1. Plucking: This occurs when meltwater from the glacier seeps into cracks in the bedrock. As the water freezes, it expands and exerts pressure on the rock, causing pieces to break off. These broken pieces are then incorporated into the ice and transported away.

2. Abrasion: This is like sandpapering the bedrock. As the glacier moves, the rocks and debris embedded in its base scrape against the underlying rock surface, smoothing and polishing it. Abrasion also creates striations (parallel scratches) and grooves in the bedrock.

3. Freeze-thaw weathering: This process, also known as frost wedging, is not directly caused by the glacier itself but is enhanced by glacial activity. Repeated freezing and thawing of water within cracks in the bedrock causes expansion and contraction, ultimately weakening the rock and making it easier for the glacier to pluck it away.

These three processes work together to shape the landscape, carving out valleys, creating cirques and arêtes, and transporting vast amounts of sediment.