Precursors of eruptions at Vesuvius (Italy)

The historical record of activity of Mount Vesuvius is uncommonly long and may serve as a guide to understand precursors before the outbreak of new activity. Reposes of different lengths have been observed in the past, with long ones preceding violent explosive eruptions. Eruptions occurring during periods of permanent activity have been preceded by possible deformation of the volcanic edifice and by short duration, earthquake swarms. Otherwise they have occurred without any reported precursors. The renewal of activity after long periods, like the current one, has been preceded by unrest lasting years to weeks, as a new eruption would require connection to the surface of a reservoir at depth ranging between 6 and 4 km. Since 1944, episodic seismic swarms, have occurred with a frequency similar to that of the violent strombolian eruptions during the last period of permanent activity; they are interpreted as intrusions and arrest of magma batches into a reservoir at the same depth of that feeding past sub-plinian eruptions.