erosional processes and landforms

• what are the landforms found at a discordant coastline

  -headlands and bays

  -beaches

  -cave, arch, stack, stump sequence
• why do headlands and bays form

  bands of softer rock eroded more quickly, so adjacent bands of harder rock stick out into the sea, forming headlands
• why are beaches formed


  a bay is sheltered by the headlands, so a low energy environment where constructive waves are able to deposit material
• why does the cave, arch, stack, stump sequence occur

  due to wave refraction so high energy waves hit the headland
• what is wave refraction


  the bending of waves as they approach a coastline
• explain the cave, arch, stack, stump sequence


  -a fault in the coastline is exploited by hydraulic action and abrasion

  -is it widened and eventually forms a cave

  -after continuous wave erosion the cave breaks through the headland to form an arch. the fault can run through the headland so caves on both sides are formed and eventually meet

  -the roof of the arch is weakened by weathering processes until it is too heavy so it collapses. this forms a stack

  -the stack is undercut and collapses to form a stump by blockfall
• what landforms are found at a concordant coastline

  coves
• why are coves found at a concordant coastline

  the softer rock behind the harder rock is eroded more quickly
• how does a wave cut platform form

  -a wave attacks a weakness such as a fault in the cliff through abrasion and hydraulic action

  -a wave cut notch is formed between high tide and low tide level

  -as exploitation of the notch/ undercutting continues the notch expands until the cliff above is unstable and collapses to form a wave cut platform

  -platform is exposed at low tide but inundated at high tide

  -weathering of platform can cause indentations which leave rock pools when exposed at low tide
• where is the notch often formed

  between the high tide mark and low tide mark
• why why is the wave cut platform often hidden at high tide

  because the platform is between the high tide mark and low tide mark
• example of cave arch stack stump sequence


  old harry rock, Dorset
• what is erosion


  the wearing and breaking off rock and removing it from a coastline
• what are the 4 erosional processes


  Hydraulic action

  Abrasion

  Attrition

  Solution
• what is hydraulic action

  -destructive waves have a large force, so when they hit the cliff face they can cause rocks to be dislodged and break from cliff face

  -waves can force air to be compressed into faults in the rock which exerts pressure and can cause micro fractures off pf the main fault, thus weakening rock until it breaks off
• what is abrasion


  where rocks in the waves are thrown against the cliff face which exerts a force and can weaken faulted rock, thus breaking it off

  softer rock most affected
• what is attrition


  -where particles in the water wear away at each other causing them to become smaller and more rounded

  -softer rock such as sandstone most affected, and they become silt and sand
• what is solution


  where rocks dissolve in sea water which contains carbonic acid
• what type of rocks are most affected by solution


  those containing calcium carbonate such as limestone
• explain how wave type affects erosional processes


  -destructive waves exert the greatest force

  -as size or power of wave doesn't affect solution, constructive waves that have longer contact time with sediment on the beach may be more effective