Here's why:
* Glacial striations are scratches or grooves carved into bedrock by rocks embedded in the base of a moving glacier. These rocks act like sandpaper, grinding away at the bedrock as the glacier moves.
Other features that can form under glacial ice include:
* U-shaped valleys: Formed as glaciers erode and widen existing river valleys.
* Cirques: Bowl-shaped depressions at the head of a glacier.
* Aretes: Sharp, narrow ridges separating cirques.
* Horns: Pyramidal peaks formed by the intersection of several cirques.
* Roche moutonnée: A bedrock hill shaped by glacial erosion, with a smooth, gently sloping up-glacier side and a steep, jagged down-glacier side.
However, glacial striations are the most direct and obvious evidence of glacial erosion on bedrock.
