CONTRIBUTION OF DISTAL ASH DEPOSITS TO THE KNOWLEDGE OF EXPLOSIVE ACTIVITY OF ITALIAN VOLCANOES INSIGHTS FOR HAZARD ZONATION.

In addition to the destruction of the sites close to the volcanoes, the accumulation of volcanic ash in distal zones can cause serious damages but the evaluation of the related hazard is not fully addressed in present day mitigation plans. The dispersion study joined with the physical and geochemical characterization, of distal pyroclastics deposits produced by explosive eruption of Italian volcanoes during late Quaternary was the focus of this PhD project. The distal deposits were investigated through the tephrostratigraphic study of three lacustrine cores from Lake Shkodra and Lake Ohrid (Albania), and one marine core from the northern Ionian Sea. Seventeen tephra layers were correlated with explosive eruptions of A.D. 472, Avellino (3.9 cal. ka BP) from Somma-Vesuvius, Monte Pilato (A.D.1200), Gabellotto-Fiumebianco (8.6 cal ka BP) and Monte Guardia (22 ka BP) from Lipari Island, FL (3.4 cal. ka BP) from Mount Etna, Astroni (4.2 cal. ka BP), Agnano Monte Spina (4.5 cal. ka BP), Agnano Pomici Principali (12.3 cal. ka BP), SMP1-Y3 (31 ka) and Campanian Ignimbrite-Y5 (39 ka) from Phlegrean Fields, X6 (107 ka) from Campanian, P11 tephra layer (131 ka) from Pantelleria Island. Five other tephra layers have the Mercato deposit composition from Somma-Vesuvius. This suggests the occurrence of interplinian activity between the eruptions of Mercato (8.9 cal ka BP) and Avellino (3.9 cal ka BP). All the data were collated into a GIS and integrated with literature data. This data-base implemented in a GIS environment allows a significant improvement of the ash dispersal and represents an useful tool for the improvement of volcanic hazard mitigation in Central Mediterranean area.