Deciphering volcanic activity: ground and satellite observations of Vulcano's La Fossa Crater and Baia di Levante (2018–2024)

This paper investigates the evolution of the La Fossa crater and Baia di Levante system at Vulcano Island between 2018 and 2024, focusing on the period following the 2021 unrest. Using a multiparametric dataset of ground and remote observations, we tracked the extent and intensity of volcanic degassing as it migrated from a primary and deeply sourced (La Fossa crater) to a peripheral and more hydrothermal zone (Baia di Levante, a bay at the base of the volcano). Our spatiotemporal analysis identified five distinct periods, each marked by specific physicochemical changes in the two areas. We observed a variable delay between the peaking of degassing in the central area and the arrival of gas in the peripheral zone, spanning from 7 months to nearly synchronous timing. Specifically, we suggest that the intense influx of deep fluids in mid-September 2021 transformed the complex network of fractures and shallow geothermal aquifers beneath Baia di Levante, significantly reducing its buffering capacity. This altered state persisted until the end of 2024, when a new deep fluid input observed at La Fossa crater was followed by an increased delay in degassing at Baia di Levante. We explain this variable delay through mechanisms such as fluid drainage and/or hydrothermal sealing of the more peripheral areas. This study underscores the critical importance of continuous monitoring of a volcano's fluid discharge capacity, particularly in identifying areas, where reduced degassing could lead to the hazardous accumulation of gas overpressure, as highlighted by the case of Vulcano Island.