Submarine structure of Vulcano volcano (Aeolian Islands) revealed by high-resolution bathymetry and seismo-acoustic data.

A new definition of the morpho-structural submarine setting of the Vulcano volcano is presented based on the integration of multibeam swath bathymetry, high-resolution seismic profiles and sea-floor sampling. A number of unknown volcanic features have been mapped on the submarine flanks of Vulcano Island as volcanic outcrops and isolated cones. For most of them a relatively old age is suggested (especially to the west of the island), while evidence of relatively recent volcanic activity characterizes the north-eastern submarine sector, offshore Vulcanello. The morphology and distribution of these features, either aligned along NNW–SSE trends or radially elongated, suggest the prevalence of regional structural control or local stresses related to the volcano structure, respectively, in the different sectors of the volcanic edifice. Shallow-water (<120 mbsl) insular shelves, related to wave action during Late Quaternary sea-level fluctuations, were recognized in correspondence of the oldest sectors of the edifice, while they are lacking in the younger sectors. Beyond the shelf edge, a strong increase of slope gradients characterizes the submarine flanks, promoting the formation of erosive-depositional and mass-wasting features at different scale, such as landslide scars, gullies, headless channelized features, crescent-shaped bedforms and volcaniclastic fans. In particular, two large volcaniclastic fans were identified on the north-eastern and south-western flanks, where marine retrogressive processes are very active and sediment is funnelled from the coasts to the foot of the volcano. These fans are created by the gradual stacking of gravity flows fed by repeated small- and medium-scale mass-wasting events, instead of being related to large-scale flank instability events. The lack of large-scale lateral collapse on the submarine flanks of Vulcano volcano has been related to the morpho-structural and volcano-tectonic setting of the volcanic edifice, characterized by the occurrence of summit caldera collapses limiting its total height and by the absence of well-defined rift zones.