Nature and importance of mass‐wasting by rock glaciers in alpine permafrost environments

Abstract Active rock glaciers are forms of and indicators for alpine permafrost. On average every individual transports a volume of 1.2‐1.6 × 10 6 m 3 of talus and ice with a speed of 5‐100 cm/yr. The amount of talus in a rock glacier is about 40‐50 per cent of the total volume. Active rock glaciers are therefore an important talus transport system of the periglacial zone of high mountains. They form below talus slopes and beneath small glaciers, and they resemble therefore talus transport systems in continuation of the talus slope or the glacier transport system. According to our estimation (Tables II, III and IV) the total volume of all 994 active rock glaciers in the Swiss Alps is 1,200‐1,600 × 10 6 m 3 . The total amount of talus on the move is estimated to be 500‐800 × 10 6 m 3 , and the mass‐wasting by active rock glaciers per year is then 450‐600 × 10 6 m × t (horizontal) and 140‐190 × 10 6 m × t (vertical) for a movement of 0.3 m/yr and a slope of 30 per cent (= 17°). In relation to the unit of area (km 2 ) these values represent 20 per cent of the total mass‐wasting in the eastern Swiss Alps according to Jäckli (1957) or 160 per cent of the mass‐wasting in Kärkevagge according to Rapp (1960).