Landforms Flashcards
(33 cards)
What are beaches?
A depositional landform, beaches are accumulations of sediment and represent important temporary stores within a sediment cell.
How are beaches formed?
Beaches form between the highest point reached by storm waves and the lowest spring tides.
Largely formed of sand and shingle, and the larger sediment tends to be at the top of the beach because it takes high energy storm waves to deposit this material.
Outline sand beaches.
Sand beaches tend to be gentle in slope (less than 5*) because the sand grains are small and easily compacted which means that little water percolates through the sand therefore the majority of water that moves up the beach also returns through backwash so the beach is smooth and flattens the beach.
Outline shingle beaches.
Shingle beaches are steeper (10 - 20*) because the larger sediment size means that it’s less easily compacted and therefore the waves, having broken, percolate back through the shingle.
Therefore the backwash doesn’t really transport material back down the beach. This creates a beach that’s unlikely to be eroded.
What are storm berms?
At the top of a beach, a wider, flat area of sediment is deposited by a strong awash during spring high tides.
What are berms?
In a beach, below a storm berm, there are a series of ridges which mark a series of high tide lines and are built by constructive waves.
What are cusps?
Cusps form where the waves break directly onto the beach where both swash and backwash are strong and generally form at the junction where the sand on the lower part of the beach meet the shingle on the upper part of the beach.
The curved sides of the cusp channel incoming swash into the centre of the cusp which creates a stronger backwash flowing out of the centre of the cusp which further deepens the cusp.
What are ripples?
They form in the sand dune due to the action of of the tide moving back and fourth across the sand.
What are ridges?
At the LWM, ridges form where backwash deposits sediment. These run parallel to the coastline and are broken by runnels where water runs through to return to the sea
What are the two types of beach?
Swash aligned and drift aligned.
Outline swash aligned beaches.
- Waves arrive parallel to the shore, therefore swash and backwash occur.
- Experience minimal longshore drift
Outline drift aligned beaches
- waves approach at an angle, therefore longshore drift occurs.
- can have considerable amounts of sediment transported long distances across them; often accumulating in the formation of a spit.
What is the difference between landforms and landscapes?
Landforms are individual components of a landscape (e.g. cliffs, beaches, arches).
Whereas landscapes are made up of a number of landforms which give them their key characteristics.
What is a good example of a negative feedback loop in landforms?
Wave cut platforms.
Outline wave cut platforms as an example of a negative feedback loop.
Originally, the wave cut platform is fairly smooth and flat (sloping at less than 5*), and may be smoothed by further abrasion.
Over time, waves break further and further out to sea and have to travel over more and more platform before the cliff. This means that the wave energy is dissipated before it reaches the cliff.
Therefore, the rate of the cliff erosion decreases and the platform caresses to grow. So unlikely to grow wider than 500m.
What is a spit?
A long, narrow ridge of deposited sediment which are joined to the mainland at one end and stick out into the sea or across the estuary or bay.
What are the 2 types of spit?
Simple and compound
What are simple spits?
Simple spits can either be straight or recurved but do not have minor spits or recurved spits along their landward edge.
What are compound spits?
Compound spits have a series of minor spits or recurved ridges along their landward side which may show their former position.
How do spits form?
Material is moved along the coast through longshore drift, but where the coast changes direction (often due to an estuary), sediment starts to build up in the sheltered lee of the headland which begins to form a spit.
During storms, larger sediment is deposited above the HWM, making the spit more permanent. Finer material continues to be moved along the spit through longshore drift and deeper into the estuary where energy is lost and the sediment is deposited which further extends the spit.
The end of the spit may become recurved as wave refraction and secondary winds and waves carry and deposit sediment round the end of the spit
How does a compound spit form?
The end of the spit becomes recurved as wave refraction and secondary winds and waves carry and deposit sediment round the edge of the spit.
If it recurved enough, this is another change in coastline direction so the spit may continue to grow in its original direction. This may happen a number of times, forming a compound spit.
How is a salt marsh formed?
A river which is flowing out to sea is likely to prevent a spit form growing right across an estuary, but very fine sediment may be deposited by the river in the ‘slack’ low energy zone behind the spit.
This forms a salt marsh which is an important coastal habitat and may be further stabilised by the growth of salt tolerant plants.
What is a tombolo?
A beach that has formed between a small island and mainland.
How is a tombolo formed?
Deposition occurs where waves lose their energy and so the tombolo begins to build up.
