Coastal Enviroments

• Coastal processes

  Divided into marine (offshore, water-based) and terrestrial (onshore, land-based) processes
• Coastal processes

  • Wave action
  • Erosion
  • Transportation
  • Weathering
  • Mass movement
• Waves

  • Formed by winds blowing over the surface of the sea
  • Height and strength dependent on fetch, time wind blows, and wind strength
• Swash

  Movement of water up the beach
• Backwash

  Return movement of water down the beach
• Types of waves

  • Destructive
  • Constructive
• Destructive waves erode the coastline in four ways: hydraulic action, attrition, corrosion, abrasion
• Abrasion (corrasion)


  Erosion by rubbing, like sandpaper
• Attrition


  Erosion by wearing down
• Longshore drift

  Main process of deposition and transportation along the coast
• Longshore drift

  1. Prevailing wind pushes waves at angle to beach

  2. Swash carries material up beach at same angle

  3. Backwash carries material down beach at right angles

  4. Repeated zig-zag movement transports material along beach
• Weathering is the breakdown of rock in-situ, different from erosion which involves movement of material
• Types of weathering

  • Mechanical (freeze-thaw)
  • Chemical
  • Biological
• Freeze-thaw weathering

  Water gets into cracks, freezes and expands, opening cracks wider
• Chemical weathering


  Rocks broken down by chemical reactions with slightly acidic rainwater
• Biological weathering


  Rocks worn away by living organisms like plants and burrowing animals
• Types of mass movement

  • Soil creep
  • Flow
  • Slide
  • Fall
  • Slump
• Soil creep


  Slow downhill movement of soil, below 1cm per year
• Flow

  Occurs on slopes 5-15 degrees, after soil becomes saturated
• Slide


  Movement of material 'en masse' that remains together until hitting bottom of slope
• Fall


  Rapid movement on steep slopes, caused by weathering, rainfall, earthquakes, hot weather
• Slump


  Rotational slip of large area of land on weaker rock types like clay
• How sub-aerial processes affect cliff shape

  1. Freeze-thaw weathering weakens cliff, allowing easier erosion

  2. Chemical weathering dissolves less resistant rock faster, changing cliff shape
• Freeze-thaw weathering


  • When temperatures rise, water melts, pressure is released and the crack contracts
  • Repeated cycles eventually breaks the rock apart
  • More freeze-thaw occurring in winter than in summer, resulting in more weathering of the cliff face
• More freeze-thaw weathering


  Cliff is weakened and can then be eroded more easily by the waves
• Chemical weathering


  • Rock type decides how quickly the rock will dissolve
  • Rainwater and seawater are both slightly acidic
  • Less resistant rock, such as limestone, will react with the acid in the water faster than granite
  • A cliff made of softer less resistant rock will weather faster than a cliff made of harder more resistant rock
• Sub-aerial processes

  • Freeze-thaw
  • Chemical
  • Biological
• You need to explain how each sub-aerial process works and then link that to how it would change the shape of a cliff