“Commander Brine having ascended on February the twenty-eighth, 1866, to the top of the crater of Nea Kaimeni, about three hundred and fifty feet high, looked down upon the new vent then in full activity. The whole of the cone was swaying with an undulating motion to the right and left, and appeared sometimes to swell to nearly double its size and height, to throw out ridges like mountain spurs, till at last a broad chasm appeared across the top of the cone, accompanied by a tremendous roar of steam and the shooting up from the new crater, to the height of from fifty to a hundred feet, of tons of rock and ash mixed with smoke and steam. Some of these which fell on Mikra Kaimeni, at a distance of six hundred yards from the crater, measured thirty cubic feet. This effort over, the ridges slowly subsided, the cone lowered and closed in, and then, after a few minutes of comparative silence, the struggle would begin again with precisely similar sounds, action, and result. Threads of vapor escaping from the old crater of Nea Kaimeni proved that there was a subterranean connection between the new and the old vents. Aphroessa, of which the cone was at length raised to a height of more than sixty feet, was united in August with the main island. This was due in part at least to the upheaval of the bottom of the sea, which is now only seven fathoms deep in the channel dividing the New and Old Kaimenis, whereas in the Admiralty chart the soundings gave a hundred fathoms.”[97]
SUBTERRANEAN HEAT--ITS POWERS ILLUSTRATED BY EARTHQUAKES.
_Earthquakes and volcanos proceed from the same common cause--Recent earthquakes in New Zealand--Vast tracts of land permanently upraised--Earthquakes of Chili in the present century--Crust of the Earth elevated--Earthquake of Cutch in India, 1819--Remarkable instance of subsidence and upheaval--Earthquake of Calabria, 1783--Earthquake of Lisbon, 1755--Great destruction of life and property--Earthquake of Peru, August, 1868--General scene of ruin and devastation--Great sea wave--A ship with all her crew carried a quarter of a mile inland--Frequency of earthquakes._
The chief effect of volcanic eruptions on the Geological structure of our Globe consists in the accumulation of cinders and molten rock, either upon the Surface of the Earth, or in the crevices and caverns that abound within its solid Crust. Sometimes, indeed, the operations of an active Volcano are accompanied by a movement of upheaval or of subsidence. Thus for instance, we have seen that a portion of the Italian coast was elevated when Monte Nuovo was thrown up, that the town of Tomboro was submerged on the occasion of the eruption of Sumbawa, and that the bottom of the sea was notably upheaved by the last outbreak of the volcanic fires of Santorini. Nevertheless it appears to be generally the case that when the Crust of the Earth is once burst open, and a means of escape thus afforded to the fiery agent below,--in other words, when the active volcano is established,--the process of upheaval gives place to that of eruption. But when, as is often the case, no such safety-valve is offered to the surplus energies of the subterranean fires, then the giant power of heat, in its struggle to escape, shakes the foundation of the hills, and uplifts the superincumbent mass of solid rocks.