How does rock debris at the base of a glacier help erode bedrock?

Glaciers erode bedrock primarily through a process called abrasion, which relies on the rock debris embedded in the ice at the glacier's base. Because pure ice is relatively soft and lacks the shear strength to erode solid rock, it functions much like a sheet of sandpaper; the ice acts as the carrier, while the trapped rock fragments serve as the abrasive tools.12

This debris ranges in size from fine rock flour—which polishes surfaces to a high luster—to large boulders capable of carving deep gouges into the substrate. As the glacier moves, these embedded particles are dragged across the bedrock, creating various "tool-marks" such as microscopic scratches and striations that reveal the direction of ice flow. Over time, this continuous grinding can erode the underlying bedrock to a depth of several tens of metres.134