The 2021-22 volcanic unrest at Vulcano Island (Italy) inside of 50 years of activity observed with geophysical data.

Vulcano Island is characterized by transitions from phreatomagmatic to minor magmatic activity. The last eruption in 1888–90 saw powerful explosive pulses and this eruption defines what we call today ‘vulcanian’ also for other volcanoes worldwide. Since then, volcanic activity at Vulcano has been limited to the form of fumarolic emanations of variable intensity and temperature, mainly concentrated at “La Fossa” crater and on its northern slope.

In September 2021, La Fossa entered a new phase of unrest with a sudden and significant increase of degassing activity from the crater and with outstanding variations to fumarole gas composition, temperature, plume emissions, diffuse soil CO2 degassing, local seismicity and ground deformation.

We discuss a set of geophysical monitoring parameters which started evidencing changes since middle 2018, and showed an important expansion of La Fossa Cone in 2021 as the result of an increased activity inside the shallow hydrothermal system just below La Fossa.

We discuss the 2021 episode within 50 years of ground deformation and seismicity data collected by INGV, trying to define the elements of comparison, similarities and differences with the hydrothermal unrests already observed during the late 1970s to early 1990s.