Coasts
Key terms
Longshore Drift - Process of sediment transported along the coast by swash and backwash
Corrosion or Abrasion - sandpaper action
Attriton - sediment bashes together to become smooth and round
Solution - slight acid in the sea that dissolves rock e.g chalk and limestone
Hydraulic Action - when a wave hits the cliff air is forced into the holes gradually eroding it
Mass Movement
Weathering
Biological Weathering - roots burrow down, weakening the structure until it breaks away
Physical Weathering - breaking down of rocks through heat or cold (freeze thaw)
Chemical Weathering - chemicals in salt, seawater and rainwater will weaken rock over time
Waves
Swash - when a wave breaks and rushes up the beach (south westerly direction)
Backwash - when a wave is pulled back to the sea by the force of gravity
Constructive Waves - build up a beach (construct a beach) and are low energy
Destructive Waves - high energy and break down a beach (erode)
speed
angle of slope - steeper slope faster movement
rainfall - lubricate the cliff and lead to mudflows
vegetation cover - if vegetation is present it will absorb some of the water and the roots will bind the soil making it more stable
Depositional Landforms
deposition - When the sea loses energy, it drops the sand, rock particles and pebbles it has been carrying.
beach bar - chesil beach
spit - mudeford spit and calshot spit
tombolo
Erosional Landforms
coastal headland - old Harry rocks
Concordant Coastline - horizontal to the sea
Discordant coastline - vertical to the sea
Hengistbury Head
spit (mudeford)
depositional landform
formed overtime by longshore drift and sediment build up
beach
depositional
constructive waves bring sediment and deposit it leading to a gradual build up of sediment that forms into a beach
Cliffs
erosional landform
destructive waves cause erosion (hydraulic action) and eat away and the cliff causing gradual backward movement or cliff slumping
sandstone
coastal defences (Hard)
rock groynes
wooden groynes
gabions
rock armour
sea wall
offshore breakwater
revetments
promote water sports
lengthen the beach
expensive (£5mil)
protects the land
if curved it can reflect the waves back to the sea
expensive £1000 per metre
undermined easily by waves washing away the sand and shingle underneath them (causes them to move)
10-20 year lifespan
some people say it is ugly
when a river meets the sea it looses its energy and forces deposition
cheap and effective at breaking waves
visually unattractive
Soft Coastal Defences