Coasts

• Sediment cells 


  Coast split into sections, considered a close system in terms of sediment

  11 in England and Wales
• Sediment Cell sources


  Where sediment originates from

  Cliffs, Offshore bars, Subaerial
• Sediment Cell Transfers


  Sediment moving alongshore

  Longshore drift, currents
• Sediment Cell Outputs


  Where sediment is deposited

  Sand dunes, Beaches, Bars
• Dynamic system


  Sediment is constantly generated, transported, deposited
• Dynamic Equilibrium


  When input of sediment are balanced with deposited
• Negative Feedback


  When change produces an effect that reduce or work against original change
• Positive Feedback


  When change produces an effect that operates to increase original change
• Littoral Zone


  Area of coast where land is subject to wave action

  constantly changing due to storm surges and climate change
• Subsections of Littoral Zones

  Backshore - area above high tide

  Foreshore - where most wave processes occur

  Offshore - open sea
• Erosional Processes

  Corrasion

  Abrasion

  Attrition

  Hydraulic Action

  Corrosion (solution)
• Corrasion


  Sand and pebbles hurled at cliffs
• Abrasion


  Sediment moved along shoreline causing it to ware down
• Attrition


  Sediment like pebbles hit each other and breakdown
• Hydraulic Action


  Waves crash against cliffs and forces air into cracks building pressure and causing a miniature explosion
• Corrosion (solution)


  Acidic seawater cause alkaline rock such as limestone to erode
• Erosion rates are highest when:

  Waves have long fetch

  Waves approach perpendicularly

  High tide

  Heavy rainfall

  During Winter
• Vulnerability to Erosion


  Clastic or Crystalline

  Amount of cracks/fractures

  Lithology (physical characteristics)
• Types of Erosional Landforms

  • Crack -> stump
  • Wave cut platform
  • Retreating cliffs
  • Blowhole
• Wave cut platform 


  Erosion at bottom of cliff and sub-aerial processes weaken top of cliff, then due to gravity it become unstable therefore collapsing leaving a platform
• Retreating Cliffs


  Repeated process of wave cut platform retreats the cliff
• Blowhole


  Pothole created at top of cliff due to weathering, cave formed in cliff. Both erode and meet form a channel, water gets pushed through and occasionally spurts water out the top hole
• Types of transport/deposition

  • longshore drift
  • Traction
  • Saltation
  • Suspension
  • Solution
• Longshore drift


  Wave hits beach at an angle caused by prevailing wind, backwash is bought back by gravity perpendicular to the beach
• Traction


  Large, heavy sediment rolls along the seabed pushed by currents
• Saltation 


  Smaller sediment bounces along seabed
• Suspension


  Small sediment carried by body of water
• Solution


  Dissolved material carried in water
• Swash-aligned

  Wave crests approach parallel to coast so there is little longshore drift
• Drift-aligned


  Waves approach at a significant angle
• Gravity-settling 


  Increases deposition

  Waves energy declines and heavy sediment is dropped
• Froccilation


  Increases deposition

  Clay particles clump together due to chemical attraction and sink due to high density
• Types of depositional Landforms

  • Spit
  • Bar
  • Tombolo
  • Cuspate forelands
  • Offshore bars
  • Sand dunes
• Spit formation


  Longshore drift occurs along coastline and as waves loose energy when reaching the end of a coastline (curve) and deposit material, can curve due to change in wind
• Bar formation


  A spit which overtime crosses and links two areas of coast, water within is called a lagoon
• Tombolo formation


  Bar or beach which connects the coast to an offshore Island, formed due to wave refraction
• Cuspate Forelands formation


  Occurs at triangular shaped headlands, longshore drift along each side creates beaches which meet
• Offshore Bars formation


  Waves don’t have enough energy to carry sediment to shore so it’s deposited early
• Sand dunes formation

  Prevailing winds blow sand to back of the beach and gets built up by an obstacle, requires tidal range for large quantity of dry sand and frequent wind
• Types of Sand dunes

  • embryo dunes
  • yellow dunes
  • grey dunes
  • dune slack
  • heath and woodland