CHAPTER VIII.
Hawaii, Sandwich Islands--Crater of Kilauea--Its awful Aspect--Fiery Lake and Islands--Jets of Lava--Depth of Crater and Surface of Lake--Bank of Sulphur--Curious Rainbow--Mouna-Kaah and Mouna-Loa--Eruption of the Latter in 1840--Recent Eruption--Great Jet and Torrent of Lava--Burning of the Forests--Great Whirlwinds--Underground Explosions--Other Volcanoes in the Pacific.
Hawaii is well known in history as being the island where the celebrated navigator Captain Cook was killed. The name used to be written Owhyhee; but a better apprehension of the native p.r.o.nunciation has led to its being altered into Hawaii. No one who visits it in the present day need be afraid of sharing the fate of poor Captain Cook; for the descendants of the savages who, in his time, inhabited the island, have now, through the labours of Christian missionaries, become a very decent sort of quiet, well-behaved Christian people.
Hawaii, which is the largest of a group called the Sandwich Islands, can boast of the greatest volcanic crater in the world. It is called sometimes Kirauea, sometimes Kilauea; for the natives seem not very particular about the p.r.o.nunciation of their _l_ and their _r_; but where one uses _l_ another as pertinaciously employs _r_, while a third set use a sound between the two, as you may have heard some people do at home.
Situated on the lower slopes of a lofty mountain called Mouna-Roa, or Loa (for there is the same dubiety about the _l_ and the _r_ here as in the former case), the crater of Kilauea is a vast plain between fifteen and sixteen miles in circ.u.mference, and sunk below the level of its borders to a depth varying from two hundred to four hundred feet--the walls of rock enclosing it being for the most part precipitous. The surface of the ground is very uneven, being strown with huge stones and ma.s.ses of volcanic rock, and it sounds hollow under the tramp of the foot.
Towards the centre of the plain is a much deeper depression. Those who have ventured to approach it, and look down, describe it as an awful gulf, about eight hundred feet in depth, and presenting a most gloomy and dismal aspect. The bottom is covered with molten lava, forming a great lake of fire, which is continually boiling violently, and whose fiery billows exhibit a wild terrific appearance. The shape of the lake resembles the crescent moon; its length is estimated at about two miles, and its greatest breadth at about one mile. It has numerous conical islands scattered round the edge, or in the lake itself, each of them being a little subordinate crater. Some of them are continually sending out columns of gray vapour; while from a few others shoots up what resembles flame. It is, probably, only the bright glare of the lava they contain, reflected upwards. Several of these conical islands are always belching forth from their mouths glowing streams of lava, which roll in fiery torrents down their black and rugged sides into the boiling lake below. They are said sometimes to throw up jets of lava to the height of upwards of sixty feet. The foregoing woodcut can convey only an imperfect idea of this immense crater.
[Ill.u.s.tration: Crater of Kilauea]
The outer margin of the gulf all round is nearly perpendicular. The height of the bounding cliffs is estimated at about four hundred feet above a black horizontal ledge of hardened lava, which completely encircles it, and beyond which there is a gradual slope down into the burning lake. The surface of the molten lava is at present between three and four hundred feet below this horizontal ledge; but the lava is said sometimes to rise quite up to this level, and to force its way out by forming an opening in the side of the mountain, whence it flows down to the sea. An eruption of this kind took place in 1859. On one side of the margin of the lake there is a long pale yellow streak formed by a bank of sulphur. The faces of the rocks composing the outer walls of the crater have a pale ashy gray appearance, supposed to be due to the action of the sulphurous vapours. The surface of the plain itself is much rent by fissures. It is said that the glare from the molten lava in the lake is so great as to form rainbows on the pa.s.sing rain-clouds.
The entire Island of Hawaii is of volcanic origin; and besides this great crater it contains two other lofty mountains, whose summits are covered with snow, and whose height is estimated at fifteen or sixteen thousand feet above the level of the sea. The one is named Mouna-Kaah or Keah, the other is Mouna-Loa--the same on whose lower flanks the crater of Kilauea is situated. Mouna-Kaah has long been in a state of repose. So also was Mouna-Loa up to 1840, when it burst forth with great fury, and it has continued more or less in a state of activity ever since. There has been a grand eruption very lately, said by the natives to have been the greatest of any on record.
A new crater opened near the top, at a height of about ten thousand feet, and for three days a flood of lava poured down the north-eastern slope. After a pause of about thirty-six hours, there was opened on the eastern slope, about half way down the mountain, another crater, whence there rose an immense jet of liquid lava, which attained a height of about a thousand feet, and had a diameter of about a hundred feet. This jet was sustained for twenty days and nights; but during that time its height varied from the extreme limit of a thousand, down to about a hundred feet. The play of this fiery fountain was accompanied by explosions so loud as to be heard at the distance of forty miles. Nothing could surpa.s.s the awful grandeur of this jet, which was at a white heat when it issued from its source, but, cooling as it ascended into the air, it became of a bright blood red, which, as the liquid fell, deepened into crimson.
In a few days there was raised around this crater a cone of about three hundred feet in height, composed of the looser materials thrown out along with the lava. This cone continued to glow with intense heat, throwing out occasional flashes. The base of this cone eventually acquired a circ.u.mference of about a mile. But the fountain itself formed a river of glowing lava, which rushed and bounded with the speed of a torrent down the sides of the mountain, filling up ravines and dashing over precipices, until it reached the forests at the foot of the volcano. These burst into flames at the approach of the fiery torrent, sending up volumes of smoke and steam high into the air. The light from the burning forests and the lava together was so intense as to turn night into day, and was seen by mariners at a distance of nearly two hundred miles.
During the day the air throughout a vast extent was filled with a murky haze, through which the sun showed only a pallid glimmer.
Smoke, steam, ashes, and cinders were tossed into the air and whirled about by fierce winds--sometimes spreading out like a fan, but every moment changing both their form and colour. The stream of lava from the fountain flowed to a distance of about thirty-five miles. The scene was altogether terrific--the fierce red glare of the lava--the flames from the burning trees--the great volumes of smoke and steam--the loud underground explosions and thunderings,--all combined to overpower the senses, and fill the mind with indescribable awe.
A remarkable volcanic chain runs along the northern and western margins of the Pacific Ocean. It embraces the Aleutian Islands, the peninsula of Kamtschatka, the Kurile, the j.a.panese, and the Philippine Islands. The most interesting are the volcanoes of Kamtschatka, in which there is an oft-renewed struggle between opposing forces--the snow and glaciers predominating for a while, to be in their turn overpowered by torrents of liquid fire.
CHAPTER IX.
Atolls, or Coral Islands--Their strange Appearance--Their Connexion with Volcanoes--Their Mode of Formation--Antarctic Volcanoes--Diatomaceous Deposits
To the southward of the Sandwich Islands, on the other side of the equator, there is a large group of islands in the Pacific, which have a very peculiar appearance. They are called Atolls or Coral Islands. Although not exactly of volcanic origin, yet the manner in which they are formed has some connexion with submarine volcanic action.
An atoll consists essentially of a ring of coral rocks but little elevated above the level of the sea, and having in its centre a lagoon or salt-water lake, which generally communicates by a deep narrow channel with the sea. The ring of rocks is flat on the surface, which is composed of friable soil, and sustains a luxuriant vegetation, chiefly of cocoa-nut palms. It is seldom more than half a mile in breadth between the sea and lagoon, sometimes only three or four hundred yards. The outer margin of the ring is the highest, and it slopes gradually down towards the lagoon; but on the outside of the ledge of rocks is a beach of dazzling whiteness, composed of powdered and broken coral and sh.e.l.ls. The appearance they present is thus not less beautiful than singular.
Some of these islands are of large size, from thirty to fifty miles long, and from twenty to thirty broad, but they are in general considerably smaller. Their most frequent form is either round or oval. The rocks composing them are all formed by different species of coral. The animal which constructs them is of the polyp tribe, and so small that it can be seen only under the higher powers of the microscope. It multiplies by means of buds like those of a tree, the individuals all combining to form a composite stony ma.s.s, which is called a polypidom. A number of such polypidoms growing close together form a coral reef. See woodcuts.
[Ill.u.s.tration: Coral]
[Ill.u.s.tration: Coral Polyp]
It was at one time supposed that these coral reefs were erected on the edges of the craters of submarine volcanoes, an opinion to which their annular form, and the lagoon in the centre, lent some countenance; but the vast size of some of them, united to several other particulars connected with them, threw great doubts over this supposition.
More recently it has been shown by Mr. Darwin that, while volcanic agency does perform a part in their formation, it is different from what had been formerly imagined. His supposition is, that these coral reefs were built round the coasts of islands which had once stood very much higher above water than they do now. He conceives that the bottom of the sea under them being very volcanic, and containing large collections of molten lava beneath a thin solid crust, the islands have gradually sunk down into the lava, until their central parts have become covered with a considerable depth of water. The central parts thus submerged, he imagines, form the lagoons in the middle of the islands, while the ring of coral reefs has gradually grown upwards, as the ground on which it rested sank downwards.
[Ill.u.s.tration: Coral Reef.]
The corals thus rise to near the surface, but immediately on their being uncovered by the water they die, and the reef ceases to grow.
Then the waves by their action break the upper part of it into pieces, which thus become heaped up by degrees on the remainder, until the ma.s.s attain so great a height that the sea can no longer wash over it. Thus the curious ring of land is gradually formed, and affords a nutritive soil, in which cocoa-nuts, on being cast ash.o.r.e, germinate and grow to be large trees. Other seeds, wafted by the waves or carried by birds, also begin to grow, until the whole surface becomes covered with vegetation. Then comes man and builds his habitation upon those fertile spots, and finds in them an agreeable and convenient abode, well suited to those who are accustomed to live by fishing and other simple means.
You will thus perceive that the connexion between the atoll and the volcano consists in this--that while the coral builds up the reef, the volcano beneath ingulfs the island and causes it to sink down.
In some instances, however, the volcano, after a while, reverses its action, and raises up the island with the reef upon it. In such cases, the coral reefs are seen standing out of the water, forming perpendicular cliffs several hundred feet in height. Then also the interior of the island becomes once more dry land, and that, too, of great fertility.
[Ill.u.s.tration: Mount Erebus.]
Almost due south of that region, in the Pacific, where the coral islands abound, but at a great distance from them, and considerably within the limits of the Antarctic zone, lies South Victoria. Here, in lat. 76 degrees S., Captain Ross discovered, in 1841, two volcanoes, which he called Erebus and Terror, after the names of his two ships. Of the former, which is the higher of the two, a view is given in the annexed woodcut. It is covered with perpetual snow from the bottom even to the tip of the summit. Nevertheless, it is continually sending forth vast columns of vapour, which glow with the reflection of the white hot lava beneath. These vapours ascend to a great height, more than two thousand feet above the top of the cone, which is itself twelve thousand feet above the level of the sea.
There is found in these frozen regions a remarkable botanical curiosity, having a certain connexion with volcanoes. The waters of the ocean, all along the borders of the icy barrier, produce in amazing abundance the family of water-plants named Diatomaceae. The Diatoms are so called from their faculty of multiplying themselves indefinitely by splitting into two; and so rapidly is this process performed, that in a month a single diatom may produce a thousand millions. The quant.i.ty found in the Antarctic regions is so immense that, between the parallels of 60 degrees and 80 degrees of south lat.i.tude, they stain the whole surface of the sea of a pale olive-brown tint. These plants, which are so minute as to be individually invisible, save under the higher powers of the microscope, have the curious property of encrusting themselves with a sheath, or sh.e.l.l, of pure silica. These sh.e.l.ls remain after the death of the plant, and are as indestructible as flint. They are marvellous objects, both as respects the elegance of their forms and the beauty of their markings. So great is the acc.u.mulation of these sh.e.l.ls at the bottom of the sea, that they have formed an immense bank 400 miles in length by 120 in breadth, between the 76th and 78th degrees of south lat.i.tude. One portion of this bank rests on the coast at the foot of Mount Erebus.
Now, it is remarkable that these microscopic sh.e.l.ls of Diatoms are not unfrequently found in the ejections of volcanoes; while it is generally supposed that, in the case of those situated near the sea, eruptions are caused by the formation of explosive steam consequent on the access of sea-water to the reservoirs of molten lava lying underground. The proximity of this Diatomaceous bed to Mount Erebus would easily explain how these minute sh.e.l.ls might be found abundant in the fine dust ejected from that volcano.
CHAPTER X.
Volcanoes of Java--Papandayang--Mountain Ingulfed--Great Destruction of Life and Property--Galoen-gong--Destructive Eruption--Mount Merapia--Great Eruption, with Hurricane--Another, very destructive--Mud Volcano Crater of Tankuban-Prahu--Island of Sumbawa--Volcano of Tomboro--Terrific Eruption--Timor--A Volcano quenches itself--Cleaving of Mount Machian--Sangir--Destructive Eruption--Bourbon.
One of the most marvellous volcanic regions in the world is that composed of the islands of the Malayan Archipelago in the Indian Ocean. They form a chain stretching from east to west, but curving up towards the north at the western extremity. The most easterly of the chain is Timor, the most westerly Sumatra.
The most interesting of the group is Java, which is almost entirely of volcanic origin, and contains no less than thirty-eight mountains of that conical form which indicates their having at one time or other been active volcanoes. Only a few of them, however, have been in activity in more recent times. The most remarkable eruption was that of the mountain named Papandayang, which occurred in 1772. During this convulsion the greater part of the mountain, which was formerly one of the largest in the island, was completely swallowed up in some great underground gulf.
On the night between the 11th and 12th of August of that year, the mountain appeared to be wholly enveloped in a remarkable luminous cloud. The inhabitants fled in consternation; but before they could all escape, the mountain began to totter, and the greater part of it tumbled down and disappeared. The crash with which it fell was dreadful, the noise resembling the discharge of volleys of artillery. Besides that part of the mountain which thus fell in, a large extent of ground in its neighbourhood was ingulfed. The s.p.a.ce measured fifteen miles in length and six in breadth. The ground for many miles round this s.p.a.ce was covered with immense quant.i.ties of ashes, stones, cinders, and other substances thrown out by the volcano. These were, on many parts of the surface, acc.u.mulated to the height of three feet; and even at the end of six weeks, the layers thus deposited retained so much heat as to render the mountain inaccessible. By this dreadful occurrence forty villages were destroyed, some ingulfed with the ground on which they stood, others buried under the loose materials which had been ejected. Not far short of three thousand of the inhabitants perished.
Another of the volcanoes of Java, called Galoen-gong, burst into eruption in 1822, commencing with a terrible explosion of stones, ashes, &c., followed by a stream of hot mud, which overspread a large tract of ground. This eruption proved still more fatal to human life, about four thousand persons having been destroyed.
So lately as September 1849, Mount Merapia, another volcano in this island, which had been supposed to be quite extinct, burst forth into an eruption, which lasted three days. It was accompanied by a violent hurricane. The bed of a river was filled up by the matter thrown out from the crater, and the destruction of property in crops, &c., was immense. Fortunately the inhabitants succeeded in making their escape, so that no lives were lost. A second eruption of this mountain however, in January 1864, was more disastrous, three hundred and fifty people having perished.
Java likewise contains a remarkable mud volcano. When viewed from a distance, there are seen to rise from it large volumes of vapour, like the spray from the billows dashing against a rocky sh.o.r.e, and there is heard a loud noise like distant thunder. On a nearer approach, the source of these phenomena is seen to be a hemispherical mound of black earth mixed with water, about sixteen feet in diameter, and which at intervals of a few seconds is pushed upwards by a force acting from beneath to a height of between twenty and thirty feet. It then suddenly explodes with a loud noise, scattering in every direction a quant.i.ty of black mud, which has a strong pungent smell resembling that of coal-tar, and is considerably warmer than the air. With the mud thus thrown out there has been formed around the mound a large perfectly level and nearly circular plain, about half a mile in circ.u.mference. The water mixed with the mud is salt, and the salt is separated from it by evaporation for economical purposes. During the rainy season the action of this mud volcano becomes more violent, the explosions are louder, and the mud is thrown to a greater height.
The crater of Tangkuban-Prahu, another of the volcanoes of Java, presents a remarkable appearance. On approaching its edge, nothing is seen but an abyss, from which dense clouds of vapour continually arise, with hideous sounds, like the steam rushing from the open valves of hundreds of steam-engines. This great abyss consists really of two craters, separated the one from the other by a narrow ridge of rock, to which it is possible to descend and view them both. Each of them is elliptical in form, and surrounded by a crater-wall. That of the western, which the natives call the poison-crater, is a rapid slope nearly a thousand feet in depth, and is densely covered with brushwood almost to the bottom. The flat floor of this deep basin is continually sending out vapours, and in its centre is a pool of boiling water of a sulphur yellow colour. The floor itself is nothing but a crust of sulphur full of rents and holes, whence vapours constantly arise. This crust covers a surface of boiling hot bitter water, and by breaking it beautiful crystals of sulphur may be obtained.
The eastern is called by the natives the king"s-crater; its walls are only between five and six hundred feet in depth, and are perfectly bare from top to bottom. The surfaces of the rocks composing them are grayish white, an effect produced upon them by the action of the vapours, to which they are continually exposed.
The bottom of this crater consists of mud mixed with sulphur; but round the edges are some stones and hard ma.s.ses. These are the remnants of an eruption which took place from this crater in 1846, when there was thrown up a great ma.s.s of sulphurous boiling mud, accompanied by quant.i.ties of sand and stones. This mountain, therefore, seems to be also more of the nature of a mud volcano, than of one which throws out burning lava.
Nearly in a right line to the eastward of Java lies the Island of Sumbawa, in which stands the volcano of Tomboro, the most violent in its eruptions of any in the world. One of the most remarkable occurred in the year 1815, beginning on the 5th of April and continuing till the middle of July. Its effects were felt over an immense tract of country, embracing the Molucca Islands, Java, and portions of Celebes, Sumatra, and Borneo. The concussions produced by its explosions were sensible at a distance of a thousand miles all round; and their sound is said to have been heard even at so great a distance as seventeen hundred miles. In Java the day was darkened by clouds of ashes, thrown from the mountain to that great distance (three hundred miles), and the houses, streets, and fields, were covered to the depth of several inches with the ashes that fell from the air. So great was the quant.i.ty of ashes ejected, that the roofs of houses forty miles distant from the volcano were broken in by their weight. The effects of the eruption extended even to the western coasts of Sumatra, where ma.s.ses of pumice were seen floating on the surface of the sea, several feet in thickness and many miles in extent.
From the crater itself there were seen to ascend three fiery columns, which, after soaring to a great height, appeared to unite in a confused manner at their tops. Ere long, the whole of the side of the mountain next the village of Sang"ir seemed like one vast body of liquid fire. The glare was terrific, until towards evening, when it became partly obscured by the vast quant.i.ties of dust, ashes, stones, and cinders thrown up from the crater. Between nine and ten o"clock at night the ashes and stones began to fall upon the village of Sang"ir, and all round the neighbourhood of the mountain. Then arose a dreadful whirlwind, which blew down nearly every house in the village, tossing the roofs and lighter parts high into the air. In the neighbouring sea-port the effects were even more violent, the largest trees having been torn up by the roots and whirled aloft. Before such a furious tempest no living thing could stand. Men, horses, and cattle were whirled into the air like so much chaff, and then dashed violently down on the ground. The sea rose nearly twelve feet above the highest tide-mark, sweeping away houses, trees, everything within its reach.
This whirlwind lasted about an hour, and then commenced the awful internal thunderings of the mountain. These continued with scarcely any intermission until the 11th of July, when they became more moderate, the intervals between them gradually increasing till the 15th of July, when they ceased. Almost all the villages for a long distance round the mountain were destroyed; and it is computed that nearly twelve thousand persons perished. By far the greatest part of this destruction was wrought by the violence of the whirlwind which accompanied the eruption.
Considerably to the eastward of Sumbawa lies the Island of Timor, in which there was for a long time a volcanic peak, whose perpetual fires served as a lighthouse to mariners navigating those seas. But in the year 1637 there took place a great eruption of the mountain, which ended in its being gobbled up whole and entire, leaving nothing behind it but a lake, in which its fires were quenched, and which now occupies its place.