U-shaped valleys provide evidence of glacial erosion.
The correct answer is glacial erosion. U-shaped valleys are a type of landform that is created by the activity of glaciers. They are characterized by steep sides and a flat bottom, resembling the shape of the letter U. Glacial erosion occurs when a glacier moves downhill and carves out the valley by plucking and abrasion. Plucking is when the glacier freezes onto rocks and picks them up as it moves, while abrasion is the grinding down and wearing away of the bedrock by the glacier's movement and the rocks it carries. So, if you encounter a question about U-shaped valleys and need to identify the geological process responsible, the answer is glacial erosion.
