Coasts

• Fetch

  Distance over which the wind has blown
• The energy of a wave depends on...

  1. Strength of Wind
  2. Length of time wind has been blowing for
  3. The Fetch
• In contructive waves the wave crests are far apart
• In destructive waves the wave crests are close together
• Constructive waves have a gently-sloping wave front
• Destructive waves have a steep wave front
• Contructive waves have a strong swash and a weak backwash
• Destructive waves have a weak swash and a strong backwash
• Contructive beaches are gentle
• Destructive beaches are steep
• The strong swash on Constructive Waves pushes sand and even pebbles up the beach
• The strong backwash on Destructive waves pulls sand and even pebbles out to sea
• Swash

  When a wave breaks, the water rushes up the beach
• Backwash

  The water runs back down the beach, back out to sea under the force of gravity
• Weathering

  The breakdown of rock overtime due to atmospheric conditions
• Two types of weathering

  Mechanical and Chemical
• What type is Freeze-thaw weathering

  Mechanical
• Freeze-thaw weathering Process

  1. Temperature goes above + below freezing
  2. Water gets into cracks of rocks
  3. When Water freezes it expands, putting pressure on the rocks
  4. When it thaws, it contracts and releases pressure on the rock
  5. This happens repeatedly - causing rock to break into smaller pieces
• Mechanical Weathering

  Breaking down of rock without changing the chemical composition
• Chemical Weathering

  Breaking down of rock by changing its chemical composition
• Carbonation Weathering

  1. Rainwater has CO2 dissolved in it which makes it weak carbonic acid
  2. This reacts with calcium carbonate e.g. limestone - so the rocks are dissolved by the rainwater
• Mass Movement


  The shifting of loose rocks down a slope caused by the force of gravity
• Rockfall 


  Fragments of rock break away from the cliff face due to freeze-thaw weathering
• Landslide


  Blocks of rock slide down hill
• Mudflow


  Saturated soil and small rocks fall down a slope
• Rotational slip / slumping


  Slump of saturated soil and weak rock along a curved surface
• Erosion


  Process of material being worn away by the action of wind, water or other natural agents
• Abrasion


  Waves throw materials at great force towards cliff face. The material acts as a 'sandpaper' and wears away and breaks off rock
• Attrition


  Materials collide with eachother within the wave becoming smaller and rounder
• Hyraulic action


  Waves get into the cracks and squash the air, putting more pressure on the cracks until rock breaks off
• Soloution


  Soluble material is dissolved by salt water in the wave
• Transportation


  Movement of material
• Suspension


  Sediment is held up in the water
• Soloution (transportation)


  Sediment has now dissolved
• Traction


  Pebbles and larger sediment rolled along the seabed as too heavy to be carried
• Saltation


  Bounces pebbles
• Wavecut Platform formation

  1. Wave attacks the foot of the cliff due to hydraulic action and abrasion between a low watermark and a high watermark
  2. This forms a Wavecut notch which is enlarged as erosion continues (Hydraulic action and Abrasion)
  3. Rock above notch becomes unstable and eventually collapses
  4. Collapsed material is washed away and a new wavecut notch starts to form
  5. Repeated collapsing results in cliff retreating
• Why do headlands and bays form

  Different layers of hard rock and soft rock along a coast
• Example of soft rock


  Clay
• Softer rock (clay) is eroded quickly and this forms a bay. Bays have a gentle slope. Bays are protected from strong destructive waves by headlands. This allows a beach to form through contructive waves.