Landforms

• corrie formation

  • north facing side (least amount of sunlight)
  • accumulates the most snow causing it to collect in a hollow
  • the snow is compressed due to high pressure
  • freeze-thaw weathering and rotational flow by basal sliding of the ice erodes the back wall of the hollow to form a nivation hollow
  • abrasion and plucking deepen the nivation hollow
  • less erosion at the front of the glacier forms a corrie lip and when the glacier melts a tarn is formed
• arete formation

  it is a narrow ridge of rock that separates two valleys

  It forms when two glaciers erode in parallel U-shaped valleys
• example of a corrie in the UK

  cwm idwal in northern snowdonia
• example of a arete in the UK

  the crib goch in snowdon
• pyrimidal peak formation

  it is a pointed mountain peak where at least three corries have formed back to back

  the glaciers erode backwards towards each other
• glacial trough

  u-shaped valleys that have steep sides and flat valley floors formed by a glacier moving through a valley
• truncated spurs

  formed when ridges of land that stick out into the main valley are cut off by the main glacier as it moves past
• Roche moutonnees

  they are a resistant mass of rock on the valley floor

  • the stoss (upstream) side is smoothed by abrasion as the glacier flows over it
  • the lee (downstream) side is rough and steep due to plucking from the glacier
• moraine types

  1. lateral moraine - on the sides of a glacier
  2. medial moraine - where two glaciers converge
  3. terminal moraine - furthest point at which a glacier ends
• till plains

  they are a large expanse of gently rolling hills of till and deposited sediment
• example of a till plain beyond the UK

  northern Ohio, USA
• drumlins

  they are a resistant core of rock on which sediment accumulates on as the glacier moves over it

  • the stoss end (upwards) is wide and tall providing a resistant front to the glacier where sediment accumulates
  • the lee end (downstream) is narrow and long where the glacier has smoothed the rock by abrasion
• erratics

  these are rocks picked up by a glacier or ice sheet and are transported to an area with a different geology
• example of a drumlin in the UK

  Ribble valley, Lancashire
• example of a pyramidal peak beyond the UK

  the Matterhorn which lies on the border between the Swiss and Italian alps
• example of an erratic in the UK

  Yorkshire Dales

  loose black Silurian rocks are seen on the landscape despite the parent geology being white carboniferous limestone

  • it has been there for over 11000 years
• outwash plain

  layers of gravel, sand and clay form in front of the glacial snout before it retreats due to melting

  the layers are sorted and stratified as the meltwater deposits sediment heaviest first
• eskers


  long winding ridges of sand and gravel that run in the same direction as the main glacier

  they are formed by sediment deposition from meltwater channels running subglacial
• kames

  these are mounds of sand and gravel on the valley floor that are formed when meltwater flowing supraglacial collects in depressions atop of the glacier and deposit debris

  as the glacier retreats and melts, these sediments are deposited on the valley floor in mounds
• ice wedges 


  these are formed from frost contraction where the ground contracts and cracks form in the permafrost

  as temperatures increase in periglacial areas during the spring, the active layer thaws and meltwater seeps into the cracks

  when the temperatures lower again in the winter, the meltwater freezes and forms ice wedges
• open pingos 


  these are formed in areas of discontinuous permafrost

  ground water is forced upwards through cracks in the permafrost causing the water to collect together in a well

  when the water refreezes, it forms a core of ice that pushes the ground upwards
• closed pingos

  these are formed in areas of continuous permafrost where there is a lake atop the surface

  this lake insulates the ground below it ensuring it remains unfrozen

  when the lake dries up, the ground is no longer insulated so the permafrost advances

  this causes water to collect in the centre of the unfrozen ground creating an ice core which pushes the ground upwards
• patterned ground

  this is formed by frost heave which is when water underneath stone freezes and expands forcing it upwards

  when it reaches the surface, it rolls down the edges of the mound forming polygonal shapes
• blockfields 


  these are lose expanses of rock which are formed by the frost shattering of the bedrock layer
• terracettes 


  these are formed when vegetation interrupts soil moving down a slope due to frost creep causing an area of flatter ground to build up behind the obstruction
• Thermokarst


  these are formed when ice in the ground melts causing the ground around it to collapse into holes

  these holes then fill with water and create an uneven marshy landscape