GCSE Geography (Edexcel B)

Topic Summaries

Glacial landform processes

Glacial landforms resulting from erosion

  • Corries: bowl-shaped hollow with a steep back wall and a raised lip at the front. These are formed when snow collects in a hollow on a mountainside and compresses into ice over time. The glacier moves due to gravity, eroding the hollow through plucking (ice pulls rocks away from the back wall); abrasion and rotational slip causes the hollow to deepen.
    • Freeze-thaw weathering breaks up rocks on the back wall, steepening it further. When the glacier melts, the hollow is left behind, often with a tarn (small lake).
  • Arêtes: a sharp, narrow ridge between two corries. These are formed when two corries form back-to-back or side-by-side on a mountain. As the glaciers erode the corries through plucking and abrasion, the ridge between it becomes narrower. 
    • Freeze-thaw weathering sharpens the ridge further.
  • Pyramidal peaks: sharp, pointed mountain peaks with steep sides. These are formed when three or more corries form around a single mountain and glaciers erode the mountain on all sides through plucking and abrasion.
    • Freeze-thaw weathering sharpens the peak into a pyramid shape.
  • Truncated spurs: steep, cliff-like edges where interlocking spurs (from a river valley) have been cut off. These are formed in a river valley when interlocking spurs form as the river bends around hard rock. When a glacier moves through the valley, it erodes through the spurs using plucking and abrasion. This results in steep, truncated (cut-off) edges.
  • Glacial troughs (U-shaped valleys): wide, flat valley floor with steep sides; often much straighter than a river valley. These are formed when a glacier moves through a V-shaped river valley and erodes it through plucking and abrasion, making it deeper, wider, and straighter. After the glacier melts, a U-shaped valley is left behind.
  • Ribbon lakes: long, narrow lake found in a glacial trough. These are formed when a glacier erodes softer rock deeper than hard rock, creating a hollow. When the glacier melts, the hollow fills with meltwater, forming a ribbon lake.
  • Hanging valleys: smaller valleys that hang above the main glacial trough; often containing waterfalls where the smaller valley meets the main valley. These are formed when smaller tributary glaciers erode less deep than the main glacier due to carrying less ice. After the glaciers melt, smaller valleys are left ‘hanging’ above the main valley.

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