Answer: Plucking.
Step-by-step explanation:
Plucking is a glacial phenomenon that cuases erosion and it moves individual pieces of bedrock. When a glacier moves down a valley, the friction melts the basal ice, which then infiltrates cracks in the bedrock. As the glacier flows, mechanical weathering releases rock on the valley walls, which drops as debris on the glacier. Glaciers can carry both giant boulders and silt.