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• Inputs


  sediment can be brought into the system in various ways. Energy inputs come from wind, waves, tides and currents.
• Outputs


  e.g. sediment can be washed out to sea or deposited further along the shore.
• Flows/Transfers


  e.g. processes such as erosion, weathering, transportation and deposition can move sediment within the system.
• Stores/Components


  landforms such as beaches, dunes and spits
• Negative Feedback


  when the effects of an action are cancelled out by its subsequent knock-on effects.
• Positive Feedback


  when the effects of an action are amplified or multiplied by subsequent knock-on effects (a loop/cycle).
• Sources of energy


  - Wind

  - Wave

  - Tidal

  - Currents
• Wave Energy


  - created by the frictional drag of the wind over the water.

  - effect of wave depends on height. height is determined by wind speed and fetch of the wind.

  - waves break as they approach the shore. Friction with the sea bed slows the bottom of the waves.

  
  

  Size of wave depends on 3 factors:

  
  

  - Distance wave has travelled

  - Time wind has been blowing

  - Strength of the wind
• Wave height


  height difference between a wave crest and the neighbouring trough
• Wavelength


  distance between successive crests
• Wave frequency


  time between one crest and the following crest passing a fixed point
• Constructive waves


  - swash greater then backwash

  - weak backwash, low-energy deposition

  - form beaches

  - long, not very high max 1m

  - frequency 6-9/minute

  - form in calm conditions with light winds

  - leads to formation of ridges (berms)
• Destructive waves


  - backwash greater than swash

  - remove material from the beach

  - erode the coastline

  - 2-3m in height and steep

  - frequency of 11-15/minute

  - form in stormy conditions

  - may form a ridge called a storm beach
• Wave refraction


  Slowing and bending of progressive waves in shallow water.

  
  

  Energy dissipates in deeper waters, waves are a lot smaller and don't slow down as much at the deeper bays.

  
  

  Energy of waves is concentrated at the headland, waves are bigger and erosion more likely in this shallow water.

  
• Wind energy


  - winds are created by air moving from areas of high pressure to areas of low pressure. During events such as storms, the jump from one to the other is large.

  - strong winds produce powerful waves.

  
  

  Most coastlines will have a prevailing wind direction. The wind will generally reach the coast from one direction.

  
  

  This therefore controls:

  1. the direction that waves approach.

  2. the direction material is transported.
• Prevailing wind


  the dominant wind direction in a particular location.
• Tides


  The periodic rise and fall of the ocean surface, caused by the gravitational pull of the moon and the sun.

  
  

  They affect the position at which waves break on the beach

  e.g. at higher tides, waves break higher up the beach.

  
• Sea currents


  Current is the general flow of water in one direction - it can't be caused by wind or by variations in water temperature and salinity.

  
  

  They move material along the coast.
• Termohaline circulation


  currents driven by the difference in water's density which is controlled by temperature and salinity.
• High energy coasts


  - typical landforms: headlands, cliffs, wave-cut platforms

  - coastlines where strong, steady prevailing winds create high energy waves

  - rate of erosion greater than rate of deposition

  
  

  - e.g. exposed Atlantic coasts of northern Europe + north America. north Cornish coast of south-west England.
• Low energy coasts


  - typical landforms: beaches, spits

  - coastlines where wave energy is low

  - rate of deposition often exceeds rate of erosion of sediment

  
  

  - e.g. many estuaries, inlets and sheltered bays. The Baltic sea, sheltered waters + low tidal range.
• Inputs of sediment at the coast


  - rivers, streams, river estuaries

  - sea level rise floods river valleys forming estuaries which input sediment

  - cliff erosion

  - biological material e.g. shells

  - offshore sand banks

  - wind

  - glaciers
• Sediment budget


  the difference between the amount of sediment that enters the system and the amount that leaves.

  
  

  Positive sediment budget: more sediment enters.

  
  

  Negative sediment budget: more sediment leaves.
• Sediment cell


  - the coast is divided into sediment cells, or littoral cells.

  
  

  These cells are self-contained, sediment doesn't move between the cells.

  
  

  Processes in one cell don't affect any other cell.

  Each cell is a closed coastal system.
• Erosional processes: CORRASION (ABRASION)


  Sediment dragged up and down/across shoreline, erodes and smooths rocky surfaces. Created wave-cut platform.
• Erosional processes: CAVITATION


  Air bubbles forming in waves implode under high pressure, generating tiny jets of water which erode rock over time.
• Erosional processes: WAVE QUARRYING

  - wave exerts considerable energy as tonnes of water hit the rock face

  - this high pressure is compressed between wave and cliff

  - if air is trapped, pressure may loosen blocks of rocks

  
• Erosional processes: SOLUTION (CORROSION)

  Weak acids in seawater dissolve alkaline rock e.g. limestone.
• Erosional processes: ATTRITION


  Bits of rock in the water smash against each other and break into smaller bits.

  
• Transportation processes: TRACTION


  rolling of coarse sediment along the sea bed that is too heavy to be picked up and carried by the sea

  
• Transportation processes: SALTATION


  sediment 'bounced' along the seabed, light enough to be picked up/dislodged but too heavy to remain within the flow of the water.

  
• Transportation processes: SUSPENSION

  smaller (lighter) sediment picked up and carried within the flow of the water.

  
• Transportation processes: SOLUTION


  chemicals dissolved in the water, transported and precipitated elsewhere. This form of transportation plays an important role in the carbon cycle, transferring and redepositing carbon in oceans.

  
• Factors affecting transportation


  - velocity (energy)

  - particle size (mass)

  
  

  e.g.

  - high energy environments: large particles can be transported

  - low energy environments: small particles can be transported
• Littoral drift


  - most waves approach a beach at an angle - usually same direction a prevailing wind

  - backwash pulls material down the beach at right angles to the shore (due to force of gravity)

  - net effect of the zigzag movement of sediment up and down the beach

  
• Marine deposition


  sediment carried by seawater is dropped.
• Aeolian deposition


  sediment carried by wind is dropped.
• Weathering


  breakdown or disintegration of rock in situ. Active at the coast where rock faces are exposed to the elements.

  
• Mechanical weathering: FROST SHATTERING


  - Water expands by 10% when it freezes

  - It enters a crack, freezes, and the expansion exerts pressure on the rock.

  
• Mechanical weathering: SALT CRYSTALLISATION


  - Salt water leaves behind salt crystals when it evaporates

  - Salt can corrode rock