coastal erosion and deposition

• destructive waves are responsible for erosional processes, are steep and high and remove material from coasts because the swash is greater than the backwash
• constructive waves and long and low, deposit material on coasts because the backwash is less powerful than the swash
• erosion is the wearing away of rock, several erosional processes happen at coastlines, with their ability to alter the shape of a coastline influences by wave type, coastline shape and lithology.
• corrosion happens when there is a chemical reaction between the seawater , that contains a weak acid, and rocks such as limestone
• attrition is when pieces of rock carried in the water hit against one another
• abrasion is when pieces of rock are picked up by waves and hit against the bed, beach or cliffs
• hydraulic action is when water is compressed into cracks in a rock
• wave cut notch 


  cliffs are created when erosion, weathering and mass movement processes cause the undercutting and collapse of unsupported rock.

  destructive waves are responsible for most of the erosion at the base of cliffs

  when destructive waves lead to abrasion undercutting the cliff face, an indent in the cliff forms and a wave cut platform is made.
• collapse of a wave cut platform

  continued erosion of the wave cut notch causes the rock above is to become less stable and it collapses
• formation of a new wave cut notch

  waves wash away the collapsed material and begin eroding away at the cliff again causing a new wave cut notch to form
• wave cut platform

  over time, multiple collapsing events lead to the cliff retreating
• destructive waves can erode weaknesses in headlands by the processes of corrosion and hydraulic action
• when the weaknesses in the rock widen, abrasion becomes more prominent
• over time, these erosional processes lead to the formation of coastal landforms , such as caves, arches, stacks and stumps
• caves

  erosion attacks lines of weaknesses in the headland

  when the crack widens into a small hollowed out area, a cave have been formed
• arches

  when caves are eroded right the way through the headland, an arch is created such as hurdle door on the Dorset coast
• stacks

  when the top of an arch collapses because of gravity, a stack is left behind
• stumps

  continued erosion and weathering causes the stack to breakdown, forming a stump
• resistant rocks with weaknesses called joints or cracks are what headlands are made of
• longshore drift

  wind approaches the coast at an angle because of prevailing wind direction

  waves are controlled by wind and so this angle will be the direction the swash moves up the beach
• backwash direction 


  gravity is the only force that acts on the backwash, so it falls back to the sea at right angles to the coastline
• overall effect

  because of the difference between the angle of the swash and the angle of the backwash, sediment repeatedly moves at a right angle, then sediment is carried along the beach
• spit 


  spits are the long fingers of sand sticking out from one side in a coastline that have been curved by wind. they often have salt marshes behind them
• bars

  a bar is formed when a spit grows across a bay
• beaches 


  beaches are made by constructive waves moving and depositing sand
• sediment cell

  sources

  the sources are subaerial processes, erosional processes and sediments
• transfers

  transfers are longshore drift, onshore and offshore winds and tides
• sinks

  the sinks are depositional landforms
• sediment cells in the uk

  the uk has 11 sediment cells and sub cells, each one has its own shoreline management plan
• the sediment cell concept is a closed system operated by sources, transfers and sinks driven by erosion, transportation and depositional processes
• weathering describes the breaking down of rocks where they are
• chemical weathering is when rocks are broken down because of their chemical composition being changes
• biological weathering is when rocks are broken down by living things, such as plant roots
• mechanical weathering is when rocks are broken down without their chemical composition being changed
• mass movement describes when rocks and loose material shifts down slopes
• slides


  slides are when material moves down a slope in a straight line
• rockfalls

  rockfalls are when material breaks apart because of erosion and weathering and then rolls down a slope
• slumps


  slumps are when material moves down a slope with a rotation