Costal Landforms Flashcards
What is a discordant coastline?
A coastline made up of different types of rock at right angles to the sea, some which are more resistant to erosion than others.
What is a concordant coastline?
A coastline with the same type of rock along the whole coastline.
what are the coastal landforms formed by erosion
*stumps
*bays
*headlines
*wavecut platform
How are headlands and Bays formed?
•A discordant coastline has layers of hard and soft rock at right angles to the coast. The sea erodes the soft rock more easily.
•Over time the less resistant rock is eroded by hydraulic action (where air is forced into the cracks in the rock, weakening them) and abrasion (small pieces of rock in the water grinding against the cliff) forming a bay.
•The resistant (harder) rock is left sticking out into the sea. This is called a headland.
•Sand is deposited in the sheltered bay forming a beach.
How are cliffs formed?
Cliffs are shaped through a combination of erosion and weathering
- the breakdown of rocks caused by weather conditions. Soft rock, e.g. sand and clay, erodes easily to create gently sloping cliffs.
-Hard rock, e.g. chalk, is more resistant and erodes slowly to create steep cliffs
How is a wave cut platform formed?
1)Waves cause most erosion at the foot of a cliff, forming a wave-cut notch which is enlarged over time.
2)Repeated erosion causes the rock above the notch to become unstable and it eventually collapses.
3)The collapsed material is washed away and a new wave-cut notch starts to form.
4)After repeated collapses the cliff retreats, leaving a wave-cut platform
How are stumps formed?
1)The resistant rock that makes up headlands often has weaknesses like cracks.
2) Waves crash into the headlands and enlarge the cracks (mainly by hydraulic power and abrasion)
3) Repeated erosion and enlargement of the cracks causes a cave to form.
4)Continued erosion deepens the cave until it breaks through the headland to form an arch
5)Erosion continues to wear away the rock supporting the arch, until it eventually collapses.
6)This forms a stack an isolated rock that’s separate from the headland which is then eroded to form a stump
what coastal landforms are caused by deposition?
-beaches
-spits
-bars
-sand dunes
How are beaches formed?
•Beaches are made up from eroded material that has been transported from elsewhere and then deposited by the sea.
•For this to occur, waves must have limited energy, so beaches often form in sheltered areas like bays where there are more constructive waves that build up beaches as they have a strong swash and a weak backwash.
•Overtime, the beach material will accumulate and will be composed of different sediments from pebbles to fine sand
What are sand dunes?
Sand dunes are large heaps/mounds of sand that are held together by long-rooted grasses. They are found at the back of the beach.
What do sand dunes need to form?
•A large flat beach
•A large supply of sand
•A strong onshore wind to move sand
•An obstacle such as driftwood for the dune to form against.
How are sand dunes formed?
1)|Sand dunes are formed when sand deposited by longshore drift is moved up the beach by the wind.
2)Obstacles (e.g. driftwood) cause wind speed to decrease so sand is deposited, forming small embryo dunes.
3) Embryo dunes are colonised by plants, e.g. Marram grass.
4)The roots of the vegetation stabilise the sand, encouraging more sand to accumulate there. This forms foredunes and, eventually, mature dunes. New embryo dunes form in front of stabilised dunes.
What is a spit?
A long narrow finger of sand or shingle jutting out into the sea from land. They form on coasts where there is significant long shore drift
How are spits and bars formed?
-The zigzag movement of sediment along a shore caused by waves going up the beach at an oblique angle (Swash) and returning at right angles (backwash). This results in the gradual movement of beach materials along the coast.
-This process continues down the entire beach, leading to mass transportation of sediment, until the mainland ends.
-At this point, sediment is deposited and builds up causing an extension of the mainland out into the sea as a spit.
-bars are formed when 2 headlines join together as a spit grows accross a bay
What are the features of a sandy beach?
•shallow gradient
•constructive waves are more dominant
•sand dunes at the back of beach
