Present-day knowledge on the Marsili Seamount (Southern Tyrrhenian Sea)

The Marsili Seamount (MS) is the biggest European volcano, measuring about 70 km in length, 30 km in width. MS, which is elongated in a NNE-SSW direction, rises up from the bathyal plain of the Marsili basin at 3500 up to 508 m below the sea level. It is interpreted as the axial ridge of the 2 Ma old Marsili back-arc basin belonging to the Calabrian Arc-Ionian Sea subduction system (Southern Tyrrhenian Sea, Italy). Despite the key role of MS in the interpretation of the dynamics lithosphere formation in the Tyrrhenian Sea and in the evaluation of tsunami-related hazard, it is still a poorly known volcano-structure. In the last decade several multidisciplinary studies (i.e. D'Alessandro et al., 2009; Ventura et al., 2013; Trua et al., 2011, Iezzi et al., 2014), show geophysical and geochemical evidences of intra-seamount seismicity, active hydrothermal/degassing processes, fissural vents producing lava flows with calcalkaline affinity and submarine explosive eruptions also in historical time. Here we present new detailed stratigraphic, geochemical and geochronological data on five tephras layer found in a 2.35 m long gravity core (Marsili1 core) recovered in the central sector of MS at 943 m b.s.l.. Our results testify, within the recent MS activity, recurrent explosive eruptions with strombolian style and increase of evolution degree with decreasing time. The occurrence of several submarine explosive eruptions in the last 7 ka implies, hence, an evaluation of the potential hazards and of a monitoring plan.