The use of satellite data to support the volcanic monitoring during the last Vulcano island crisis

The “La Fossa” summit crater of Vulcano island (Sicily, Italy) showed increasing volcanic activities, characterized by strong gases emissions and high soil temperatures, during July 2021 (https://cme.ingv.it/stato-di-attivita-dei-vulcani-eoliani/crisi-idrotermale-vulcano-2021). The National Civil Protection Department declared the “yellow alert” level and the Mayor of the island issued an order to prohibit citizens to stay in areas surrounding the harbor due to large amounts of gases emitted; an alternative accommodation was sought for about 250 persons. In this work, we report and analyze the surface temperature estimated by using satellite data (ASTER and Landsat-8) from 2000 to 2022. These analyses extend the study described in “Silvestri et al., 2018” which reports a time series of thermal anomalies from 2000 to 2018, with a focus on two specific sites of the Vulcano island: “La Fossa” and “Fangaia”. So, we updated the dataset up to 2022 and analyzed space-borne remotely sensed data of the surface temperature on the whole island. We applied the Pixel Purity Index technique to ASTER and Landsat-8 satellite data (GSD=90 m) in order to detect pixels that are most relevant from the thermal point of view; thus, we used these pixels as significant points for the time series analysis. Moreover, strong carbon dioxide emissions could be detected from satellite data acquired by the new Italian space mission PRISMA (GSD=30 m) carrying onboard a hyperspectral sensor operating in the range 0.4-2.5 µm; this possibility will be explored by analyzing data on active fumaroles in the island. The goal of the analysis is also to verify if volcanic activity variations (in terms of thermal anomalies and gases emissions), in the Vulcano island, can be detected by satellite data.