Coastal Environments Flashcards
What are waves caused by?
Winds blowing over sea.
How is the power of the waves determined by?
- Stronger wind, bigger waves.
- Length of time wind blows.
- Fetch.
What is the fetch?
Greater distance of open water, larger waves.
E.g. contrast east and west of Ireland, Atlantic and Irish Sea.
How do waves form?
As wave approaches shallow water near coastline, friction caused by seabed slows lower section of wave more than upper section.
Upper section of wave reaches crest then topples over (breaks) and either hits cliff face or surges up beach as swath of wave.
As wave retreats, creates backwash.
Waves with strong swans and weak backwash called constructive waves as push material up beach.
Waves with strong backwash pull material out to sea, destructive waves erode coasts.
What are the characteristics of destructive waves?
- Strong backwash compared to swash.
- High in relation to length.
- Form frequently (break at rate around 15 per min).
What are the characteristics of constructive waves?
- Weak backwash compared to swash.
- Long in relation to height.
- Are gentle ( break at rate 6-9 per min).
What are the 4 processes of coastal erosion?
Corrasion, attrition, solution and hydraulic action.
How does corrasion erode a coastline?
When wave hits coast, throws pebbles and sand against cliff face.
Knock off small parts of cliff and cause undercutting.
Also known as abrasion.
How does attrition erode a coastline?
Particles transported by sea hit against one another, reducing size and making them more rounded, like in rivers.
How does solution erode a coastline?
Seawater dissolve away rocks from seabed or cliffs.
Process especially effective on limestone coasts and can create spectacular caves.
Also known as corrosion.
How does hydraulic action erode a coastline?
Power of sea can physically wash away soft rocks like boulder clay.
Under storm conditions with strong waves, hundreds of tonnes seawater hit coast.
Also, air can be trapped in small cracks within cliff when wave breaks against it.
Compressed air widens cracks, leading to sections of cliff breaking away from main cliff face.
What are the 4 processes of transportation along a coastline?
Solution, suspension, saltation, traction.
How does solution transport particles along a coastline?
Minerals dissolved in seawater and carried in solution.
Load not visible.
Load can come from cliffs made of chalk or limestone, and calcium carbonate carried along in solution.
How does suspension transport particles along a coastline?
Small particles carried in water (e.g. silts and clays), can make water look cloudy.
Currents pick up large amounts of sediment in suspension during storms, when strong winds generate high energy waves.
How does saltation transport particles along a coastline?
Load bounced along seabed (e.g. small pieces shingle or large sand grains).
Currents cannot keep larger and heavier sediment afloat for long periods.
How does traction transport particles along a coastline?
Pebbles and larger sediment rolled along seabed.
How does the sea transport material?
Longshore drift occurs when waves hit beach at angle.
Swash moves up beach at angle, but backwash draws down straight.
Over time, material transported along coast.
How does the sea deposit material?
When load of seas and oceans builds up on coastline it forms beaches, spits and sand dunes.
Material added by constructive waves.
Occurs during periods of light winds.
Summer most common period for deposition in UK.
Constructive waves most effective in sheltered coastal locations such as bays.
How do headlands form?
Stretches of coastline do not erode evenly.
Sections of cliff made from hard resistant rock resist hydraulic action and corrosive power of sea.
They stick out forming headlands.
Face full force of destructive waves and often located at coastal landforms created by erosion, such as caves, arches and stacks.
What are bays like?
Crescent-shaped indents between two headlands, made from soft rock (e.g. clay or sandstone), erode easily.
Water is shallow and calm as sheltered, enables sand to be deposited, forming beaches.