Coasts

• weathering = weakening of rocks at their orginial place
• Mechanical weathering= disintegration of rocks which piles of fragment rocks are formed+

  Freeze-thaw : water enters a crack in a rock, this freezes and widens the crack, ice melts and water goes deeper into the crack, process repeats untill rock breaks.
• Chemical weathering = acidic substances slowly dissolve rocks and minerals+

  carbonation - rainwater absorbs carbon dioxide and becomes acidic, when in contact with alkaline rocks such as limestone neutralisation reaction happens causing rocks to slowly disolve
• Biological weathering = plants grow in rock cracks and animals burry in rocks causing them to break+

  e.g roots enter a small crack, they grow enlarging the cracks before it finally breaks
• mass movement = movement of material downhill due to gravity+

  • rockfall - fragments of rock fall away from cliff face+
  • landslide - blocks of rock fall downwards+
  • mudflow - saturated soil and weak rocks fall down a slope +
  • rotational slip - saturated soil fall down a curved surface
• erosion = wearing away rock


  Hydraulic action = waves smash and erode a cliff

  Solution = chemicals in waterdissolve rocks

  Attrition = rocks crash into eachother and erode

  Abrasion = rocks get eroded by dragging against sea bed
• Transportation = carrying sediment

  Deposition = water looses energy so drops sediment

  • no wind
  • shallow water
  • waves slow down
• Longshore drift = movement of sediment on a beach

  1. waves aproach the coastline at an angle due to prevaling wind (strongest wind)
  2. swash carries material up the beach
  3. backwash carries material back down the beach at a right angle due to gravity and process repeats
• transportation processes

  suspension = small sediments are carried in the water

  traction = large boulders are rolled along the sea bed

  solution = small minerals are disolved in water

  saltation = pebbles are bounced along the surface
• cave, arch, stack

  1. fault in cliff face caused by HA and abrasion
  2. continues until crack is widened to form a cave
  3. erosion meets the other side of the cliff to form an arch
  4. weathering weakens arch causing the top to become too heavy and collapse due to gravity
  5. this leaves behind an isolated pillar known as a stack+
• cliffs and wave cut platforms

  1. weathering weakens top of cliff
  2. HA and abrasion erode base of cliff producing a wave cut notch
  3. erosion continues undercutting the cliff and causing it to collapse
  4. backwash carries material back out to sea creating a rocky platform
• bays

  concordant = only one type of rock

  discordant = alternating bands of hard and soft rock

  bays (studlant bay) : formed when soft rock erodes quickly forming an inlet into sea

  
• wave cut platform

  .

  
• cave arch stack

  
• headland (ballard point)

  during the erosion of a disconcordant cliff harder rock such as limestone are less susceptible to erosion so sticks out

  • wave refraction happens here so more energy is focused on the headlands and less at the quieter bays
• Beaches

  Built by constructive waves, waves have a strong wash so deposit material such as sediments and silts which form the beach, have a weak backwash so much less sediment is taken back.
• sand dunes

  Onshore winds blow sand which settles on a rock forming an embryo dune. Over time vegetation such as marram grass stablises the sand forming foredunes. As vegetation around the foreground decomposes leaving behind nutriets allowing more vegetation to grow
• Spit = extended strech of land or shingle

  1. longshore drift carries sediments
  2. where the coast changes shape this is deposited as a small ridge
  3. change in prevailing wind can cause the ridge to hook

  
• Bar = a spit which covers a bay and joins two headlands together


  This traps water behind it known as a lagoon. This will not last forever as it may fill up with sediment
• Swanage : in dorset, along jurassic bay

  • ballard point - headland
  • studland bay
  • Kimmeridge cliff - wave cut platform
  • arches - durdle door
  • old harry - stack
  • knoll beach
  • studland bay sand dunes
  • hurst castle spit
• Hard engineering = using artificial structures to control natural processes

  • SEA WALLS curved face defects wave back out to sea, effective, expensive, unnatural
  • GROYNES prevent longshore drift, inexpensive, starve beaches of sand further down
  • GABIONS rocks in cages which absorb wave energy, can be sat on, need to be replaced often
  • ROCK ARMOUR rocks used to absorb wave energy, can be used for fishing, rocks are expensive to transport
• Soft engineering = using less intrusive methods and working with the natural processes

  • BEACH NOURISHMENT replacing sand on a beach, looks natural, wears away quickly
  • BEACH REPROFILING using sand already there to reshape the beach, looks aesthetic, beach can't be used during restoration
  • SAND DUNE RESTORATION creating or restoring sand dunes, liked by tourists, needs to be done often
• Managed retreat = retreat of the coastline, allowing flooding of low lying areas


  Advantages : cheap, creates a salt marsh - habitat

  Disadvantages : land is lost, owners need to be compensated
• Medmerry : costal management scheme in west sussex from 2011 to 2014

  • needed due to high flood risk which would damage 348 properties and water treatment plant
  • managed retreat was created - embankment built behind interdial area, channel to interdial area, rock armour to link ridge and embankment
  • + : 10km of walking paths, fishing nursery, 3k hectacres of mudflats
  • - : Habitats destroyed, expensive (£28 million)