Vesuvius, Mount

an active volcano in southern Italy, near Naples.

Vesuvius is shaped like three cones placed one inside the other. Remains of the exterior (oldest) cone show the arc-shaped swell of Monte Somma; the remains were preserved only on the northern and western slopes of Vesuvius. Inside this exterior cone rises the main cone, which is younger and higher (Vesuvius proper; 1,277 m), with a crater at its peak. A third, temporary cone, which is destroyed during more violent eruptions (for example, in 1906), appears periodically at the bottom of the crater. The outline and height of the main cone vary somewhat; it is composed of intermingled strata of lava and volcanic tufa. Steam and gases with temperatures of up to 400° C erupt at various places in the crater and lava flows. The weathering of lavas and tufas has made the soil on Vesuvius’ slopes fertile. There are orchards and vineyards on the lower slopes. Higher, at elevations of up to 800 m, there are mostly pine groves. During an eruption, plants and inhabited areas are frequently victims of the elements.

Violent eruptions of Vesuvius usually alternate with periods of weak activity. The first known eruption took place in A.D. 79, but it has also been suggested that the first eruption was during the eighth century B.C. There were major eruptions in 1631, 1794, 1822, 1872, 1906, and 1944. Lava from the eruption in 1944 destroyed the city of San Sebastiano. Since then, Vesuvius has been in a period of weak fumarole activity. In the past, the eruptions of the volcano have been characterized by the ejection of large amounts of ash and gases, which then spread upward into a cloud resembling an Italian pine. The formation of these “pines” has often been accompanied by a thunderstorm and downpour; the mixture of rain and ash creates a flood of mud no less dangerous than the lava. In A.D. 79 the city of Herculaneum was destroyed by such a flood; the city of Stabiae was inundated by lava, and Pompeii was completely buried by volcanic ash that covered its buildings with a layer nearly 8 m thick. Since 1842 there has been a volcanic observatory on Vesuvius at an elevation of about 600 m.