Glaciation

• Glacial processes


  1. Freezes in winter and thaws in summer

  2. Repeatedly freezes and thaws

  3. Pieces of rock

  4. Freeze

  5. Thaw weathering

  6. Water weakens rock

  7. Crack

  8. Scree slopes

  9. Solid flows
• Glacier movement


  • Slow movement through internal deformation (when downhill due to gravity)
  • Basal slip (sliding on a layer of meltwater)
  • Movement depends on whether glacier is frozen to rock or has a layer of meltwater
• Moraine


  Material transported by glacier
• Deposition


  1. Glaciers deposit material when they melt

  2. Most material deposited at glacier's snout

  3. Piles of material left behind are known as till or boulder clay
• Outwash


  Smaller and finer material carried further away from the snout of the glacier by meltwater
• Freeze-thaw weathering


  1. Water continuously gets into cracks and freezes, expanding the cracks

  2. Eventually leads to rock breaking apart
• Glacial erosion


  1. Abrasion as glacier moves downhill, rocks and pebbles embedded in base and sides scrape along land

  2. Plucking as glacial meltwater freezes and sticks to rocks, pulling them away from land
• Corrie


  • Snow collects in small hollow on mountainside, compacted over time into ice
  • Rotational slip, plucking, abrasion and freeze-thaw weathering enlarge the hollow
• Arête


  • Sharp knife-like ridge formed by corries eroding back by processes of erosion and freeze-thaw weathering
• Pyramidal peak


  • Pointed mountain peak formed when three or more corries form, eroding back to meet at a central point
• Truncated spur


  • Steep-sided valley created when a glacier erodes through the interlocking spurs of an old river valley
• Glacial trough


  • U-shaped valley widened and deepened through glacial processes
• Ribbon lake


  • Long thin lake found in glaciated valleys, formed in places where the glacier had more erosive power
• Hanging valley


  • Valley created by a tributary connected to the main glacier, often smaller as less erosion occurred
• 1. shaped valley


  • Wide valley carved out by glaciers, with steep sides and a flat floor
• Misfit streams meander through the flat wide U-shaped valley floor, not having eroded much after the larger glacier had formed the valley
• Glacial transportation


  1. Rocks plucked from bottom and sides are moved downhill

  2. Bulldozing as rocks and debris are pushed downhill by sheer force of moving ice