The large Acqualoreto landslide (Umbria, Italy): an example of recurrent landslides evolving from a deep-seated gravitational movements

The link between pre-existing deep-seated gravitational movements and surface landslides reactivations is well known in literature. In particular, where geological and topographic conditions are favourable, large earthflows can evolve from a slope affected by deep-seated gravitational movements. The Acqualoreto landslide is an excellent example of mass movements linked to a slope condition due to deep-seated movements where clay-arenaceous litotypes outcrops. For a long period, and still nowadays, the village of Acqualoreto (Umbria, central Italy) was affected by gravity mass movements. The village lies on the edges of a narrow, procumbent ridge which coincides with part of the niche of a large paleo-landslide, classified as a flow. The paleo-landslide does not show any evidence of possible re-activation, but over sixty active or dormant landslides classified as slides or flows have been identified along its surface. Several field evidences, also well detectable with three-dimensional views of the area, validate this proposition. The aim of this paper is to crosscheck the link of the widespread landslide susceptibility attitude of this area with a slope attitude to deep-seated gravitational movements caused by its lithological, tectonic, and topographic conditions.