Coasts Flashcards
litoral cell
area near coastline where high and low tide occur
sediment inputs
if deposition is bigger then coats is expanding
if erosion is bigger the coast is retreating
energy inputs
tides
currents
precipitation
gravity
foreshore zone
part of shore between high and low tide marks
nearshore zone
shallow waters nearest land
backshore zone
area furthest from sea
only affected by waves in big storms or spring tides
the 5 processes
weathering
erosion
deposition
transport
mass movement
outputs
erosional landforms
depositional landforms
different types of coasts
rocky coastlines
high relief
resistant rock
high wave height
destructive waves erosion is greater than deposition
sandy coastlines
low relief areas
not resistant rock
low wave height
constructive waves
deposition is greater than erosion
esturaine coastlines
low relief
salt marshes and mudflats
low energy
soft rock
constructive waves
example of discordant coastline and concordant coastline in Britain
d - holderness
c - dorset
concordant coastline
alternating bands of hard n soft rock parallel to coast causing lower rates of erosion
discordant coastline
alternating bands of hard and soft rock at 90 degrees to coast
what forms at concordant coastline
Dalmatian coats
what forms at discordant coastline
headlands and bays
igneous rocks
formed by magma crystallization the crystals interlock , resistant to erosion, contain few joints and weaknesses (Basalt and Granite)
metamorphic rocks
formed by change in heat and pressure, resisant to erosion as crystals overlap but don’t interlock . (Slate and Marble)
sedimentary rocks
formed by build up of sediment , not resistant to erosion . Limestone and chalk
permeable rocks
poreous - contain pores that allow water
numerous joints
less resistant to erosion as surface vulnreable to chemical weathering is increased
dune order
embryo , fore , yellow, grey, mature
what dunes to sea rocket and crouch form in
embryo and fore dune
how dunes change as you get further away from coast
stronger
more vegetation
more sheltered
embryo dunes
form at coastline
have pioneer plants - these increase soil nutrients and allow other plants to grow
xerophyetes
tolerate dry conditions
halophyetes
tolerate salt
constructive waves
strong swash
weak backwash
deposition greater than erosion
destructive waves
larger height
shorter wave length
strong backwash, weak swash
create steep, narrow beach
erosional processes - hydraulic action
wave gets into cracks of cliff and widens them - force of water breaks rocks
destructive waves are more effective
erosional processes - abrasion
pieces of rock hit against the sea bed
destructive waves are more effective
erosional processes - attrition
pieces of rock hit against eachother becoming smaller and more rounded
destructive waves are more effective
erosional processes - corrosion
chemical reaction between sea water leaving minerals and a solution
susceptible rock such as limestone
constructive waves are more effective
mechanical weathering
application of force onto rock
( freeze thaw weathering , wetting and drying , salt crystal growth)
chemical weathering
a weak chemical reaction between water and rock where rainwater mixed with carbon dioxide forms carbonic acid , this reacts with carbonate in limestone to form bicarbonate which is soluble.
biological weathering
rocks broken down by living things
( plants roots widening cracks in rocks, rock boring where animals live in a rock)
inputs / sources of a sediment cell
cliff erosion
subaerial processes
onshore currents
transfer’s of sediment cell
processes that move sediment between sources and sinks
( LSD , swash , backwash , wind)
sinks of sediment cell
areas and landform where sediment is stored
( sand dunes , beaches , barriers)
eustatic change
rising of sea level due to ice age - ice melts and sea rises
isostatic change
rise in land as ice was sat on it and melts so land rebounds
tectonic change
land rises and sinks at boundaries
emergent coastlines
coast line rises relative to sea level
submergent coastlines
coast being flooded by sea due to rising sea levels
5 depositional landforms
Spits, Bars, Bayhead Beaches, Tombolos, cuspate forlands
depositional landforms- spit
long finger of sand sticking out from beach caused by LSD ( Duriston head)
depositional landforms- bar
spit grows accross a bay ( start bay devon)
depositional landforms - curved spit
spit curves inland due to prevailing winds
depositional landforms - cuspate foreland
triangle shape caused by LSD from 2 directions
depositional landforms- bayhead beach
beaches formed in bays by constructive waves
( Durdle door)
depositional landforms- tombolo
spit that has joined two landscapes ( portland bill)
Caves
weakness in a cliff widens
Arches
cave erodes whole way through
( durdle door)
stack
top of arch collapses
stump
stack erodes futher
Longshore drift
wave approaches at an angle , backwash pushes it straight, difference in angles between swash and backwash mean sediment is transported along the coast
wave cut notch and wave cut platform
sea attacks base of cliff which then collapses and creates an overhang
overhang eventually collapses
once this has collapsed the rubble watches away and creates a wave cut platform
3 soft engineering strategies
beach nourishment , cliff regrading, dune stabilisation
beach nourishment and a positive and negative ( Lyme Regis)
transporting sediment from elsewhere to beach.
Costs - £300,000 for 100 metres
positive - cheap and easy to maintain, looks natural , increases tourism
negative - needs constant maintenance because of erosion
cliff re grading and a positive and negative
reducing angle of cliff to help stabilise it
positive - works on clay or loose rock where other methods don’t work
negative - can cause cliff to retreat
marsh creation and a positive and negative
allowing low lying areas to flood so land becomes a salt marsh
positive - cheap , creates natural defence and habitat to wildlife
negative - agricultural land is lost
dune stabilisation and a positive and a negative
creation or restoration of dunes by either fencing them off or planting maram grass
positive - maintains environment for wildlife and is cheap
negative - planting marram grass is time consuming
5 hard engineering strategies
sea walls , rip rap , groynes , revtments, off shore breakwater
sea walls and a positive and negative
concrete walls that refract wave energy
positive - little maintainence
negative - expensive
rip rap and a positive and negative
pile of boulders to reduce energy
positive - cheap
negative - limit beach access
revetments and a positive and negative
angled sea wall
positive - most cost effective
negative - regular maintenance
offshore break waters and a positive and negative
pile of rocks parralell to coast
positive - calm beach conditions
negative - expensive