Abstract
ABSTRACTDeep-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.
Highlights
Due to the large volumes involved and their kinematics, massive rock slope failures such as deep-seated gravitational slope deformations (DSGSDs) and large landslides represent effective mechanisms of natural rock mass-wasting, and can dramatically influence mountain-valley morphology, on a long-term basis and at a large scale
In the northern Cottian Alps, major tectonic features have exerted a strong influence on the drainage network and slope morphology: sub-vertical NE–SW and NNW–SSE fault systems control the rectilinear pattern of the Dora Riparia and Chisone rivers and their tributaries, sometimes arranged in an almost orthogonal pattern; in the outcrop area of the Albergian unit, the presence of low-angle (20–35°) southwestward-dipping shear zones parallel to the regional foliation has imposed a cuesta morphology, giving rise to an asymmetrical cross profile of valley flanks
Since the end of the Last Glacial Maximum (LGM), in the northern Cottian Alps deepseated rock slope failure such as DSGSDs and large landslides has occurred on a large scale
Summary
Due to the large volumes involved and their kinematics, massive rock slope failures such as deep-seated gravitational slope deformations (DSGSDs) and large landslides represent effective mechanisms of natural rock mass-wasting, and can dramatically influence mountain-valley morphology, on a long-term basis and at a large scale These instability phenomena can affect the mountain landscape in different ways:. Deep-seated rock slope failures are widespread throughout the Alps (Crosta, Frattini, & Agliardi, 2013), the upper Susa and Chisone valleys (northern Cottian Alps) represent a peculiarity in the alpine landscape because of their extraordinary concentration They are caused by a specific combination of many predisposing factors such as lithology (Mortara & Sorzana, 1987), structural setting (Giardino & Polino, 1997), glacial and post-glacial geomorphological history (Polino, Borghi, Carraro, Dela Pierre, Fioraso, & Giardino, 2002), local topographic factors, groundwater conditions and seismicity (Perrone, Eva, Cadoppi, Solarino, & Fioraso, 2011). As demonstrated by monitoring systems, there are presently a significant number of deep-seated instability phenomena that are affected by slow (
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