THE WONDER BOOK OF
VOLCANOES AND EARTHQUAKES

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]

[FULL PAGE ILLUSTRATIONS]

[ILLUSTRATIONS IN TEXT]

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.

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.

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.

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.

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.

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.

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."

Fig. 7. Panorama of Mokuaweoweo
From U. S. Geological Survey

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.

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...."

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.

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.

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.

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.

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.