Recent extreme slope failures in glacial environments : effects of thermal perturbation

This paper describes recent exceptional slope failures in high-mountain, glacial environments: The 2002 Kolka-Karmadon rock-ice avalanche in the Caucasus, a series of ice-rock avalanches on Iliamna Volcano, Alaska, the 2005 Mt. Steller rock-ice avalanche in Alaska, and ice and rock avalanches at Monte Rosa, Italy in 2005 and 2007. Deposit volumes range from 10 to 10 m and include rock, ice and snow. Here we focus on thermal aspects of these failures reflecting the involvement of glacier ice and permafrost at all sites, suggesting that thermal perturbations likely contributed to the slope failures. We use surface and troposphere air temperatures, near-surface rock temperatures, satellite thermal data, and recent 2D and 3D thermal modeling studies to document thermal conditions at the landslide sites. We distinguish between thermal perturbations of volcanicgeothermal and climatic origin, and thermal perturbations related to glacier-permafrost interaction. The data and analysis support the view that recent, current and future climatic change increases the likelihood of large slope failures in steep glacierized and permafrost terrain. However, some important aspects of these settings such as the geology and tectonic environment remain poorly understood, making the identification of future sites of large slope instabilities difficult. In view of the potentially large natural disasters that can be caused by such slope failures, improved data and understanding are needed.