Coastal Processes Flashcards
What is fetch?
-the amount of open water over which a wave has passed
What does the energy of the wave depend on?
- strengths of the wind
- length of time
- fetch
- depth of the seabed
What is backwash?
-movement of water down the beach
What is swash?
-movement of water up the beach
What are the prevailing winds?
-the wind which blows most often
What are constructive waves and their properties?
- build up beaches
- each wave is low
- as the wave breaks it carries material up the beach in its swash
- beach material is deposited as the backwash soaks into the sand or slowly drains away
- gentle waves
What are destructive waves and their properties?
- destroy beaches
- waves are usually high and very frequent
- backwash has less time to soak into the sand
- as waves continue to hit the beach there is more running water to transport the material out to sea.
What is attrition?
-material carried by waves collide with one another and so are smoothed and broken down into smaller particles
What is hydraulic action?
-process involves the force of water against the coast
1-waves enter cracks in the coastline and compress the air within the crack
2-when the wave retreats the air in the crack expands quickly causing a minor explosion
3-process is repeated continuously
What is abrasion?
- process by which the coast is worn down by material carried by the waves
- waves throw these particles against the rock, sometimes at high velocities
What is solution?
- chemical action of sea water
- acids in the salt water slowly dissolve rocks on the coast
How are cliffs created?
- erosion: hydraulic action, abrasion, solution, attrition
- currents generated by waves and tides
- weathering
- human activity: can increase runoff and erosion, sea defences
Where does weathering affect ?
-weathering affects the top of the cliff
What does erosion affect?
-erosion affects the bottom of the clim
What are some hard coastline features?
- bays and headlands
- wave-cut notches, platforms and cliffs
How are bays and headlands formed?
- formed when soft and hard rock are together
- soft rock, such as clay, erodes easier than harder rocks, such as limestone
- the hard rock will erode slower than the soft rock and the two areas of hard rock surround an area of soft rock, a bay and headland will be formed
How are wavecut cliffs, platforms and notches created?
1-weather weakens the top of the cliff
2-sea attacks the base of the cliff forming a wave cut-notch, and above a wave-cut cliff
3-notch increases in size and causes the cliff to collapse
4-the backwash carries the rubble towards the sea forming a wave-cut platform
5-process repeats and the cliff continues to repeat
How are stumps created?
1-hydraulic action causes faults in hard rock to become caves
2-the waves attack both sides of the headland, causing the back walls of two caves to erode and the caves to meet up, forming an arch
3-weathering and erosion continue to attack the arch and the top becomes weak and collapses, forming a stack (or pinnacle if it is very narrow)
4-over time the stack becomes smaller and smaller and will form a stump
How does slumping occur?
1-dry weather causes cracks to appear
2-rainfall causes cliffs to soak up the rain and the cliff becomes saturated and heavier and unstable
3-due to gravity and the lubrication provided by the rainfall, the rocks become increasingly unstable and slump under their own weight down the slipping planes
What is longshore drift?
- prevailing winds cause the waves to swash at 45 degrees the coast and backwash at 90 degrees.
- as the waves hit the coast, sediment is transported up and down the beach, depositing sediment on the beach before transporting it elsewhere
What is a drift aligned beach?
-formed when waves approach at an angle to the coastline.
The swash moves sediment up the beach at the same angle, while the backwash move the beach under the force of gravity
-sediment is moved along the beach by a process called long shore drift
-creates an beach with an uneven profile
-can be slowed down with groynes
What is a swash aligned beach?
- formed when waves approach parallel to the coastline, and swash and backwash move sediment up and down the beach.
- creates a wide beach with an even profile along the shore line
How are spits formed?
1-are formed where large amounts of sediment are transported and where the coastline suddenly changes direction to leave a shallow area of water
2-deposition occurs in shallow water by the headland and the spit slowly builds up and extends length
What are some uses for spits?
- provides different/rare/specific habitats (salt marshes)
- attracts wild life (making e.g. bird watching possible)
