Coasts

• Dynamic equilibrium


  A balance between inputs & outputs in a coastal system
• Where is the backshore and when does activity take place here?

  The area between the high water mark and the landward limit of marine activity. Changes take place here only during storm activity
• Foreshore


  The area lying between the HWM and the LWM. It is the most important zone for marine processes in times that are not influenced by storm activity.
• Inshore


  The area between the LWM and the point where the waves cease to have any influence on the land beneath them.
• Offshore


  The area beyond the point where waves have an impact upon the seabed and in which activity is limited to deposition of sediments.
• Nearshore


  The area extending seaward from the HWM to the area where waves begin to break
• Swash zone


  The area where a turbulent layer of water washes up the beach following the breaking of a wave
• Surf zone


  The area between the point where the waves break, forming a foamy, bubbly surface and where the waves move up the beach as swash in the swash zone.
• Swash


  Turbulent layer of water that washes up the beach after a wave has broken
• What is the breaker zone and at what depth does it occur?

  The area where waves approaching the coastline begin to break, usually where the water depth is 5-10m
• Littoral zone


  The area of land between the cliff's or dunes in the coast and the offshore area that is beyond the influence of the waves.
• Isolated systems


  Have no interactions with anything outside the system boundary. There are no inputs of energy or matter. Many controlled laboratory experiments are this type of system and they are very rare in nature
• Closed systems


  Have inputs and outputs of energy but not matter
• Open systems


  There are inputs and outputs of matter and energy across the boundary. Most ecosystems are examples of this type of system.
• Oscillatory waves


  Regular movement of marine waves created by wind stress in open oceans.
• Translatory waves


  When waves travel into areas of shallow water, they begin to be affected by the ocean floor. The free orbital motion of the water is disrupted by friction with the ocean bed.
• Wave height defenition


  vertical distance between crest and trough
• Wave length defenition


  Distance between 2 crests
• Wave period definition

  Time taken for a wave to travel through one wave length
• Wave height of constructive and destructive waves

  Constructive- less than 1m

  Destructive- over 1m
• Wave steepness of constructive and destructive waves

  Constructive- 0.01

  Destructive- more than 0.05
• Wavelength of constructive and destructive waves

  Constructive- up to 100m

  Destructive as low as 20m
• Wave period for constructive and destructive waves

  Constructive- 7.5-10 seconds

  Destructive- 4-6 seconds
• Frequency per minute of constructive and destructive waves

  Constructive- 6-8 per minuteDestructive- 10-14 per minute
• Are constructive waves high or low energy?

  Low
• Do constructive waves increase or decrease the beach gradient?

  Increases the beach gradient
• Which wave type has a stronger swash?

  Constructive
• Soil creep


  Slow movement of individual soil particles downhill due to gravity
• What is solifluction and what type of biome does it occur in?

  Tundra
• What is earth flow and what is it triggered by?

  Occurs in clay rich materials . Debris and weathered material gather and the movement is set off by heavy rainfall.
• Mudflow


  Earth and mud flows downhill over weak bedrock such as clay after heavy rainfall. Water gets trapped within the rock, increasing pore water pressure, forces rock particles apart and leads to slope failure
• What is slumping and what is the plane of movement?


  Occurs on clay or sand where permiable rock overlies impermiable rock which causes a build up of pore water pressure. The plane of movement is curved
• What is a landslide and what is it triggered by?


  A block of rock that moves rapidly downhill along a planar surface. Triggered by earthquakes or heavy rainfall due to reduced friction.
• What is a rockfall and what is it caused by?

  Sudden collapse or breaking off of (resistant) rock at a cliff face. Triggered by mechanical weathering or an earthquake.
• Define mass movement

  The downhill movement of weathered material due to gravity
• Describe freeze-thaw weathering

  Mechanical weathering- occurs when water enters a crack in the rock when it rains and then freezes. Water expands by about 10% when it freezes which exerts pressure on the rock and causes the crack to widen. Repeated freezing and thawing causes fragments of rock to break away.
• Describe thermal expansion and contraction

  Mechanical weathering- On a hot day the sun warms the outer parts of the rock. At night, the loss of heat makes the rock cooler. This heating and cooling leads to expansion on contraction of different parts of the rock.
• Describe salt crystallisation

  Mechanical weathering- when salt water evaporates, it leaves salt crystals behind. These grow over time and exert stresses in the rock.
• What is oxidation an how can you tell?

  Chemical weathering- oxygen in water reacts with some rock minerals forming oxides and hydroxides. It especially effects iron rich rocks. Evident by yellowish/brown staining on the rocks.
• Describe hydration weathering

  Chemical weathering- mineral structure in the rock forms a weak bond with water causing the rock to expand. This creates stress that can widen joints and cause rock to disintegrate.