Mt. Etna Paroxysms of February–April 2021 Monitored and Quantified through a Multi-Platform Satellite Observing System

Abstract

On 16 February 2021, an eruptive paroxysm took place at Mt. Etna (Sicily, Italy), after continuous Strombolian activity recorded at summit craters, which intensified in December 2020. This was the first of 17 short, but violent, eruptive events occurring during February–April 2021, mostly at a time interval of about 2–3 days between each other. The paroxysms produced lava fountains (up to 1000 m high), huge tephra columns (up to 10–11 km above sea level), lava and pyroclastic flows, expanding 2–4 km towards East and South. The last event, which was characterised by about 3 days of almost continuous eruptive activity (30 March–1 April), generated the most lasting lava fountain (8–9 h). During some paroxysms, volcanic ash led to the temporary closure of the Vincenzo Bellini Catania International Airport. Heavy ash falls then affected the areas surrounding the volcano, in some cases reaching zones located hundreds of kilometres away from the eruptive vent. In this study, we investigate the Mt. Etna paroxysms mentioned above through a multi-platform satellite system. Results retrieved from Advanced Very High Resolution Radiometer (AVHRR), Moderate Resolution Imaging Spectroradiometer (MODIS), and Spinning Enhanced Visible and Infrared Imager (SEVIRI), starting from outputs of the Robust Satellite Techniques for Volcanoes (RSTVOLC), indicate that the 17th paroxysm (31 March–1 April) was the most powerful, with values of radiative power estimated around 14 GW. Moreover, by the analysis of SEVIRI data, we found that the 5th and 17th paroxysms were the most energetic. The Multispectral Instrument (MSI) and the Operational Land Imager (OLI), providing shortwave infrared (SWIR) data at 20/30 m spatial resolution, enabled an accurate localisation of active vents and the mapping of the areas inundated by lava flows. In addition, according to the Normalized Hotspot Indices (NHI) tool, the 1st and 3rd paroxysm (18 and 28 February) generated the largest thermal anomaly at Mt. Etna after June 2013, when Landsat-8 OLI data became available. Despite the impact of clouds/plumes, pixel saturation, and other factors (e.g., satellite viewing geometry) on thermal anomaly identification, the used multi-sensor approach allowed us to retrieve quantitative information about the 17 paroxysms occurring at Mt. Etna. This approach could support scientists in better interpreting changes in thermal activity, which could lead to future and more dangerous eruptions.

The magmatic evolution of South-East Crater (Mt. Etna) during the February–April 2021 sequence of lava fountains from a mineral chemistry perspective

“…A new cyclical eruptive phase started at the SEC on December 13, 2020, producing over 60 paroxysms up to February 21, 2022 (Andronico et al 2021 ; Bonaccorso et al 2021 ; Marchese et al 2021 ; Calvari and Nunnari 2022 ). The activity went through a relatively intense sequence from February 16 to April 1, 2021, with a paroxysm occurring every 1.85 days (± 0.67 days) until March 19 and longer repose times for the last two events (March 23–24 and March 31–April 1, Fig.…”

The FastVRP automatic platform for the thermal monitoring of volcanic activity using VIIRS and SLSTR sensors: FastFRP to monitor volcanic radiative power

“…This latter event was one of the most powerful and peculiar, because was accompanied by the formation of lava fountains which fed a very high eruptive column and an extensive ash plume [Calvari et al, 2021;. Marchese et al [2021] investigated the Mt. Etna paroxysms of February-April 2021 and for the 12 March 2021 paroxysm indicated a lower value of radiative power, about 7 GW from MODIS observations.…”

“…Sometimes VIIRS VRP showed lower values than MODIS VRP and this may be due to the presence of plume above the crater and the atmospheric absorption of carbon dioxide at VIIRS M13 band, used for VRP calculation [Fu et al, 2020]. During the 31 March -1 April paroxysm, VRP retrieved from VIIRS data (~ 5.5 GW, VIIRS image of 1 April at 11:12 UTC) appeared underestimated compared to the temporally coincident MODIS observations (~ 14 GW, MODIS image of 1 April at 09:33 UTC -14 GW), retrieved from Marchese et al [2021]. This impact on VIIRS estimates could be caused by the volcanic plume and partial cloud cover above the crater.…”

Characterization of Volcanic Cloud Components Using Machine Learning Techniques and SEVIRI Infrared Images

“…Between 13 December 2020 and 21 February 2022, a new explosive phase took place at Mt. Etna, giving rise to 66 paroxysmal lava fountain episodes (from INGV weekly bulletins at , accessed on 1 July 2022) [ 53 , 54 , 55 ]. These events were characterized by Strombolian explosions, lava fountains, formation of short-lived lava flows and generation of eruptive columns [ 56 ].…”