Mt. Vesuvius

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model predicts that such a reservoir should contain a core of partially molten magma (6) that can be detected by high-resolution seismic tomography. The earliest outcropping volcanic deposits date back to about 25,000 years ago. The lavas observed at a -1125 m bore-hole are about 0,3-0,5 million years old. It is known for the first eruption of which an eyewitness account is preserved, in 79 AD. Geologically, Vesuvio is unique for its unusual versatility. Its activity ranging from Hawaiian-style release of liquid lava, fountaining and lava lakes, over Strombolian and Vulcanian activity to violently explosive, plinian events that produce pyroclastic flows and surges. Vesuvius is
a complex volcano. A complex volcano is "an extensive assemblage of spatially, temporally, and genetically related major and minor [volcanic] centers with there associated lava flows and pyroclastic flows." Vesuvius has a long history. The oldest dated rock from the volcano is about 300,000 years old. It was collected from a well drilled near the volcano and was probably part of the Somma volcano. After Somma collapsed about 17,000 years ago, Vesuvius began to form. Four types of eruption have been documented: a) Plinian (AD 79, Pompeii type) events with widespread air fall and major pyroclastic surges and flows; b) sub-Plinian to Plinian, more moderately sized eruptions (AD 472, 1631) with heavy tephra falls around the volcano and pyroclastic flows and surges; c) small to medium-sized, Strombolian to Vulcanian eruptions
(numerous events during the 1631-1944 cycle, such as 1906 and 1944) with local heavy tephra falls and major lava flows and small pyroclastic avalanches restricted to the active cone itself. The fourth type it is the smallest of all eruption types observed at Vesuvio. It is the persistent Strombolian to Hawaiian style eruption that characterizes almost all of an eruptive sub-cycle, such as was the case during the period 1913-1944. Activity of thi...