Abstract

This paper describes and analyzes the exceptionally large rock-ice avalanche of 40 to 60 million m3 volume that occurred in 2005 from the south face of Mt. Steller (Bering Glacier region, Alaska), which has steep glaciers at the summit. Analysis of seismic signals revealed a series of precursory rock/icefalls and a special sequence interpreted as slip and deformation in glacier ice. Reconstruction of the thermal conditions based on regional climate and radiosonde data yielded mean annual ground surface temperatures of -10 to -15°C for the failure area. Because the slope failure was at depths of meters to decameters we also performed numerical modeling of a 2D temperature profile across the mountain. Results showed that the existence of a hanging glacier in the summit area induces a deep-seated thermal anomaly. We subsequently outline a number of processes that may be effective for slope destabilization with the given thermal conditions.