Although a relatively young volcano, Vesuvius had been dormant for centuries before the great eruption of 79 ce that buried the cities of Pompeii, Oplontis, and Stabiae under ashes and lapilli and the city of … Mount Vesuvius Geology and Hazards. Vesuvius probably originated somewhat less than 200,000 years ago. The cone known as Mount Vesuvius began growing in the caldera of the Mount Somma volcano, which last erupted about 17,000 years ago. Most rocks erupted from Vesuvius are andesite, an intermediate volcanic rock (about 53-63% silica).Andesite lava creates explosive eruptions on a variety of scales, which makes Vesuvius an especially dangerous and … Mount Vesuvius erupts On August 24, after centuries of dormancy, Mount Vesuvius erupts in southern Italy, devastating the prosperous Roman cities of …