Coasts

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coasts intro & definitions

concordant - rock that runs parallel 

discordant - bands of run running perpendicular 

tide - alternate rise & fall of the sea, twice in lunar day due to the moon & sun 

cliffed coast - when the transition from the land to sea is abrupt, low tide reveals a rocky platform 

sandy coast - flat coastline, high tide conceals sand but not vegetation dunes

estuarine coast - extensive mud flats & salt marshes, gradual transition from land to sea `

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salt marsh formation

1. algal stage - growth on mud, binds particles together 

2. pioneer stage - roots stabilise mud, allow further mud accretion (growth)

3. establishment stage - carpet of vegetation established, marsh grows in height

4. stabilisation - the area of salt marsh is now rarely submerged 

5. climax vegetation - developed soil profile & marsh is only submerged once or twice a year

things impacting salt marshes 

weather               sea level             human action            sediment supply 

climate                wave type          tidal regime 

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dune formation

-coastal dunes begin with colonisation of embryo dunes (pioneer plants) which stabilise the sand 

-roots help this, and plants reduce wind speeds which allows more sand to be deposited 

-dead matter is also added which creates soil formation 

-embryo dunes then change conditions from harsh & salty, to those that can accomodate other plants 

-the more plants, the more sand that builds up & the more stable the dune becomes 

embryo dunes --> fore dunes --> yellow dunes --> grey dune --> dune slack 

coastal plants:

Halophytes - can tolerate salt water 

Xerophytes - can tolerate dry conditions 

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coasts definitions cont.

psammosere: plant growth occuring on bare sand which creates a new environment 

vegetation succession: 

evolution of plant communities over time

at each stage the microclimate is altered meaning new plants can grow in the new condition 

one plant is then replaced by another 

when equlibrium is reached, there is a climax community (no further species)

if human inteference takes place a plagioclimax is reached instead 

plagioclimax: human intervention stops the environment developing any further 

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high & low energy coasts

LOW (east anglian coast)

-constructive waves                     -lowland coasts 

-deposition & transport                -beaches & spits   

HIGH (atlantic coast, scotland)

-destructive waves                      -cliffs, rocky landscapes, wave cut platforms 

-erosion & transport.                   -stormy conditions & long fetch 

coastal plains: 

low lying areas close to the coast, low energy environments 

contain marshes & wetlands as they are flat and do not drain 

form from sea level change or deposition of sediment 

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the coast

backshore - area between high water mark and landward limit of marine activity. changes normally take place during storms 

foreshore - between high & low water mark and an important zone for marine activity 

nearshore - LSD occurs, between the low water mark & where the waves cease to effect the land beneath them 

offshore - beyond point of waves impacting land beneath, sediment is deposited 

littoral zone: wider coastal zone including adjacent land areas & shallow parts of the sea just offshore 

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the coast

backshore - area between high water mark and landward limit of marine activity. changes normally take place during storms 

foreshore - between high & low water mark and an important zone for marine activity 

nearshore - LSD occurs, between the low water mark & where the waves cease to effect the land beneath them 

offshore - beyond point of waves impacting land beneath, sediment is deposited 

littoral zone: wider coastal zone including adjacent land areas & shallow parts of the sea just offshore 

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sea level change

change happens daily due to 

high/low tides          atmospheric pressure         winds       wave height 

long term change as a result of global warming and isostatic readjustment 

EUSTATIC is GLOBAL change 

ISOSTATIC is LOCAL change 

accretion: when sediment is deposited and builds up 

post glacial isostatic readjustment: uplift of land following the removal of weight (melting ice sheets)

SUBMERGENT features occur when sea level rises 

EMERGENT features occur when sea level falls 

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sediment cells

along the coast, erosion, transportation & deposition operate in a linked system

sediment cells have sources, transfers and sinks 

each cell can be regarded as a closed system

sediment budget = amount of sediment available within a cell 

negative feedback: maintaining balance within a system 

positive feedback: change in the balance until a new equilibrium is reached e.g. after a storm 

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sub-aerial processes

mass movement is the downward movement of rock or soil e.g. landslieds & rockfall 

frost shattering - freeze thaw, water trapped between rock freezes, expands, and forces the rock to shatter 

oxidation - when rocks are exposed to air or water, rusting occurs 

solution - dissolving of minerals in water 

thermal expansion - rocks expand when when heated and contract when cool, when this process occurs quickly it causes stress which causes the rock to break 

acid rain - lower Ph levels in rain can cause some rocks to corrode 

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coastal landforms

landforms of erosion 

headlands & bays 

wave cut notches & platforms 

cliffs 

blow holes 

arches, coves, stacks & stumps 

landforms of deposition

beaches 

recurved & double spits

offshore bars 

barrier beaches 

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beaches

storm beach --> berm --> cusp --> ripple 

storm beach: noticeable, semi-permanent ridges found at high tide level 

berm: small ridges built up by successive levels of tides & storms 

cusps: semi-circular embayments found in the shingle 

ripples: formed by waves and tidal currents, ripples along the sand 

SWASH ALIGNED BEACH 

sheltered, low energy environment, bars are formed, bay beaches e.g. Lulworth cove 

DRIFT ALIGNED BEACH 

develop when waves approach coast at an angle, backwash at a right angle so that sand drifts along the beach- creates spits e.g. Spurn head, Yorkshire 

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coastal flooding

caused by storm surges, sea level rise & local factors (e.g. land relief, land use)

LECZ: low elevation coastal zone 

adaptation: changing to suit the environment 

mitigation: putting in protective measures 

storm surges: caused by a drop in atmospheric pressure which allows the sea to swell and create waves, which travel towards the coast and create storm surges 

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coastal management

hard engineering 

groynes 

revetments

rip rap 

rock armour 

sea walls 

soft engineering 

beach replenishment 

cliff drainage & cliff regrading 

marsh creation 

dune stabilisation 

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managing the coast

holistic management protecting the coast as a whole instead of segregating specific areas 

ICZM: integrated coastal zone management 

manages the coast as one, aims to establish sustainable techniques & resolve environmental challenges 

Options include: 

hold the line           advance the line       managed retreat          do nothing approach 

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