Processes of glacial erosion
Occurs in cold climates with temperature near or around freezing
The exposed rock needs to contain many cracks
Water enters the cracks during the warmer day and freezes during the colder night
As the water turns to ice it expands and exerts pressure on the surrounding rock
When temperatures rise, the ice melts and pressure is released
Repeated freezing and thawing widens the cracks and causes pieces of rock to break off
Abrasion and plucking
The angular rock fragments produced by freeze-thaw weathering are vital tools for glacial erosion. They work their way
under the ice, acting like sand on a sheet of sandpaper enabling the ice to grind away at the valley floor and sides. The scree fragments themsleves become shattered and pulverised by the weight of the ice, turning them into tiny pieces.
Glaciers only move very slowly but are still capable of tremendous amount of erosion.
Abrasion – when the material carried by a glacier rubs against, and, like sandpaper, wears away the sides and floors of the valley.
Plucking: as the glacier moves the bottom layers of ice stick to rock and the landscape. As the glacier moves it ‘plucks’ or rips the rocks out of the ground.
Glacial movement: In areas such as the Alps in Europe, melting ice in the summer produces a great deal of meltwater. This water helps lubricatethe glacier, enabling it to slide downhill. This type of movement is called basal slip and it can simetimes cause sudden movements of a glacier. In winter, the glacier is frozen to the rocky surface. The weight of the ice and gravity cause the ice to deform and the glacier slowly moves down the slope.