glacial valleys

breaches

troughs

diversion of drainage

rock slope failures

 

Alps or valley benches

Definition: The upper limit of a glacierís erosion on a valley side is usually marked by a break of slope, above which is a more gentle sloped alp or bench. This may represent the former floor of the preglacial valley.

Where glacier ice has occupied a broad preglacial valley, glacial erosion often has been concentrated along the valley axis. This leaves a deep glacial trench or trough, but elements of the original valley floor may survive as flat-topped ridges along the valley margins.

In the Cairngorms, the best preserved alps lie in the valley of the upper Dee and Geldie, where the valley benches may be up to 2 km wide and lie at 600-700 m asl. The alps can be traced west from Braemar along the upper Dee, Geldie and upper Feshie valleys and demonstrate that, prior to glaciation, the Dee's source lay in the hills southwest of the Cairngorms.