Geography Revision – Coasts
Inputs are from - river sediment, sediment from cliffs that have been eroded or suffered landslides, and sediment transported by waves from offshore.
Processes are from - wave action, tidal movement, erosion, weathering, transportation, and deposition.
Outputs are - sediment washed out to sea, and deposited further along the coast.
Waves, Erosion and Deposition:
1. Waves are created by blowing over the sea. Friction from wind and sea makes the water go in a circular motion.
2. Effect of wave depends on the height. Height is affected by wind speed and fetch. Fetch is the maximum distance of a sea, the wind has blown over in creating the waves. A high wind speed + long fetch creates high waves.
3. Waves approach the shore they break. Friction with the sea shows the bottom of the waves and makes motion elliptical.
4. Water washing up on the beach is swash. The opposite is backwash.
Low frequency (6, to, 8 waves per minute).
Low and long, which gives them more elliptical cross profile.
Powerful swash carries material up the beach and deposited.
Higher frequency (10, to, 14 waves per minute).
High and steep, which gives them more circular cross profile.
Strong backwash removes material.
Sub-aerial weathering occurs along the coastline:
1. Sub-aerial weathering are coastal processes that are not linked to the actions of the sea. Including freeze-thaw weathering and salt weathering. Weathering weakens cliffs and makes them more vulnerable to erosion.
2. Throughflow + run off caused by heavy rain can make cliffs unstable and increase probability of mass movement.
3. Mass movement is the movement of material downhill due to gravity, it includes landslides, slumping and rockfalls.
5 ways of eroding the coast:
1. Abrasion or Corrasion - rocks smash and grind against rocks and cliffs.
2. Hydraulic action - air in cracks in cliffs are compressed when waves crash in. Pressure exerted by the compressed air breaks off rock pieces.
3. Quarrying - the energy of a wave as it breaks against a cliff is enough to detach bits of rock
4. Corrosion - soluble rocks got gradually dissolved by the seawater.
5. Attribution - bits of rock in the water smash against each other and break into smaller bits.
Rates at which a stretch of coastline is eroded depends on several factors:
1. The width of a beach - distance between high + low tide marks. Beaches slow down waves reducing erosion power. Therefore a wide, flat beach will protect cliffs more than a narrow one.
2. Breaking point of waves - a wave that breaks at the foot of a cliff transfers the most energy to the cliff causing most erosion.
3. The aspect - if the coastline faces the dominant wind and wave direction, erosion will be faster.
4. Fetch - the longer…