Abstract
Talus cones in Spitsbergen are commonly modified in their lower part into lobate rock glaciers. Meteoric and melt waters apparently refreeze as interstitial ice in the lower portion of the talus cones during summer months when air temperatures fluctuate near 0°C. At a critical thickness of rock and ice, the mass flows outward as lobate rock glaciers which, in places, override raised beach ridges. Along straight scarps, lobate rock glaciers from closely juxtaposed talus cones coalesce into apron-like terraces 20-40 m high. These have been confused with raised beaches, lateral moraines, kame terraces and protalus ramparts. Several lines of evidence discredit these interpretations for the origin of the terraces. Ice filling of the interstices effectively occludes the permeability of the rock glaciers as indicated by ponding on the surface. Interstitial ice and active movement create a steeper angle of repose of 38°-40° on the advancing rock glacier front while the ice-free talus behind the rock glaciers stabilizes at 30°-35°. Ice wedging may be responsible for linear crevasse-like depressions on the upper surfaces of the rock glaciers. Evidence indicates that these rock glaciers are currently active.
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