Coastal Landscapes

• 4 processes of coastal erosion

  • hydraulic action
  • abrasion
  • attrition
  • solution
• What is hydraulic action?

  Hydraulic action is the sheer power of the waves as they smash against the cliff. Air becomes trapped in the cracks in the rock and causes the rock to break apart.
• What is abrasion?

  Abrasion is when pebbles grind along a rock platform, much like sandpaper. Over time the rock becomes smooth.
• What is attrition?

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

  Solution is when sea water dissolves certain types of rocks. In the UK, chalk and limestone cliffs are prone to this type of erosion. (acidic/alkaline chemical reaction)
• When the wind blows over the sea, it creates waves. The size and energy of the wave depends on certain factors:

  • the fetch - how far the wave has travelled
  • the strength of the wind
  • how long the wind has been blowing for
• There are two different types of wave - constructive and destructive. They can affect the coastline in different ways. When a wave reaches the shore, the water that rushes up the beach is known as the swash. The water that flows back towards the sea is known as the backwash. The energy of the swash and backwash determine the type of wave.
• 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

  
• 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

  
• Types of weathering at coasts

  • freeze-thaw
  • biological
  • chemical
• Freeze-thaw weathering:

  Freeze-thaw weathering occurs when rocks are porous (contain holes) or permeable (allow water to pass through).

  1. Water enters cracks in the rock.
  2. When temperatures drop, the water freezes and expands causing the crack to widen.
  3. The ice melts and water makes its way deeper into the cracks.
  4. The process repeats itself until the rock splits entirely.

  
• Biological weathering:

  Plants and animals can also have an effect on rocks. Roots burrow down, weakening the structure of the rock until it breaks away.

  1. Plant roots can get into small cracks in the rock.
  2. As the roots grow, the cracks become larger.
  3. This causes small pieces of rock to break away.

  
• Chemical weathering:

  Rainwater and seawater can be a weak acid. If a coastline is made up of rocks such as limestone or chalk, over time they can become dissolved by the acid in the water.
• Mechanical weathering:

  The breakdown of rock without changing its chemical composition. One type of mechanical weathering that affects coasts is freeze-thaw weathering.
• Chemical weathering:

  The breakdown of rock by changing its chemical composition. Carbonation weathering is a type of chemical weathering that happens in warm and wet conditions.
• Carbonation weathering:

  1. Rainwater has carbon dioxide dissolved in it, which makes it a weak carbonic acid.
  2. Carbonic acid reacts with rock that contains calcium carbonate (e.g. carboniferous limestone) so the rocks are dissolved by the rainwater.
• Fetch

  The distance of open water over which wind can blow. The longer the fetch, the more powerful the wave.
• Swash

  The forward movement of a wave up a beach.
• Backwash

  The backward movement of water down a beach when the wave has broken.
• Beach

  A deposit of sand and shingle at the coast, often found in a bay.
• Crest

  The top of a wave.
• Difference between weathering and erosion

  Weathering is the break up of material like rock on site. Erosion is the break up of material like rock along with some sort of transport process.
• Mass movement

  The downward movement or sliding of material under the influence of gravity.
• Mass movement and weathering create loose material, much of which is carried away by waves and eventually deposited elsewhere.
• 4 types of mass movement:

  • Rockfall
  • Mudflow
  • Landslide
  • Rotational Slip
• Rockfall

  When fragments of rock break away from the cliff face. This is often due to freeze-thaw weathering.

  
• Landslide

  Blocks of rock sliding downhill. It is either caused by an excessive force such as earthquakes or how rain acts as a lubricant and large material easily slips and becomes displaced.

  
• Mudflow

  Saturated soil and weak rock flowing down a slope.

  
• Rotational Slip

  A slump of saturated soil and weak rock along a curved surface.

  
• Erosion is the geological process in which earthen materials are worn away and transported by natural forces such as wind or water. (land gets smaller)
• Deposition is when material/sediment that is being transported is dropped by constructive waves. It happens because waves have less energy. (land gets bigger)
• Coastal transportation is the movement of material in the sea and along the coast by waves. The movement of material along the coast is called longshore drift.
• 4 processes of transportation:

  • suspension
  • traction
  • saltation
  • solution
• Headlands and Bays form along Discordant Coastlines

  • Headlands and bays form where there are alternating bands of resistant (hard) and less resistant (soft) rock along a coast.
  • The less resistant rock is eroded faster forming a bay with a gentle slope
  • Because the resistant rock erodes more slowly, it juts out, forming a headland with steep sides

  
• Headlands are eroded to form Caves, Arches and Stacks and Stumps


  1. The resistant rock that makes up headlands often has weaknesses like cracks.
  2. Waves crash into the headlands and enlarge the cracks by hydraulic power and abrasion.
  3. Repeated erosion and enlargement of the cracks causes a cave to form.
  4. Continued erosion deepens the cave until it breaks through the headland to form an arch.
  5. Erosion continues to wear away the rock supporting the arch, until it eventually collapses.
  6. This forms a stack - an isolated rock that's separate from the headland.

  
• Waves erode cliffs to form Wave-cut Platforms


  1. The sea erodes the cliff at high tide through erosion and hydraulic action.
  2. This creates a wave-cut notch.
  3. Weathering such as freeze-thaw or biological weakens the top of the cliff.
  4. Due to a lack of support the cliff collapses leaving a platform of rock at the foot.
  5. Abrasion smooths out the wave-cut platform.

  
• 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.
• 2 types of beaches:

  • sand
  • shingle
• Sand beaches are created by low energy waves and are flat and wide - sand particles are small so the weak backwash can move them back down the beach, creating a long, gentle slope.
• Shingle beaches are created by high energy waves and are steep and narrow - sand particles are washed away but larger shingle is left behind (which have been eroded from nearby cliffs). The shingle particles build up to create a steep slope.