U1: Coasts

• Fetch - distance of open sea for wind to blow over
• Constructive wave - Larger swash than backwash

  • Sheltered bays
  • Sandy beaches

  
• Destructive wave - Stronger backwash than swash

  • Exposed bays
  • Pebble beaches
  • Winter

  
• Biological weathering - breakdown of rock naturally
• Chemical weathering - breakdown of rock using chemicals from seawater or rain
• Freeze-thaw weathering - water enters a crack in a cliff, freezes (causing it to expand) and therefore breaking the rock
• Attrition - Rock on rock

  
• Abrasion - rock on cliff

  
• Hydraulic action - water traps air in cracks in cliff = increased pressure = collapses

  
• Mudslide:

  • steep slopes
  • little vegetation to hold the soil in place

  
• Landslumps:

  • Rapid

  
• Soil creeps:

  • Very slow
  • Very shallow slope
  • Wet soil expands at right angles, then dries vertically

  
• Rockfall:

  • very steep slope of fallen rocks
  • free falling rocks from a steep cliff face

  
• LSD (Longshore Drift) - the process of sediment being transported along a coastline
• LSD

  1. Prevailing wind drives wands towards beach at an angle
  2. Swash takes the sand up the beach at an angle
  3. Backwash takes sediment back at 90 degrees
  4. Process repeats = beach moves
• Softs rocks

  • Sanstone
  • Clay
• Hard rocks

  • Granite
  • Limestone
• Bays + Headland formation

  • Discordant coastline

  1. Soft rocks erodes faster than hard rock
  2. Waves erode the soft rock, pushing it back, whilst hard rock erodes far less
  3. As the bay retreats, the energy of the wave decreases, leading to more deposition = beaches

  
• Discordant coastline - where bonds of different rock types meet at 90 degrees to the coast

  
• Concordant coastline - where bonds of different rocks run parallel to coastline

  
• WCP (Wave cut platform)

  • coverred at high tide
  • rock pools
  • lots of seaweed
• WCP formation

  1. Base of cliff is continually eroded via abrasion an hydraulic action
  2. Eventually, the unsupported cliff collapses
  3. As the cliff retreats, the former is known as a WCP

  
• Caves, Arches, Stacks, Stumps

  • Concordant coastline

  1. Waves attack weak points in a cliff via abrasion and hydraulic action, forming a crack in the hard rock
  2. Continued erosion at this weak point enlarges the crack
  3. This causes the waves to break through to the soft rock
  4. Soft rock erodes faster than the hard rock, forming a cave
  5. Eventually the waves break through the order side, forming an arch
  6. Eventually the arch causes the cliff to collapse, leaving a stack (Eg. Old Harry)
  7. Continued erosion of the stack forms a stump (Eg. Old Harry's wife)

  
• Sand dune formation

  1. A large flat beach with an obstacle nearer the back
  2. Wind blows sand towards the obstacle
  3. Sand builds up to form a crest
  4. Eventually the crest becomes an obstacle, meaning that sand migrates behind it forming larger dunes

  
• Spit formation

  1. When a coastline changes shape, the waves begin to lose energy so there is more deposition at the proximal end, and the spit grows out to the sea
  2. LSD moves material along the beach
  3. As LSD weakens and attrition increases, pebbles become smaller and smaller
  4. A dominant wind causes the distal end to hook towards the land
  5. Previous hooks mark a former end to the spit
  6. Salt marshes form behind the spit

  
• Bar formation

  1. A bay bar is a ridge of sand stretching from one side to the other
  2. This forms a lagoon behind
  3. LSD transports sediment from one side to the other forming the bar
  4. At high tide, bar is submerged
  5. At low tide, bar looks like a beach