Slope Instabilities in High-Mountain Rock Walls. Recent Events on the Monte Rosa East Face (Macugnaga, NW Italy)

The Monte Rosa east face (Macugnaga, Italian Alps) is one of the highest flanks in the Alps. Steep hanging glaciers and permafrost cover large parts of the wall. Since the end of the Little Ice Age (about 1850) the Monte Rosa east face is undergoing a progressive reduction of its ice cover; moreover new instability phenomena related to permafrost degradation and rapid deglaciation have been occurring since over a decade ago. The progressive destabilization of high-mountain faces is a consequence of many factors, such as topography, geological and structural conditions, intense freeze-thaw activity and oversteepened slopes from glacial erosion. Two major events, an ice avalanche occurred in August 2005 and a rock avalanche occurred in April 2007 are briefly described in this paper. In both cases, the accumulation area was located on the Belvedere Glacier at the foot of the Monte Rosa east face. A 3D dynamic model (DAN3D) was applied in order to back analyze the runout of the events, enabling the calibration of the input parameters for the assumed rheological models.