systems and processes

• sources of energy in coastal environments

  winds

  tides

  currents

  waves
• what causes waves?

  caused by wind blowing over surface of the sea
• what causes waves to have a circular motion?

  friction between wind + surface of sea
• what's fetch?

  maximum distance of sea that wind has blown over in creating waves
• long fetch and high wind speed equals?

  more powerful waves

  • build up of energy
• what are tides?

  the periodic rise and fall of ocean surface, caused by gravitational pull of Moon and Sun
• high tide causes what?

  waves to break further up the shore
• what causes winds?

  air moving from areas of high to low pressure
• why are winds stronger during storms?

  due to the pressure gradient
• what is prevailing winds?

  when wind blows in the same direction
• destructive coastlines

  • high inputs of energy
  • strong winds
  • longer fetches
  • high erosion rates
• constructive coastlines

  • low inputs of energy
  • short fetches
  • higher rates of deposition
  • gentle winds
• example of destructive coastline

  Dorset Coast
• example of constructive coastline

  The Bristol Channel
• 6 sources of sediment

  rivers

  cliff erosion

  longshore drift

  glaciers

  wind

  offshore
• how do rivers transport sediment?

  sediment depositied in river mouths and estuaries where it'll be reworked by tides
• how does cliff erosion deposit sediment?

  common in areas with soft or unconsolidated rock
• how does longshore drift deposit sediment?

  sediment is transported from one stretch of coastline to the other
• how do glaciers deposit sediment?

  ice sheets calve into sea , deposit sediment trapped inside ice such as in Greenland
• how does wind deposit sediment?

  in glacial or hot arid environments, wind blown sand can be deposited in coastal regions eg sand dunes
• how is sediment deposited from offshore?

  sediment from offshore can be transferred into the coastal zone by waves , tides and currents
• what is a sediment cell?

  a stretch of coastline , bordered by two prominent headlands where te movement of sediment is contained.
• what type of system is a sediment cell?

  closed
• how many sediment cells are there in the UK?

  11
• Stores in a sediment cell

  beach , sand dunes and offshore deposits
• inputs of sediment in a sediment cell

  river , coastal erosion , offshore sources e.g bars or banks
• flows of sediment in a sediment cell

  longshore drift , offshore and onshore processes such as rip currents
• what is the sediment budget?

  the difference between the amount of sediment that enters the system and amount that leaves
• what's a positive sediment budget?

  if more sediment enters than leaves - coastline builds outwards
• what's a negative sediment budget?

  more sediment leaves than enter - coastline retreats
• factors that would leave to a positive sediment budget

  beach nourishment

  deforestation along the coast

  sea level rise
• factors that would cause a negative sediment budget

  dam built along a river

  dredging of a river

  creation of a sea wall
• types of erosion

  • abrasion
  • hydraulic action
  • cavitation
  • wave quarrying
  • solution (corrosion)
  • attrittion
• what's abrasion?

  when bits of sediment is transported by waves , they grind against cliffs and cause them to erode
• hydraulic action?

  air cracks in cliff are compressed when waves crash in. Pressure is exerted by compressed air , breaks off rock pieces
• cavitation?

  waves recede , compressed air expands violently , puts pressure on rock which causes pieces to break off
• wave quarrying


  energy of a wave as it breaks against a cliff is enough to detach bits of rock
• solution (corrosion)

  soluble rocks e.g chalk get dissolved by seawater - chemical reaction
• attrition


  bits of rock in water smash against each other , break against each other and break into smaller pieces
• 4 forms of transportation

  • solution
  • saltation
  • suspension
  • traction