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Geography AQA Coasts and Landforms - Coggle Diagram
Geography AQA Coasts and Landforms
Erosion
Abrasion
Eroded rocks in the sea's load are hurled at the cliff face, or grind along a rock platform, eroding away and smoothing the cliff and sea bed.
Hydraulic Action
Also called hydraulic power, the force of the waves as they hit the cliff. this forces air into pre-existing cracks sin the rock face and causes the rocks to break apart.
Solution
This is where the sea water dissolves certain types of rocks and erodes them away
Attrition
Rocks in the sea's load hit and rub against each other, becoming smaller and more rounded - erosion of the rocks themselves on the load, not the cliff itself.
Transportation
Solution
The same as the erosional process, rocks are dissolved into the sea and carried invisibly via solution
Suspension
Small particles such as sand and silts are carried by being suspended in the flow of the water
Saltation
Small rocks/pieces of shingle are bounced along the sea bed
Traction
Larger rocks and pebbles are rolled along the sea bed
Constructive Waves
Build up beaches, deposit sediment
Strong swash
Weak backwash
Don't have enough energy to erode the beach
Deposition:
Waves lose energy as they roll up the beach, deposit their load
Low frequency
Long and low waves
Destructive Waves
Remove sediment, erode beaches and coastlines
High frequency
High and steep
Weak swash
Strong backwash
Enough energy to pick up sediment and drag it back out to sea
Erosion
Hydraulic action
Attrition
Longshore Drift
What conditions are needed
A prevailing wind
Beach with constructive waves
Sediment to be carried
What is it
Longshore drift is a process by which sediment is moved along the coastline in a zigzag movement perpendicular to the angle of the beach
Step by Step
Prevailing wind blows waves carrying sediment onto the beach at a 45 degree angle
As the backwash goes out to sea, sediment is brought back down the beach straight back into the ocean
The sediment is carried out to sea perpendicular to the angle of the coastline
Over time as this process repeats, sediment is shifted along the beach in a zig -zag pattern
This can cause a build up of sediment at the end of the bay or beach coastline
This, finally, can cause a change in the shape of the beach
Spits and Bars
Conditions
A beach with the process of longshore drift occurring
Deposition processes
Prevailing wind
Headlands for the bar/spit to grow across
What is it?
Spits are a projected stretch of sediment that reaches out to sea from a headland. A bar is when further material is deposited on the end of the spit and the sediment re-joins the mainland on both ends, cutting off the bay behind it
Step by step
Longshore drift blows the sediment down the beach until it reaches the end of the coastline
From here, the sediment is deposited out to sea, in the water between the bay and the next headland.
Often, a curved hook is created by a second wave and wind direction curving the end of the spit
Waves cannot get past the spit, creating salt marshes in the sheletered area behind them
As time grows on, the spit lengthens until is has reached to the other side of the bay, the next headland
It is now called a bar, and the water behind it, a lagoon
Headlands and bays
What are they?
Headlands and bays make up the coastline. Headlands are sections of harder rock that jut out to the sea whilst bays are sections of softer rock that become eroded inland
Conditions needed
A discordant coastline (bands of alternating hard and soft rock)
Erosions processes of abrasion and hydraulic action
Destructive waves
Step by step
A discordant coastline with alternating bands of hard and soft rock begins to be eroded by destructive waves
The processes of abrasion and hydraulic action erode the coastline as the waves are hurled against the cliff
The soft rock erodes faster than the hard rock and begins to retreat inland, while the hard rock is left jutting out to sea
The hard rock creates a headland jutting out to sea whilst the eroded soft rock creates a sheltered bay with constructive waves.
Caves, arches, stacks and stumps.
What are they?
Caves are hollow features in the face of a headland, arches are caves that hollow through the headland, stacks are free standing columns of rocks and stumps are collapsed stacks.
Conditions needed
For a cave to form, there must be a headland protruding out to sea, and the processes of hydraulic action, and abrasion.
For and arch to form, there must be a pre-standing cave and the continuation of hydraulic action, and the other key erosional processes
For a stack to form, there must be an unsteady, top heavy cave and the continued key erosional processes
For a stump to form, there must be a stack and the key erosional processes
Step by Step
Firstly, a headland begins to be eroded by weathering and hydraulic action. The air and sediment forced into the natural cracks in the headlands eroded a hole into the headland which becomes a cave after a long time.
After the continuation of hydraulic actions, abrasion on the cave, it becomes eroded through to the other side forming an arch.
The destructive waves at the headland attack the base of the arch with hydraulic action and abrasion, causing it to become top heavy.
Eventually, the eroded bases cannot support the weight of the arch anymore, and so it collapses to leave a tall free-standing column of rock, and the now separate headland.
Over time, hydraulic action and abrasion wear down the stack until it collapses, leaving a stump just above the level of the water.
Coastal management schemes
Hard engineering
Hard engineering is the expensive and short-term construction of physical features to protect the coast from erosion.
Soft engineering