Evolution of volcanic sources at Vulcano Island preceding the 2021 unrest from GNSS data

September 2021 on Vulcano island (Aeolian Islands, Sicily) was marked by the beginning of a new phase of volcanic unrest, during which the volcano underwent a dramatic increase in geophysical and geochemical parameters: a notable radial ground deformation centred around the Gran Cratere della Fossa crater occurred alongside increased seismicity, soil CO₂ flux, plume SO₂ flux, and fumarole outlet temperatures.

However, this period of volcanic unrest did not occur in isolation but was, in fact, preceded by two minor periods of ground deformation and increased soil CO₂ flux occurring in 2018 and subsequently 2019. Global Navigation Satellite System (GNSS) and tilt data recorded during March – August 2018 have been used to create an analytical model of the deformation source, which shows a deeper source of inflation with respect to the source proposed for the 2021 unrest. The position of the 2018 source model is potentially indicative of a deeper recharge of the plumbing system beneath Vulcano, which reached progressively shallower levels before ultimately triggering the hydrothermal crisis of 2021.

This approach offers not only insight into the temporal evolution of a complex volcanic system before unrest periods, but also further implications as to the role played by tectonics. This is especially important in light of Vulcano’s position within a pull-apart-type structure along the Aeolian-Tindari-Letojanni fault system, a transtensional fault system which has shed light on the complex interplay between regional geodynamics in the southern Tyrrhenian Sea and volcanic activity at Vulcano.