Structural Control at Monte Somma and Vesuvio during the Last 5600 Years, through Time and Space distribution of Volcanic Vents.

Vesuvio is likely the most if not one of the most dangerous volcanoes in the world. It is an active volcano, quiescent since 1944. The activity of the Monte Somma and Vesuvio volcanic complex is commonly referred to as two central volcanic edifices, namely Monte Somma and Vesuvio. Nevertheless, the opening of numerous eruptive fissures and related vents have characterized Monte Somma and Vesuvio throughout their lives. Spatter cones, spatter ramparts, and related eruptive fissures are disseminated downslope of Vesuvio’s main cone and on the southern slopes of the volcano. Similarly, cinder cones, spatter cones, and welded spatters are distributed in the sequence cropping out on the Monte Somma cliff and on the northern slopes of Monte Somma. In this work, a total of 168 eruptive vents have been identified and characterized in a GIS environment in which field data have been merged with relevant information from historical maps and documents. These vents have been arranged into units bounded by unconformities (Unconformity Bounded Stratigraphic Units) defining the eruptive history of the volcano. Alignments of vents and eruptive fissures within each unit have been compared with regional tectonic elements and the volcano-tectonic features affecting Monte Somma and Vesuvio during the last 5600 years, thus inferring that different structural trends were active in the different stratigraphic units. In particular, we show that the N300°–320° regional, Apennine, left-lateral, strike-slip fault system, the N040°–055° Torre del Greco direct fault system, the N70° and the EW fault system, and the generally NS oriented group of local brittle elements, all analyzed here, were differently active during the investigated time span. These tectonic trends might control the position of the eruptive fissures and vents in case of future unrest of the volcano.