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Glaciers and glacial landscapes
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Thousands of years ago, ice sheets covered much of Britain. They carved the dramatic mountain scenery of the Lake District, Snowdonia and the Scottish Highlands.
How glaciers erode
Plucking: meltwater freezes onto rock, and the moving ice pulls pieces away.
Abrasion: rocks frozen into the ice scrape the land like sandpaper.
Freeze-thaw weathering breaks up the rock above the ice.
Erosional landforms
Arete: a sharp ridge between two corries, such as Striding Edge on Helvellyn.
Pyramidal peak: a pointed peak where three or more corries meet, like the Matterhorn in the Alps.
U-shaped valley (glacial trough): a wide, steep-sided, flat-floored valley. It may hold a long ribbon lake, such as Windermere.
Deposition
Moraines are ridges of till. Drumlins are egg-shaped hills of till.
Erratics are boulders carried far from where they came from, so they differ from the local rock.
Explain how a U-shaped valley forms.
- A glacier flows down an existing V-shaped river valley.
- Plucking and abrasion erode the sides and floor of the valley.
- Because the ice fills the whole valley, it widens and deepens it into a U shape.
Answer: A glacier fills a river valley and erodes its sides and floor, turning a V shape into a U shape.
Glaciers erode by plucking and abrasion. Landforms: corries, aretes, pyramidal peaks, U-shaped valleys and ribbon lakes. Deposits: till, moraines, drumlins and erratics. UK examples: Striding Edge, Red Tarn, Windermere.
The interactive lesson includes the diagrams for this topic.
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