New insights on the evolution of the Linosa volcano (Sicily Channel) from the study of its submarine portions

Linosa Island represents the emergent tip of a mostly submarine volcanic edifice, with at least 96% of its areal extent lying below sea level. Its morphology is the result of volcanic subaerial activity dated from ~1.06 Ma to 0.5 Ma (Rossi et al., 1996). Until now, the scant knowledge on its submarine extension led to consider this volcanic edifice as extinct. Marine geological surveys carried out by ISMAR CNR of Naples in 2016 and 2017 allowed to reconstruct the submarine portions of Linosa down to a depth of 1000 m, indicating a much wider submarine extension than expected. The new multibeam data, integrated by seismic profiles and ROV inspections, provided new insights on the evolution and biological colonization of this little-explored volcanic edifice. Overall, it extends for about 20 km in the NW-SE direction, evidencing a tectonic control from the main structural system of the Sicily Channel, as already suggested for the subaerial portions (Rossi et al., 1996). Along the same direction, also a marked tectonic lineament and a field of pockmarks can be observed at the base of the W/SW flanks, respectively. The shallow-water SE and NW portions of the volcanic edifice show wide insular shelves, giving evidence on the original extent of the early eruptive centres at the time of emersion stage, prior to their erosion during late-Quaternary sea-level fluctuations (Romagnoli, 2004). These areas are the seat of a very rich ecosystem with a pristine coralligenous habitat. Where insular shelves are lacking, canyons and gullies develop with a radial pattern from shallow water down to the base of the submarine flanks. A number of volcanic features such as lava fields, lava flows and are recognized on the submarine flanks, which appear punctuated by several eruptive centres. A specific morphometric investigation of the volcanic cones mapped on the Linosa submarine flanks was carried out, pointing out a strong similarity with the Pantelleria volcano, especially for what regards the distribution and morphometric characteristics of eruptive cones occurring in the submarine portions (Calarco et al. 2011). The study of the submarine extension of Linosa suggests that the growth and evolution of the volcanic edifice has likely been more complex than what inferred from its subaerial volcanism, and gives new insights on the development of volcanism in the Sicily Channel and on related potential hazard.