« EelmineJätka »
LAKE OF MASAYA.
erecting a steam pump to raise the water for the supply of the town. At the bottom of this section are seen great cliffs of massive trachyte (No 1. in section). Above this is an ash bed, then a bed of breccia containing fragments of trachyte, then another bed of cinders, which looks like a rough sandstone, but is pisolitic, and contains pebbles of the size of a bean. This bed is surmounted by one that possesses great interest (No. 5 in section). It is composed of fine tufa, in which is imbedded a great number of large angular fragments of trachyte, some of which are more than three feet in diameter. It is the last bed but one, the surface being composed of lightly coherent strata of tufaceous ash, worn into an undulating surface by the action of the elements.
I believe there is but one explanation possible of the origin of these strata ; namely, that the great bed of trachyte at the base is an ancient lava bed; and that this, perhaps, long after it was consolidated, was covered by beds of ashes and scoriæ thrown out by a not far distant volcano, and that at last a great convulsion broke through the trachyte bed and hurled the fragments over the country along with dense volumes of dust and ashes. The angular blocks of trachyte imbedded in the stratum No. 5 in section are exactly the same in composition as the great bed below, and in them I think we see the fragments of the rocks that once filled the perpendicularsided hollow now occupied by the lake. Looking at the vast force required to hollow out the basin of the lake, by blasting out the whole contents into the air, distributing them over the country, so that they have not been piled up in a volcanic cone round the vent, but lie in comparatively level beds, I cannot expect that this explanation will be readily received ; and I should not myself have advanced it if I could in any other way account for the phenomena. Fortunately, within historical times, there have been volcanic outbursts, not of such magnitude, certainly, as was required to excavate the basin of the lake of Masaya, but still of sufficient extent to show that such an origin is not beyond the limits of possibility.
Thus in the same line of volcanic energy, not far from the boundary line of the states of Nicaragua and San Salvador, there was an eruption of the volcano of Cosaguina, on the 20th of January, 1835, when dense volumes of dust and ashes, and fragments of rocks, were hurled up in the air and deposited over the country around. The vast quantity of material thrown out by this explosion may be gathered from the fact that one hundred and twenty miles away, near the volcano of San Miguel, the dust was so thick that it was quite dark from four o'clock in the evening until nearly noon of the next day; and even at that distance there was deposited a layer of fine ashes four inches deep. The noise of the explosion was heard at the city of Guatemala, four hundred miles to the westward, and at Jamaica, eight hundred miles to the north-east.
In St. Vincent, in the West Indies, there was a great eruption on April 27th, 1812, which continued for three days, and was heard six hundred and thirty miles away on the llanos of Caraccas. This great eruption has been so graphically narrated by Canon Kingsley that I shall once more quote from his eloquent pages. “That single explosion relieved an interior pressure upon the crust of the earth which had agitated sea and land from the
Azores to the West Indian islands, the coasts of Venezuela, the Cordillera of New Granada, and the valleys of the Mississippi and Ohio. For nearly two years the earthquakes had continued, when they culminated in one great tragedy, which should be read at length in the pages of Humboldt. On March 26th, 1812, when the people of Caraccas were assembled in the churches, beneath a still and blazing sky, one minute of earthquake sufficed to bury, amid the ruins of churches and houses, nearly ten thousand souls. The same earthquake wrought terrible destruction along the whole line of the northern Cordilleras, and was felt even at Santa Fé de Bogota and Honda, one hundred and eighty leagues from Caraccas. But the end was not yet. While the wretched survivors of Caraccas were dying of fever and starvation, and wandering inland to escape from ever-renewed earthquake shocks, among villages and farms which, ruined like their own city, could give them no shelter, the almost forgotten volcano of St. Vincent was muttering in suppressed wrath. It had thrown out no lava since 1718, if, at least, the eruption spoken of by Moreau de Jonnés took place in the Souffrière. According to him, with a terrific earthquake, 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. Now there is no eastern end to St. Vincent nor any mountain on the east
and the Souffrière is at the northern end. It is impossible, meanwhile, that the wreck of such a mountain should not have left traces visible and notorious to this day. May not the truth be, that the Souffrière had once
a lofty cone, which was blasted away in 1718, leaving the present crater-ring of cliffs and peaks; and that thus may be explained the discrepancies in the accounts of its height, which Mr. Scrope gives as 4,940 feet, and Humboldt and Dr. Davy at 3,000, a measurement which seems to me to be more probably correct? The mountain is said to have been slightly active in 1785. In 1812, its old crater had been for some years (and is now) a deep blue lake, with walls of rock around, 800 feet in height, reminding one traveller (Dr. Davy) of the lake of Albano. But for twelve months it had given warning, by frequent earthquake shocks, that it had its part to play in the great subterranean battle between rock and steam ; and on the 27th April, 1812, the battle began.
“A negro boy-he is said to be still alive in St. Vincent—
was herding cattle on the mountain-side. A stone fell ncar him, and then another. He fancied that other boys were pelting him from the cliffs above, and began throwing stones in return. But the stones fell thicker, and among them one and then another too large to have been thrown by human hand. And the poor fellow woke up to the fact that not a boy but the mountain was throwing stones at him; and that the column of black cloud which was rising from the crater above was not harmless vapours, but dust, and ash, and stone. He turned and ran for his life, leaving the cattle to their fate, while the steam mitrailleuse of the Titans-to which all man's engines of destruction are but pop-guns -roared on for three days and nights, covering the greater part of the island in ashes, burying crops, breaking branches off the trees, and spreading ruin from which Ch. XIX.] GREAT ERUPTION OF ST. VINCENT.
several estates never recovered; and so the 30th of April dawned in darkness which might be felt.
“Meanwhile, on the same day, to change the scene of the campaign two hundred and ten leagues, ' a distance, as Humboldt says, ' equal to that between Vesuvius and Paris,' the inhabitants, not only of Caraccas, but of Calabozo, situate in the midst of the Llanos, over a space of four thousand square leagues, were terrified by a subterranean noise, which resembled frequent discharges of the loudest cannon. It was accompanied by no shock, and, what is very remarkable, was as loud on the coast as at eighty leagues inland; and at Caraccas, as well as at Calabozo, preparations were made to put the place in defence against an enemy who seemed to be advancing with heavy artillery.' They might as well have copied the St. Vincent herd boy, and thrown their stones, too, at the Titans; for the noise was, there can be no doubt, nothing else than the final explosion in St. Vincent far away. The same explosion was heard in Venezuela, the same at Martinique and Guadaloupe ; but there, too, there were no earthquake shocks. The volcanoes of the two French islands lay quiet, and left their English brother to do the work. On the same day, a stream of lava rushed down from the mountain, reached the sea in four hours, and then all was .over. The earthquakes which had shaken for two years a sheet of the earth's surface larger than half Europe were stilled by the eruption of this single vent.
“ The strangest fact about this eruption was, that the mountain did not make use of its oid crater. The ori
. ginal vent must have become so jammed and consolidated, in the few years between 1785 and 1812, that it could