erosion

coastal erosion

• Permanent loss of land along the shoreline

natural causes

• Changes in wave climate

  • Height

  • Angle of approach

  • Frequency of high magnitude waves

• Reduction in the amount of sediment delivered to the coast from reef

• Rising sea levels

coastal erosion

• Permanent loss of land along the shoreline

natural causes

• Changes in wave climate

  • Height

  • Angle of approach

  • Frequency of high magnitude waves

• Reduction in the amount of sediment delivered to the coast from reef

• Rising sea levels

human induced

• Sand extraction from the beaches - reduces sand volume of the coast

• Coral mining

• Insertion of structures that locally alter wave processes - change sediment transport patterns

  • Seawalls

• Removal of mangroves

contirbuting factors

• Coastal development

  • Loss of dune protection

  • Disruption to the sand cycle

• Climate change

  • Storms and rise in sea levels

• Removal of dune vegetation - stability lost

shaping coastlines

• wind erode headlands

  • Controls plants that grow on them

  • Strong wind = smaller plants

• Waves wash against coastline

  • eroding cliffs

  • Moving rocks and sand along the coast

• Larger river systems deposit mud and silt where they meet the ocean

weathering

• Re-shaping process where rock of the foreshore is disintegrated and decomposed by the water

physical weathering

• Abrasive action of sand particles in the moving sea and wave actions

  • Waves compress into the crevices of rocks and forces them apart

chemical weathering

• Water dissolves minerals out of the rock

• Removal of debris

• Breaks rock -> sand

rocky coasts

• Continually wash against the coastline eroding the cliff base

  • Forms sheer cliffs

• Then forms notches in the headland

  • Material above the notch eventually collapses

• Wind and wave action creates caves, arches, and stacks

caves

• Softer rocks are eroded faster than surrounding rocks

arch

• Prolonged wave action may turn waves into an arch

stack

• Top of arch breaks of to form a stack

blowhole

• In a cave a joint of weakness may go further up a cliff to form blowhole

attrition

• Materials carried by the waves bump into each other

• Smoothed and broken down into smaller particles

hydraulic action

• Force of water against the coast

• Waves enter cracks (faults) in the coastline and compress the air within the crack

• Wave hits

• Air in crack expands quickly

• Minor explosion

• Process repeated continuously

corrosion

• Chemical action of sea water

• Acids in salt water slowly dissolve rocks

• limestone and chalk particularly prone to this process

abrasion/corrasion

• Coast is worn down by material carried by the waves

• Waves throw particles against the rock

• Sometimes at high velocity