Geography - Physical model answer notes

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Cliffs and Wave cut platforms

  • Hard rock eroded by constant thrashing of waves.
  • Erosion concentrated at base of cliff cuts a wave cut notch.
  • Over-hanging cliff collapses 
  • New wave-cut notch causes coastline to retreat, leaving a wave-cut platform of gently sloping rock.
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Caves, Arches and Stacks

  • Corrasion and hydraulic action erode cracks in headland, forming a cave.
  • Waves erode either side of headland due to wave refraction.
  • Waves cut through headland leaving an arch.
  • Arch roof weakens by weathering and erosion at the base.
  • Rock collapses, leaving a pillar of isolated rock.
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Beaches

  • Buffer zone
  • Consists of loose material that has been deposited.
  • Composed of rock fragments from eroded cliffs.
  • Shape - wave energy, steepness and seasons of the year.
  • Wide and flat/steep and narrow.
  • Smallest material is deposited near water, larger material further back.
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Spits

  • Accumulation of sand sticking out into sea.
  • Large amounts of sediment transported via longshore drift, coastline suddenly changes direction.
  • Material builds up above sea level. Wind direction changes - waves force material inland, creating a curved end.
  • Salt marsh forms behind.
  • Sandpit across bay forms a sand bar with a lagoon behind.
  • If sand goes into open water and reaches an island, a tombolo is formed.
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Corrie

  • Snow accumulates in North facing hollows.
  • Compressed into dense glacial ice.
  • Moves downhill due to gravity.
  • Rotational sliding deepens base by abrasion.
  • Plucking and freeze-thaw create a steep jagged back wall.
  • Ice retreats
  • Corrie lake
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Truncated Spurs

  • Straight course, eroding obstacles.
  • Spurs of rock were eroded by abrasion and plucking.
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Hanging Valleys

  • Tributary glaciers fed into main valley.
  • Smaller and contained less ice, so eroded less.
  • Hang above main valley.
  • Often marked by a waterfall.
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Arete

  • Snow collects in adjacent hollows on North Facing slopes
  • Compacted into glacial ice.
  • Plucking steepens backwalls where pressure melting and refreezing plucks rock away.
  • Freeze-thaw causes rocks to fall off meaning further retreat.
  • Adjacent backwalls retreat into each other.
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Pyramidal Peak

  • Several aretes on same mountain. 
  • Central peak where aretes radiate out from.
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U-shaped valley

  • Formed in a corrie, glacier moves downhill.
  • Moved down v-shaped river valley.
  • Ice was more ersoive so deepened, widened and bull-dozed a straighter U-shape.
  • Abrasion - deepened and straightened.
  • Plucking - steep sides.
  • Misfit stream post glaiation.
  • Ribbon lake left in deepest parts where ice eroded more deeply.
  • 'dam of terminal moraine'.
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