Coastal Processes

• Hydraulic Action

  • High pressure water causes cracks to force apart and widen
• Abrasion

  • Rocks eroding by rubbing on the river bed
• Attrition

  • Rocks eroding by hitting each other
• Constructive waves

  • Strong swash, weak backwash
  • Builds up beaches
  • Small wave height, long wavelength
• Destructive waves

  • Weak swash, strong backwash
  • Destroys beaches
  • Large wave height, short wavelength
• Mechanical weathering is the breakup of rock without changing its chemical composition
• Chemical weathering is the breakdown of rock by changing its chemical composition
• Slightly acidic rain can chemically weather rocks causing them to dissolve
• Mass movement is the downhill movement of cliff material under the influence of gravity
• Types of mass movement are

  • Sliding
  • Slumping
  • Rock falls
• Slumping occurs when the base of a cliff is eroded and then the saturated weight causes it to collapse

  
• Landslides occur when the base of a cliff is eroded leaving a wave cut notch and then the cliff collapses under it weight
• Rockfall occurs when rock fragments break away from the cliff face often due to freeze-thaw weathering
• Longshore drift is the movement of material along the shore by wave action
• Longshore drift

  • Swash moves at an angle due to the prevailing wind
  • Backwash is perpendicular to the beach due to gravity
  • Process repeats and sediment is transported across the beach
• Deposition is when material that is being transported is dropped by constructive waves because waves have less energy