How Waves Erode-Hydraulic Action, Abrasion/Corrasion, Attrition, Soloution/Corrosion
Factors effecting the rate of erosion- wave steepness and breaking point, fetch, Coastal configurment, Geology, Beach Width & presence, Human Activity
How Waves Erode
Hydraulic Action- as a wave breaks onto a cliff the force of the water traps air and compresses it into gaps in the rock face which creates pressure with the fissure/joint. As the water retreats the pressure of compressed air is released with a explosive effect which weakens and breaks away at the rock face
Abrasion/Corrasion-(sandpaper type effect) Bit of material is picked up by the sea and hurles and scraped against the cliff by the waves- this is visable on intertidal rock platforms (wave cut platforms)
Attirtion- the eroded material is smashed against each other and break into smaller rounder smoother pieces.
Soloution/Corrosion- the dissolving of calcium rocks(limestone etc) by carbonic acid in sea water
Factors Effecting the rate of erosion
Rock Type-Geology- hard rocks e.g granite and clay are more resistant to erosion in comparision to softer rocks e,g clay. the difference is often the cause of the formation of landfroms such as headlands and bays
Fetch- how far the wave has travelled. Waves with a longer fetch are higher and steeper and have more energy which will result in more erosion.
Wave steepness&Breaking Point- steeper waves have hiher energy and greater erosive powers that low-enegry waves. Waves that break at the foot of the cliff creat more damage than the waves that break some distance away.
Coastal Configeration- headland attract more waves through refraction where the waves move towards the headland due to the changine in sea depth
Beach Presence- beaches provide wave energy and therefore provide some protection against marine erosion,
Human Activity- The removal of material from the beach causes greater erosion. However the construction of sea defences may protect the coast line by absorbing & reflecting away the power of the waves (e.g sea wall & gabions) or may prevent the movement of material down the coast by LSD (Groynes.
This however may effect the rate of erosion further down the coast because the beaches are not being naturally replenished by the material moved by LSD. This results in increased erosion