booklet 6

• marine processes


  - occur at / below water line

  - base of cliff
• erosion


  - wearing away and removal of material

  TYPES:

  - hydraulic action

  - wave quarrying

  - abrasion / corrasion

  - attrition
• hydraulic action


  - impact on rocks of the sheer force of water itself

  - exert enormous pressure on rock surface, weakening it

  - sometimes referred to as wave pounding
• wave quarrying


  - breaking wave traps air as hits cliff face

  - force of water compresses air into any gap in rock face

  - create enormous pressure within fissure or joint

  - as water pulls back, explosive effect of air under pressure of air being released
• abrasion / corrasion


  - material sea picks up wears away rock faces

  - sand, shingle and boulders hurled against a cliff line will do enormous damage

  - also apparent on inter-tidal rock platforms where sediment is drawn back and forth grinding at platform
• attrition


  - rocks in sea which carry out abrasion are slowly worn down into smaller and more rounded pieces
• solution (corrosion)


  - not really a process of erosion

  - water dissolves rock, mostly chalk or limestone
• factors that lead to marine erosion

  - rock type (lithology)

  - rock structure, variation and dip

  - beach shape (steeper shelf = steeper waves)

  - subaerial processes

  - breaking point of wave

  - wave steepness

  - depth of sea, length of fetch

  - presence / absence of protective beach

  - human activity, eg coastal management
• lithology


  - rock characteristics (permeability and resistance)

  - very resistant rocks are eroded less than weaker materials
• dip


  angle at which rock strata lie
• concordant coast


  - bands of diff rock run parallel to coast

  - results in distinctive landforms

  - slower erosion as more resistant layers act as barrier to erosion
• discordant coast


  - bands of diff rock run at right angles to coast

  - headlands and bays usually form as rock resistance is varied

  - faster erosion as weaker rocks erode faster and wave energy is refracted on headland
• transportation


  - processes move material from site where erosion took place to site of deposition
• traction


  large stones and boulders rolled along
• saltation


  small stones bounced along
• solution


  chemicals dissolved in water
• suspension


  very small particles of sand and silt are being carried
• marine deposition takes place when ...

  - rapid coastal erosion providing an abundant supply of material

  - inputs exceed outputs

  - sheltered areas

  - low energy environments

  - where coast suddenly changes direction
• aeolian deposition


  When sediment carried by wind is deposited
• aeolian depositions take place when...

  - wind is a constant feature

  - large tidal range

  - sand sized sediment is most significant in terms of depositional features

  - sand may roll or slide under the wind (surface creep)

  - where wind is strong enough it may be lifted (saltation)

  - contributes to beaches and dunes