Rock glaciers : II models and mechanisms

Abstract

This second part of a review deals with the mechanisms of rock glacier formation and flow. The presence of a copious debris supply is important in all models, although the source of ice necessary for deformation of the debris is in dispute. Evidence for the three main models: permafrost creep, debris-covered glaciers and talus deformation (rockslide), are reviewed. Seismic and resistivity evidence suggests a nonglacial (permafrost) origin where such measurements have been made. There is also good evidence that glacier ice can be seen and its extent determined in other examples. Morphological characteristics are presented; in some cases they seem to be applicable to the permafrost creep model but can also be explained by the debris-covered glacier model. The consequences of both these models are discussed in the light of the appropriate flow law models. Several different ways in which talus deformation have been suggested and these can be applied in some cases. Because of confusion in the designation of 'valley side rock glaciers' these are here termed 'protalus lobes'. The origin of these features is still problematical and may not be the same as for rock glaciers sensu stricto. It is argued that there is still no conclusive evidence for a single flow mechanism for all the features ascribed as rock glacier or protalus lobes.