Timely mapping and quantification of volcanological parameters: the 2021-2022 Etna lava flows

The 2021 eruptive activity at Mt Etna was characterized by 57 paroxysmal events at the South-East Crater, the most active among its four summit craters. These episodes of Strombolian activity and high lava fountains fed lava flows towards East, South, and South-West and caused ashfall in the surroundings of the volcano. In 2022 the SEC gave rise to only two paroxysms in February and effusive activity in May-June and since November (still ongoing). Although the impacted area does not include permanent infrastructures it is of high tourist attraction. Hence, timely mapping of each lava flow field was mandatory for hazard mitigation. The high frequency of the 2021 paroxysms, up to two events in 24 hours, forced us to implement a multidisciplinary approach based on various remote sensing techniques, with different spatial resolutions and revisiting time. In particular, several satellite images were processed, depending on data availability and weather conditions. Data acquired by Sentinel-2 MSI, Skysat, Landsat-8 OLI, and TIRS allowed us to map the lava flow fields at a spatial resolution ranging from 0.5 to 90 meters. High-spatial resolution (from 4.5 up to 55 cm) DEMs and orthomosaics were also realized elaborating the visible and thermal images acquired through Unmanned Aerial Systems (UASs) surveys. Moreover, data acquired by the thermal cameras of the Istituto Nazionale di Geofisica e Vulcanologia permanent network were re-projected into the topography for analyzing the lava flow field evolution at 5-meter spatial resolution. These multi-platform remote sensing data allowed for mapping the lava flows and compiling a geodatabase reporting the main geometrical parameters (e.g. length, area, average thickness, and volume). The resulting multi-sensor methodology enabled, for the first time on Etna, to timely and accurately characterize frequently occurring effusive events.