Mt. Vesuvius

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Mount Vesuvius is a volcano located in southern Italy, near the bay of Naples and the city of Naples. It is the only active volcano on the European mainland. Vesuvius rises to a height of 1277m (4190 ft). Vesuvio (Vesuvius) is probably the most famous volcano on earth, and is one of the most dangerous. Mount Vesuvius is a strato-volcano consisting of a volcanic cone (Gran Cono) that was built within a summit caldera (Mount Somma). The Somma-Vesuvius complex has formed over the last 25,000 years by means of a sequence of eruptions of variable explosiveness, ranging from the quiet lava outpourings that characterized much of the latest activity (for example from 1881 to 1899 and from 1926 to 1930) to the explosive Plinian eruptions, including the one that destroyed Pompeii and killed thousands of people in 79 A.D. At least seven Plinian eruptions
have been identified in the eruptive history of Somma-Vesuvius (1). Each was preceded by a long period of stillness, which in the case of the 79 A.D. eruption lasted about 700 years. These eruptions were fed by viscous water-rich phonotitic to tephritic phonolitic magmas that appear to have differentiated in shallow crustal conditions. They are believed to have slowly filled a reservoir where differentiation was driven by compositional convection. A minimum depth of about 3 km was inferred for the top of the magmatic reservoir from mineral equilibria of metamorphic carbonate ejecta (2). Fluid inclusions ([CO.sub.2] and [H.sub.2]O-[CO.sub.2]) in clinopyroxenes from cumulate and nodules indicate a trapping pressure of 1.0 to 2.5 kbar at about 1200 [degrees]C, suggesting that these minerals crystallized at depths of 4 to 10 km (3).
The differentiated magma fraction was about 30% of the total magma in the reservoir, and a volume of about 2 to 3 [km.sup.3] was inferred for the reservoir (4). The magma ascent to the surface occurred through a conduit of possibly 70 to 100 m in diameter (5). A thermal ...