Coastal Depositional Landforms - Beaches, Sand Dunes, Spits & Bars | AQA GCSE 9-1 Geography

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What are the coastal depositional landforms? What is the sand dune succession? What are shingle beaches? How are sand dunes formed? How are spits and bars formed? What is a lagoon?

This is the fortieth video for the AQA GCSE 9-1 Geography course, and the seventh video of the Physical Landscapes topic.

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Video Script:
Depositional landforms are formed by the sediment that is deposited by the sea along the coast.

Beaches are formed in sheltered areas like bays by the deposition of sediment. Constructive waves build up beaches due to their strong swash and weak backwash.

Beaches are not always made of sand. Sandy beaches are formed in low-energy environments where the water is shallower. In higher-energy environments, shingle beaches are formed, which are covered in pebbles. This is because the waves wash away the sand, only leaving behind pebbles that have been eroded from nearby cliffs.

A beach profile shows the cross-profile of a beach. Berms are ridges that show the high tide and storm tide lines. Sandy beaches typically have gently sloping profiles whereas shingle beaches can be steeper.

The cross-profile also shows the next depositional feature, sand dunes.

Sand dunes are developed in a succession, known as a psammosere.
Embryo dunes are the first sand dunes, formed around small obstacles such as wood or rocks.
Pioneer plants such as prickly saltwort begin to colonise the dunes, which helps to stabilise them.
Sand continues to accumulate, forming foredunes, which have more vegetation such as lyme grass.
Yellow dunes are found just beyond foredunes with species such as marram grass.
Over time, decaying vegetation adds organic matter to the soil resulting in a much wider range of vegetation at grey dunes, which are named for the colour of the soil.
Eventually, far away from the influence of the sea, the climatic climax is reached, which is forest in the UK.
Another feature of sand dunes are dune slacks which are small ponds that can form between dunes due to the wind.

Spits are another coastal depositional feature, with a notable example being Spurn Point on the Holderness Coast. They are long, narrow stretches of sand reaching out into the sea. They form where there is a sudden change in the shape of the coastline, such as at the mouth of a river. Longshore drift carries sediment along the coast and starts to deposit it out to sea, forming the spit. This continues over time, extending further out to sea.

Strong winds can cause the end of the spit to curve; this is called a recurved end. The area behind a spit is very sheltered, resulting in the formation of salt marshes or mudflats.

Some spits can continue to grow until they reach the other side of a bay. This forms a bar. The water trapped behind the bar is known as a lagoon.

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GCSE Geography
12/05/2023
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