Contrasting Coasts Flashcards
What two types of rock do hard rock coasts contain?
Resistant rocks (e.g. granite) and sedimentary rock (e.g. limestone).
Give two examples of hard rock coasts.
Flamborough Head and Lulworth Coast.
What two materials are soft rock coasts made of?
Clay and shale.
What are two examples of soft rock coasts?
Christchurch Bay and the North Norfolk Coast.
Describe how a crack in the coastline can become a stump?
1) Hydraulic action creates a crack in the coast.
2) The crack grows until it becomes a cave.
3) The cave breaks through the headland to form an arch.
4) The arch is eroded until it collapses leaving a stack.
5) The stack is eroded until it leaves a stump.
What are the three ways erosion happens on the coastline?
- Hydraulic Action
- Attrition
- Abrasion
What is hydraulic action?
Air is compressed into cracks in the cliff face by water. When the wave retreats the air explodes out.
What is attrition?
When small pieces of sediment are knocked into each other.
What is abrasion?
When small pieces of sediment are picked up by waves and slammed into the cliff face.
What is a concordant coastline?
A coastline where the strata run parallel to the sea. This means the coastline is made of one type of rock.
What is a discordant coastline?
A coastline where the strata are perpendicular to the sea. This means the coastline is made up of lots of different types of rock.
At what type of coastline are coves formed?
Concodrant
Describe how coves are formed.
1) Erosion breaks through the first layer of rock at a coastline, revealing less resistant rock behind it.
2) The waves erode the softer rock forming a cove.
3) The cove stops widening when it hits harder rock again.
At what type of coastline are headlands and bays made?
Discordant
How are headlands and bays made?
The rocks at discordant coastlines erode at different speeds. The softer rock erodes faster forming bays whereas the harder rocks form headlands.
What coastline is a good example of headlands and bays?
The South-West Irish coast.
How are waves formed?
Wind blows across the sea create friction which becomes waves.
What three factors affect the size of a wave?
- The strength of the wind
- The duration of the wind
- The fetch of the wind
What is the fetch of a wind?
How far the wind has travelled.
What type of waves do we get in the summer?
Constructive waves
What are constructive waves like?
- Strong swash
- Long wavelengths
- Low amplitudes
What effects do constructive waves have on sediment on the beach?
They transport sediment up the beach.
What type of waves do we get in the winter?
Destructive waves
What are destructive waves like?
-•Strong backwash
- Short wavelengths
- Larger amplitudes
What effects do destructive waves have on sediment on beaches?
- They erode and making the beach steeper.
* Some sand is carried offshore and form an offshore bar.
Describe longshore drift.
•The prevailing winds push waves to shore.
2) The swash pushes sediment up the beach in the direction of the prevailing wind.
3) The sediment falls back with the backwash at a 90 degree angle.
How are sand dunes formed?
Onshore winds blow sand inland forming sand dunes parallel to the shore.
How are bars formed?
When there’s a sudden change in the shape of the landscape, longshore drift continues to deposit sediment until it reaches land again.
What do you call the body of water on the other side of a bar?
A lagoon