deep weathering

preglacial drainage

The gentle granite slopes of the Cairngorm high tops incised by the headward growth of corries

Erosion Surfaces

Definition: Gently undulating land surface that cuts indiscriminately across underlying geologic structures and that is the end-product of a long period of erosion

The erosion surfaces of the Cairngorms are the highest representatives of a series of stepped surfaces of low relative relief that dominate the landscape of much of north-east Scotland. Two main breaks of slope at 800 m and 910 m OD are represented on the margins of the Cairngorms (Sugden, 1968). The Monadhliath and the Mounth are dominated by extensive, ramp-like surfaces and the Gaick Plateau represents another high level erosion surface.

The Cairngorm erosion surfaces are incised by glacial valleys and corries and so predate glaciation. The Cairngorm surfaces have evolved under fluvial regimes at elevations well above sea level over periods of many millions of years. Although the surfaces have gentle slopes, the detail of the topography comprises a range of landforms and materials indicative of long-term differential weathering and erosion, including basins, inselbergs and deep weathering remnants. The ages of the surfaces are unclear but some appear to have been modified by differential tectonics in the Neogene (Hall, 1991).

Major preglacial break of slope at c. 800 m OD below Clach Bun Rudhtair, northern Ben Avon