Subglacial rock polish

This picture, taken within 100 m of the modern terminus of the Gannett Glacier (Wind River Range, Wyoming), shows the effects of subglacial abrasion. Ice flowing from left to right has polished the reddish oxidation off of the high spots. The tools used to polish the bed were clasts plucked from fractured rock (as along the center of this picture) or from lee or down-ice sides (as on the right). The oxidation remaining on the rough, plucked surfaces clearly shows bridging by basal ice over subglacial cavities: the ice moved laterally faster than it could deform vertically into the cavities.