Magma budget, plutonic growth and lateral spreading at Mt. Etna

Abstract

The quantitative estimation of eruptible magma is essential to assess volcanic hazard. In case of high and frequent volcanic activity, different episodes and cycles can be observed and used to gain insights on magma residence and volcano dynamics. Here, by using surface ground deformation for 26 inflation and 14 deflation phases at Mt. Etna, we inferred two partially overlapping magmatic reservoirs located beneath the summit area in the 4-9 km (inflation sources) and in the 3-6 km (deflating sources) depth ranges. Our geodetic models highlight a continuous magma supply of 10.7 x106 m3/yr that took place in the last two decades. About 28.5% of this magma (i.e. volume loss inferred by geodetic models) contributed to the effusive activity at the surface, while the remaining 71.5% fed the endogenous volumetric growth of the plutonic crystallized mush and promoted the lateral spreading of Mt. Etna. The consistency of this behavior through time sets strong constraints on the eruptible quantity of magma in forecasting activity during a paroxysm.A two decade-long ground deformation dataset collected on Mt. Etna enables estimation of the volume of the magma budget entering and leaving the volcanic system and can give constraints for forecasting volcanic activity.