Coastal systems and processes Flashcards
Constructive waves
Add sediment to beaches
Strong swash, weak backwash
Weak wind
Wide sloping beaches
Destructive waves
Removes sediment from the beach
Weak swash, strong backwash
Strong wind
Steep beach
Winds
Movement of air from one place to another
Areas of high atmospheric pressure to low
Prevailing wind in the UK is south-west
Moves sediment along the coastline
Currents
Permanent or seasonal movement of surface water in seas/oceans
3 main types: longshore, rip and upwelling
Tides
Changes in the level of seas/oceans caused by the gravitational pull of the moon (greater force as it is nearer) and the sun
2 types: spring and neap
Low energy coastline
Deposition is greater than erosion rates
Sandy coastline
Landforms: beaches, spits
High energy coastline
Erosion is greater than deposition rates
Rocky coastlines
Landforms: headlands, cliffs, wave-cut platforms
Sediment cells
Closed systems
Inputs and outputs are balanced
11 sediment cells in the UK
Separated by distinct boundaries (eg- headlands)
Sediment budgets
Balance between sediment being added to and removed from a sediment cell coastal system
Weathering
Breakdown/disintegration of rock in situ (in its original place)
Mass movement
Downhill movement of material under the influence of gravity
Transportation
Transfer/flow of material from one place to another
Deposition
Velocity of water falls below a critical value for a particular size of sediment and can no longer be transported
Erosion
Removes debris from foot of the cliff
Removal of material by wind, waves, tides and sea currents
Hydraulic action
Air is forced inside cracks in the rock by water and is highly compressed
Enormous pressure is exerted
Explosive effect with the air under pressure being released
Over time it weakens the cliff
(Cavitation)
Wave quarrying
Sheer force of water exerting pressure upon a rock surface
Weakens and dislodges parts of the rock
Corrasion
Material picked up by the sea wears away the rock face
Waves hurl material at the base of the cliff
Abrasion
Sediment is dragged over rocky surfaces
Smooths and erodes the rock
Sandpapering effect
Solution
Weak acids can dissolve alkaline rock (chalk/limestone)
Dissolved particles are then removed
Attrition
Material is rolled over eachother by the waves and are smoothed and reduced in size by eachother
Traction
Large stones and boulders rolled along the seabed
Suspension
Very small particles are carried along by moving water
Run off
Where overland flow occurs down a slope or cliff face
Fetch
Wave that has built up over a great distance will have generated more energy