Seven years of UV camera-based SO2 flux observations at Mount Etna

Volcanic SO2 flux observations are relevant to understanding the magmatic processes that occur within the shallower portions of magmatic plumbing systems, and the mechanisms governing transition from open-vent quiescent degassing to explosive activity. Here, we review a SO2 flux dataset acquired at Mt. Etna volcano from a permanent UV camera system during more than 7 years of observations, from June 2015 to December 2022. Our fully automated UV camera system, housed in the Montagnola INGV-OE hut, is designed to spatially resolve SO2 emissions from the southern portion (SEC + Central Craters) of the summit craters’ terrace. The observed period encompasses a variety of eruptive phenomena, including the Voragine Crater (VOR) paroxysmal episodes in 2015-2016, several effusive and lateral eruptions (including the late 2019 “Christmas eruption”) and the two most recent paroxysmal sequences of the South-East Crater (SEC) in December 2020/April 2021 and May/October 2021. We find large temporal variations in the SO2 flux in response to changes in volcanic activity style and vigour. Our results, in particular, demonstrate a clear acceleration in SO2 degassing during effusive eruptions and paroxysmal episodes, relative to non-eruptive (quiescent) periods. Escalating SO2 flux (>5000 t/d) is especially relevant prior (circa 1 month before) onset of the December 2020/April 2021 SEC paroxysmal sequence, whilst reduced degassing (<3000 tons/d) characterises the quiescent phases in between the paroxysmal sequences. This 2020-2021 paroxysmal sequences is characterised in more detail by complementing gas observations with volcanic tremor results and thermal output records (both ground- and satellite-based). Results are interpreted in view of a S degassing model lead that explain elevated SO2 fluxes as caused by augmenting rate of magma transport into the shallow (< 5 km) Etna’s plumbing system.