Spectral analysis in time and space of lava flows erupted by Etna (Italy), Cumbre Vieja (Spain) and Geldingadalir (Iceland) volcanoes.

Satellite optical sensors allow to measure the lava spectral radiance in time and space in terms of both emitted and reflected radiation. Since the latter contribution is prevalent when lava flow is cooled, under this condition its spectral signature, i.e., radiation reflected as a function of wavelengths, can be retrieved. Lava spectral signature depends on several factors, e.g., lava composition and age, revegetation and temperature of fusion and crystallization. Thus, a deeper knowledge about lava properties can be inferred by investigating its measured spectral signature. Here, we compare the spectral response of lava in time and space inspecting visible to infrared satellite images. Firstly, we analyze the temporal changes from 2016 to 2021 in the spectral response of a lava flow emplaced on Mt. Etna in 2002. Secondly, we compare the spectral responses of chemically different lava flows, from different volcanoes. We use the ESA Sentinel-2 MSI TOA reflectance images to address these tasks. Our results allow to give an insight into physical-chemical properties of the investigated lavas using the spectral response obtained with high spatial resolution satellite data.