Spatiotemporal Analysis of Fluid Flow causing Hydrothermal Alteration Using Google Earth Engine: A Case Study of Lastarria Volcano, Chile

Research on hydrothermal alteration investigates the impacts of hot, corrosive fluids circulating within a volcano, which are crucial for comprehending volcanic risks, slope instability, and steam-driven eruptions. Observable phenomena like fumaroles and mineral deposits at the surface offer direct evidence of subterranean hydrothermal systems or volcanic unrest, detectable through remote sensing techniques. In this study, we introduce a novel Hydrothermal Alteration Index (HAI) derived from Ultra Blue, Red, SWIR 1, and SWIR 2 bands of multispectral satellite imagery, facilitated by Google Earth Engine (GEE), to monitor hydrothermal changes. Identifying three primary alteration zones covering a total area of 600,000 m² at Lastarria Volcano, our findings are corroborated by field surveys, affirming the utility of HAI. Through temporal analysis, we pinpoint three distinct events indicating expansion, contraction of alteration zones, and the emergence of new sulfur flows. By aligning spatiotemporal patterns detected by HAI with independent monitoring data, we infer heightened hydrothermal activity. Lastly, we offer fresh insights into the progression of surface hydrothermal phenomena, starting from the summit crater and extending towards the flank region.