Seafloor doming driven by degassing processes unveils sprouting volcanism in coastal areas

We report evidences of active seabed doming and gas discharge few kilometers offshore from theNaples harbor (Italy). Pockmarks, mounds, and craters characterize the seabed. These morphologiesrepresent the top of shallow crustal structures including pagodas, faults and folds affecting thepresent-day seabed. They record upraise, pressurization, and release of He and CO2 from mantle meltsand decarbonation reactions of crustal rocks. These gases are likely similar to those that feed thehydrothermal systems of the Ischia, Campi Flegrei and Somma-Vesuvius active volcanoes, suggestingthe occurrence of a mantle source variously mixed to crustal fluids beneath the Gulf of Naples. Theseafloor swelling and breaching by gas upraising and pressurization processes require overpressures inthe order of 2-3 MPa. Seabed doming, faulting, and gas discharge are manifestations of non-volcanicunrests potentially preluding submarine eruptions and/or hydrothermal explosions