Popular Science Monthly/Volume 1/June 1872/Vesuvius
GEOGRAPHERS say there are some two hundred volcanoes on the surface of the earth; of these one is situated on the continent of Europe—Vesuvius. This mountain has had a remarkable history, and is now an object of renewed interest, as it has been again in profound convulsion.
Vesuvius stands about 10 miles southeast of Naples, in Southern Italy. Seen from the city it is a mountain with two summits. That on the left is the peak of Somma, 3,747 feet above the sea; the peak on the right being the volcano itself, about 200 feet higher. Between the two summits is a valley at the entrance to which, on a plateau, is situated the Hermitage and the Observatory. The mountain stands on the plain of Campania, and has a base of some 30 miles in circumference.
Vesuvius was an active volcano in very ancient times, and then was in a state of repose for a long period. This is inferred from the fact that writers before the Christian era never alluded to it as in eruption, but do refer to the igneous character of its rocks, and to its "many signs of having been burning in ancient times." It awoke to great activity A. D. 79, and from that time to the present has been the scene of about sixty grand eruptions.
The sides of the mountain, as described by Strabo, were clothed with gardens and vineyards filled with luxuriant vegetation; beautiful farms and rich woods extended to its top, which was flat, barren, and slaggy. Its dangerous character was hot suspected: villas were scattered over the sloping landscape; the cities of Herculaneum, Pompeii, and Stabias, were planted at its base, and were fashionable resorts for wealthy Romans.
A premonition of what was coming occurred in the year A. D. 63, in the form of a violent earthquake, which overthrew many houses; but its significance was of course not understood, and the houses were rebuilt.
The first great recorded eruption of Mt. Vesuvius occurred August 24th, in the year 79, and has been described by the younger Pliny in a letter to Tacitus. His uncle, the elder Pliny, was at the time in command of the Roman fleet at Misenum, and his nephew was with him. From this point they first descried the eruption. Rising from the top of the mountain they saw what appeared like a column of dense, black smoke, but which was in reality a mass of dust, ashes, stones, and vapors, the form of which was likened by Pliny to a tall pine-tree throwing out great branches at its top.
Struck with surprise at the new phenomenon, the elder Pliny, a man of philosophical mind, hastened to the shore, that he might examine it more closely. He disembarked at Stabiæ, and went to the house of his friend Pomponianus. Here he remained till evening, gazing at the spectacle, and trying to quiet the fears of those around him. The streaks of fire on the mountain he attributed to the burning of the woods and villages, and when he became weary of the spectacle retired to bed and fell asleep. Meanwhile the shower of stones increased fast in Stabiæ, and began to fill the streets and the courts of the villa. Pliny's servants became alarmed and aroused their master, who joined his friend Pomponianus and his assembled family. What follows is best described in the graphic words of the younger Pliny:
The materials ejected from the mountain consisted of scoriae and ashes, and their quantity far exceeded its own bulk. The shower of ashes, dust, pumice, and stones, continued to fall for eight successive days, accompanied by torrents of rain, and the cities of Stabiæ, Herculaneum, and Pompeii, were entirely buried. Pompeii was situated several miles farther from the crater than Herculaneum, and was buried only in ashes and loose stones; while Herculaneum was entombed deeper, and in a much more consistent substance, which was evidently plastic, and appears to be composed of volcanic ashes cemented by mud.
The volcano then rested 124 years; the second eruption taking place A. D. 203; and the third, which was much more violent, occurred 269 years later, in the year 472. On this occasion the ashes fell over nearly the whole of Europe; they were transported to Constantinople, and even to Egypt and Syria. In 1036 there occurred a violent eruption, during which lava was for the first time ejected.
The eruption of Vesuvius in 1631 was of extreme violence, and was accompanied by great currents of lava, which flowed over the villages at its base on the side of the Bay of Naples. There were at the same time thrown out immense torrents of hot water, which wrought great desolation.
The eruption of 1779 is described by Sir William Hamilton as among the grandest and most terrible of these phenomena. White sulphurous smoke like heaps of cotton rose up in piles four times as high as the mountain, and spread about it to a proportional extent. Into these clouds, stones, scoriæ, and ashes, were projected to the height of at least 2,000 feet. On subsequent days columns of fire shot forth to full three times the height of the mountain. Masses of rock of great size were projected out of the crater, one of which measured 108 feet in circumference and 17 feet in height. Ponton says the jets of lava were thrown up to a prodigious height. A portion of the ashes and stones was drifted away to some distance; but the greater proportion of these, and nearly all the lava, still red-hot and liquid, fell upon the cone, on part of Monte Somma, and into the valley between them. The whole mass which thus fell, still vividly glowing, formed a continuous fiery expanse about two and a half miles in breadth, which, with the lofty column of fire issuing from the top, presented a magnificent but very terrific spectacle. The heat, radiating from this vast glowing surface, is said to have been perceptible at a distance of six miles all around.
In June, 1794, occurred a terrible eruption, which destroyed the town of Torre del Greco. A single stream of lava was estimated by Breislak as containing more than 46,000,000 cubic feet. A vent opened near the bottom of the mountain, 2,375 feet in length and 237 feet in breadth, which became filled with lava, and on the hardening of this presented a dike in every respect similar to the ancient basaltic dikes.
The eruption of 1822 broke up the whole top of the mountain, and formed an elliptical chasm about three miles in circumference, and supposed to be 2,000 feet deep. The principal cone tumbled in, with a terrible crash, on October 22d, and the following evening there began an eruption which lasted 12 days. The internal detonations of the mountain were described as terrific, while the ashes and dust were so great as to produce at noon in the neighboring villages a darkness deeper than midnight.
The eruption of 1855 presented a most imposing spectacle. We have referred to the valley or ravine between the two mountains, the first descent to which on the side of Vesuvius is a sheer precipice. A great stream of lava, about 200 feet in width, issuing from the crater, took the direction of this ravine, and on arriving at the edge of the precipice fell heavily over it, forming a magnificent fiery cascade about 1,000 feet in height. On reaching the valley beneath, it wended its way through the woods, consuming the trees in its course, and destroying several villages through which it flowed. A grander sight than this cascade of fire must have presented, it would be difficult for the human mind to imagine.
Monnier says that, "since 1850, springs of lava have opened near the base of the cone in the ravine which separates the two mountains; they are seen springing from the lava much as the water of rivers flows from a glacier. In 1855 and 1858 it rolled slowly through the ravine like the Thames in flames. To be really startling, the lava must be seen, not from above, but coming directly toward the spectator, as I saw it in 1855. Then it was no longer a river, but a burning, moving rampart. This wall was at least a mile wide and 20 feet high. It came slowly, irresistibly, covering the ground, burning the trees and houses; you could walk backward before it as a captain does before his company.
"The lava, as it issues from the crater of Vesuvius, is perfectly liquid, and glows with an intense white brilliancy, like that of molten silver; but, as it descends, it begins to cool at the top, and a quantity of broken slag is formed on the surface of the stream, becoming ere long a continuous coating. The speed of the current, very rapid at first, gradually slackens, until, on the level at some distance from the mountain, its progress is scarcely perceptible."
Vesuvius is much more active in modern times than in ancient; several grand eruptions having taken place within the present generation. The recent convulsion has been marked by the usual impressive features, but comparisons with former eruptions must be accepted with hesitation, for, where the imagination is so powerfully affected, and the data are so uncertain, the judgment may be much at fault. The following description of the present display was telegraphed from Naples, April 29th:
"The view of Mount Vesuvius from this city is now the grandest that has been witnessed since the year 1631. Many persons have taken advantage of the panic among the people of the towns which were threatened with destruction, to take whatever goods they could find, and the government has been compelled to order troops to those places to prevent the stealing of abandoned property. In this city the Bourse has closed, and business is almost entirely suspended. The people use umbrellas to protect themselves from the falling ashes.
"A sound as of thunder accompanies the discharges. The wind was blowing in this direction this morning, carrying dense clouds of smoke and ashes over the city. The ashes were falling in the streets like snow, and reached a depth of two or three inches. The rumbling inside the volcano continued, but no fresh craters have opened, and the lava has ceased flowing.
"Showers of sand have succeeded the rain of ashes which was falling this morning. The eruption is now accompanied by fearful electric phenomena. Lightning darts incessantly from the summit of the volcano and the quakings of the mountain are more violent and frequent. The thunder is continuous. Burning cinders, stones, and scoriæ, are falling fast and thick in the town of Massa di Somma, which is entirely deserted."