Characterizing Paroxysmal Sequences at Mount Etna by Integrating Geodetic and Petrological Analysis

Mount Etna experienced a remarkable eruptive cycle between 2020 and 2022. In December 2020 the South East Crater —one of Etna’s four main craters and the most active over the last 25 years— started exhibiting a series of paroxysmal events characterized by strong, short bursts of lava fountaining accompanied by increased seismic activity. This eruptive period intensified in February 2021 and continued until the end of March (Sequence 1). After a brief pause, a second paroxysmal period began in May 2021 continuing until October 2021 (Sequence 2). The last paroxysms of this cycle were observed in February 2022. A total of 64 events occurred between December 2020 and February 2022.

To investigate the ground deformation patterns and magmatic processes associated with these paroxysmal sequences, we integrated GNSS, InSAR, and petrological analysis (Corsaro et al., 2024). The eruptive sequences showed markedly different characteristics in terms of magma supply rates, eruptive styles, and ground deformation patterns. Sequence 1 was characterized by higher magma supply rates, larger erupted volumes, progressive mixing with deeper magma corresponding to larger paroxysms and dominant lava effusion. In contrast, Sequence 2 exhibited lower supply rates, more frequent but smaller paroxysms, a gradual trend from evolved toward primitive compositions together with prevalent explosive activity (Corsaro et al., 2024 and references therein). According to InSAR and GNSS time series, the volcano edifice experienced inflation during most of 2020, followed by a period of intense and continuous deflation, matching the occurrence of 17 lava fountain episodes during the first sequence. A second deflation trend is observed during the second paroxysmal sequence, although with reduced deformation intensity. The 48-day repose period between both sequences is interpreted as a critical phase in which conditions within the shallow reservoir changed, thereby facilitating the transition from predominantly effusive activity in Sequence 1 to more explosive behavior in Sequence 2. This period likely introduced increased complexity, manifesting not only in the potential magmatic processes during the second sequence, but also in the modeling of the associated deformation source.

Our analysis provides insights into how variations in magma storage conditions can influence both ground deformation patterns and eruptive styles. Furthermore, the joint analysis highlites the potential of integrating geodetic and petrological data for a more comprehensive understanding of the dynamics of Mount Etna’s magmatic system and its magma charging regime.

References:

Corsaro et al., 2024. The 2020–2022 paroxysmal episodes of the South-East Crater (Mt. Etna): insights into high-frequency eruptive activity from petrological monitoring. Bulletin of Volcanology, 86 (10), 85.