L 5 Corries, Aretes Pyramid Peaks

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L 5 Corries, Aretes Pyramid Peaks

  1. 1. Corries Arêtes Pyramidal Peaks Key idea: distinctive land forms result from different processes
  2. 2. Lesson objectives <ul><li>To describe the characteristic landforms resulting from erosion – characteristics and formation of corries, arêtes, pyramidal peaks, </li></ul><ul><li>To explain the formation of each of these landforms </li></ul>
  3. 3. Corries (=cirque, cwm) NT pg 130 <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. Corrie 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. 9. Aretes
  9. 10. Aretes and map Look for a high, narrow, rocky ridge
  10. 11. ANOTHER ARETE <ul><li>Catslycam </li></ul>
  11. 12. Pyramid Peaks K2 in the Himalayas 8,611metres high!
  12. 13. 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>
  13. 14. Pyramid Peak Arete Valley Glacier Corrie

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