Coastal landforms of deposition

Beaches

A is a build-up of sand and shingle (pebbles), deposited by waves between low tide and the highest storm waves. Beaches form where the waves lose energy, especially in .

Sand beaches are wide and gently sloping: the swash soaks into the sand, so the backwash is weak.
Shingle beaches are narrower and steeper: the backwash drains away through the gaps between pebbles.

The sea builds beaches up when constructive waves are common, often in summer, and wears them down in winter storms, when destructive waves are common.

Key terms

Sand dunes

are hills of sand built by the wind behind a beach:

At low tide, the wind dries the sand and blows it inland.
The sand piles up against an obstacle, such as driftwood or a plant, making a small .
grows on it. Its long roots hold the sand together, and the plant grows up through new sand, so the dune keeps getting higher.
Behind, older dunes have more plants and soil, and are grey with dead matter; the newer dunes nearest the sea are yellow.

Dunes protect the land behind them from the sea, but walkers and vehicles can easily damage them.

Key terms

Spits

carries sand and shingle along the coast.
Where the coast changes direction, as at the mouth of a river, the drift carries on, depositing material out into the sea.
Over time, this builds a long, narrow ridge of sand and shingle, joined to the land at one end: a .
Changes in the wind and waves curve the end round into a recurved (hooked) end.
In the sheltered water behind the spit, mud is deposited and a forms.

Key terms

Bars

A forms when a spit grows right across a , joining two headlands.

Longshore drift carries material across the mouth of the bay.
If the water is shallow and the waves are gentle, the ridge can reach the other side.
The water trapped behind the bar becomes a .

For example: Slapton Sands, in Devon, is a shingle bar with a freshwater lagoon, Slapton Ley, behind it.

Exam tip

To explain a spit or bar, say where the material comes from, how it moves, and why it is deposited.

Key terms

Exam practice

Plan your own answer first, then open the model answers to see what each level looks like.

6 marks · about 6 minutes

Explain the formation of a spit.

Explain means: Give the reasons why something happens, developing each point with "because" or "so".

Level 1 (Basic)· 2/6 marks (band 1–2)

A spit is made by longshore drift moving sand along the coast. It sticks out into the sea.

Why this level: Correct basic idea, but not explained. To reach Level 2: explain why material is deposited out to sea where the coast changes direction, and how the spit grows.

Level 2 (Clear)· 4/6 marks (band 3–4)

Longshore drift carries sand and shingle along the coast. Where the coast changes direction, such as at a river mouth, the drift carries on, and material is deposited out into the sea. Over time, this builds up a long, narrow ridge of sand attached to the land at one end, called a spit.

Why this level: Clear explanation of how a spit forms. To reach Level 3: develop the curved (recurved) end and the salt marsh behind it.

Level 3 (Detailed)· 6/6 marks (band 5–6)

Longshore drift carries sand and shingle along the coast in a zigzag, as the swash moves material up the beach at an angle and the backwash pulls it straight back. Where the coast changes direction, such as at a river mouth, the drift carries on in the same direction, and material is deposited out into the sea in the calmer water. Over time, this builds a long, narrow ridge of sand and shingle joined to the land at one end: a spit. Changes in wind direction and waves curve its end into a hook, called a recurved end. The spit shelters the water behind it, so mud is deposited there and salt marsh forms.

Why this level: Detailed sequence covering longshore drift, deposition, growth, the recurved end and salt marsh, with correct terms. This is Level 3.

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