1.2 What are the processes of coastal erosion and what are the resultant landforms? G3 Alevel WJEC including case studies

Created by: Maxine La Grange
Created on: 30-05-13 16:23

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1.2 What are the processes of coastal erosion and what are the resultant landforms?
- weathering and erosion in the coastal zone
  - physical disintegration caused by
    - freeze-thaw
    - salt crystallisation
    - wetting drying
  - chemical decomposition
    - solution
      - depends upon temperature and acidity of water
    - carbonation
  - the variety of intertidal organic life encourages biotic weathering
    - activity ranging from
      - roots of seaweed
      - acid secretion by limpets, barnacles, seagulls
  - 3 processes of erosion
    - Hydraulic action
      - hammering of waves on the rock
    - abrasion/corrasion
      - pebbles and sand get flung against rock, scraping and scouring it away
      - along a short stretch of the North Yorkshire coast near Whitby where cliff erosion increases by a factor of 15 where sediment is available
    - attrition
      - rock fragments are flung against each other, wearing each other away
- Landforms of coastal erosion
  - cliff
    - undercutting at base
      - formation of wave cut notch
        then collapses by falling or slumping
        depends upon lithology and dip of rock
        cliff profiles: the influence of lithology
        6 types
        uniform horizontal strata produce steep cliffs
        bedding planes
        
        rocks dip gently seawards with near vertical joints
        joints opened by weathering and pressure release
        
        castellated cliffs in granite, Jersey.
        
        steep seaward dip
        rock slabs slide down the cliff along bedding planes
        
        slumping in marl cliffs, east Devon
        
        rocks dip inland, producing a stable, steep cliff profile
        
        rocks dip inland but with well developed joints at right angles to bedding planes
        joints act as side planes
        
        slope-over-wall cliffs
        
        progressive retreat of cliff
        will leave wave cut platform
        2 types
        sloping
        
        sub-horizontal
        
        gently sloping platform in resistant Jurassic sandstone and ironstone, Saltwick Bay, North Yorkshire
  - caves
    - develop
      - lines of weakness
        joints
        
        faults
        exploited
        joints
  - Marsden Rock, Tyne an Wear
    - example of an arch breaking to a stack
  - stacks and stumps, Bedruthan, Cornwall
- sea level rises and erosion
  - eustatic adjustment
    - a worldwide change in sealevel
      - land based ice is most significant to eustatic change
  - landforms created with rises of sea level
    - eustatic rise after glacial retreat
      - flandrian transgression
        rapid rise of north sea after glacial retreat between 8000 and 500 BC from about 55m to 6m below at present time
    - local areas of subsidence
      - south East of England
  - landforms features associated with marine erosion ans submergance
    - ria
      - drowned river valleys where river has cut deep into underlying rocks
        therefore steep sided
        
        v-shaped
      - Milford Haven ria, South Wales
      - Helford Ria, Conwall. 67metres above sea level
    - Fjord
      - ice cover was extensive
        altered coastal valleys
        valleys-straightened, deepened and u-shaped cross section- created glacial trough
        post glacial drowning of lower stretches of trough
        created fjords
        Milford Sound Fjord, New Zealand
      - some have sills at mouths
        glacial deposition
        
        solid rock or
    - raised beaches
      - elevated area of sloping ground sitting above the present tide line
        in the past this was at sea level
      - emergent coastline in North west Scotland
      - raised beaches of gower which are wave-cut platforms eroded during a period with higher sea levels
  - isostatic change
    - localised changes in the absolute level of land
      - result of tectonic influences or redistribution of weight
    - Mississippi Delta- **** by some 165m in past 10000 years
      - due to large quantities of sediment deposited in the river basin

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1.2 What are the processes of coastal erosion and what are the resultant landforms? G3 Alevel WJEC including case studies

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