Glaciers erode rock by using basal sliding and abrasion or plucking to move it around in new places.
glaciers’ unique process of dislodging rocks and depositing them elsewhere differs significantly from water erosion; it results in numerous unique landforms including bowl-shaped cirques, ribbon lakes, and the sharp-sided horns formed when glaciers flow down opposing sides of mountains.
Abrasion
Abrasion occurs when glaciers run across rocks that they move over, wearing away material until it can be carried away by them. It is an integral component of glacial landform formation.
Abrasion rates depend on several factors, including glacier size and speed as well as bedrock lithology. They’re also affected by debris embedded within it (till) which acts to decrease friction between ice and rock surfaces and decrease frictional rates over time. A higher concentration of basal debris reduces abrasion rates by lessening frictional forces between them.
Erosion of rock particles creates fine-grained material known as rock flour, which is carried by melting glaciers and deposits as streams with distinctive milky-white hues. Glaciers may transport large boulders as well as silt, which they deposit as glacial till. When one boulder differs in rock type from its surroundings it is known as an “erratic.”
Plucking
As glaciers move forward, gravity causes their rocks to scrape against mountainside terrain and erode it – leaving behind landforms such as corries, aretes, horns, drumlin fields ribbon lakes and truncated spurs. Abrasion is usually the method by which glaciers directly erode rock; however plucking can also play an integral part.
Plucking (also referred to as quarrying or joint-block removal) occurs when large fragments of bedrock – typically granite clasts – become trapped within glacial ice. These may have either been carried along on its bottom by glaciers, or have become embedded within it itself.
Plucking rates depend on several factors related to bedrock’s lithology, including its structure and any preexisting cracks that can be exploited. They’re also affected by hydraulic pressure fluctuations caused by changes in temperature affecting cavities under glaciers that allow hydraulics to come through; these fluctuations cause rock to break apart along preexisting joints or cracks and contribute to creating the characteristic angular clasts seen in glacial deposits.
Freeze-thaw weathering
Ice is a potent material capable of dramatically altering any landscape. Its effects range from erosion by abrasion and plucking to freeze-thaw weathering in cold areas where cracking water leaks out during warmer days before refreezeing at night, widening cracks until eventually breaking rocks apart.
This process releases minerals and nutrients from rocks into the soil, where they are then taken up by plants for sustained ecosystem health.
Glacial erosion can give rise to various landforms, including cirques, aretes, pyramidal peaks, ribbon lakes, rock drumlins and moutonnee roche moutonnee. Furthermore, erosional features like striations grooves and glacial pavements may result from this form of natural wear-and-tear.
Landforms
Glaciers scrape the land surface, transporting rocks, sediment, and other material across it. Furthermore, they shape the landscape by depositing and carving features into it.
These processes create classic glacial landforms such as U-shaped valleys, cirques, aretes, moutonees roches moutonees roches moutonees rock steps and fjords.
Glacial erosion transforms narrow and V-shaped valleys created by streams and rivers into U-shaped ones, broadening out their sides while deepening their bottoms, as small rock fragments transported by glaciers deposit in its bottom.
Glacial erosion also produces large lakes that fill basins created by glaciers, including many of North America’s great lakes such as Lake Winnipeg, Great Slave Lake and Bear Lake in Canada, where glaciers moved outward over hard crystalline rock before encountering more sedimentary rocks that can form sedimentary lakes.