1. COASTAL EROSIONAL AND DEPOSIONAL FEATURES

2. Coasts are shaped by the sea and the action of waves
Coasts are shaped by the sea and the action of waves. The processes that take place are erosion, transportation and deposition.

3. The action of waves
The power of waves is one of the most significant forces of coastal change.
Waves are created by wind blowing over the surface of the sea. As the wind blows over the sea, friction is created - producing a swell in the water. The energy of the wind causes water particles to rotate inside the swell and this moves the wave forward.

4. The size and energy of a wave is influenced by:
how long the wind has been blowing
the strength of the wind
how far the wave has travelled (the fetch)

5. Waves can be destructive or constructive.
When a wave breaks, water is washed up the beach - this is called the swash. Then the water runs back down the beach - this is called the backwash. With a constructive wave, the swash is stronger than the backwash. With a destructive wave, the backwash is stronger than the swash.

6. Constructive and destructive waves

7. Destructive waves are created in storm conditions.
They are created from big, strong waves when the wind is powerful and has been blowing for a long time.
They occur when wave energy is high and the wave has travelled over a long fetch.
They tend to erode the coast.
They have a stronger backwash than swash.
They have a short wave length and are high and steep.

8. Constructive waves

11. They are created in calm weather and are less powerful than destructive waves.
They break on the shore and deposit material, building up beaches.
They have a swash that is stronger than the backwash.
They have a long wavelength, and are low in height.

12. Coastal erosion
The sea shapes the coastal landscape. Coastal erosion is the wearing away and breaking up of rock along the coast. Destructive waves erode the coastline in a number of ways:
Hydraulic action. Air may become trapped in joints and cracks on a cliff face. When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion.

13. Abrasion. Bits of rock and sand in waves grind down cliff surfaces like sandpaper.
Attrition. Waves smash rocks and pebbles on the shore into each other, and they break and become smoother.
Solution. Acids contained in sea water will dissolve some types of rock such as chalk or limestone.

14. Transport
There are various sources of the material in the sea. The material has been:
eroded from cliffs
transported by longshore drift along the coastline
brought inland from offshore by constructive waves
carried to the coastline by rivers

15. Coastal transport
There are four ways that waves and tidal currents transport sediment. These can then contribute to the movement of sediment by longshore drift.

17. Deposition
When the sea loses energy, it drops the sand, rock particles and pebbles it has been carrying. This is called deposition. Deposition happens when the swash is stronger than the backwash and is associated with constructive waves.

18. Deposition is likely to occur when:
waves enter an area of shallow water.
waves enter a sheltered area, eg a cove or bay.
there is little wind.
there is a good supply of material.

19. Longshore drift
Longshore Drift: This is the process of waves moving (transporting) material (load) along a coastline. Longshore drift only happens when the waves hit the beach at an angle. It is the process of the swash transporting material up the beach at an angle and the backwash returning directly under the force of gravity that causes material to be transported along the beach.

20. Erosional landforms
Along a coastline there are features created by erosion. These include cliffs, wave-cut platforms and wave-cut notches. There are also headlands and bays, caves, arches, stacks and stumps.

22. Cliffs, wave-cut platforms and notches
One of the most common features of a coastline is a cliff. Cliffs are shaped through a combination of erosion and weathering - the breakdown of rocks caused by weather conditions.

23. Soft rock, eg sand and clay, erodes easily to create gently sloping cliffs. Hard rock, eg chalk, is more resistant and erodes slowly to create steep cliffs.

27. The process of cliff erosion
Weather weakens the top of the cliff.
The sea attacks the base of the cliff forming a wave-cut notch.
The notch increases in size causing the cliff to collapse.
The backwash carries the rubble towards the sea forming a wave-cut platform.
The process repeats and the cliff continues to retreat.

28. Headlands and bays
Headlands are formed when the sea attacks a section of coast with alternating bands of hard and soft rock.
The bands of soft rock, such as sand and clay, erode more quickly than those of more resistant rock, such as chalk. This leaves a section of land jutting out into the sea called a headland. The areas where the soft rock has eroded away, next to the headland, are called bays.

30. Caves, arches, stacks and stumps

32. Weathering and erosion can create caves, arches, stacks and stumps along a headland.
Caves occur when waves force their way into cracks in the cliff face. The water contains sand and other materials that grind away at the rock until the cracks become a cave. Hydraulic action is the predominant process.

33. If the cave is formed in a headland, it may eventually break through to the other side forming an arch.
The arch will gradually become bigger until it can no longer support the top of the arch. When the arch collapses, it leaves the headland on one side and a stack (a tall column of rock) on the other.

34. The stack will be attacked at the base in the same way that a wave-cut notch is formed. This weakens the structure and it will eventually collapseto form a stump.
One of the best examples in Britain is Old Harry Rocks, a stack found off a headland in the Isle of Purbeck.

36. Depositional landforms
Along a coastline you find features created by deposition. These include beaches, spits and tombolos.
Beaches
Beaches are a common feature of a coastline. Beaches are made up of eroded material that has been transported from elsewhere and deposited by the sea.

37. Spits
Spits are also created by deposition. A spit is an extended stretch of beach material that projects out to sea and is joined to the mainland at one end.
Spits are formed where the prevailing wind blows at an angle to the coastline, resulting in longshore drift. An example of a spit is Spurn Head, found along the Holderness coast in Humberside.

39. Tombolos
A tombolo is a spit connecting an island to the mainland. An example of a tombolo is Chesil Beach, which connects the Isle of Portland to the mainland of the Dorset coast.