Plucking (glaciation)

Plucking, also referred to as quarrying, is a glacial phenomenon that is responsible for the weathering and erosion of pieces of bedrock, especially large "joint blocks".

The freezing and thawing action of the ice enlarges, widens, or causes further cracks in the bedrock as it changes volume across the ice/water phase transition (a form of hydraulic wedging), gradually loosening the rock between the joints.

[4] Glacial plucking is most significant where the rock surface is well jointed or fractured or where it contains exposed bed planes, as this allows meltwater and clasts to penetrate more easily.

[2] Plucking of bedrock also occurs in steep upland rivers, and shares a number of similarities with glacial examples.

As the glacier slides down a mountain, energy from friction, pressure or geothermal heat causes glacial meltwater to infiltrate the spaces between rocks.

Erosion is largely dependent on the amount of water flow and its velocity, the clast size and hardness with relation to the stability of the slope.

Although striations can form on any sort of rock, they are usually present on more stable bedrock such as quartzite or granite where erosion processes are more readily preserved.