Coasts Flashcards
Features of constructive waves
Low energy, low frequency, low height, strong swash, long length, leave gently sloped beaches, cause deposition.
Features of destructive waves
High energy, high frequency, high height, strong backwash, short length, leave steep beaches, cause erosion.
What are 4 coastal erosion processes?
Hydraulic action, abrasion, attrition, solution.
What is hydraulic action?
The sheer power of the waves crashing against the rocks, forces air and water into cracks in the rocks, compresses it, and blows the rock apart when the pressure is released.
What is abrasion?
Rocks and pebbles carried by the waves eroding the rocks as they are thrown against the cliffs.
What is attrition?
Rocks and pebbles from the waves smash against each other, wearing each other away, gradually becoming smaller, rounder and smoother.
What is solution?
Chemicals in the seawater dissolve minerals in the rocks, causing them to break up.
Concordant coastlines?
Areas of the coast where there is only one rock type.
Discordant coastlines?
Areas of the coast with more than one rock type.
Formation of headlands and bays
Due to some rock types e.g. limestone being more resistant, differential erosion occurs meaning the softer rock band (like clay) are eroded more quickly than the harder rock types.
The waves cause erosion of the cliffs through processes such as hydraulic action where the force of the waves push air into cracks, causing pieces of rock to weaken and break away.
Over time, the softer rock erodes further inland, creating a sheltered area known as a bay which often has a beach.
Bands of more resistant rock types are left jutting out into the sea, these are known as headlands.
Formation of a wave cut platform
The sea attacks the bottom of a cliff through the processes of hydraulic action, where the water smashes against the rock, abrasion, where the material in the water smashes against the rock, and solution, where chemicals in the water react with the rock causing more erosion.
All of the processes come together to form a wave cut notch at the base of the cliff. Over time, the wave cut notch is eroded further backwards and when the weight and force of the cliff above becomes too great, the cliff will fall into the sea.
The backwash from the sea carries the material away from the cliff face. The process starts again and repeats itself over time. As the process is repeated, the remaining rock at the base of the cliffs reduces the force of the waves, this means a wave cut platform is left on the landscape leading up to the new cliff face.
Formation of a stack
-Small crack in a cliff is hit by waves
-Crack is widened by hydraulic action
-The rock is eroded further by erosional processes like abrasion
-A cave is formed
-A sea arch forms when the cave is eroded through the front and back of the cliff
-Waves erode the sides of the sea arch, widening it, and the top collapses when it doesn’t have enough support
-Stack is the material left standing, independent from the main island
-The bottom of the stack is eroded until it collapses and leaves a stump
Longshore drift
The swash transports material in constructive waves towards the beach.
The direction of the swash is determined by the angle of the prevailing wind.
The swash deposits materials on the beach.
Backwash removes materials from the beach at a right angle and carries it back out to sea, before swash takes over and transports it back to the beach.
The processes of swash and backwash continues and effectively moves materials along the beach.
What is a sand spit?
A long narrow ridge of sand/shingle.
Sand spit formation
-Coastline changes direction.
-Sand is transported by longshore drift.
-It is deposited in a sheltered area.
-Deposited sand builds up.
-Deposition continues until the beach extends into the sea = spit.
-Spits can also develop a curved/hooked end - prevailing wind/wind direction.
-Mud flats or salt marshes can develop in an area of calm water behind the spit.
