In the year 1638 a colossal cone called the Peak, in the Isle of Timor, one of the Moluccas, was entirely destroyed by a paroxysmal explosion. The whole mountain, which was before this continually active, and so high that its light was visible, it is said, three hundred miles off, was blown up and replaced by a concavity now containing a lake.
Again, according to M. Moreau de Jonnes, in 1718, on March 6–7, at St. Vincent’s, one of the Leeward Isles, the shock of a terrific earthquake was felt, and clouds of ashes were driven into the air, with violent detonations, from a mountain situated at the eastern end of the island. When the eruption had ceased, it was found that the whole mountain had disappeared like the baseless fabric of a dream.
The disastrous effects of the showers of sand, pumice, and lapilli ejected by a volcanic eruption are increased by the transporting power of water. The aqueous vapours which are evolved so copiously from volcanic craters during eruptions, and often for a long time subsequently to the discharge of scoriæ and lava, are condensed as they ascend in the cold atmosphere surrounding the high volcanic peak; and the clouds thus formed, being in a state of high electrical tension, give rise to terrific thunderstorms. The lightning flashes in all directions from the black canopy overhanging the mountain, the perpetually rolling thunder adds its loud voice to the dreadful roar of the labouring volcano, while torrents of rain, sweeping along the light dust and scoriæ which they carry down with them from the air, or meet with on their way, produce currents of mud, often more dreaded than streams of lava, from the far greater velocity with which they move.
It not seldom happens that the eruptions of volcanoes rising above the limits of perpetual snow are preceded or accompanied by the rapid dissolution of the ice which clothes their summits or their sides, owing to the high temperature imparted to the whole mass of the mountain by the vast conflict raging within. Thus in January 1803 one single night sufficed to dissolve or sweep away the enormous bed of snow which in times of rest covers the steep cone of Cotopaxi (18,858 feet high), so that on the following morning the dark mountain, divested of its brilliant robe, gave warning to the affrighted neighbourhood of the terrific scenes that were about to follow. The volcanoes of Iceland, which mostly rise in the midst of vast fields of perpetual ice, frequently exhibit this phenomenon. On October 17, 1758, the eruptive labouring of Kötlingia gave birth to three enormous torrents, which carried along with them such masses of glacier fragments, sand, and stones as to cover a space fifty miles long and twenty-five miles broad. Blocks of ice as large as houses, and partly bearing immense pieces of stone on their backs, were hurried along by the floods; and soon after the eruption took place with a terrific noise.
A very singular phenomenon sometimes occurs in the gigantic volcanoes of the Andes. By the infiltration of water into the crevices of the trachytic rock of which they are composed, the caverns situated at their declivities or at their foot are gradually changed into subterranean lakes or ponds, which frequently communicate by narrow apertures with the Alpine brooks of the highlands of Quito. The fish from these brooks live and multiply in these subterranean reservoirs thus formed, and when the earthquakes which precede every eruption of the Andes chain shake the whole mass of the volcano, the caverns suddenly open and discharge enormous quantities of water, mud, and small fish.
When in the night between the 19th and 20th of June 1698, the summit of Carguairazo (18,000 feet high) was blown up, so that of the whole crater-rim but two enormous peaks remained, the inundated fields were covered, over a surface of nearly fifty square miles, with fluid tuff and clay-mud enveloping thousands of dead fish. Seven years before, the malignant fever which prevailed in the mountain-town of Ibarra to the north of Quito was attributed to the effluvia arising from the putrid fish ejected by the volcano of Imbaburu.
Amidst all these terrible phenomena—the dreadful noise, the quaking of the earth, the ejection of stones and ashes—which, often continuing for weeks or months, shake the deepest foundations of the volcano, fiery streams of liquid lava gush forth sooner or later as from a vase that is boiling over. Their appearance generally indicates the crisis of the subterranean revolution, for the rage of the elements, which until then had been constantly increasing, diminishes as soon as the torrent has found an outlet. The lava rarely issues from the summit crater of the mountain; much more frequently it flows from a lateral rent in the volcano’s side, which, weakened and dislocated in its texture by repeated shocks, at length gives way to the immense pressure of the lava column boiling within. From the vast size of these eruptive rents, we may form some idea of the gigantic power of the forces which give them birth.
Thus during the great eruption of Etna in 1669, the south-east flank of the mountain was split open by an enormous rent twelve miles long, at the bottom of which incandescent lava was seen. The extreme length of the fissure which gave lateral issue to the lava of Kilauea in 1840 was twenty-five miles, as could distinctly be traced through the disturbance of the surface rocks above; and in the terrific eruption of Skaptar Jökul, which devastated the west coast of Iceland in 1783, lava gushed forth from several vents along a fissure of not less than 100 miles in length. In some cases the whole mass of the volcano has been cleft in two. Vesuvius was thus rent in October 1822 by an enormous fissure broken across its cone in a direction N.W.—S.E.
Here and there along the line of such a rent, cones of eruption are thrown up in succession at points where the gaseous matter obtains the freest access to the surface, and has power to force up lava and scoriæ. Few indeed, if any, of the greater volcanic mountains are unattended by such minor elevations, clustering about its sides like the satellites of a planet. Professor Dana found Mauna Loa covered with numerous parasitic cones, and Mr. Darwin counted several thousands on one of the Gallapagos Islands. On the flanks of Etna, according to Professor Sartorius von Waltershausen, more than 700 of them are to be seen, almost all possessing craters, and each marking the source of a current of lava. Though they appear but trifling irregularities when viewed from a distance as subordinate parts of so imposing and colossal a mountain, many of them would nevertheless be deemed hills of considerable height in almost any other region. The double hill near Nicolosi, called Monte Rossi, formed in 1669, is 450 feet high and two miles in circumference at its base; and Monte Minardo, near Bronte, on the east of the great volcano, is upwards of 700 feet in height.[[8]]
‘On looking down from the lower borders of the desert region of Etna,’ says Sir Charles Lyell, ‘these minor volcanoes, which are most abundant in the woody region, present us with one of the most delightful and characteristic scenes in Europe. They afford every variety of height and size, and are arranged in beautiful and picturesque groups. However uniform they may appear when seen from the sea, or the plains below, nothing can be more diversified than their shape when we look from above into their craters, one side of which, as we have seen, is generally broken down. There are indeed, few objects in nature more picturesque than a wooded volcanic crater. The cones situated in the higher parts of the forest zone are chiefly clothed with lofty pines, while those at a lower elevation are adorned with chestnuts, oaks, and beech-trees.’