Mastering Skills for the TOEFL® iBT

The two main types of glacial erosion are plucking and abrasion. Plucking occurs when blocks of rock are pulled away from the bedrock. The glacier works like a backhoe. Water flows into cracks in the rock. It then refreezes and expands, causing the chunk of rock to separate from the bedrock. A The two main types of glacial erosion are plucking and abrasion. Plucking occurs when blocks of rock are pulled away from the bedrock. The glacier works like a backhoe. Water flows into cracks in the rock. It then refreezes and expands, causing the chunk of rock to separate from the bedrock. A glacier can then pick up these loose chunks as it passes over the bedrock. This process creates a lot of loose debris, which causes abrasion. Now, abrasion works like sandpaper with the debris grinding away at the bedrock. If the debris is coarse, it will create long grooves in the bedrock called striations. On the other hand, if the debris is fine, it will create a smooth surface. more