protalus ramparts







The rock glacier/rock slope failure in upper Strath Nethy


Rock glaciers

Definition: a glacier whose motion and behaviour is characterized by a large amount of embedded or overlying rock material

A rock glacier may be composed of:
1. Ice-cemented rock formed in talus that is subject to permafrost.
2. Ice-cemented rock debris formed from avalanching snow and rock.
3. Rock debris that has a core of ice; either a debris-covered glacier or a remnant end moraine.

Ballantyne (1996) lists as many as 8 possible rock glaciers in the Cairngorms. One of the more interesting examples occurs in Coire Beanaidh, on the N facing wall below Braeriach. The former flow of the material is shown by the parallel, traverse ridges and furrows on the surface of the mass of blocks. The former rock glacier is large, with a maximum length and width of 480 m and 240 m (Chattopadhyay, 1984). The estimated volume of debris is >200,000 m3. Ballantyne and Harris (1994) suggest that development of the rock glacier took place under conditions of severe cold (Mean Annual Air Temperature = -11-16C) and aridity (375-550 mm per year). These estimates require the existence of deep and continuous permafrost in the Cairngorms.

More details on rock glaciers in Britain can be found here.