Fig. 14. Mt. Etna
From Map of State and Government
The great lava streams which flowed down the side of the mountain during this eruption, destroyed fourteen towns and villages, and at length reached Catania. A great wall had been raised around this city to prevent the lava from entering it. The molten rock, however, accumulated, until it rose to the top of the wall, which was sixty feet high, and then pouring over it in a fiery cascade, overwhelmed part of the city. It is said that during the first part of its journey, the lava streams moved over thirteen miles in twenty days, or at the rate of 162 feet an hour. Beyond this, after the lava had thickened by cooling, it had a velocity of only twenty-two feet per hour.
[Fig. 14] represents a plan of Mt. Etna reduced from a map by the Italian Government. During the eruption of 1865, a rent was made in the mountain extending from Mount Frumento (B in the preceding map) for one and one-half miles, and six cones from 300 to 350 feet in height were formed along the fissure.
During the eruption of 1874, great fissures three miles in length were formed in the mountain.
There exists on the slopes of Mt. Etna vast subterranean grottoes formed by the sudden conversion into steam of great quantities of water that were overwhelmed by the molten mass. These immense volumes of steam produced enormous bubbles in the molten lava. When the lava hardened irregular grottoes were left. Lyell describes one of these as follows:
"Near Nicolosi, not far from Monte Rosso, one of these great openings may be seen, called the Fossa della Palomba, 625 feet in circumference at its mouth and seventy-eight deep. After reaching the bottom of this, we enter another dark cavity, and then others in succession, sometimes descending precipices by means of ladders. At length, the vaults terminate in a great gallery ninety feet long, and from fifteen to fifty broad, beyond which there is still a passage, never yet explored, so that the extent of these caverns remains unknown. The walls and roofs of these great vaults are composed of rough bristling scoriæ of the most fantastic forms."
Besides the eruptions mentioned there have been many others, such as those of 1811, 1819, and 1852. The last of these was greater than any eruption except that of 1669. It began in August, 1852, and continued until May, 1853, and was remarkable for the immense quantity of lava thrown out.
