2.3 Coasts Flashcards
Corrasion
Large waves through material at the cliff
Corrosion
Acids and salts slowly dissolve a cliff.
Attrition
Waves cause stones to bounce on each other and break down.
Hydraulic action
Force of waves compresses air in cliffs, causing the rock to weaken.
Explain how longshore drift transports material along the coast.
Waves approach the coast in the direction of the prevailing wind.
Swash moves up the beach at an angle.
Backwash drains straight back down the beach (due to gravity.
Material moves in a zig-zag motion.
Swash
When a wave breaks and washes up the beach.
Backwash
When water drains back to the sea
Characteristics of a constructive wave
Strong swash
Weak backwash
Deposits material
Create a gentle beach gradient.
Characteristics of a destructive wave
Strong backwash
Weak swash
Erodes material
Create a steep beach gradient
Explain how cliffs are eroded and wave-cut platforms created
Erosion is concentrated at the foot of the cliff
A wave-cut platform is created
Cliff is undercut and collapses
This causes the cliff to retreat
How are caves, arches, stack and stumps created?
A crack/weaker rock in the headland is eroded to form a cave.
More erosion produces an arch through the headland.
Eventually the roof is weak and collapses forming a stack.
Further erosion causes the stack to ‘sink’ and forms a stump.
Why are beaches formed in bays?
In bays, waves diverge outwards.
This creates a low energy environment and therefore material is deposited to form beaches.
Why are bays and headlands formed?
Bays are parts of the coast with softer rock that has been eroded faster/more easily.
Headlands are parts of the coast with harder rock that erodes really slowly.
How are spits formed?
The coastline changes direction
Longshore drift keeps carrying material in same direction.
When the material reaches more open sea, it deposits material to form a spit.
End of spit curves due to a change in wind.
How are sand dunes formed?
Onshore winds pick up sand from the beach and carry it landward.
This winds then find an obstacle and deposit the sand.
Eventually a dune is formed.
Plants grow, stabilising the dune and trapping more sand.
Mangrove swamps
Trees and shrubs that grow in saline coastal habitats in the tropics and subtropics.
Why are mangrove swamps important? (4)
Provide habitat and protection for species.
Slow down water so that sediment is deposited, cleaning the water.
Protect the coast from erosion, storms, tsunamis…
Source of food and resources.
What do coral reefs need to grow? (5)
\+20C temperatures Sallow water Light Oxygen Plankton
Fringing reef
Coral reefs grow in the shallow water of the coast.
Barrier reefs
Island starts to sink and reef keeps growing, forming a lagoon between the reefs and the land.
Coral atoll
Island is sunk and all that is left is a ring of coral reef with a lagoon at the middle.
Coastal opportunities (7)
Tourism Sport Fishing Industry (transport) Transport (ports) Oil and gas reserves in coastlines. Housing
Coastal hazards (4)
Sea level rise
Erosion
Storms
Polluted water
Rip-rap
Hard engineering. Giant boulders placed to absorb waves energy.
Gabion
Hard engineering. Boulders placed in cages.
Groynes
Hard engineering. Walls that stop longshore drift from transporting beach material away.
Sea wall
Hard engineering. Wall made out of concrete that absorbs wave energy.
Breakwater
Hard engineering. Boulders placed into the sea so that waves break there and not on the coast.
Revetments
Hard engineering. Walls built on wood that absorb the wave energy.
Dune stabalisation
Soft engineering. Plant vegetation to stabilise the dunes.
Cliff regrading
Soft engineering. Make cliffs less steep to stop undercutting and collapsing.
Beach nourishment
Soft engineering. Adding sand to the beach.
Beach drainage
Soft engineering. Removing excess water to reduce stress on the cliff.
Managed retreat
Soft engineering. Allow flooding of low value land
Lagoon
Used to be a bay, but was cut by a bar.
Notch
Undercut part of base of cliff.
Tombolo
Spit connecting to an island.
