Vesuvius vəso͞oˈvēəs [key], Ital. Vesuvio, active volcano, S Italy, on the eastern shore of the Bay of Naples, SE of Naples. The only other active volcano on the European mainland is the Campi Flegrei (se Phlegraean Fields) caldera on the Gulf of Pozzuoli to the east. The height of Vesuvius's main cone changes with each eruption, varying within a few hundred feet of the 4,000-ft (1,219-m) level; in 1969 the height was 4,190 ft (1,277 m). The second summit, Monte Somma (3,770 ft/1,149 m) is a ridge that half encircles the cone and is separated from it by a valley (c.3 mi/5 km long). The sides of Vesuvius are deeply scarred by lava flow, but its lower slopes are extremely fertile, dotted with villages, and covered with vineyards which produce the famous Lachryma Christi wine. The base of the mountain (circumference c.45 mi/70 km) is encircled by a railroad, and a chairlift reaches almost to the rim of the crater (diameter c.2,300 ft/700 m). On the western slope, at 1,995 ft (608 m), there is a seismological observatory (built 1840–45). The outline of Vesuvius forms part of the backdrop of Naples; it is often surmounted by a faint plume of smoke.

The earliest recorded eruption (a.d. 79) was described by Pliny the Younger in two letters to Tacitus; the eruption buried Pompeii, Herculaneum, and Stabiae under cinders, ashes, and mud. Pliny the Elder was killed by the eruption, which he had come to investigate. Frequent eruptions have been recorded since Pompeii was destroyed, notably in 512, in 1631, six times in the 18th cent., eight times in the 19th cent. (notably in 1872), and in 1906, 1929, and 1944. The eruptions vary greatly in severity, but the geological record shows that Vevusius experiences a truly devastating eruption every 2,000–3,000 years.

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