Plucking is the process in which a glacier removes rock by freezing onto loosened fragments of bedrock.
Meltwater can seep into cracks and joints beneath a moving glacier. When the water freezes, it expands and widens those fractures, helping detach blocks from the valley floor or walls. The moving ice then grips and carries away the loosened pieces. Plucking is also called quarrying.
The process is especially effective where bedrock is heavily jointed, fractured, or layered. Glaciers can remove blocks several metres across, leaving behind steep, irregular surfaces and contributing to the formation of distinctive alpine landforms. The entrained rocks may later scrape against the bedrock, producing abrasion, striations, and polished surfaces.
Plucking is commonly confused with abrasion, but the two processes work differently. Plucking tears or lifts blocks from the underlying rock, whereas abrasion is the grinding and scratching caused by sediment embedded in the glacier. Regelation describes pressure-related melting and refreezing of ice; it can assist glacial movement and is related to plucking, but it is not the name of the rock-pickup process itself.