‘The removal of pre-loosened bed material and/or material resulting from bed failure’ (Rea and Walley (2006) Earth Surf. Procs & Landfms 19, 7). Since the tensile strength of ice is low, glacial quarrying is not possible unless the rock is shattered.

Glasser and Bennet (2004) PPG 28, 1 observe that there is now general agreement that quarrying is favoured beneath thin, fast-flowing ice, and Drake and Shreve (1973) Procs Royal Soc. London, Ser. A 332, propose a heat pump effect: water that is melted in high-pressure areas flows away and does not refreeze at the immediately adjacent low-pressure area, and this leaves cold patches that advect downglacier. Fluctuations in basal water pressure also play an important role in the formation of glacially quarried landforms; see Glasser and Bennet (2004) PPG 28, 1. Landforms of glacial quarrying include roches moutonnées, rock basins, and zones of areal scouring.