ABSTRACTGlacial erosion by plucking and abrasion is relatively well understood at the small scale of individual bed-forms several metres in dimension. Erosion at this scale is controlled by basal ice pressure, ice regelation and freeze/ thaw. Explanations are lacking for the formation of medium scale landforms of glacial erosion several hundred metres in dimension, where processes such as regelation and cavitation are less well understood.Study of a medium scale glacial erosional feature in South Greenland shows that the distribution of abraded and plucked surfaces is similar to that found on small scale features of glacial erosion. Polished surfaces are found on the stoss side of the larger feature, with plucked surfaces restricted to the lee side. Lateral cliffs have developed parallel to the ice movement direction, possibly related to the constricted flow of flanking ice.It is suggested that the distribution of these landforms of glacial erosion is related to the pressure fluctuations in basal ice developed over large bedrock obstacles. The processes important in the formation of medium scale features of glacial erosion are essentially small scale, but their relative dominance is controlled by meso - scale basal ice conditions.