Distinctive landscapes

• Destructive wave


  Waves which remove material from the beach. The swash is weaker than the backwash.
• The characteristics of a destructive wave are: weak swash and strong backwash the strong backwash removes sediment from the beach the waves are steep and close together
• Constructive wave

  Waves which help build up material on the beach. They tend to have a low frequency and strong swash
• The characteristics of a constructive wave are: strong swash and weak backwash the strong swash brings sediments to build up the beach the backwash is not strong enough to remove the sediment the waves are low and further apart
• Freeze thaw weathering 


  When water in rocks freezes and expands, breaking the rock apart.
• Plants and animals can have an effect on rocks. Roots burrow into the rock, weakening the structure of the rock until it breaks away. Plant roots can get into small cracks in the rock. As the roots grow, the cracks become larger. This causes small pieces of rock to break away.
• Rainwater and seawater can be a weak acid. Over time a coastline made up of rocks such as limestone or chalk can become dissolved by the acid in the water.
• Mass movement

  A large-scale downward movement of rocks and material
• Another way material can be moved on the coastline is through mass movement. Mass movement is the downhill movement of sediment that moves because of gravity. There are four different types of mass movement
• Saturated soil (soil filled with water) flows down a slope.
• Erosion is the wearing away of rock along the coastline. Destructive waves are responsible for erosion on the coastline. Erosion occurs where waves have direct contact with the rock
• Hydraulic action

  the sheer power of the waves as they smash against the cliff. Air becomes trapped and compressed into cracks in the rock with explosive force causing the rock to break apart.
• Abrasion

  when pebbles grind along a rock platform or cliff base much like sandpaper. Over time the rock becomes smooth.
• Attrition

  when rocks that the sea is carrying knock against each other. They break apart to become smaller and more rounded.
• Solution

  when sea water dissolves certain types of rocks. In the UK, chalk and limestone cliffs (soft rock) are prone to this type of erosion.
• Weather also has an impact on the coastline. Rainwater can cause surface erosion and frost (in cold climates) can cause rock to shatter. Strong winds can also contribute to the erosion of cliffs.
• Beach material can be moved in four different ways. These are: Solution - when minerals in rocks like chalk and limestone are dissolved in sea water and then carried in solution. The load is not visible. Suspension - small particles such as silts and clays are suspended in the flow of the water. Saltation - where small pieces of shingle or large sand grains are bounced along the sea bed. Traction - where pebbles and larger material are rolled along the sea bed.
• Sediment is carried by the waves along the coastline. The movement of the material is known as longshore. Waves approach the coast at an angle because of the direction of prevailing wind. The swash will carry the material towards the beach at an angle. The backwash then flows back to the sea, at 90° to the slope of the beach. The process repeats itself along the coast in this zigzag movement.
• Deposition

  When material is deposited or left behind, eg when a river loses its energy and is unable to carry its load any further, or waves move sand onto a beach but lack the energy to carry it away.
• Factors leading to deposition

  waves starting to slow down and lose energy shallow water sheltered areas, eg bays little or no wind
• Bands of soft rock such as clay and sand are weaker so therefore they can be eroded quickly. This process forms bays. A bay is an inlet of the sea where the land curves inwards, usually with a beach.
• Bands of soft rock such as clay and sand are weaker so therefore they can be eroded quickly. This process forms bays. A bay is an inlet of the sea where the land curves inwards, usually with a beach.
• Cave

  Recess in a cliff where waves have enlarged a crack in the rock face
• What is an arch

  natural rock formation often created by two sea caves eroding backwards towards each other until the back walls disappear.
• Cracks are formed in the headland through the erosional processes of hydraulic action and abrasion. As the waves continue to grind away at the crack, it begins to open up to form a cave.
• The cave becomes larger and eventually breaks through the headland to form an arch.
• The base of the arch continually becomes wider through further erosion, until its roof becomes too heavy and collapses into the sea. This leaves a stack (an isolated column of rock).The stack is undercut at the base until it collapses to form a stump.
• 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.Constructive waves build up beaches as they have a strong swash and a weak backwash
• Sandy beaches are usually found in bays where the water is shallow and the waves have less energy. Pebble beaches often form where cliffs are being eroded, and where there are higher-energy waves
• A cross-profile of a beach is called the beach profile. The beach profile has lots of ridges called berms. They show the lines of the high tide and the storm tides. A sandy beach typically has a gentle sloping profile, whereas a shingle beach can be much steeper. The size of the material is larger at the top of the beach, due to the high-energy storm waves carrying large sediment. The smallest material is found nearest the water as the waves break here and break down the rock through attrition
• A spit is an extended stretch of sand or shingle jutting out into the sea from the land. Spits occur when there is a change in the shape of the coastline or there is a river mouth.
• This is how spits are formed: Sediment is carried by longshore drift.When there is a change in the shape of the coastline, deposition occurs. A long thin ridge of material is deposited. This is the spit.A hooked end can form if there is a change in wind direction. Waves cannot get past a spit, therefore the water behind a spit is very sheltered. Silts are deposited here to form salt marshes or mud flats.
• Dorset is located in the south of England. Its coastline has examples of many erosional and depositional landforms. For example: Swanage is an example of a headland and bay Old Harry Rocks has examples of caves, arches, stacks and stumps at Chesil Beach there is a barDurdle Door is an example of an arch
• Old Harry Rocks are located on the headland between Swanage and Studland Bay. The headland is made out of chalk, a hard rock. The headland juts out into the sea, so it is more vulnerable to high-energy waves. This caused the formation of Old Harry, a stack. Over time Old Harry will collapse to form a stump
• Chesil Beach is an example of a bar. Sediment has been deposited over time to form a spit . The spit has continued to join to the Isle of Portland. Behind the spit there is The Fleet, a lagoon.
• Erosion is a natural process which shapes cliffs. Over time, erosion can cause cliff collapse - therefore the coastline needs to be managed. Hard engineering involves building artificial structures which try to control natural processes. Each engineering strategy has its advantages and disadvantages.
• Advantages of sea walls

  Effective at protecting the base of the cliff. Sea walls usually have promenades so people can walk along them.
• Disadvantages of sea walls

  Waves are still powerful and can break down and erode the sea wall. Expensive - approximately £2,000 per metre. Do not look natural.
• Disadvantages of rock armour

  They look different to the local geology, as the rock has been imported from other areas. The rocks are expensive to transport.
• Gabion

  Gabions are mesh cages that hold rocks and are placed in areas affected by erosion.