Glaciation Lesson 4


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Glaciation Lesson 4

  1. 1. Key idea: distinctive land forms result from different processes Landforms resulting from erosion – characteristics and formation of corries, arêtes, pyramidal peaks, truncated spurs, glacial troughs and hanging valleys. Landforms resulting from transportation and deposition – drumlins, lateral, medial, ground and terminal moraine.
  2. 2. Glacial Erosion – Swiss Alpine Glacier Corrie where snow accumulation takes place. Glacier flows downhill from corrie.
  3. 3. Corries (=cirque, cwm) <ul><li>Start as sheltered hollows near the top of a mountain </li></ul><ul><li>Snow collects in the hollow (snow fields = neves). The weight of the snow compacts the base of the snow patch to form glacier ice </li></ul><ul><li>Ice moves downhill due to gravity </li></ul><ul><li>As it moves it plucks rocks from the back wall and the hollow is deepened by process of abrasion </li></ul><ul><li>Plucking and freeze thaw make the back wall steep. The loosened rocks fall on to the glacier to form moraine. </li></ul><ul><li>The glacier becomes thicker away from the back wall. Thicker ice can erode more than thinner ice, so the floor of the corrie is deepened. At the same time the glacier is moving due to rotational slip which deepens the hollow. </li></ul><ul><li>The rotational movement also means that the ice is moving upwards near the mouth of the corrie. Ice erodes less at the front edge and so a corrie lip is formed </li></ul><ul><li>When the ice malts a small lake may form behind the lip. This is called a corrie lake or tarn </li></ul>
  4. 4. Helvellyn <ul><li>One of the highest peaks. This is Red Tarn - a lake within a corrie. </li></ul><ul><li>What are the key features? </li></ul><ul><li>Arêtes </li></ul><ul><li>Steep back wall </li></ul><ul><li>Corrie lip </li></ul>
  5. 5. Coe appearance – diagram and map Steep contours Armchair shaped hollow Corrie lip tarn
  6. 6. RED TARN
  7. 7. Arêtes <ul><li>This is a knife edge ridge which separates two corries. </li></ul><ul><li>E.g. Striding Edge </li></ul>
  8. 8. What does an arête look like? Steep back wall Corrie lake ( or Tarn) This is Striding Edge above Red Tarn in the Lake District arête
  9. 10. Aretes
  10. 11. Aretes and map Look for a high, narrow, rocky ridge
  11. 12. Pyramidal Peaks <ul><li>These are formed when three or more corries form around a mountain. They cut backwards to leave a ‘horn’ or pyramidal peak. </li></ul>
  12. 13. Glacial features on an OS map
  13. 14. Pyramid Peak Arete Valley Glacier Corrie
  14. 16. Pyramid Peaks K2 in the Himalayas 8,611metres high!
  15. 17. U shaped Valleys
  16. 19. U-shaped valley formation
  17. 20. Langdale – a U-shaped valley Steep valley sides Flat valley floor
  18. 21. On an O.S. map
  19. 22. <ul><li>What is this feature? </li></ul><ul><li>Look at how this valley appears to be suspended above the valley below </li></ul><ul><li>It is a hanging valley </li></ul><ul><li>How is it created? </li></ul>
  20. 24. Receding tributary glacier Medial moraines Former height of glacier Main valley glacier Hanging valley Truncated spur U shaped valley ‘ Misfit’ stream Waterfall Corrie Pyramid peak Truncated spur