AUFBAU UND ENTSTEHUNG DES AKTIVEN BLOCKGLETSCHERS IM SULZKAR, WESTLICHE STUBAIER ALPEN (TIROL)

The Sulzkar rock galcier is one of the bigger active rock glaciers present in the catchment area of the Sulztal in the western Stubai Alps (Tyrol, Austria). The front of this active rock glacier is very steep and bare of vegetation. The surface morphology is characterized by longitudinal and transverse ridges and furrows. The debris layer is up to several meters thick and composed of debris derived from micaschists, amphibolites and gneisses. The debris layer is coarse-grained at the surface, the grain size varies considerably from place to place. The Sulzkar rock glacier overrides an older fossil rock glacier. The meltwater runs off the active rock glacier as groundwater flow within the debris of the fossil rock glacier. Within the debris layer, temperature decreases rapidly with increasing depth during summer. Diurnal temperature variations are absent in a depth of 120 cm. On the rock glacier temperatures at the base of the winter snow cover are mostly between -3 and -5°C, beside the rock glacier temperatures never decreased below -1,6°C. Due to the presence of a depression and glacier ice in the rooting zone, which represents the remnants of a former cirque glacier and continues under the debris cover of the rock glacier, we interpret the Sulzkar rock glacier not as a permafrost phenomenon, but as a rock glacier that developed from the debris-covered tongue of a former cirque glacier during a phase of glacier retreat.