Deep in the southern Tyrrhenian Sea lies the largest submarine volcano in Europe. Lying in the depths between Calabria and Sicily. Contrary to popular belief, Marsili is an active volcano, lying about 3 kilometers deep, with its summit at about 500 meters below sea level.
The dimensions of the Marsili are impressive: about 70 kilometers long and 30 wide, covering an area of about 2100 square kilometers.
Knowledge of the Marsili volcano is linked to geophysical data and core samples taken from its summit. We know that it has an active hydrothermal activity and a seismic activity linked to surface fracturing events, and to degassing in the central area. This area appears lighter because it is affected by superficial fractures and by the circulation of hydrothermal fluids.
The core samples revealed that the most recent eruptions occurred near the central sector, at a depth of about 850 meters, about 5000-3000 years ago, among other things with a low explosive index. Considering the data collected, the scientists estimated that, if a new underwater volcanic eruption occurs, at that depth (i.e. between 500-1000 meters) the only effect on the surface would be the boiling of the water as a result of degassing and floating, in suspension of loose volcanic material (pumice stones).
Therefore, volcanologists believe that the risk associated with possible underwater eruptions is to be considered, at the moment, negligible, or extremely low. In this case, as a preventive measure, only a temporary re-routing of merchant traffic could be assumed. What is not yet known, however, is the historical repeatability of the eruptions of the Marsili, because the inherent data, in number and frequency, are still too limited, and do not allow significant evaluations and statistics.