The process by which glaciers pick up rocks is called plucking.

Here's how it works:

1. Melting Water: As a glacier moves, meltwater seeps into cracks and crevices in the bedrock.

2. Freezing: When temperatures drop, the water freezes and expands, putting pressure on the rock.

3. Fragmentation: This pressure can cause the rock to fracture and break apart.

4. Entrapment: The broken rock fragments are then entrapped in the ice as the glacier moves forward.

This process contributes to the erosive power of glaciers, shaping the landscape and transporting rock material over long distances.