Deep-seated gravitational slope deformations in volcanic settings: examples from italian volcanoes

Abstract

Volcanic areas are characterized by slow and rapid vertical ground deformations due to deep thermal instabilities or the resurgence of magma bodies in delimited sectors of a volcanic edifice. Moreover volcanic areas are often the loci of both tectonic and volcanic seismicity. For these reasons, in active or quiescent volcanoes, slope instability is common and may occur as sector or flank collapses gravitationally controlled, involving large rock volumes. Volcanoes experience this type of failure when they reach high relief and oversteepening in a relatively rapid period of activity. Many morphological and structural features affecting unstable volcanic edifices subjected to instability are similar to those described as associated to DGSD (Deep-Seated Gravitational Deformation). The most common features include horseshoe-shaped craters or calderas and associated large debris avalanche deposits. Most of the Italian volcanoes, active, quiescent or dormant, show distinctive horseshoe-shaped craters opened at one end. Some of them are well known and studied features, some others have received less attention due to their state of preservation. For most cases of both categories triggers and favourable factors are still debated. This paper presents case studies of slope deformations that may potentially be classified as DGSD affecting different types of volcanoes and volcanic islands in Italy.