Coasts

• Describe rotational slumping

  • Heavy rain or water from storm surges is absorbed by unconsolidated material making up a cliff. Cliff face becomes heavier causing it to separate from material behind at a slip plane. An example of rotational slumping is Christchurch bay in New Zealand
  • The slumping exposes a rotational scar, which is unprotected by vegetation. The detached slope section forms a beach or terraced cliff profile
• Describe rockfalls

  • Material breaks apart due to erosion and weathering of a cliff.  This causes rocks to roll down  and accumulate at cliff foot, forming a talus scree slope.
• What are the causes of isostatic and Eustatic change?

  • Past tectonic activity- Indian ocean earthquake caused a sea level rise of 0.1mm. Dormant volcanoes turn into mountains increasing land level e.g Scotland had a volcanic era millions of years ago
  • Climate change- Global warming= eustatic rise- thermal expansion. Global cooling= eustatic fall because ice is less dense than water
• Describe emergent coastal land forms

  •  Relict cliff- a steep slope found at the back of a raised beach- suggesting that they were once formed through erosion but are now above high tide level
  • Relict cave- Caves formed from erosion but tectonic uplift has occurred so they are now above high tide level
• What forms of beaches form at depositional coastlines?

  Drift-aligned beaches

  • Waves break at angle to coast
  • Material is transported by long-shore drift
  • Swash occurs at an angle but backwash occurs perpendicular to beach

   

  Swash-aligned beaches

  • Long-shore drift moves material up +down beach
  • Waves break in line with coast
  • Coast is curved
  • Beach face is orientated parallel to the fronts of dominant waves
• What landforms are at depositional coastlines?

  Tombolo

  • Ridges of sediment that has formed a small island away from mainland
  • Formed when deposition occurs when waves lose energy-builds up over time
  • E.g Chesil beach

  Spits

  • Long narrow, ridge which extends from land in sea
  • Formed when sediment that has been transported by long-shore drift is deposited when the river meets an estuary
  • Plant succession can occur to stabilise spit
  • E.g Spurn Head

  Barrier beaches

  • Beach/spit extends across a bay to join 2 headlands up
  • Traps water behind them to form lagoons
  • Salt marshes can build up behind spit- plant succession
  • E.G Slapton in Devon
• Describe submergent landforms

  • Rias- V- shaped submerged river valleys.
  • Fjords- U shaped submerged glacial valleys
  • Dalmatian coasts- form on concordant coastlines where river flows parallel to coast- causes river channels to become  wider and deeper due to erosion, includes off shore islands and coastal inlets e.g. Croatia
• How do sand dunes develop?

  • Constructive waves deposit tidal litter on coast
  • Tidal litter decomposes- release nutrients
  • Pioneer species colonise area- they are  halophytes  (plants specialised to survive in high salt environments)- creates embryo dune
  • Fore-dunes: Upwards growth of embryo dunes allow it to be reachable by only the highest storm tides, Absorption of rain water creates a  less salty environment- allows species diversity to increase
  • Fixed dunes- vegetation is so developed that is forms a full cover over the ground
• What are factors that affect wave strength

  •  Time it has blown for
  • Fetch- the distance that it has blown for
  • Strength of the winds
• Describe concordant coast lines.

  alternating bands of hard and soft rock parallel to the coast.

  Features:

  Dalmatian coasts- form on concordant coastlines where river flows parallel to coast- causes river channels to become wider and deeper due to erosion, includes off shore islands and coastal inlets e.g Croatia

  Coves:- Differential erosion exploits weaknesses, exposes headland. e.g Lulworth Cove
• Describe discordant coastlines.

  alternating bands of hard and soft rock at 90 degrees to the coast

  Fjords- U-shaped glacial valleys making the river channel much wider

  Bays- Differential erosion to form bay (e.g Swanage Bay) - changes the direction of the coastline to

  cause an increase in the rate of erosion on the headlands, leading to caves, stacks and stumps
• Describe the types of waves

  Constructive waves:

  • Small/ gentle waves
  • Low energy- Waves spill over + all wave energy is absorbed by beach
  • Strong swash- weak backwash
  • Berms of shingle created by deposition by wave

  Destructives waves:

  • High, steep waves
  • High energy- plunges over+ little wave energy absorbed by beach
  • Weak swash, Strong backwash
  • No deposition, more erosion
  • Wave erode cliff face- wave cut notches created.
• Factors that increase risk of storm surges

  • Storm depressions
  • Spring tides
  • Season of the year
• What is a storm surge?

  • A sudden rise in sea level caused by a fall in air pressure because the weight of air pressing on a seabed drops
• What are deltas?

  Wetlands that form as rivers empty their water and sediment into another body of water, often home to megacities e.g. Dhaka- Ganges Delta (Bangladesh)
• Why do people live on low-lying coastlines?

  • Fertile soil
  • Fishing
  • Trade
• What are the disadvantages of living near deltas?

  • Storm surges from hurricanes flood the delta more frequently.
  • Sea level rise increases risk of flooding and erosion.
  • Delta subsidence- over exploitation of  ground water aquifers in Jakarta- Indonesia has led to isostatic fall because land sinks when water is not able to recharge
• What is the environmental impact assessment?

  • Used to assess the short and long-term implications of using management on the environment. e.g. used on Jurassic coast to protect the natural heritage sites
• Why does geology affect rate of erosion and weathering?

  Sedimentary rocks contain more joints and faults
• Explain solifluction

  Surface layer melts but permafrost layer stays frozen, surface layer melts and mudflow/ Earthflow flows over permafrost. Occurs mainly in Tundra areas
• What are the factors that affect geological structure?(the formation of joints, the angle of the dip, faulting and folding)

  Deformation and stress placed on them from tectonic processes.
• What is dip?

  The angle that the rock layer forms with the horizontal bedding plane
• Compare seaward and landward dip

  • Bedding planes that dip towards the sea create a gentler cliff profile. But these cliffs are vulnerable to mass movement processes, like rockfalls.
  • Bedding planes that dip towards land tend to create a steeper cliff profile. But these cliffs are more vulnerable to erosion processes, like hydraulic action and abrasion.