coastal processes

• Weathering


  The breakdown of rock in situ (where it is)
• Types of weathering


  • Mechanical
  • Chemical
• Mechanical weathering


  • Breakdown of rock without changing its chemical composition
• Example of mechanical weathering


  • Freeze-thaw weathering
• Freeze-thaw weathering


  1. Water enters rock through a crack

  2. Water freezes and expands, putting pressure on rock

  3. Water thaws and contracts, releasing pressure on rock

  4. Repeated freezing and thawing widens cracks and causes rocks to fall and break
• Chemical weathering


  • Breakdown of rock by changing its chemical composition
• Example of chemical weathering

  • Carbonation
• Carbonation


  1. Rain water has carbon dioxide dissolved in it, making it a weak carbonic acid

  2. Carbonic acid reacts with rock containing calcium carbonate

  3. Rock is dissolved by rain water
• Mass movement


  The shifting of rocks and loose material down a slope
• Types of mass movement

  • Sliding
  • Slumping
  • Rockfall
• Sliding


  • Materials shift in a straight line along a slip plane
• Slumping


  • Material rotates along a curved slip plane
• Rockfall


  • Material breaks up along bedding planes and falls down a slope
• When wind blows over the surface of the sea, it creates waves
• Types of waves


  • Destructive
  • Constructive
• Destructive waves


  • Erode the coast and destroy the beach
• Constructive waves


  • Deposit material at the coast and build up the beach
• Destructive waves


  Backwash (water moving down the beach) is more powerful than the swash (water moving up the beach)
• Constructive waves


  Swash (water moving up the beach) is more powerful than the backwash
• Erosion


  Rocks are broken down and carried away by something (e.g. sea water)
• Types of erosion


  • Hydraulic power
  • Abrasion
  • Attrition
  • Solution
• Hydraulic power


  Waves crash against rock and compress the air within the cracks, putting pressure on the rock and widening the cracks, causing bits of rock to break off
• Abrasion


  Eroded particles in the water scrape and rub against the rock, removing small pieces of the seabed
• Attrition


  Eroded particles in the water collide and break into smaller pieces, becoming more rounded
• Longshore drift


  The way water moves in a specific direction, following the direction of the prevailing wind, with the swash carrying material up the beach and the backswash carrying it down the beach at right angles, causing the material to zigzag along the coast
• Longshore drift


  1. Waves hit the coast at an angle

  2. Swash carries material up the beach

  3. Backswash carries material down the beach at right angles

  4. Material zigzags along the coast

  5. Repeated over time
• Processes of transportation


  • Traction (large particles like boulders pushed along the seabed)
  • Saltation (pebble-sized particles bouncing along the seabed)
  • Suspension (smaller particles like silt and clay carried in the water)
  • Solution (soluble materials dissolved in the water)
• Deposition


  Occurs when water carrying sediment loses energy and slows down, letting go of the material
• Factors affecting rate of deposition

  • Rate of erosion elsewhere (material availability)
  • Amount of material already transported into the area