The role of pre-eruptive conditions on magma ascent dynamics during the 2020-2022 paroxysmal activity at Mt. Etna: a numerical investigation

Mt. Etna is one of the most active basaltic volcanoes on Earth, producing a wide range of eruptive styles, from relatively gentle effusive eruptions to highly hazardous explosive eruptions. During the last three decades, Etna has produced numerous highly explosive paroxysmal events, generating intense lava fountaining and ash clouds that reached several kilometres in height. In particular, between 13 December 2020 and 21 February 2022, a series of 62 paroxysms occurred at Mt. Etna. Petrological and geochemical analyses of erupted samples collected throughout the entire eruptive period suggest that the activity can be divided into two main sequences. These two sequences are both associated with the arrival of a more primitive, hotter, and volatile-rich magma from an intermediate magma chamber at a depth of 9 km (relatively to the vent of the conduit) into a shallower magma chamber at a depth of 3 km where a more evolved, colder and volatile-poor magma was present.

Here, we investigate the role of the evolution in magma composition and the resulting variations in the pre-eruptive conditions (pressure, temperature, crystal and volatile content) on the magma ascent dynamics observed during the 2020-2022 paroxysmal activity at Mt. Etna. Specifically, we use a 1D steady-state model of magma ascent to simulate the ascent dynamics at Mt. Etna. We consider different magma compositions, emulating the progressive mixing between a more evolved magma with a more primitive magma, as suggested by petrological and geochemical analyses. We also explore different thermodynamic conditions of the shallow magma chamber, simulating the evolution of the pre-eruptive conditions due to the interaction of the two magmas.