Coasts Flashcards
what is the function of a sea wall
sea walls reflect the energy of the waves back to the sea. They protect the base of the cliffs, lands and buildings from erosion and can prevent coastal flooding.
What is the function of rock armour
rock armour consists of larger boulders piled up on the beach. These absorb the energy of the waves and may allow the build up of a beach
explain how different landforms may be created by the transport and deposition of sediment along the coast (6)
The landforms are created by the process of longshore drift.
Some eroded material is up caught up within the waves and is
carried by the sea along the coastline. Material is carried along
the shore in a zigzag fashion by waves as they swash material
up the beach at an angle and backwash material down the
beach at a right angle. The angle of swash is determined by the
prevailing wind. On the map the direction is from west to east
as shown by the prevailing wind, and the shape and growth of
the spit.
Beaches are areas of sand, pebbles and shingle that are
formed by deposition produced by wave processes and by
longshore drift. Gently sloping beaches are formed by strong
destructive waves that backwash more material away from the
beach than they swash up the beach
explain the process of long shore drift
- when the prevailing wind is at 45 degrees to the coastline
- the swash is parallel and the backwash is at 90 degrees due to gravity
-the swash deposits sediment and the backwash picks it up
-this moves sediment in a zigzag pattern across the beach
-this will cause a build up of sediment on one end of the beach
explain how headlands and bays form
- headlands and bays form where there is a discordant coastline
-alternating layers of hard and soft rock
-soft rock such as clay is eroded faster than the hard rock such as chalk
-over time, the softer rock will retreat leaving a headlands of hard rock sticking out on either side
explain how cliffs and wave cut platforms are formed
- when waves break against a cliff, usually of hard rock, erosion close to the high tide will wear away at the cliff, forming a wave cut notch
- over time the notch will get deeper, undercutting the cliff
- Sub-aerial weather also weakens the cliff from above.
- eventually, the overlying cliff can no longer support its own weight and collapses due to gravity.
- This process repeats leaving a gently sloping rocky platform called a wave-cut platform.
explain the formation of cave, arch, stack and stump
- abrasion and ha from the waves will from a crack in a headland where there is a fault in the rock
- wave refraction occurs around a headland, so wave energy is also concentrated on either side of the headland.
- Repeated wave action will widen to form a cave
- the cave will continue to be eroded until it cuts through the headland to make an arch.
- the force of the waves, ha, and sub-aerial weathering will cause the arch to expand until the roof of the arch is too heavy and collapses
- this leaves a tall stack.
- the stack is eroded and collapses carving a stump
explain how a beach is formed
a beach normally forms in a sheltered area such as a bay. Wave refraction causes wave energy to be concentrated on the headland and dispersed at the bay. as the waves lose their energy, they deposit the sediment they are carrying to form a beach. A constructive wave will have a stronger swash than backwash which builds up a beach. Destructive waves have a stronger backwash so will remove sediment from the beach
how is a spit formed
- when the prevailing wind is at 45 degrees to the coastline
- the swash is parallel and the backwash is at 90 degrees due to gravity
-the swash deposits sediment and the backwash picks it up
-this moves sediment in a zigzag pattern across the beach
-this will cause a build up of sediment on one end of the beach - when there is a change in the direction of the coastline, the sediment continues to be deposited out into the sea
- when there is a change in the prevailing wind direction a hook can form on the end
how is a bar formed
- when there is a change in the direction of the coastline, the sediment continues to be deposited out into the sea
- when there is a change in the prevailing wind direction a hook can form on the end
- continued lsd can cause a spit to grow across a bay to join two headlands
- this forms a bar, behind which is a bay wherein the sea is trapped forming a lagoon
how are sand dunes formed
when there is a plentiful supply of sand, a wide beach and a strong onshore wind, sand will be blown indland. When sand hits an obstacle, it will get deposited and start too build up. Embryo dunes form first and will become stabilised by marram grass, which is adapted to strong winds and high salinity. The roots help bind the sand together forming foredunes and tall yellow dunes. Over time, decomposing vegeatation adds organic matter to the sand making it more fertile, allowing a great range of plants to colonise the dunes.
