Impact of massive deep-seated rock slope failures on mountain valley morphology in the northern cottian alps (Nw italy)

Deep-seated rock slope failures represent effective mechanisms of natural rock mass-wasting, able to radically change mountain-valley morphology. In the northern Cottian Alps, an extraordinary concentration of instability phenomena occurs in extensive areas of the Susa and Chisone valleys. In the Main Map, at a scale of 1:30,000, a new representation of these deep-seated rock slope failures is proposed. Major effort has been invested in properly distinguishing between sackung-type deep-seated gravitational slope deformations and large landslides. Gravitational phenomena have affected the mountain landscape, with the development of impressive morphostructural features such as multiple-crested ridges and ridge top depressions. In the middle and distal portions of the slopes, sagging and toe bulging impose a marked change in the valley-slope profiles, in turn inducing secondary slope instabilities. Furthermore, mature deep-seated gravitational deformations and large landslides have, in some cases, made a significant impact on valley bottom morphology due to a partial or complete valley dam.