General Overview

In the period of time preceding a volcanic eruption there are generally significant chemical-physical variations in the underground water table of a volcanic area. In the case of increased volcanic activity on Vesuvius, possible temperature increases of fumarole gases may be hypothesised, and chemical variations towards more typical 'magma-like' compositions (appearance of SO2, absent at present, more oxidant redox conditions, a decrease in CH4 and H2 etc.), an increase in the flows of CO2 from the areas of widespread emission.
Geochemical monitoring of Vesuvius, which aims to recognise these processes, is carried out by continuous and discontinuous monitoring both of the crater area and the water table.

Collection of samples for geochemical inquiries.

At present the Somma-Vesuvius volcano complex has a relatively low level of volcanic-hydrothermal activity. The major evidence of this activity is:

• weak fumarole emissions with widespread emission of CO2 from the ground in the summit area of the crater;

• the presence of underground water with anomalous CO2 contents, on the southern side of the volcano and the adjacent plain;

• the underwater gas emissions along the southern coastline in the area over the cities of Torre Greco and Torre Annunziata.

The history of thermal developments in the fumarole plain from 1944 shows a continual decrease in maximum temperatures and suggests that the hydrothermal system may be acting as a cooling system on the volcanic apparatus of Vesuvius at this time.