costal environment

• what are the erosional landforms


  cliffs

  wave cut platforms

  caves arches stacks and stumps
• how are cliffs formed


  when destructive waves break repeatedly on steep sloping coastlines, undercutting occurs between high tide and low tide mark this forms a wave cut notch, continues undercutting weakens support for cliff above which eventually collapses producing a steep profile and a cliff

  
  

  cliff retreats parallel to the coast
• how are wave cut platforms formed


  this is the gently sloping area at the foot of the cliff

  it gets wider as the cliff slowly retreats inland
• factors affecting how easy a cliff is eroded

  rock type- resistant rock, soft or unconsolidated

  rock structure- layers of hard rock dipping towards the sea, layers of hard rock dipping away from sea

  cliff profiles

  porous at cliff top
• how do bays and headlands form at discordant coastlines


  form due to bands of rock with differing resistance to erosion, these bands of rock will be perpendicular to the coastline, width of bay is determined by width of the weaker rock which is eroded easier than resistant rock
• what happens at concordant coastlines


  rocks are lying parallel to the coastline, if the most resistant rock is on the seaward side then it protects any weaker rocks inland from erosion, small bays or caves may be produced in weaknesses
• how are caves arches stacks and stumps formed


  Caves are formed when cracks get wider because of hydraulic action abrasion and attrition.

  Arches form when the cave erodes so much that the hole goes all the way through the cliff to the other side.

  Stacks form when the rock not supported collapses due to sub aerial processes

  Stumps form when the stack erodes until it gets shorter.

  
• what are the depositional landforms


  beaches, spits, tombolos, bars, dunes, saltmarshes and mangroves
• how are beaches formed


  through deposition, made from sand and shingle

  
  

  usually form between high tide and low tide mark
• what are the beach zones

  backshore- fairly large sediment usually pebbles- deposited by storm waves

  
  

  foreshore- zone between high tide and low tide, often made of sand,

  
  

  nearshore- zone between low tide and the level of lowest spring tides,

  
  

  offshore- always underwater,

  
• factors affecting beach zones


  tides

  waves

  sediment
• what are berms and how are they formed


  smaller ridges that develop at position of mean high tide mark resulting from deposition from swash

  
  

  generally created by smaller waves
• what are beach cusps and how are they formed


  semi circular depressions, small and temporary

  
  

  formed when a collection of waves reach the same point
• difference between swash aligned and drift aligned beaches


  swash aligned- beach cusps and cuspate tombolos

  
  

  drift aligned- longshore drift is important- spits, tombolos, bars and cuspate forelands

  
• what are simple spits and how are they formed


  long narrow beaches of sand or shingle that are attached to the land at one end and extend across a bay estuary or indentation on the coastline

  
  

  form as a result of longshore drift

  
  

  end of the spit often becomes recurved- length limited by action of river currents

  
  

  deposition occurs behind the spit as wave energy is reduced
• what is a compound spit


  has a narrow base attaching it to the mainland but it widens into a broad recurved end, consists of a series of ridges

  
• what is an onshore bar and how is it formed


  develops when a spit develops across an indentation until it joins into the land the other end
• what is a tombolo

  beaches which connect the mainland to an offshore island
• what is a cuspate foreland and how are they formed


  low lying triangular shaped headlands extending out from the shoreline

  
  

  formed when longshore drift currents from opposing directions converge at the boundary of 2 sediment cells

  
• what are barrier beaches


  long sandy beaches detached from the coastline, start as an offshore bar
• what factors are needed for sand dunes to form

  a wide sandy beach that dries out at low tide

  
  

  a strong prevailing wind

  
  

  some sort of obstacle sat the top of the beach to trap sediment

  
  

  vegetation to stabilise the dune
• key features of sand dunes


  embryo dunes- small

  foredunes- further from beach

  yellow dunes- more plants and vegetation

  grey dunes- more organic matter in soil, colonialisation of vegetation

  
  

  wind blow sediment up beach, vegetation or objects trap sediment this is how the dunes are built up

  
• what are estuaries


  partly enclosed body of water, with one or more rivers or streams flowing into it with a free connection to the open sea
• tidal sedimentation in estuaries


  in tidal estuaries the incoming freshwater flow is opposed by both the mass of the sea water and the tide

  heavier sediment is deposited during the period between rising and falling tides, once sediment is in lower parts of circulation it may not reach the sea until a flood event
• where do salt marshes form


  where there is a sheltered area on the coast in an estuary or behind a spit, fine sand silt and clay are deposited each tidal cycle to form a mudflat and eventually a salt marsh
• what factors are required to form a salt marsh


  low energy

  large tidal range

  large consistent supply of silts and clays
• salt marshes


  vegetation helps stabilise sediment

  
  

  higher the marsh becomes the shorter period of submergence and less saline

  
  

  flocculation is important, freshwater + salt water mix- clays join together combine and sink

  
  

  low marsh- high salinity, long periods of submergence, low species diversity

  
  

  profile- shallow gradient sloping seaward, higher parts of slat marsh has more vegetation

  
• what are mangroves and where are they found


  mangroves provide an important habitat for fish insects birds and mammals, they act as filters removing sediment and organic matter that flow into them from adjacent land

  
  

  found in intertidal zones

  
  

  they have adaptations- conditions

  -salt water- salt glands to excrete salt, concentrate salt in leaves, salt excluders

  
  

  -water clogged soil- pneumatophores which are breathing roots

  
  

  -stability- prop roots provide extra stability
• what is eustatic and isostatic change

  eustatic- global changes in volume of water in global ocean stores

  
  

  isostatic- local, relative sea level changes
• what leads to sea level fall


  decrease in temperature- more snow so water stored on ice- reduction in amount of water in the ocean so worldwide fall in sea level

  
  

  decrease in temp- water molecules contract leading to a reduced volume
• what are emergent landforms


  landforms which were shaped by wave process at time of high tide, these become exposed when sea level drops

  
  

  begin to appear when isostatic rebound (melting land ice) takes place faster than eustatic rise in sea level

  
  

  
  

  raised beaches- areas of former shore platforms that were left tat a higher level than the present sea level

  
  

  abandoned cliffs- behind a raised beach it is not uncommon to find abandoned cliffs
• what leads to sea level rise


  increase in temperature- higher rates of melting land ice- global increase in volumes of water in ocean store therefore sea level rise

  
  

  increased temp- water molecules expand leading to an increased volume- thermal expansion
• landforms from sea level rise


  rias- submerged river valleys- lowest part of river course and the floodplains may be drowned

  
  

  fjord- submerged glacial valleys- steep cliff like, valley sides and the water is uniformly deep

  
  

  shingle beaches- when sea levels fall large areas of new land emerge- sediment accumulates so when sea levels rise again wave action pushes these sediments onshore creating shingle beaches
• Coral


  Living organism living in clear, tropical waters, Corals live in communities known as reefs. They secrete lime and build a skeleton

  
• Formation of coral


  Begin life as polyps which attach themselves to hard surface in shallow seas where there is sufficient light for growth. As they grow, many of these polyps exude calcium carbonate, which forms their skeleton. Then as they grow and die the reefs are built up
• Zooxanthellae


  Algae that live in a symbiotic relationship with coral and give it its colour
• Symbiotic relationship between the polyps and algae


  The algae get shelter and foo from the polyp, while the polyp also gets some food via photosynthesis

  This photosynthesis means that algae need sunlight to live, hence corals only grow where the sea is shallow and clear.
• Photosynthesis


  Conversion of light energy from the sun into chemical energy.
• Fringing reefs


  Lie along the coast of a landmass. They are usually characterised by an outer reef edge capped by an algal ridge, a broad flat reef and a sand-floored 'boat channel' close to the shore. Many fringing reefs grow along shores that are protected by barrier reefs and are thus characterised by organisms that are best adapted to low-wave energy conditions.

  
• Example of fringing reef


  Ningaloo Reef, Western Australia- stretches 300km along the coastline

  Australia's largest fringing reef that whale sharks, manta rays, and turtles make their home