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Coastal landscapes and change EQ3 coastal landscape, Concordant…

- - - - high energy coasts
        -high energy coasts are characterised by:
        
        destructive waves, long fetches, high rates of erosion, caves, arches, stacks and stumps, cliffs and wave cut platforms
        
        low energy coasts
        
        characterised by constructive waves, shorter fetches, higher rates of deposition, spits and bars, beaches, sand drunes and salt marshes
- - - - discordant coastlines
        -alternating bands of hard and soft rock at 90 degrees to the coast
        
        erosional landforms are more common on discordant coastlines because erosion happens at diffrent rates along their length
        
        example of discordant coast
        -Dorset (portland rock and greensands)
        
        the greensands is less resistant to erosional processes, and so retreats at a faster rate than the portland limestone
        
        this has resulted in the creation of a bay and headlands
  - - - atlantic coasts
        -headlands and bays often form on discordant coastlines
        
        as the faster eroding, less resistant rock retreats (eg the clays at swanage bay), this leaves behind the more resistant rock as headland
        
        bays and headlands
        -on discordant coastlines, the retreating, less resistant rock and the exposed resistant rocks cause a change in the shape of the coastline. this leads to wave refration
        -this change in the way in which waves approach the coastline can cause an increase in the rate of erosion on the headlands
        -this leads to the formation of headland features like caves, arches, stcacks and stumps
  - - - joints and faults
        -the geological structure of rocks (the formation of joints, the angle of the dip and folding) is caused by the deformation and stress placed on them from tectonic processes
        -rocks with the presense of more joints and faults, like sedimentary rocks, are more susceptible to the processes of erosion and weathering. this is because these processes exert forces on the weaknesses found in the layers of the rocks
- - - - igneous rocks
        -igneous rocks, such as Basalt and granite, form from the crystallisation of magma. they are more resistant to erosion and weathering
        -this is because igneauos rocks contain crystals which increase the strength of the rocks and reduce the number of lines of weaknesses that would be exploited by physical processes
        -igneous rocks can be either be intrusive (formed from magma inside the earth) or extrusive (formed when magma escapes through vents on the earths surface)
        -the average rate of erosion of igneous rocks is 0.1-0.5 cm per year
        
        sedimentary rocks
        -sedimentary rocks such as limestone and sandstone form from the build up compacting and hardening of sediments into layers over time by lithification
        -sedimentary rocks that have been formed in a shorter geological time scale tend to be more susceptible to erosion and weathering and erode at a faster rate compared with those formed over a longer geological time
        eg limestone and chalk
        -the avergae rate of erosion of sedimentary rocks is 2-6 cm per year
        
        metamorphic rock
        -metamorphic rocks, suh as slate and marble, are formed from the change in the structure of sedimentary and igneous rocks, caused by cvariations in heat and pressure
        -the process of change is referred to as the rocks having been metamorphosed
        -marble is an example of a metamosphic rock that has been formed from the changing structure of limestone caused by re-crystallisation of calcite
        -metamorphic rocks are resistant to erosion
  - - - vegitation succession on dunes
        -typical plats that colonise embryo and foredunes are sea rocket and sea crouch. these plats have deep roots and can tolorate high concentrations of salt
        -yellow dunes tend to be colonised by marram grass. these plants also have long deep roots and are salt toleramt
        -heathers are commonly found in grey dunes because of the highr rates of humus