Unweathered, Glaciated Bedrock on an Exposed Lake Bed in Wales

Abstract

AbstractIn Snowdonia, norh-west Wales, the construction of a hydro-electric scheme involved the exposure of a lake bed. Despite the fact that it is over 13 000 years since the bed was glaciated, erosional features on the slate and grit bedrock have been preserved from weathering below the lake waters. Examples of abrasion, bedrock fracture, plucking, and melt-water erosion are described. The formation of transverse friction cracks is briefly discussed and it is suggested that not all crescentic gouges are associated with rolling blocks as recently proposed. The relationship of small-scale erosional forms to the direction of ice movement is briefly reviewed.