Evolutionary kinematics and geological features of the large Pisciotta rock slide (Cilento Geopark, Campania, southern Italy)

In the Pisciotta municipality (Province of Salerno, Cilento Geopark, southern Italy), a large and slow moving landslide is known since several decades for having damaged continuously an important provincial road which crosses its body and to have requested repetitively maintenance works for permitting vehicle traffic. The almost uninterrupted state of activity, existed in the last seventy years at least, the slow kinematics, not yet evolved in a paroxysmal global failure stage, and the exposition to risk also of a railway tunnel make this landslide a special case of geoharzard to be analyzed. The landslide involves entirely a hilly slope constituted of a Paleogene turbidite series belonging to the Saraceno Formation (Nord-Calabrese tectonic unit), which is formed by intercalated calcarenites, marls and mudrocks and is completely deformed by a polyphasic folding. In this research, engineering geological, geomorphological and topographical analyses were finalized to understand geological factors and kinematics of the Pisciotta landslide. Among principal results, the landslide spatial occurrence and its kinematics re controlled by specific geological and stratigraphic factors such as the existence of an argillaceous member, whose dominant attitude of bedding is downslope dipping with a dip that is generally equal or lower than the local slope angle, and of a fault that bounds the landslide on its left flank. Furthermore, results derived by the displacement of the provincial road, since 1955, as well ground displacements measured by an on-purpose monitoring campaign (September 2006-March 2009) allowed to econstruct the landslide kinematics and to understand further the deep-seated mass movement behavior. Based on such analyses, the Pisciotta landslide is classified as an active, very slow to slow, deep-seated rock slide involving a volume of rock-mass varying between 4 and 6 × 106 m3.