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Multiparameter insights into the months-long evolution of Mt. Etna discharge system prior to the December 2018 eruption

Daniele Carbone1 , Flavio Cannavò1, Marco Liuzzo2, Filippo Greco1, Giovanni Giuffrida2

  • Affiliations: 1Istituto Nazionale di Geofisica e Vulcanologia, Sez. di Catania, Oss. Etneo, Catania, Italy; 2Istituto Nazionale di Geofisica e Vulcanologia, Sez. di Palermo, Palermo, Italy

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 49

  • Programme No: 2.3.35

  • Theme 2 > Session 3

Abstract

Insight into the deep processes that set the conditions for the breakout of the December 2018 flank eruption of Mt. Etna is obtained through the joint analysis of gravity, ground deformation and soil CO2 flux data. During June to September 2018, reduced permeability of the central discharge system favored flushing of CO2 along peripheral paths and the development of a pistoning effect inducing cyclic mass changes in a magma reservoir at 2 - 3 km below the sea level. Successively, the permeability of the central conduit system increased, leading to a decrease in the soil CO2 flux. Between early October and early November 2018, a gravity increase developed, indicating the addition of new mass at a depth of about 2 km below the sea level. Ground deformation data point to a volume change at deeper depth, suggesting that the shallower magma influx was accommodated by compression of the magma already residing in the reservoir. Since early November, further overpressurization could no more be buffered by the compressibility of the magma at 2 km b.s.l., due to the decrease in the volume fraction of exsolved gas, and was more effectively transmitted to the host rock, which enhanced transfer of gas and magma through the uppermost part of the discharge system, accompanied by growing unrest. We speculate that the magma accumulation during early October to early November pushed the plumbing system of Mt. Etna under disequilibrium conditions, ultimately favoring the emplacement of the dike which fed the December 2018 eruption.