D. Earthquakes triggered by seismic and volcanic activity also plague the area. The most recent earthquake in 1980 killed 3,000 people, and records indicate a major earthquake in 62 A.D. preceded the 79 A.D. eruption (Allison 112). The modern mountain rose out of the eruption of 79, as a geologic expert notes, "The violent explosions shattered the crater rim, of which only a part remains in Monte Somma, and the later cone of Vesuvius proper was built upon the floor of the old crater, surrounded on three sides by its rim" (Grabau 127). Thus, Vesuvius rests on an ancient foundation but its formation is relatively recent. .

             Vesuvius is most famous for the 79 A.D. eruption that buried the towns of Pompeii and Herculaneum. Pompeii was buried under nearly ten feet of ash and tephra (debris from the eruption of a volcano), while Herculaneum was covered in up to 75 feet of ash as a result of a pyroclastic flow. Dr. Wood defines a pyroclastic flow as "Lateral flowage of a turbulent mixture of hot gases and unsorted pyroclastic material (volcanic fragments, crystals, ash, pumice, and glass shards) that can move at high speed (50 to 100 miles an hour)" (Wood). Historians and scientists have been able to study this ancient eruption because it was witnessed by Pliny the Younger, who wrote an account of it after the eruption. In fact, Vesuvius' distinctive type of eruption has been named "Plinian" in honor of this man's records of the event. .

             Most scientists believe the mountain erupted in August 79, and the eruption continued for nearly a day. Volcano expert Boris Behncke writes, "The two major towns of the area were Pompeii, situated about 8 km SSE of Vesuvio's summit, with about 20,000 inhabitants, and Herculaneum, some 6 km W of the summit, hosting about 5000 residents. Numerous smaller communities and lots of isolated villae lay scattered around the volcano" (Behncke). The eruption began with a tall eruption column visible for many miles that finally reached about 33 km (20 miles) in height.