of diamonds, so small as to be scarcely +distinguishable under the microscope. The high temperature to which +the materials inside the tube were exposed resulted in the production +of numerous minute crystals of different minerals. In order to get rid +of as many of these as possible Moissan adopted the plan of subjecting +the material to the action of powerful solvents, such as sulphuric +acid, aqua regia, or a mixture of sulphuric and nitric acid, and +hydrofluoric acid. These acids destroyed most of the minute crystals +of other minerals, but left the minute crystals of diamonds unaffected. + +Now it will be observed that the theory proposed by Prof. Carvill +Lewis as to the probable origin of the diamonds of the Kimberly mines +bears a wonderfully close resemblance to the method adopted by Moissan +for the production of artificial diamonds, since it supposes the +diamonds to have been formed by the sudden cooling or chilling within +the pipe of various molten materials brought up from great depths by +the volcanic forces. If this be true, then besides the comparatively +large crystallized and perfect diamonds found in the blue ground +of the Kimberly mines, there should also be found large quantities +of microscopic diamonds, just as are found in Moissan's electric +furnaces, in which he produced artificial diamonds. + +Moissan, considering this, obtained a specimen of the blue ground +from the Kimberly diamond pipe and on subjecting it to the action of +the different solvents before named, found in the mass that was left +undissolved a great number of microscopic diamonds. It would seem, +therefore, that there is no reasonable doubt but that the Kimberly +diamond fields had their diamonds produced by the sudden chilling in +the volcanic pipes of molten materials brought from great depths by +the force of volcanic eruption. + + + + +CHAPTER XXXVII + +THE FABLED CONTINENT OF ATLANTIS + + +Besides the sudden changes of level that frequently occur during +earthquake shocks there are gradual changes of level that take place +very slowly throughout long periods of time. + +These are believed to be due to the warpings produced by the cooling +of an originally highly heated globe. + +It is not true, therefore, that the earth's surface is fixed, or that +its land and water areas remain always the same. On the contrary, what +is land at one time is water at another time, and so, too, water areas +may become changed into land areas. + +For the most part these changes go on so slowly as not to be +noticeable in an ordinary lifetime. Indeed, in some cases, they are so +extremely gradual that Methuselah himself might have gone to his grave +in ignorance of their progress. + +Let us briefly note a few well-known gradual changes of level. + +One of the most extensive of these is the sinking of an immense area, +over 6,000 miles in diameter, that covers a large part of the bed or +floor of the Pacific Ocean. + +It is an easy matter to observe the gradual changes of level on the +coasts, since the old water line can be at once found, but it is very +difficult to detect such changes in the bed of the ocean, hidden as +it is by a covering of water. Yet many things that seem impossible to +the uninitiated are readily solved by those familiar with physical +science. Little signs, meaningless to others, are easily read, and +these prove beyond doubt the gradual sinking of the ocean's bed. + +It was once believed that the coral polyps or animalculæ from the +hard, bony skeletons of which coral reefs are formed, could live +at the greatest depths of the ocean. These minute animals were, +therefore, generally credited with filling up the deep ocean, +in certain places, and converting it into dry land, and poetic +philosophers were pleased to point to their indefatigable labors as an +object lesson to the slothful. + +But these charming, though fallacious, ideas were rudely overthrown by +the sounding line and the drag-net. It had long been known that pieces +of coral rock were brought up by dredging apparatus from the bottom of +the ocean at all depths, but it was eventually shown that such pieces +of coral rock never contained living animalculæ, when brought from +water at greater depths than from 100 to 120 feet. + +It puzzled scientific men no little at first to explain this apparent +inconsistency. If the coral polyp could not live in water at greater +depths than from 100 to 120 feet, how could the presence of coral rock +at a depth of thousands of feet be explained? Happily, however, this +problem was solved by the great naturalist, Charles Darwin, who showed +that coral islands can only be formed in parts of the ocean whose beds +are sinking at the same gradual rate at which the coral rock is being +deposited. The presence, therefore, of coral islands on the bed of the +Pacific, as well as along parts of its coasts, are, to scientific men, +as good indications of its gradual sinking as if such facts had been +written in the clearest language. + +But there are other instances of gradual changes of level besides +the bed of the Pacific. About 600 miles along the coast of Greenland, +from Disco Bay, near lat. 69° N., south to the Firth of Igaliko, lat. +60° 43' N., the bed of the ocean has been slowly sinking through 400 +years. Old buildings and islands have been covered by the waters, so +that fishermen have been compelled to provide new poles for their +boats. As Sir Charles Lyell remarks: + + "In one place the Moravian settlers have been obliged more + than once to move inland the poles upon which their large + boats are set, and the old poles still remain beneath the + water as silent witnesses of the change." + +Besides these gradual changes of level there are many others, but +only one more need be cited: the gradual movements of the coasts of +North America between Labrador and New Jersey that are rising in some +places, and sinking in other places. + +The evidences of these gradual changes of level are sometimes of +such a character that he who runs may read them. One of the most +interesting is, perhaps, that of the old Roman temple of Jupiter +Serapis, at Pozzuli, on the borders of the Mediterranean. This temple, +when completed, was 124 feet in length and 115 feet in width. Its roof +was supported by forty-six columns, each forty-two feet in height, and +five feet in diameter. Only three of these columns are now standing. +They give, however, unquestionable evidence of having been submerged +for about half their height. Nor, indeed, is the evidence wanting that +this submergence continued a considerable time; for, while the lower +twelve feet of the columns remain smooth and unaffected, yet, for a +distance of nine feet above this portion, they have been perforated +by various stone-boring mollusks of a species still living in the +Mediterranean. This witnesses that the columns, when submerged, were +buried in mud for twelve feet, and surrounded by water nine feet +deep. According to Dana, the pavement of the temple is still under +water. The fact that another pavement exists below it shows that these +changes of level had occurred before the temple was deserted by the +Romans. It appears, that, prior to 1845, a gradual sinking of this +part of the coast had been going on, but that since then there has +ensued a gradual rising. + +The evidences of these gradual changes of level in the land and water +surfaces of the earth cannot be doubted by even the most skeptical. +Again and again has the dry land disappeared below the surface of the +waters of the ocean. Again and again, the ocean's bed has been raised +to the surface and been converted into dry land. Suppose we attempt to +follow one of the latter movements. + +We will imagine an extensive area to have slowly appeared above the +ocean. In due process of time this land surface, which we will assume +to have continental dimensions, gradually becomes covered with plant +and animal life. If it remains above the water for a sufficient +length of time, its simple plants and animals acquire more and more +complex forms, so as to make it difficult to detect any traces of the +original species from which they have descended, or, more correctly, +ascended. Moreover, where favorable conditions exist, the continent +becomes peopled with men, who gradually advance from barbarism to +semi-barbarism and eventually become a most highly civilized nation, +sending to different parts of the world colonies, who carry with them +the language and religious customs of the land of their birth. + +But, a sudden or paroxysmal change of level occurs. The highly +developed and densely populated region is suddenly swept out of +existence and completely covered by the waters of the ocean until, in +a few thousand years, all traces of its existence have so completely +disappeared that but few, if any, can be found willing to acknowledge +it ever had an existence. + +Such, it is claimed, was the fate of the fabled Continent of Atlantis. +It will, therefore, be interesting to endeavor briefly to review its +past history and to read some of the things that have been written +about this part of the world, which appears in the opinion of some of +the ancients to have actually existed. + +References to Atlantis have been made by various early writers. Solon, +the great Athenian lawgiver, who flourished 600 years B. C., +began a description of this place in verse. This description was never +completed. At a later date one of Solon's descendants, Plato, who +lived about 400 B. C., prepared a description of Atlantis, +giving in detail its location, the general character of its surface, +a description of its principal city, and the civilization of its +inhabitants, as well as a brief reference to its sudden destruction. +In another place this record of Plato will be given in full. It will +suffice now to quote briefly what he says concerning its location. + + "There was an island situated in front of the straits which + you call the Columns of Heracles (Straits of Gibraltar). + The island was larger than Libya and Asia put together, + and was the way to other islands, and from the island you + might pass through the whole in the opposite continent, + for this sea which is within the Straits of Heracles is + only a harbor, having a narrow entrance, but that other is + the real sea, and the surrounding land may most truly be + called a continent. Now, in the island of Atlantis, there + was a great and wonderful empire, which had ruled over the + whole island and several others, as well as over part of + the continents; and, besides these, they subjected the + parts of Libya within the Columns of Heracles as far as + Egypt, and of Europe as far as Tyrrhenia. The vast power, + thus gathered into one, endeavored to subdue at one blow + our country and yours, and the whole of the land which was + within the straits, and then, Solon, your country shone + forth, in the excellence of her virtues and strength, among + all mankind, for she was the first in courage and military + skill, and was the leader of the Hellenes. And when the + rest fell off from her, being compelled to stand alone, + after having undergone the very extremity of danger, she + defeated and triumphed over the invaders, and preserved + from slavery those who were not yet subjected, and freely + liberated all the others who dwelt within the limits of + Heracles. + + "But afterwards, there occurred violent earthquakes and + floods, and in a single day and night of rain, all your + warlike men in a body sunk into the earth, and the island + of Atlantis in a like manner disappeared, and was sunk + beneath the sea. And that is the reason why the sea in + those parts is impassable and impenetrable, because there + is such a quantity of shallow mud in the way; and this + was caused by the subsidence of the island." ("Plato's + Dialogues," ii, 517, Timæus). + +But besides Solon and Plato there are other ancient writers who refer +to the lost island of Atlantis. + +Ælian, in his "Varia Historia," lib. iii, chap. xvii, states that +Theopompos, who flourished 400 B. C., refers to an interview +between Midas, King of Phrygia, and Sielus, in which the latter speaks +of a great continent larger than Asia, Europe, and Libya together that +existed in the Atlantic. + +Proclus quotes a statement from an ancient writer, who speaks about +the islands of the sea beyond the Pillars of Hercules (Straits of +Gibraltar). + +Marcellus, in a book on the Ethiopians, refers to seven islands in +the Atlantic whose inhabitants preserve legends of a greater island +(possibly Atlantis), that had dominion over the small islands. + +Diodorus Siculus asserts that the Phoenicians discovered a large +island in the Atlantic beyond the Pillars of Hercules several days' +sail from the coast of Africa. + +Homer, Plutarch, and other ancient writers, refer to several islands +in the Atlantic situated several thousand stadia from the Pillars of +Hercules. (A stadium was a Greek measure of length equal to 600 feet. +It was equal to one-eighth of a Roman mile, or 625 Roman feet.) + +Ignatius Donnelly, in his book, called "Atlantis, the Ante-Diluvian +World," claims that Plato's description of Atlantis which has +generally been regarded as imaginary, was, on the contrary, historic; +that the prehistoric continent of Atlantis was the cradle of the human +race; that here man reached his highest civilization; that Atlantis +was the site of the Garden of Eden, the Gardens of the Hesperides, the +Elysian Fields, as well as Olympus; that, under the forms of the gods +and goddesses of the ancient Greeks, the Phoenicians, the Hindoos, +and the Scandinavians, are related the stories of the kings, queens, +and heroes of Atlantis. + +Much that has been claimed for the lost continent can hardly be +regarded in any other light save that of imagination. For example, it +has been asserted that it was from Atlantis that the colonies were +sent out that peopled the coast countries of the Gulf of Mexico, of +parts of the valley of the Mississippi, the basin of the Amazon, the +western coasts of South America, parts of Europe, the shore lands of +the Mediterranean Sea, the coasts of Europe, including the Caspian and +the Black Seas, and even of parts of Africa. + +It has also been asserted that this mighty nation of Atlantis carried +the worship of the sun to Egypt, which was one of its first colonies, +and, therefore, the civilization of Egypt was but an offshoot of +prehistoric Atlantis. + +But it will be reasonably objected that, if such a mass of land ever +existed in the North Atlantic, some evidences should still be found +on the bed of the ocean. Even though great periods of time have +elapsed since the disappearance of Atlantis, some traces of its former +existence should still remain on the floor of the ocean. Are there +any evidences of an old land mass on this part of the floor of the +Atlantic? The answer is unmistakable. + +Deep-sea soundings show beyond question that there still exists in +the North Atlantic in the region where Atlantis is said to have been +located a submarine island, the summits of which appear above the +waters in the Azores and the Canary Islands. This submarine island +has been traced southwest over the bed of the ocean for a distance of +several thousand miles with a breadth of fully 1,000 miles. Toward the +south there is connected with it another submarine island, the summits +of which reach above the surface in the islands of Ascension, St. +Helena, and Tristan d'Acunha. + +But the testimony of the submarine islands extends further than this. +According to a number of careful soundings it appears that the bed +of these parts of the ocean, instead of being characterized by a +comparatively level surface due to the gradual accumulation of silt, +possesses, to a great extent, the peculiarly sculptured surfaces which +are only produced by exposure for a long time to the atmosphere. + +Other facts might be adduced to show that some time during the first +appearance of man on the earth there was a large land mass connecting +the Eastern and Western Continents. These facts include the wonderful +resemblances existing between the plants and animals of the Eastern +and Western Continents, the close resemblances of the myths and +legends of the races of the Eastern and Western Continents, as well +as the identity of their religious ideas, and the close similarity of +their language so far as relates to certain fundamental ideas. These +facts all point unquestionably to the existence of some large land +mass between the two continents, and to this extent to throw light on +the probable existence of prehistoric Atlantis. + + + + +CHAPTER XXXVIII + +PLATO'S ACCOUNT OF ATLANTIS + + +The following is a translation of Plato's record in full: + + Critias. Then listen, Socrates, to a strange tale, which + is, however, certainly true, as Solon, who was the wisest + of the seven sages, declared. He was a relative and great + friend of my great-grandfather, Dropidas, as he himself + says in several of his poems, and Dropidas told Critias, my + grandfather, who remembered, and told us, that there were + of old great and marvellous actions of the Athenians, which + have passed into oblivion through time and the destruction + of the human race--and one in particular, which was the + greatest of them all, the recital of which will be a + suitable testimony of our gratitude to you.... + + Socrates. Very good; and what is this ancient famous + action of which Critias spoke, not as a mere legend, but + as a veritable action of the Athenian State, which Solon + recounted? + + Critias. I will tell an old-world story which I heard from + an aged man; for Critias was, as he said, at that time + nearly ninety-years of age, and I was about ten years of + age. Now the day was that day of the Apaturia which is + called the registration of youth; at which, according to + custom, our parents gave prizes for recitations, and the + poems of several poets were recited by us boys, and many + of us sung the poems of Solon, which were new at the time. + One of our tribe, either because this was his real opinion, + or because he thought that he would please Critias, said + that, in his judgment, Solon was not only the wisest of men + but the noblest of poets. The old man, I well remember, + brightened up at this, and said smiling: "Yes, Amynander, + if Solon had only, like other poets, made poetry the + business of his life, and had completed the tale which he + brought with him from Egypt, and had not been compelled, by + reason of the factions and troubles which he found stirring + in this country when he came home, to attend to other + matters, in my opinion, he would have been as famous as + Homer, or Hesiod, or any poet." + + "And what was that poem about, Critias?" said the person + who addressed him. + + "About the greatest action which the Athenians ever did, + and which ought to have been most famous, but which, + through the lapse of time and the destruction of the + actors, has not come down to us." + + "Tell us," said the other, "the whole story, and how and + from whom Solon heard this veritable tradition." + + He replied: "At the head of the Egyptian Delta, where the + river Nile divides, there is a certain district which is + called the district of Sais, and the great city of the + district is also called Sais, and is the city from which + Amasis the king was sprung. And the citizens have a deity + who is their foundress: she is called in the Egyptian + tongue Neith, which is asserted by them to be the same + whom the Hellenes called Athene. Now, the citizens of + this city are great lovers of the Athenians, and say that + they are in some way related to them. Thither came Solon, + who was received by them with great honor; and he asked + the priests, who were most skilful in such matters, about + antiquity, and made the discovery that neither he nor any + other Hellene knew anything worth mentioning about the + times of old. + + "On one occasion, when he was drawing them on to speak of + antiquity, he began to tell about the most ancient things + in our part of the world--about Phoroneus, who is called + 'the first,' and about Niobe; and, after the Deluge, to + tell of the lives of Deucalian and Pyrrha; and he traced + the genealogy of their descendants, and attempted to + reckon how many years old were the events of which he was + speaking, and to give the dates. Thereupon, one of the + priests, who was of very great age, said: 'O Solon, Solon, + you Hellenes are but children, and there is never an old + man who is an Hellene.' Solon, hearing this, said, 'What do + you mean?' 'I mean to say,' he replied, 'that in mind you + are all young; there is no old opinion handed down among + you by ancient traditions, nor any science which is hoary + with age. And I will tell you the reason of this: there + have been, and there will be again, many destructions of + mankind arising out of many causes. + + "'There is a story which even you have preserved, that + once upon a time Phaëthon, the son of Helios, having yoked + the steeds in his father's chariot, because he was not + able to drive them in the path of his father, burnt up all + that was upon the earth, and was himself destroyed by a + thunder-bolt. Now, this has the form of a myth, but really + signifies a declination of the bodies moving around the + earth, and in the heavens, and a great conflagration of + things upon the earth recurring at long intervals of time: + when this happens, those who live upon the mountains and in + dry and lofty places are more liable to destruction than + those who dwell by rivers or on the sea-shore; and from + this calamity the Nile, who is our never-failing savior, + saves and delivers us. + + "'When, on the other hand, the gods purge the earth with a + deluge of water, among you herdsmen and shepherds on the + mountains are the survivors, whereas those of you who live + in cities are carried by the rivers into the sea; but in + this country neither at that time nor at any other does + the water come up from below, for which reason the things + preserved here are said to be the oldest. The fact is, + that wherever the extremity of winter frost or of summer + sun does not prevent, the human race is always increasing + at times, and at other times diminishing in numbers. And + whatever happened either in your country or in ours, or in + any other regions of which we are informed--if any action + which is noble or great, or in any other way remarkable has + taken place, all that has been written down of old, and is + preserved in our temples; whereas you and other nations are + just being provided with letters and the other things which + States require; and then, at the usual period, the stream + from heaven descends like a pestilence, and leaves only + those of you who are destitute of letters and education; + and thus you have to begin all over again as children, and + know nothing of what happened in ancient times, either + among us or among yourselves. + + "'As for those genealogies of yours which you have + recounted to us, Solon, they are no better than the tales + of children; for, in the first place, you remember one + deluge only, whereas there were many of them, and, in the + next place, you do not know that there dwelt in your land + the fairest and noblest race of men which ever lived, of + whom you and your whole city are but a seed or remnant. And + this was unknown to you, because for many generations the + survivors of that destruction died and made no sign. For + there was a time, Solon, before that great deluge of all, + when the city which now is Athens, was first in war, and + was preëminent for the excellence of her laws, and is said + to have performed the noblest deeds, and to have had the + fairest constitution of any of which tradition tells, under + the face of heaven.' + + "Solon marvelled at this and earnestly requested the priest + to inform him exactly and in order about these former + citizens. 'You are welcome to hear about them, Solon,' said + the priest, 'both for your own sake and for that of the + city; and, above all, for the sake of the goddess who is + the common patron and protector and educator of both our + cities. She founded your city a thousand years before ours, + receiving from the Earth and Hephæstus the seed of your + race, and then she founded ours, the constitution of which + is set down in our sacred registers as 8,000 years old. As + touching the citizens of 9,000 years ago, I will briefly + inform you of their laws and of the noblest of their + actions; and the exact particulars of the whole we will + hereafter go through at our leisure in the sacred registers + themselves. If you compare these very laws with your own, + you will find that many of ours are the counterpart of + yours, as they were in the olden time. + + "'In the first place, there is the caste of priests, + which is separated from all the others; next there are + the artificers, who exercise their several crafts by + themselves, and without admixture of any other, and also + there is the class of shepherds and that of hunters, as + well as that of husbandmen; and you will observe, too, that + the warriors in Egypt are separated from all the other + classes, and are commanded by the law only to engage in + war. Moreover, the weapons with which they are equipped + are shields and spears, and this the goddess taught first + among you, and then in Asiatic countries, and we among the + Asiatics first adopted. + + "'Then, as to wisdom, do you observe, what care the law + took from the very first, searching out and comprehending + the whole order of things down to prophecy and medicine + (the latter with a view to health); and out of these divine + elements drawing what was needful for human life, and + adding every sort of knowledge which was connected with + them. All this order and arrangement the goddess first + imparted to you when establishing your city; and she chose + the spot of earth in which you were born, because she saw + that the happy temperament of the seasons in that land + would produce the wisest of men. + + "'Wherefore the goddess, who was a lover both of war and + of wisdom, selected, and first of all settled that spot + which was the most likely to produce men likest herself. + And there you dwelt, having such laws as these and still + better ones, and excelled all mankind in all virtue, + as became the children and disciples of the gods. Many + great and wonderful deeds are recorded of your State in + our histories; but one of them exceeds all the rest in + greatness and valor; for these histories tell of a mighty + power which was agressing wantonly against the whole of + Europe and Asia, and to which your city put an end. + + "'This power came forth out of the Atlantic Ocean, for in + those days the Atlantic was navigable; and there was an + island situated in front of the straits which you call the + Columns of Heracles: the island was larger than Libya and + Asia put together, and was the way to other islands, and + from the island you might pass through the whole of the + opposite continent which surrounded the true ocean; for + this sea which is within the Straits of Heracles is only + a harbor, having a narrow entrance, but that other is a + real sea, and the surrounding land may be most truly called + a continent. Now, in the island of Atlantis there was a + great and wonderful empire, which had rule over the whole + island and several others, as well as over parts of the + continent; and, besides these, they subjected the parts of + Libya within the Columns of Heracles as far as Egypt, and + of Europe as far as Tyrrhenia. + + "'That vast power, thus gathered into one, endeavored to + subdue at one blow our country and yours, and the whole of + the land which was within the straits; and then, Solon, + your country shone forth, in the excellence of her virtue + and strength, among all mankind, for she was the first + in courage and military skill, and was the leader of the + Hellenes. And when the rest fell off from her, being + compelled to stand alone, after having undergone the very + extremity of danger, she defeated and triumphed over the + invaders, and preserved from slavery those who were not + yet subjected, and freely liberated all the others who + dwelt within the limits of Heracles. But afterward there + occurred violent earthquakes and floods, and in a single + day and night of rain all your warlike men in a body sunk + into the earth, and the island of Atlantis in like manner + disappeared, and was sunk beneath the sea. And that is + the reason why the sea in those parts is impassable and + impenetrable, because there is such a quantity of shallow + mud in the way; and this was caused by the subsidence of + the island.' ('Plato's Dialogues,' ii, 517, Timæus.)... + + "But in addition to the gods whom you have mentioned, I + would specially invoke Mnemosyne; for all the important + part of what I have to tell is dependent on her favor, and + if I can recollect and recite enough of what was said by + the priests, and brought hither by Solon, I doubt not that + I shall satisfy the requirements of this theatre. To that + task, then, I will at once address myself. + + "Let me begin by observing first of all that nine thousand + was the sum of years which had elapsed since the war which + was said to have taken place between all those who dwelt + outside the Pillars of Heracles and those who dwelt within + them. This war I am now to describe. Of the combatants on + the one side the city of Athens was reported to have been + the ruler, and to have directed the contest; the combatants + on the other side were led by the kings of the islands + of Atlantis, which, as I was saying, once had an extent + greater than that of Libya and Asia; and, when afterwards + sunk by an earthquake, became an impassable barrier of mud + to voyagers sailing from hence to the ocean. The progress + of the history will unfold the various tribes of barbarians + and Hellenes which then existed, as they successively + appear on the scene; but I must begin by describing, first + of all, the Athenians as they were in that day, and their + enemies who fought with them; and I shall have to tell of + the power and form of government of both of them. Let us + give the precedence to Athens.... + + "Many great deluges have taken place during the nine + thousand years, for that is the number of years which have + elapsed since the time of which I am speaking; and in all + the ages and changes of things there has never been any + settlement of the earth flowing down from the mountains, as + in other places, which is worth speaking of; it has always + been carried round in a circle, and disappeared in the + depths below. The consequence is that, in comparison with + what then was, there are remaining in small islets only the + bones of the wasted body, as they may be called, all the + richer and softer parts of the soil having fallen away, and + the mere skeleton of the country being left.... + + "And next, if I have not forgotten what I heard when I was + a child, I will impart to you the character and origin + of their adversaries; for friends should not keep their + stories to themselves, but have them in common. Yet, before + proceeding further in the narrative, I ought to warn you + that you must not be surprised, if you should hear Hellenic + names given to foreigners. I will tell you the reason + of this: Solon, who was intending to use the tale for + his poem, made an investigation into the meaning of the + names, and found that the early Egyptians, in writing them + down, had translated them into their own language, and he + recovered the meaning of the several names and retranslated + them, and copied them out again in our language. My + great-grandfather, Dropidas, had the original writing, + which is still in my possession, and was carefully studied + by me when I was a child. Therefore, if you hear names such + as are used in this country, you must not be surprised, for + I have told you the reason of them. + + "The tale, which was of great length, began as follows: + I have before remarked, in speaking of the allotments + of the gods, that they distributed the whole earth into + portions differing in extent, and made themselves temples + and sacrifices. And Poseidon, receiving for his lot the + island of Atlantis, begat children by a mortal woman, and + settled them in a part of the island which I will proceed + to describe. On the side toward the sea, and in the centre + of the whole island, there was a plain which is said to + have been the fairest of all plains, and very fertile. + Near the plain, and also in the centre of the island, at a + distance of about fifty stadia, there was a mountain, not + very high on any side. In this mountain there dwelt one of + the earth-born primeval men of that country, whose name was + Evenor, and he had a wife named Leucippe, and they had an + only daughter, who was named Cleito. + + "The maiden was growing up to womanhood when her father + and mother died; Poseidon fell in love with her, and had + intercourse with her; and, breaking the ground, enclosed + the hill in which she lived all around, making alternate + zones of sea and land, larger and smaller, encircling + one another; there were two of land and three of water, + which he turned as with a lathe out of the centre of the + island, equidistant every way, so that no man could get + to the island, for ships and voyagers were not yet heard + of. He himself, as he was a god, found no difficulty in + making special arrangements for the centre island, bringing + two streams of water under the earth, which he caused to + ascend as springs, one of warm water and the other of cold, + and making every variety of food to spring up abundantly + in the earth. He also begat and brought up five pairs of + male children, dividing the island of Atlantis into ten + portions; he gave to the first-born of the eldest pair his + mother's dwelling and the surrounding allotment, which was + the largest and best, and made him king over the rest; the + others he made princes, and gave them rule over many men + and a large territory. + + "He named them all: the eldest, who was king, he named + Atlas, and from him the whole island and the ocean received + the name of Atlantic. To his twin brother, who was born + after him, and obtained as his lot the extremity of the + island toward the Pillars of Heracles, as far as the + country which is still called the region of Gades in that + part of the world, he gave the name which in the Hellenic + language is Eumelus, in the language of the country which + is named after him, Gadeirus. Of the second pair of twins, + he called one Ampheres and the other Evæmon. To the third + pair of twins he gave the name Mneseus to the elder, and + Autochthon to the one who followed him. Of the fourth pair + of twins he called the elder Elasippus and the younger + Mestor. And of the fifth pair he gave to the elder the name + of Azaes, and to the younger Diaprepes. + + "All these and their descendants were the inhabitants + and rulers of divers islands in the open sea; and also, + as has been already said, they held sway in the other + direction over the country within the Pillars as far as + Egypt and Tyrrhenia. Now Atlas had a numerous and honorable + family, and his eldest branch always retained the kingdom, + which the eldest son handed on to his eldest for many + generations; and they had such an amount of wealth as + was never before possessed by kings and potentates, and + is not likely ever to be again, and they were furnished + with everything which they could desire both in city and + country. For, because of the greatness of their empire, + many things were brought to them from foreign countries, + and the island itself provided much of what was required by + them for the uses of life. + + "In the first place, they dug out of the earth whatever + was to be found there, mineral as well as metal, and that + which is now only a name, and was then something more + than a name--orichalcum--was dug out of the earth in many + parts of the island, and, with the exception of gold, was + esteemed the most precious of metals among the men of those + days. There was an abundance of wood for carpenters' work, + and sufficient maintenance for tame and wild animals. + Moreover, there were a great number of elephants in the + island, and there was provision for animals of every kind, + both for those who live in lakes and marshes and rivers, + and also for those which live in mountains, and on plains, + and therefore for the animal which is the largest and most + voracious of them. + + "Also whatever fragrant things there are in the earth, + whether roots, or herbage, or woods, or distilling drops + of flowers, or fruits, grew and thrived in that land; and + again, the cultivated fruit of the earth, both the dry + edible fruit and other species of food, which we call by + the general name of legumes, and the fruits having a hard + rind, affording drinks, and meats, and ointments, and good + store of chestnuts and the like, which may be used to play + with, and are fruits which spoil with keeping--and the + pleasant kinds of dessert which console us after dinner, + when we are full and tired of eating--all these that + sacred island lying beneath the sun brought forth fair and + wondrous in infinite abundance. + + "All these things they received from the earth, and they + employed themselves in constructing their temples, and + palaces, and harbors and docks; and they arranged the + whole country in the following manner: first of all they + bridged over the zones of sea which surrounded the ancient + metropolis, and made a passage into and out of the royal + palace; and then they began to build the palace in the + habitation of the god and of their ancestors. This they + continued to ornament in successive generations, every king + surpassing the one who came before him to the utmost of his + power, until they made the building a marvel to behold for + size and for beauty. + + "And, beginning from the sea, they dug a canal three + hundred feet in width and one hundred feet in depth, and + fifty stadia in length, which they carried through to the + outermost zone, making a passage from the sea up to this, + which became a harbor, and leaving an opening sufficient + to enable the largest vessels to find ingress. Moreover, + they divided the zones of land which parted the zones + of sea, constructing bridges of such a width as would + leave a passage for a single trireme to pass out of one + into another, and roofed them over; and there was a way + underneath for the ships, for the banks of the zones were + raised considerably above the water. + + "Now the largest of the zones into which a passage was cut + from the sea was three stadia in breadth, and the zone of + land which came next of equal breadth; but the next two, + as well a zone of water as of land, were two stadia, and + the one which surrounded the central island was a stadium + only in width. The island in which the palace was situated + had a diameter of five stadia. This, and the zones and the + bridge, which was the sixth part of a stadium in width, + they surrounded by a stone wall, on either side placing + towers, and gates on the bridges where the sea passed + in. The stone which was used in the work they quarried + from underneath the centre island and from underneath the + zones, on the outer as well as the inner side. One kind of + stone was white, another black, and a third red; as they + quarried, they at the same time hollowed out decks, double + within, having roofs formed out of the native rock. + + "Some of their buildings were simple, but in others they + put together different stones, which they intermingled for + the sake of ornament, to be a natural source of delight. + The entire circuit of the wall which went around the + outermost one they covered with a coating of brass, and + the circuit of the next wall they coated with tin, and the + third, which encompassed the citadel, flashed with the red + light of orichalcum. The palace in the interior of the + citadel was constructed in this wise: in the centre was + a holy temple, dedicated to Cleito and Poseidon, which + remained inaccessible, and was surrounded by an enclosure + of gold; this was the spot in which was originally begotten + the race of ten princes, and thither they annually brought + the fruits of the earth in their season from all the ten + portions, and performed sacrifices to each of them. + + "Here, too, was Poseidon's own temple, of a stadium in + length and half a stadium in width, and of a proportionate + height, having a sort of barbaric splendor. All the outside + of the temple, with the exception of the pinnacles, they + covered with silver, and the pinnacles with gold. In the + interior of the temple the roof was of ivory, adorned + everywhere with gold and silver and orichalcum; all the + other parts of the walls and pillars and floor they lined + with orichalcum. In the temple they placed statues of + gold: there was the god himself standing in a chariot--the + charioteer of six winged horses--and of such a size that + he touched the roof of the building with his head; around + him were a hundred Nereids riding on dolphins, for such was + thought to be the number of them in that day. + + "There were also in the interior of the temple other images + which had been dedicated by private individuals. And around + the temple, on the outside, were placed statues of gold + of all the ten kings and of their wives; and there were + many other great offerings, both of kings and of private + individuals, coming both from the city itself and the + foreign cities over which they held sway. There was an + altar, too, which in size and workmanship corresponded to + the rest of the work, and there were palaces in like manner + which answered to the greatness of the kingdom and the + glory of the temple. + + "In the next place, they used fountains both of gold and + hot springs. These were very abundant, and both kinds + wonderfully adapted to use by reason of the sweetness and + excellence of their waters. They constructed buildings + about them, and planted suitable trees; also cisterns, + some open to the heaven, others which they roofed over, + to be used in winter as warm baths: there were the king's + baths, and the baths of private persons, which were kept + apart; also separate baths for women, and others again for + horses and cattle, and to them they gave as much adornment + as was suitable for them. The water which ran off they + carried, some to the grove of Poseidon, where were growing + all manner of trees of wonderful height and beauty, owing + to the excellence of the soil; the remainder was conveyed + by aqueducts which passed over the bridges to the outer + circles: and there were many temples built and dedicated + to many gods; also gardens and places of exercise, some + for men, and some set apart for horses, in both of the + two islands formed by the zones; and in the centre of the + larger of the two, there was a racecourse of a stadium + in width, and in length allowed to extend all round the + island, for horses to race in. + + "Also there were guard-houses at intervals for the + body-guard, the more trusted of whom had their duties + appointed to them in the lesser zone, which was nearer the + Acropolis; while the most trusted of all had houses given + them within the citadel, and about the persons of the + kings. The docks were full of triremes and naval stores, + and all things were quite ready for use. Enough of the plan + of the royal palace. Crossing the outer harbors, which were + three in number, you would come to a wall which began at + the sea and went all round; this was everywhere distant + fifty stadia from the largest zone and harbor, and enclosed + the whole, meeting at the mouth of the channel toward the + sea. + + "The entire area was densely crowded with habitations; + and the canal and the largest of the harbors were full + of vessels, and merchants coming from all parts, who, + from their numbers, kept up a multitudinous sound of + human voices and din of all sorts, night and day. I have + repeated his descriptions of the city and the parts about + the ancient palace nearly as he gave them, and now I must + endeavor to describe the nature and arrangement of the + rest of the country. The whole country was described as + being very lofty and precipitous on the side of the sea, + but the country immediately about and surrounding the city + was a level plain, itself surrounded by mountains which + descended toward the sea; it was smooth and even, but of + an oblong shape, extending in one direction three thousand + stadia, and going up the country from the sea through the + centre of the island two thousand stadia; the whole region + of the island lies toward the south, and is sheltered from + the north. + + "The surrounding mountains were celebrated for their number + and size and beauty, in which they exceeded all that are + now to be seen anywhere; having in them also many wealthy + inhabited villages, and rivers and lakes, and meadows + supplying food enough for every animal, wild or tame, and + wood of various sorts, abundant for every kind of work. + I will now describe the plain, which had been cultivated + during many ages by many generations of kings. It was + rectangular, and for the most part straight and oblong; and + what it wanted of the straight line followed the line of + the circular ditch. The depth and width and length of this + ditch were incredible, and gave the impression that such a + work, in addition to so many other works, could hardly have + been wrought by the hand of man. But I must say what I have + heard. + + "It was excavated to the depth of a hundred feet, and its + breadth was a stadium everywhere; it was carried round the + whole of the plain, and was ten thousand stadia in length. + It received the streams which came down the mountains, + and winding round the plain, and touching the city at + various points, was there let off into the sea. From above, + likewise, straight canals of a hundred feet in width were + cut in the plain, and again let off into the ditch, toward + the sea. These canals were at intervals of a hundred + stadia, and by them they brought down the wood from the + mountains to the city, and conveyed the fruits of the earth + in ships, cutting transverse passages from one canal into + another, and to the city. Twice in the year they gathered + the fruits of the earth--in winter having the benefit of + the rains, and in summer introducing the water of the + canals. As to the population, each of the lots in the plain + had an appointed chief of men who were fit for military + service, and the size of the lot was to be a square of ten + stadia each way, and the total number of all the lots was + sixty thousand. + + "And of the inhabitants, of the mountains and of the rest + of the country there was also a vast multitude having + leaders, to whom they were assigned according to their + dwellings and villages. The leader was required to furnish + for the wars the sixth portion of a war-chariot, so as + to make up a total of ten thousand chariots; also two + horses and riders upon them, and a light chariot without + a seat, accompanied by a fighting man on foot carrying a + small shield, and having a charioteer mounted to guide the + horses; also, he was bound to furnish two heavy-armed men, + two archers, two slingers, three stone-shooters, and three + javelin men, who were skirmishers, and four sailors, to + make up a complement of twelve hundred ships. Such was the + order of war in the royal city. + + "That of the other nine governments was different in each + of them, and would be wearisome to narrate. As to offices + and honors the following was the arrangement from the + first: each of the ten kings, in his own division and in + his own city, had the absolute control of the citizens, + and in many cases, of the laws, punishing and slaying + whomsoever he would. + + "Now the relations of their governments to one another + were regulated by the injunctions of Poseidon as the law + had handed them down. These were inscribed by the first + men on a column of orichalcum, which was situated in the + middle of the island, at the temple of Poseidon, whither + the people were gathered together every fifth and sixth + years alternately, thus giving equal honor to the odd and + to the even number. And when they were gathered together + they consulted about public affairs, and inquired if any + one had transgressed in anything, and passed judgment on + him accordingly--and before they passed judgment they gave + their pledges to one another in this wise: + + "There were bulls who had the range of the temple of + Poseidon; and the ten who were left alone in the temple, + after they had offered prayers to the gods that they might + take the sacrifices which were acceptable to them, hunted + the bulls without weapons, but with staves and nooses; and + the bull which they caught they led up to the column. The + victim was then struck on the head by them, and slain over + the sacred inscription. Now on the column, besides the law, + there was inscribed an oath invoking mighty curses on the + disobedient. When, therefore, after offering sacrifices + according to their customs, they had burnt the limbs of the + bull, they mingled a cup and cast in a clot of blood for + each of them. The rest of the victim they took to the fire, + after having made a purification of the column all round. + + "They then drew from the cup in golden vessels, and, + pouring a libation on the fire, they swore that they would + judge according to the laws on the column, and would punish + any one who had previously transgressed, and that for the + future they would not, if they could help, transgress any + of the inscriptions, and would not command, or obey any + ruler who commanded them, to act otherwise than according + to the laws of their father Poseidon. + + "This was the prayer which each of them offered up for + himself and for his family, at the same time drinking, and + dedicating the vessel in the temple of the god; and, after + spending some necessary time at supper, when darkness came + on and the fire about the sacrifice was cool, all of them + put on most beautiful azure robes, and, sitting on the + ground at night near the embers of the sacrifices on which + they had sworn, and extinguishing all the fires about the + temple, they received and gave judgment, if any of them had + any accusation to bring against any one; and, when they had + given judgment, at daybreak they wrote down their sentences + on a golden tablet, and deposited them as memorials with + their robes. + + "There were many special laws which the several kings had + inscribed about the temple, but the most important was the + following: that they were not to take up arms against one + another, and they were all to come to the rescue, if any + one in any city attempted to overthrow the royal house. + Like their ancestors, they were to deliberate in common + about war and other matters, giving the supremacy to the + family of Atlas; and the king was not to have the power of + life or death over any of his kinsmen, unless he had the + assent of the majority of the ten kings. + + "Such was the vast power which the god settled in the lost + island of Atlantis; and this he afterward directed against + our land on the following pretext, as traditions tell. For + many generations, as long as the divine nature lasted in + them, they were obedient to the laws, and well-affectioned + toward the gods, who were their kinsmen, for they possessed + true and in every way great spirits, practicing gentleness + and wisdom in the various chances of life, and in their + intercourse with one another. + + "They despised everything but virtue, not caring for + their present state of life, and thinking lightly on the + possession of gold, and other property, which seemed only a + burden to them; neither were they intoxicated by luxury, + nor did wealth deprive them of their self-control; but + they were sober, and saw clearly that all these goods are + increased by virtuous friendship with one another, and that + by excessive zeal for them and honor of them, the good of + them is lost, and friendship perishes with them. + + "By such reflections, and by the continuance in them of a + divine nature, all that which we have described waxed and + increased in them; but when this divine portion began to + fade away in them, and became diluted too often, and with + too much of the mortal admixture, and the human nature + got the upper hand, then, they being unable to bear their + fortune, became unseemly, and to him who had an eye to see, + they began to appear base, and had lost the fairest of + their precious gifts; but to those who had no eye to see + the true happiness they still appeared glorious and blessed + at the very time when they were filled with unrighteous + avarice and power. Zeus, the god of gods, who rules with + law, and is able to see into such things, perceiving that + an honorable race was in a most wretched state, and wanting + to inflict punishment on them, that they might be chastened + and improved, collected all the gods into his most holy + habitation, which, being placed in the centre of the world, + sees all things that partake of generations. And when he + had called them together, he spake as follows:" + +The story abruptly ends here, for Plato left no further record. + + + + +CHAPTER XXXIX + +NATURE'S WARNING OF COMING EARTHQUAKES + + +That there are signs of coming earthquakes which might be read by +man, had he sufficient knowledge, there would seem to be but little +doubt. These phenomena follow natural laws so that the approach of an +earthquake must necessarily be in a definite order both as regards +the phenomena which precede as well as those which follow it. There +should, therefore, be signs that would enable one to predict its +coming, although it must be acknowledged that these signs, so far as +we actually know, are indistinct. + +It may seem to the unthinking and unobservant that the awful +catastrophe of an earthquake comes entirely unheralded; that, +apparently, it is not until the earth's surface begins to rock to +and fro under the mighty forces that are causing destruction that +its presence can be known. There are, however, many reasons for +believing that in, perhaps, the greatest number of cases, it might +have been foreseen, if greater attention had been given to the +slight indications of its probable approach a short time before its +occurrence. + +It is evident that the conditions of great pressure or stress in the +earth's crust which finally result in a disastrous earthquake have +been slowly accumulating for a long time, and that when the pressure +at last reaches a point where the crust has to yield or slip, the +ground is suddenly crushed and tossed to and fro while vast fissures +and chasms are produced in the subterranean regions. At those points +of the earth immediately above or in the neighborhood of such regions +it is possible that there are many signs of the coming quake; +and, although indistinguishable by our duller senses, are readily +appreciated by the more highly developed senses of the lower animals. +Indeed, had we accustomed ourselves to reading the various indications +of nature as the lower animals have, we, too, might be able to read +these warnings of the coming earthquake. + +At great distances from the place where the earthquake starts there +would necessarily be a better opportunity for predicting its approach. +As already stated, what is called an earthquake does not consist +of a single shaking of the ground, but of a highly complex series +of shakings. According to Mallet, the following waves start at the +same time from the place of origin of an earthquake, when located +on the bed of an ocean; i. e., an earth sound wave and a earth wave +constituting the earth's shake; a sound wave through the ocean, +another through the air; a sea wave called by him a forced sea wave, +and finally the great sea wave. + +These waves reach a distant point in the following order: the sound +wave through the earth and the great earthquake or shake which +produces the damage. Then a smaller sea wave called the forced sea +wave. This is followed almost immediately by the sound wave through +the sea. Next come the air sound wave and finally the great sea wave; +which, rushing in on the shore, sweeps nearly everything before it. + +In other words, the disturbances produced by the great earthquake +follow in this order of sequence. If, therefore, the great earthquake +wave proper transmitted through the earth should for any reason be +delayed in reaching a distant place, the great sound waves should be +able to give warning of the coming disturbances. + +Again, as we have already seen, the earthquake wave is preceded by a +number of preliminary tremors, and is followed by a number of after +tremors or _earthquake echoes_. Since, therefore, the preliminary +waves reach a place first, it would seem that the approach of an +earthquake must be heralded by the preliminary tremors. These, +perhaps, at least in part, enable the lower animals to detect its +coming. + +Again, in almost all instances there are a number of preliminary +shocks that precede the great earthquake shock. Some of these +preliminary shocks continue at intervals for several days or even +longer. Sometimes, indeed, these subterranean sounds fail to be +followed by earthquakes. Milne thinks that these sounds are caused +by the preliminary tremors which precede the principal shock of the +earthquake and that they reach the place first. Here again then it +is evident that, were we able to interpret properly these sounds, we +would probably be able to foretell the coming quake with a fair degree +of certainty. + +There would appear to be no reasonable doubt that in some manner +which we have not yet been able to discover, but probably along some +of the lines indicated above, animals are capable of recognizing a +coming earthquake. Long before the coming of the catastrophe they are +said to exhibit extreme terror, and in many cases appear to seek the +companionship of man, as if for protection. + +That the senses of smell and hearing are far more acute in the lower +animals than in man no one can reasonably doubt. The manner in which +a trained dog can follow a scent, for a long time after the animal +or thing producing it has passed, far exceeds the power of scent +possessed by man, and it is more than likely that this same power is +possessed by all animals who live upon or prey upon other animals. It +is probable that faintly odorous vapors or gases escape from the crust +shortly before the great shock occurs, and that these faint odors are +warnings to the animals of the approaching calamity. The sense of +hearing also is much more acute in the lower animals. + +Daubeny is evidently of this belief, as will be seen from the +following: + + "These gases and vapors (alluding to emanations given off + from the ground during earthquakes) exert an influence + on the barometer, which does appear to be indirectly + affected by the earthquake. Then, similar properties + also may occasion that uneasiness which animals are said + to evince before any such event. Thus, according to the + accounts of some writers, rats and mice leave their holes, + alligators seek the dry land, quadrupeds snuff the ground, + and manifest such signs of the impending calamity that in + countries where earthquakes are common, the inhabitants + take the alarm in consequence, and escape from their + houses. It is right, however, to add, that more recent + authorities dispute altogether the correctness of these + statements." + +Dutton doubts the ability of animals to foretell coming earthquake +shocks. + +But that the lower animals do exhibit signs of fear at the approach of +an earthquake has been repeatedly asserted by good observers. + +Hamilton, who made a careful examination of the neighboring country +during the great earthquake at Calabria, asserts that horses and oxen +during the shocks extended their legs widely in order to avoid being +thrown down, "and that hogs, oxen, horses, and mules, and also geese, +appeared to be painfully aware of the approach of the earthquake of +Calabria; and the neighing of a horse, the braying of an ass, or the +cackling of a goose, even when he (Hamilton) was making his survey +(after the occurrence of the great earthquake shock), drove the people +out of their temporary sheds in expectation of a shock." + +It is asserted that birds appear to be especially sensible to a coming +earthquake shock. That geese will quit the water in which they were +swimming before the earthquake and will not return to it. It is quite +possible that these birds with their heads immersed in the water can +hear the distant murmurings long before they become audible in the air. + +Von Hoff makes the following statement: + + "It has been remarked that at such times (immediately + before the coming of an earthquake shock), domestic animals + showed a decided uneasiness, dogs howled mournfully, horses + neighed in an unusual manner, and poultry flew restlessly + about. These latter phenomena might easily be produced by + mephitic vapours, which often ascend to the surface of the + earth before the breaking out of an earthquake." + +Mallet states that there is abundant evidence that earthquake shocks, +even when not of very great intensity, produce nausea in both men and +women. This would seem natural, since, as everyone knows, until one +is accustomed to sea-voyages, merely to be tossed to and fro by the +motion of the waves results in the production of sea-sickness. + +It has been also noticed that during earthquakes fish which under +ordinary circumstances live in the mud at the bottom of bodies of +water come near to the surface and at such times can be caught in +great numbers. + +Mallet cites the following effects produced by earthquakes: + + "Amongst the effects supposed to be produced by the + earthquake on the atmosphere were reckoned tempestuous + winds, thunder-storms, meteors, coldness of the air, + severe winters, heavy rains, miasmata, producing diseases + and affecting vegetation. A very remarkable instance of + the latter is quoted, namely, that in Peru, after the + earthquake of 1687, wheat and barley would not thrive at + all, though formerly the country was remarkably favourable + for them." + +Sir Charles Lyell notes the following phenomena attending earthquakes: + + "Irregularities in the seasons preceding or following the + shocks; sudden gusts of wind, interrupted by dead calms; + violent rains at unusual seasons, or in countries where, + as a rule, they are almost unknown; a reddening of the + sun's disk, and haziness in the air, often continued for + months; an evolution of electric matter, or of inflammable + gas from the soil, with sulphurous and mephitic vapours; + noises underground, like the running of carriages, or + the discharge of artillery, or distant thunder; animals + uttering cries of distress, and evincing extraordinary + alarm, being more sensitive than men to the slightest + movement; a sensation like sea-sickness, and a dizziness in + the head, experienced by men. These, and other phenomena, + less connected with our present subject as geologists, have + recurred again and again at distant ages, and in all parts + of the globe." + + +THE END + + + + +FOOTNOTES: + +[Footnote 1: A point on the other side of the earth directly opposite +a given point.] + +[Footnote 2: A fracture of a stratum, or a general rock mass, with a +relative displacement of the opposite sides of the break. + +The plane or fracture of a fault, known as the fault-plane, is seldom +vertical. The higher side is called the heaved or upthrow side; the +opposite side the thrown or downthrow side.] + +[Footnote 3: _Tectonic Earthquake_. An earthquake due to the sudden +slip of faulted strata.] + +[Footnote 4: _I. e._, burnt out mountain, extinct volcano.] + +[Footnote 5: _Epicentre._ A point on the surface of the earth +vertically above the point of origin of an earthquake, or the place +where it starts.] + + + + +Transcriber's Notes + + +Obvious printer errors have been silently corrected. + +Some illustrations have been moved to paragraph breaks. + +Page 43: Kamehamoha could be a typo for Kamehameha. + +Page 68: Changed "salter" to "saltier." + (Orig: another with water salter than the sea,) + +Page 76: Changed "Ena" to "Etna." + (Orig: during his time Mt. Ena had lost so much of its height) + +Page 115: "eruption during the winter of 1841-43," could be a typo for +1841-42 or 1842-43. + +Page 122: "Mont Pelée" could be a typo for "Mount Pelée." + +Page 136: 43° C." (109° 4' F.). could be a typo for (109.4° F.). + +Page 341: Changed one-eight to one-eighth. + (Orig: It was equal to one-eight of a Roman mile) + +Retained the following spelling variations: + + Page 49: The largest volcano in Iceland, the Dyngjufköll, + Page 57: The largest volcano in Iceland is Dyngjufjoll. + + Pages 52, 193, 311: Geikie + Page 181: Geicke + + Pages 17, 156, 257: Hindostan + Page 165: Hindustan + + Page 63: Lucullis + Page 76: Lucullus + + + + + + + +End of the Project Gutenberg EBook of The Wonder Book of Volcanoes and +Earthquakes, by Edwin J. Houston + +*** END OF THE PROJECT GUTENBERG EBOOK 43320 *** |