Etna, or ÆTNA (called by the modern Sicilians MONTE GIBELLO—the last part of the name being the Arabic Jebel Italianised), an isolated volcanic mountain close to the east coast of Sicily, with a base 90 miles in circumference, and a height of 10,850 feet. The mountain mass rises with gentle and regular slopes up to a single cone, containing the crater, a chasm about 1000 feet in depth and from 2 to 3 miles in circumference. The regularity of the slope is, however, broken by the Val del Bove, an immense gully excavating the eastern flank of the mountain, 4 or 5 miles in diameter, and surrounded by nearly vertical precipices from 2000 to 4000 feet high; it has a singularly dreary and blasted appearance. A striking feature is the very great number of secondary cones dotted all over the flanks of the mountain. Of these the principal are the Monti Rossi, 450 feet high, twin peaks which were cast up during the eruption of 1669. The slopes of the mountain are divided into three sharply defined zones, the cultivated, the woody, and the desert region. This last, extending from about 6300 feet upwards, is a dreary waste of black lava, scoriæ, ashes, and sand, covered during the greater part of the year with a sheet of snow. The wooded region, which stretches down to the line of 2000 feet, though with considerable variation of breadth, is planted with forests of chestnuts, beeches, birches, pines, maples, and oaks. Below this lies the cultivated zone, a thickly peopled region of great fertility, where the vine, date-palm, bananas, sugar-cane, oranges, lemons, olives, figs, almonds, &c. are grown. The ascent is usually made from Catania, a town on the coast to the south. The origin of the mountain goes back to the Pliocene age, when its foundation was probably begun in a submarine bay penetrating into the west coast of Sicily. The geological structure of the Val del Bove lends support to the view that there once existed a second great crater, the centre of permanent eruption.
The most remarkable of the recorded eruptions of Etna are the following: 1169, when Catania and 15,000 of its inhabitants were destroyed; 1329, when a new crater opened near the Val del Bove; 1444, when the cone fell into the crater; 1537, on which occasion two villages and many human beings perished; from 1603 to 1620 Etna was almost continually in activity; in 1666 three new craters were formed. The most violent outburst of all was, however, that of 1669, when a chasm 12 miles long opened in the flank of the mountain, and from it issued a line of flames, whilst a new crater was made. During an outburst in 1755 a large flood of water was poured down from the Val del Bove. In 1852–53 there was a violent eruption which lasted nine months; a torrent of lava, 6 miles long by 2 broad, and some 12 feet in depth, was ejected. About 100 eruptions have been pretty accurately described, 16 having occurred in the 19th century. In 1880 an observatory was built on the south side of the mountain, at a height of 9075 feet above the sea, being the highest inhabited house in Europe (nearly 1000 feet higher than the hospice of the Great St Bernard). See Ferrara, Descrizione dell' Etna (1818); Rodwell, Etna and its Eruptions (1878); and Sartorius von Waltershausen, Der Aetna, edited by Von Lasaulx (2 vols. Leip. 1880).