Mount Vesuvius is a volcano located in southern Italy, near the bay of Naplesand the city of Naples. It is the only active volcano on the European mainland. Vesuvius rises to a height of 1277 m (4190 ft). Vesuvio (Vesuvius) is probablythe most famous volcano on earth, and is one of the most dangerous.
MountVesuvius is a strato-volcano consisting of a volcanic cone (Gran Cono) that wasbuilt within a summit caldera (Mount Somma). The Somma-Vesuvius complex hasformed over the last 25,000 years by means of a sequence of eruptions ofvariable explosiveness, ranging from the quiet lava outpourings thatcharacterized much of the latest activity (for example from 1881 to 1899 andfrom 1926 to 1930) to the explosive Plinian eruptions, including the one thatdestroyed Pompeii and killed thousands of people in 79 A. D. At least sevenPlinian 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 the79 A. D. eruption lasted about 700 years. These eruptions were fed by viscouswater-rich phonotitic to tephritic phonolitic magmas that appear to havedifferentiated in shallow crustal conditions. They are believed to have slowlyfilled a reservoir where differentiation was driven by compositional convection.
A minimum depth of about 3 km was inferred for the top of the magmatic reservoirfrom mineral equilibria of metamorphic carbonate ejecta (2). Fluid inclusions(CO. sub. 2 and H.
sub. 2O-CO. sub. 2) in clinopyroxenes from cumulate andnodules indicate a trapping pressure of 1. 0 to 2.
5 kbar at about 1200 degreesC,suggesting that these minerals crystallized at depths of 4 to 10 km (3). Thedifferentiated 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). Themagma ascent to the surface occurred through a conduit of possibly 70 to 100 min diameter (5). A thermal model predicts that such a reservoir should contain acore of partially molten magma (6) that can be detected by high-resolutionseismic tomography.
The earliest outcropping volcanic deposits date back toabout 25,000 years ago. The lavas observed at a -1125 m bore-hole are about0,3-0,5 million years old. It is known for the first eruption of which aneyewitness account is preserved, in 79 AD. Geologically, Vesuvio is unique forits unusual versatility. Its activity ranging from Hawaiian-style release ofliquid lava, fountaining and lava lakes, over Strombolian and Vulcanian activityto violently explosive, plinian events that produce pyroclastic flows andsurges.
Vesuvius is a complex volcano. A complex volcano is “an extensiveassemblage of spatially, temporally, and genetically related major and minorvolcanic centers with there associated lava flows and pyroclastic flows. “Vesuvius has a long history. The oldest dated rock from the volcano is about300,000 years old. It was collected from a well drilled near the volcano and wasprobably part of the Somma volcano. After Somma collapsed about 17,000 yearsago, Vesuvius began to form.
Four types of eruption have been documented: a)Plinian (AD 79, Pompeii type) events with widespread air fall and majorpyroclastic surges and flows; b) sub-Plinian to Plinian, more moderately sizederuptions (AD 472, 1631) with heavy tephra falls around the volcano andpyroclastic flows and surges; c) small to medium-sized, Strombolian to Vulcanianeruptions (numerous events during the 1631-1944 cycle, such as 1906 and 1944)with local heavy tephra falls and major lava flows and small pyroclasticavalanches restricted to the active cone itself. The fourth type it is thesmallest of all eruption types observed at Vesuvio. It is the persistentStrombolian to Hawaiian style eruption that characterizes almost all of aneruptive sub-cycle, such as was the case during the period 1913-1944. Activityof this kind is mainly restricted to the central crater where one or moreintracrateral cones form, and to the sides of the cone. Lava flows from thesummit crater or from the sub terminal vents extend beyond the cone’s base. Asomewhat particular kind of persistent activity is the slow release of largeamounts of lava from sub terminal fractures to form thick piles of lava withlittle lateral extension, such as the lava cupola of Colle Umberto, formed in1895-1899.
(7) Vesuvius lies over a subduction zone. The two plates are theAfrican plate and the Eurasian plate. The African plate is moving northward atabout one inch (2-3 cm) per year and is slowly closing the Mediterranean basin.As it moves to the north, .
