Dorset coast, Southern England Flashcards
1
Q
The Foreland, Old Harry and his wife
A
- Discordant coastline (perpendicular).
- Swanage and Studland bay either side of the headland (The Foreland).
- Waves attacked vertical lines of weakness in the headland until a crack forms by hydraulic action.
- the crack continues to expand until it becomes a cave.
- The rock continues to erode until the cave brakes through the headland to form an arch.
- Marine erosion and sub-aerial processes cause the roof to collapse forming a stack (Old Harry).
- Weathering and erosion continue to attack the stack until a stump is left (Old Harry’s Wife).
2
Q
Durdle Door (arch)
A
- Concordant coastline (parallel).
- Limestone arch.
- Formed on a headland near Lulworth.
- Crack => cave => arch.
- The arch is gradually been broken down by mechanical (freeze-thaw and salt), chemical (acid rain) and biological weathering.
3
Q
Lulworth Cove
A
- Concordant coastline (parallel).
- Small bay formed after a gap was eroded in a band of Purbeck limestone.
- Behind the limestone is a band of shale and clay that is less resistant to erosion.
- Therefore it has bee eroded and transported away, forming a bay.
- The limestone cliffs forming the back of the bay are vulnerable to mass movement, and sometimes experience small slides or slumps.
4
Q
Chesil Beach (depositional landform)
A
- Tombola (a type of spit that extends out to an island).
- It joins the Isle of Purbeck to the mainland.
- Formed by longshore drift (transportation).
- Behind Chesil Beach is a shallow lagoon called the Fleet Lagoon.
5
Q
Swanage Bay
A
- Discordant coastline (perpendicular).
- The cliffs backing Swanage Bay are made of clay (soft rock).
- Towards the northern end of the bay, the cliffs are covered in vegetation, stabilising them and protecting them from weathering.
- Elsewhere, the cliffs are not stabilised by vegetation, so wet weather weakens them and can cause slumps.
- Longshore drift carries material away (mainly gravel) from the south to the north of the beach in the bay.
- Erosion is the dominant process in the bay - the beach has been losing material for decades.
6
Q
Mudeford spit (depositional landform)
A
- A spit is an extended stretch of beach material that projects out to sea and is joined to the mainland at one end.
- Longshore drift brings material from Bournemouth beach.
- When there is a break in the coastline and a slight drop in energy, longshore drift will deposit material at a faster rate than it can be removed.
- A change in prevailing wind direction often causes the end of spits to become hokes.
- Water is trapped behind the spit, creating a low energy zone. As the water begins to stagnate, mud and marshland begins to develop (Stanpit Marsh).
- Mudeford spit will never fully close off Christchurch Harbour because it crosses the River Stour where the flow of the river removes the material faster than it can be deposited.
7
Q
Beach formation (depositional landform)
A
- Longshore drift transports material from further down the coast.
- Constructive waves help to build up beaches.
- At the back of the beach, strong swash at spring high tide level will create a storm beach (a ridge of big boulders thrown by the largest waves usually above the high tide mark).
- Below this will be a series of ridges called berms marking the lower tide levels.
- Large material is deposited at the back of the beach during times of high energy e.g. during a storm.
- Most waves break near the shoreline, so sediment near the water is more effectively broken down by attrition.
- Sandy beaches have gently sloping profiles (around 5°). This is because its small particle size allows very little percolation, so most swash returns as backwash and material is carried down the beach.
- The larger the size of material, generally the steeper the gradient of the beach (around 10°-20°). This is because water rapidly percolates through shingle, so the backwash is somewhat limited in its ability to transport material back down the beach.
