Lessons from the 2021–2023 unrest crisis on Vulcano (Italy)

Abstract Since its last eruption in 1888–1890, Vulcano has experienced several episodes of unrest. The most recent, in 2021– 2023, was characterized by intense fumarolic activity on La Fossa crater along with increased seismicity and ground deformation, and diffuse emission of carbon dioxide (CO 2 ) in inhabited areas. While the crisis manifested after the tourist season, the augmented gas hazard and potential for phreatic explosions threatened the residential and commercial area of Vulcano Porto, prompting an evacuation of the local population. The crisis well illustrates the challenges faced by volcanologists in responding to the sudden onset of unrest in volcanic island contexts. These include: (i) prompt organization of the scientific response and effective coordination with civil protection authorities operating at different levels (national, regional and local), (ii) rapid deployment of additional monitoring systems and identification and quantitative assessment of multiple hazards, and (iii) effective communication and outreach to the population at risk throughout the crisis. Lessons learned during the 2021–2023 crisis can inform the response to future episodes of unrest on Vulcano and other island volcano settings.