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| The erupting crater of Vesuvius illustrated by P. Fabris
From W. Hamilton 1776 Campi Phlegrei, Observations on the Volcanoes of the two Sicilies. Naples: Published privately |
Vesuvius
Vesuvius is one of the best-known volcanoes in the world and is arguably Europe’s most dangerous volcano. The AD 79 eruption responsible for the destruction of the Roman cities of Pompeii and Herculaneum is an indicator of its potential destructive capabilities. During the last 20,000 years it has been characterised either by long quiescence periods, interrupted by plinian or subplinian eruptions, or by periods of persistent strombolian activity, lava effusions and phreato-magmatic eruptions, such as the one that started after the 1631 AD eruption and lasted until 1944 AD, the date of the last eruption. Since that time Vesuvius has not shown any major signs of unrest apart from moderate volcano-tectonic seismicity and fumarolic activity.
Vesuvius is a very dangerous volcano because its record of volcanic history suggests that the longer the quiescence period the more violent is the renewal of its activity.
The risk to human life of a future eruption is very high due to the intense urbanisation at the base (the city of Naples) and on the upper slopes of the volcano; i.e. the eastern part of the city of Naples, and 18 small towns, total 600,000 people . Therefore, improved knowledge of how the magmatic system works is fundamental for both the interpretation of any change in the dynamics of the volcano and the prediction of future eruptions.
Any attempt to forecast the behaviour of Vesuvius and Campi Flegrei requires a detailed understanding of both the present state of the high-level magma storage systems (well constrained by the extensive geophysical and geochemical monitoring systems already in place) and the geological record of the past (eruptive) behaviour of the volcanoes and their magmatic systems. All the currently available petrological and geophysical data suggest that both magmatic systems are multi-stage, characterised by several magma storage reservoirs at different depths within the crust. Deep, complex magma reservoirs occur at 10-20 km depth in the lower crust, beneath the two volcanoes, in which mantle-derived magmas differentiate. Shallower storage systems, located at only 1-3 km depth are characterised by episodic arrivals of distinct magmas that, after undergoing mixing and differentiation processes, feed the eruptions.