glaciation

• plucking: as ice moves, there’s friction between it and the rock underneath, some ice melts, seeping into cracks of rock. the meltwater freezes again and sticks to glacier. as glacier moves, it pulls or plucks chunks of rock with it
• abrasion: as ice carries the plucked rocks, they scrape or scratch the rock surface where it passes over. this wears down the rock, scratches are called striae