Chap 9

• Factors of coastal erosion

  • strength of waves
  • rainfall
  • rock texture
• 3 Jobs of Waves

  1. Erode
  2. Transport
  3. Deposits
• Erosion - meaning

  • eating away
• Abrasion

  • materials brought by waves are thrown and scrapped against a coast/cliff
  • gradually eroding the coast
• Types of waves :

  Constructive

  • creates ( put sand on beach )
  • strong swash
  • weak backwash
• Prevailing winds

  • wind that blows strongly from a single general direction
• Swash

  • water washed up to the shore ( moves upwards )
• Types of waves:

  Destructive

  • destroys ( takes beach away )
  • strong backwash
  • weak swash
• Backwash

  • water runs back down the sea ( moves backwards )
• Formation of cave, arch, stack, and stump

  1. Lines of weakness such as faults occur in headlands
  2. Abrasion and hydraulic actions erode the fault to form a cave
  3. The cave is widened and deepened
  4. The sea pushes through to form an arch
  5. The sea erodes the foot of the arch and widens it
  6. The roof of the arch becomes too heavy and collapses
  7. Part of the former cliff is now isolated as a stack
  8. Over time the stack is undercut and collapses
  9. A stump is the remains of the eroded stack
• Solution

  • water in waves reacts chemically with soluble minerals in the rock along the coast and dissolves them
• Longshore Drift

  • sediment is carried up the beach at an angle with the swash
  • prevailing winds help waves approach beach at an angle
  • sediments travels with backwash down the beach in a straight line due to gravity
  • process continues and sediment gets moved along the beach
• Formation of Headlands and Bays

  • when the coastline is made up of different types of rocks, erosion takes place at a different speed
  • less resistant rock (soft rock) is eroded (by hydraulic action and abrasion) faster, forming a bay
  • more resistant rock (hard rock) at each side of the bay erodes slowly, forming headlands at either side of the bay
• Hydraulic Action

  • force of moving waves rushing/crashing into cracks in rock/cliff face
• Attrition

  • when materials are carried by waves they collide with one another
  • eventually, materials break down into smaller pieces and become smoother and more rounded over time