The Living World
21 Topics | 21 Quizzes

Understanding Glacial Processes


There are two main types of erosion carried out by glaciers:

  • Abrasion: As the glacier travels downhill, the rocks that are frozen into the mass scrape rocks that are underneath the glacier. This acts like large sandpaper, grinding away the rock, and leaving scratches behind called striations.
  • Plucking: The glacier ‘plucks’ rocks as it travels downhill. This happens due to the glacier’s extreme cold temperatures, which freeze rocks to the sides and bottom of its mass. 

Glaciers act as chisels, gradually carving away at the land. As glaciers move, they pluck and scrape rocks, loosening them from the ground and leaving behind distinctive features on the landscape.

U-shaped Valleys

Glacial erosion creates U-shaped valleys with steep sides and flat bottoms. This happens as the sheer force of the moving ice scours the sides of the valley, wearing them down.

As glaciers retreat, the valleys are often filled with water, forming picturesque lakes.

Glacial Grooves and Striations

Glacial grooves and striations are parallel scratches or grooves found on exposed bedrock. They are caused by rocks embedded in the glacier’s base, which scrape against the underlying rock surface.

Glacial grooves and striations provide evidence of the direction and magnitude of glacial movement.


Freeze-Thaw Weathering

Freeze-thaw weathering is a common process in glaciated areas and is the main type of weathering when it comes to glaciers. 

When temperatures are warm, typically during the day, the snow melts and water enters the cracks in rocks. As temperatures drop again, the water freezes and expands in volume by about 9%. This widens the cracks in the rock, through which the water entered. 

Over time, repeated cycles of freezing and thawing cause the rock to crack even more, eventually leading to pieces of rock breaking off.

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