Sammendrag
Two tongue-shaped rock glaciers on Svalbard have been investigated. The results of surface velocity measurements reveal horizontal surface velocities of 0.05-0.10 m a-1. The oldest surface of these rock glaciers is roughly estimated to 4000 yr. based on a tentative dating by calculation of the length-surface velocity ratio (LSVR). With respect to rock glacier dynamics and long term initial development of their particular forms, it is likely that the rock glaciers started to develop at the onset of the Holocene. DC-resistivity results indicate an inner structure with an 20-35 m thick high-resistivity ice-rich layer (100-900 k0m) laying on a lower resistive layer (5-70 k0m) interpreted as ice-saturated sediments. Ground penetrating radar (f=50MHz) shows clear reflection horizons or layers along the longitudinal profile of the rock glacier. In a short zone at the rear of the profile, the layers are orientated parallel or slanting downwards in relation to the rock glacier surface. In the frontal part the layers slant upwards. The orientation of the layers changes in a narrow transition zone. The layers can be recognized clearly down to 15-20 m depth. They are interpreted to represent sediments supersaturated with ice alternating with layers of rockslide debris. The supersaturated layers are interpreted as snowdrifts later covered with debris from rockslides. Repeated mass movement events result in aggregational ice layers gradually becoming part of the creeping rock glacier. This mechanism is assumed to be the most important accumulation process for the development of the investigated rock glaciers.
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