Coastal Landscapes

• Describe how freeze-thaw weathering works

  • Water enters the cracks and holes of rocks
  • Water freezes and expands which exerts pressure on rocks
  • This breaks down the rocks
• Describe how salt weathering works

  • Water enters the holes of rocks and eventually evaporates
  • This causes salts to crystallise and put extra pressure on the rocks
  • Eventually, the rocks are weakened and begin to crack and break apart
• Weathering is the break down of rocks in situ and doesn't involve the movement of the material, unlike erosion
• Describe how chemical weathering works

  • Rainwater is slightly acidic due to dissolved carbon dioxide
  • Rainwater falls on rocks and reacts with the minerals in the rocks
  • Over time, this weakens the rocks and breaks it down
• Describe how biological weathering works

  • Trees and plants can grow within the cracks in rocks
  • As roots grow bigger, they push open cracks in the rocks and make them wider and deeper
  • Over time, the rocks break apart
• What is meant by mass movement?

  The downwards movement of sediment due to gravity
• Describe how a landslide happens

  This occurs when large blocks of rocks slide down. It is usually due to coastal erosion where a wave cut notch is formed. Material above the notch is too heavy to be supported by cliff, causing a landslide
• Describe how rockfall occurs

  Fragments of rocks break off a cliff and fall down, usually due to freeze thaw weathering. This leaves scree at the bottom of the cliff which is left over pieces of rocks
• Describe how slumping/ rotational slip occurs

  When saturated soil slumps along a curved surface
• Coastal erosion is the wearing away of rocks by the sea, usually due to destructive waves
• Describe how hydraulic action occurs

  This is caused by the power of waves. Air is forced into cracks in the rocks and when the wave retreats, air rushes out, widening the cracks and causing rocks to eventually break apart
• Describe how abrasion occurs

  Rocks are picked up by waves and hurled at cliffs
• Describe how attrition occurs

  Rocks carried by the sea are knocked against each other, becoming smaller and rounder each time
• Transportation is the movement of beach material
• Describe how solution occurs

  When minerals from dissolved rocks are carried in solution in the sea water
• Describe how suspension works

  When small particles are suspended in the flow of water
• Describe how saltation occurs

  When small pieces of sediment too heavy to be suspended in the sea are bounced along the sea bed
• Describe how traction occurs

  When large sediments too heavy to be suspended in the sea are rolled along the sea bed
• What is longshore drift?

  The movement of sediment by waves along the coast. The direction of the prevailing wind results in waves approaching the coast at an angle. The swash carries material up the beach at this angle but the backwash retreats perpendicular to the cliff

  
• Constructive waves have a strong swash but weak backwash, so they deposit material on the coast and build up the beach. They have a lower wave height but longer wavelength

  
• Destructive waves have a weak swash but strong backwash so they erode the coast and destroy the beach. They have a short wavelength but big waveheight

  
• Deposition happens when sediment material is dropped onto coasts and happens due to waves possessing little to no energy
• Bays and headlands form along discordant coastlines where there are alternating bands of hard and soft rocks which run perpendicular to oncoming waves
• Describe how headlands and bays are formed

  Along a discordant coastline, there are alternating bands of soft and hard rocks. Soft rocks are more prone to erosion, so they erode backwards first. As it erodes, it curves inwards and forms a bay. The hard rock left sticking out is known as a headland
• Describe how cliffs and wave cut platforms are created

  • Weathering processes weakens the rocks along a cliff
  • At the bottom of the cliff between the high and low wave mark, hydraulic action, a form of erosion, weakens the rocks and undercuts the base of cliffs
  • Abrasion hurls rocks to the cliffs and wears away the rocks
  • The rocks break away from the cliff base and collect on the beach before material is removed by destructive waves, leaving a wave cut platform
  • Process repeats and causes the cliff to retreat

  
• Describe how a cave, arch, stack and stump is formed

  • The sea enlarges a crack in a headland into a wide hole through abrasion and hydraulic action
  • Eventually, a cave is formed
  • The cave gets bigger and wider and goes through the headland, forming a natural arch
  • The roof of the arch is very unstable; due to weathering and erosion processes, the roof of the arch collapses into the sea
  • A standing section of the rock is left behind called a stack
  • The base of the stack is vulnerable to abrasion and hydraulic action. Eventually the stack gets narrower until it falls off to create a stump

  
• Beaches are formed in sheltered areas like bays due to the deposition of sediment. Sandy beaches are formed by constructive waves in low energy environments while shingle beaches are formed in high energy environments by destructive waves washing away the sand and leaving behind pebbles

  
• Describe how sand dunes are formed

  • Embryo dunes form around small obstacles like wood and rocks due to sand depositing there, blown by the wind. Over time, pioneering plants develop and colonise the sand dunes
  • Fore dunes form behind the embryo dunes as a result of having protection against the prevailing wind. Marram grass grows and stabilises the dunes with its long roots
  • Yellow dunes form and start to add humus and decaying matter to the dunes which brings more biodiversity
  • Eventually, mature dunes are formed which are the most stable and capable of supporting flora and fauna

  
• Describe the formation of a spit

  • Longshore drift carries sediment along the coast. When the coastline changes direction, a shallow area allows for the deposition of sediment
  • Eventually, a peninsula builds up to sea level and extends along the coast
  • This forms a spit
  • If the direction of the prevailing wind changes, the wave pattern is altered and a hooked end is formed

  
• Describe the formation of a bar

  When a spit grows across a bay, it may join two headlands together known as a bar. This isolates the water from the bay and forms a lagoon

  
• Soft engineering are strategies which work with nature to protect coastlines from erosion. They tend to be cheaper than hard engineering strategies but less effective against flooding and erosion.
• In beach nourishment, sediment is replaced by bulldozers. Sediment is either pumped from the seabed or from surrounding areas onto the beach

  
• Beach nourishment allows wide beaches to develop which absorbs more wave energy and decreases pressure on the coast. It looks natural and attracts more tourists so it's good for the economy and protects them against flooding
• Beach nourishment takes several weeks to happen and cuts off large areas of land. It is also very expensive
• Beach reprofiling uses existing sediment from the beach to artificially reshape the beach after destructive waves have removed sand and shingle
• Beach profiling means there will be a bigger beach so residents are protected against erosion, cheap and looks natural. However, bulldozers restrict access to the beach and can look unnatural
• Mangroves involves restoring existing dunes or artificially creating new ones to provide a physical barrier between the sea and land to prevent erosion
• Mangroves is good as it provides good walking routes for tourists, cheap and uses local volunteers. It also maintains wildlife habitats
• Using mangroves fences off large areas of the beach and can impact tourism. It has to be checked carefully and frequently. Sand dunes are also dynamic ecosystems and not very stable so they can be easily destroyed during storms
• Managed retreat is when the sea is allowed to flood low lying areas. This occurs in low value lands like farmlands. It's cheap and sustainable and allows the survival of certain ecosystems which acts as a natural buffer to the sea