Magma ascent simulations of Etna's eruptions aimed at internal system definition

Abstract

The internal system of Etna was studied by employing a nonequilibrium two‐phase flow model of magma ascent which accounts for different gas‐magma flow regimes and gas loss to surrounding conduit fractures when the magma pressure exceeds the local lithostatic pressure. Simulations of different phases of the 1974 and 1989 eruptions of Etna with different flow regimes in conduits suggest that the pyroclastic, strombolian, lava fountaining, and effusive lava flow activity can be modeled by effectively accounting for different physical processes of magma ascent. Results from simulations and geophysical and geological data suggest that magma ascent at Etna may occur along a central conduit or inclined conduits from a magma storage region located from 8 to 9 km below the summit, depending on the regional tectonic stresses and characteristics of the magma supply system. The results also suggest the existence of a structurally weak zone from 1 to 4 km below the summit where magma may accumulate and from which fracture systems and magma ascent with gas loss to fractures may propagate to the eruptive vents at the surface. The predicted excess magmatic pressure over lithostatic in the upper regions of conduits without gas loss to fractures suggests fracturing of the volcanic edifice during initial stages of eruptions and subsequent magma ascent and gas loss along these fractures. Modeling of the changes of activity at Etna requires significant new efforts in geophysics aimed at high‐resolution internal system definition.