Landforms and glacial erosion

• • A corrie is an armchair-shaped hollow found on the side of a mountain. This is where a glacier forms. In France corries are called cirques and in Wales they are called cwms.
• Corries produce the following erosional features:

  • arêtes - this is a narrow ridge of land that is created when two corries erode back towards each other
  • pyramidal peak - if three or more corries erode back towards each other, at the top of a mountain a pointed peak is left behind
• When a glacier moves downhill it erodes everything in its path through abrasion and plucking. Glaciers usually follow the easiest route down a mountain, which is often an old river valley. Interlocking spurs created by a river are eroded at the ends by the glacier to create truncated spurs. After the glacier has melted it leaves a U-shaped glacial trough. Sometimes the glacial trough fills with water, called a ribbon lake. Old tributaries, which would have once fed into the valley are left suspended and are known as hanging valleys.
• Labelled diagram #1

  A) Steep Back Wall

  B) Crevasse

  C) Plucking

  D) Rotational Slip

  E) Abrasion

  F) Moraine builds as ice melts at the corrie lip

  
• Labelled Diagram #2

  A) Hanging Valley

  B) U-shaped valley with flat floor and steep sides

  C) Truncated spur

  D) Ribbon lake

  
• • interlocking spur - Hill that a river meanders around in a V-shaped valley. When viewed from downstream, these spurs appear to be locked together.
• • truncated spur - A rounded area of land at the edge of a U-shaped valley.
• • glacial trough - A deep U-shaped valley formed by a glacier.
• • ribbon lake - a large, narrow lake occupying a U-shaped valley. It forms in a hollow where a glacier has more deeply eroded less resistant rock or it may fill up a valley behind a wall ofmoraineacross the valley.
• • hanging valley - A smaller valley which is located high above the main U-shaped valley.
• Pyramidal Peak - formed where three or more corries and arêtes meet. Glaciers erode backwards towards each other, carving out the rocks by plucking and abrasion. Freeze thaw weathers the top of the mountain, creating a sharply pointed summit.
• Arete - a knife-edge ridge. It is formed when two neighbouring corries run back to back. As each glacier erodes either side of the ridge, the edge becomes steeper and the ridge becomes narrower.
• Misfit streams/rivers meander through the flat, wide U-shaped floor. They have not eroded the valley, as they formed there after glaciation had carved out the much larger U-shaped valley.
• Labelled Diagram

  A) Pyramidal Peak

  B) Arete

  C) Corrie

  D) Tarn

  E) Alluvial fan

  F) Ribbon lake

  G) Truncated Spur\

  H) Misfit stream

  I) Hanging Valley

  J) U-shaped valley

  
• U-shaped valley - A valley formed by a glacier that is U-shaped.

  • Formed when a glacier had rubbed down at a v-shaped valley, smoothing out the V bottom into a U
• hanging valley - a valley that is cut into the side of a cliff by erosion.