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Coasts as a system (Waves (transfer of energy fro the wind to the water =…
Coasts as a system
Waves
transfer of energy fro the wind to the water = greater wind means greater wave
have a direct impact on the morphology of the coastline
other factors include - the size of the fetch, the time the wind has blown for, wind strength
crest - highest point of wave
trough - lowest point of a wave
wavelength = trough to trough/crest to crest
swash - movement of water up the beach
backwash - down the beach
wave refraction - waves dont approach a regular coastline, change in velocity caused by friction of seabed as wave approaches headland, the wave changes from parallel to wrap around the headland
Factors that affect the coastline
rock type - some rocks are more resistant to erosion than others eg granite v clay
wind strength - stronger energy transfer = more powerful waves
greater fetch - the larger the fetch the larger the wave etc
weather conditions - temp and rainfall, diurnal and acidic rain
wave type - destructive and constructive, erosional and depositional
beach size
human defences
vegetation - biological weathering
Tides
the periodic rise and fall, a vertical displacement of the water in the level of the sea
the gravitational pull of the sun and moon
the pull of the moon is greater
spring high tide - greatest tidal range, sun and moon in line, furthest up beach, strongest pull
both - 2 of each per month
neap high tide - perpendicular alignment, lowest tidal range, weakest pull, least likely to be linked to flooding
Sediment cells
11 around england and wales
subcells within those 11
ideally show dynamic equillibrium
eg River Severn to Lands End
movement of sand and shingle in the near shore zone by longshore drift has been found to occur in discrete functionally separate cells
Processes
erosion, weathering, mass movement, deposition
dynamic equilibrium
- the coast is in a state of equality, there is no net loss or gain of sediment
positive feedback
- where flow or transfer leads to an increase in sediments eg constructive waves and beach replenishment
negative feedback
- this is where flow or transfer leads to a decrease or decline in sediment eg destructive waves, groynes and sediment starvation
Erosion
abrasion - sediment thrown at cliff face
hydraulic action - sheer force of water pushes air into cracks
corrosion - salt water reacts with rocks and weakens them
attrition - collision of sediment which breaks it apart
transport
traction - large boulders are dragged and rolled across the seabed
saltation - sediment is bounced along sea floor
suspension material is small enough to be held in the flow
solution - dissolved material
weathering
mechanical weathering
freeze thaw weathering
frost shattering
high diurnal temperature
rainfall and temperature are the main factors
chemical weathering
acidic rain ph of 4
limestone and chalk have natural faults
biological weathering
root systems grow into rocks weakening them
sea creatures such as piddocks drill into rock surfaces and weaken them
wave types
destructive waves
example of negative feedback
break at a steep angle
remove sediment from the beach
strong backwash and weak swash
high amplitude
erosional
high frequency
11-15/minute
constructive waves
low frequency 6-9/minute
long wavelength
low amplitude
strong swash and weak backwash
positive feedback
depositional waves
Inputs
waves, tides, sediment, suns energy, wind, pollution, engineering
outputs
stack, caves, arches, headlands, beaches, spits, wave cut platform, bays, bars