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Coastal and Marine Processes

IGCSE Geography, coasts

Waves

  • Swash: the movement of a wave up onto the beach
  • Backwash: the movement of a wave returning to the sea
  • Constructive waves: build up beaches by depositing material
    • They have a stronger swash than backwash.
  • Destructive waves: erode the beach as they remove more material than they deposit.
    • They have a stronger backwash then swash.
  • Fetch: the distance across the ocean that the wind has been blowing on it.

 

waves

Erosion

Waves erode the coastline through the processes of:

  • Hydraulic Action: the force of the waves crashing against the cliffs & weakening faults & widening cracks.
  • Abrasion: The sand & small material carried in the waves scraping against the rocks/cliffs & wearing them away.
  • Attrition: Rocks & boulders in the water crash into each other and break into smaller pieces.
  • Corrosion: The sea water dissolves soluble material in the coastline ( especially in limestone & chalk).
coastal erosion

Longshore Drift

  • Longshore drift is the movement of material along the coastline.
  • It occurs due to the swash bringing material up the beach at an angle
  • The backwash then drags the material backwards into the sea & the process repeats

Deposition

Spits are ridges of sand extending into the sea. IGCSE Geogrpahy, coasts, bar
Tombolos are spits that join up with an island located close to the coastline. IGCSE Geography tombolo
Bars are ridges of sand that run parallel to the coastline, sealing off bays. IGCSE Geography spit

Coastal Management

  • Wooden groynes can be built along beaches to reduce the effects of longshore drift.¬†They do not stop it but slow it down.
  • Sea walls can be constructed at the back of beaches to absorb and deflect the waves energy, protecting cliffs or promenades.
  • Beach nourishment is the practise of bringing in extra sand to top up beaches.¬† It is expensive and will need repeating.
  • Gabions are wire cages filled with rocks that serve a similar purpose to sea walls but are cheaper and can be removed easily.