Characteristics and formation of coastal landforms Flashcards
types of erosional landforms
bays & headlands
wave cut platforms
cliffs
wave-cut notches -> caves -> arches-> stacks -> stumps
types of depositional landform
beaches
simple and compound spits
tombolos
offshore bars
barrier beaches
coastal dunes
tidal sedimentation in estuaries: coastal saltmarshes
mangroves
two types of coastline:
concordant
discordant
what type of coastline has bays and headlands
discordant
what is a discordant coastline
is in disagreement with the geology of the coastline
Purpendicular to the geology
what is a concordant coastline
parallel to the lithology of the coastline
formation of wave-cut platforms
a flat rock area in the intertidal zone created by destructive waves concentrating its energy on the base of the cliff causing it to erode leaving an overhang which will become unstable and drop onto the platform. This sediment is then carried out into the sea with the tides
erosion of a headland
cracks in the intertidal zone become exposed by hydraulic action
cracks are widened to become wave-cut notches
wave refraction causes destructive waves to concentrate their energy on the sides of the headland, creating caves
if aligned these will create arches
over time the arch will become unstable and will drop, creating a headland and a stack
the stack will be eroded and weathered, then becoming a stump
what are the two types of beach
swash and drift aligned
swash aligned beaches are…
formed in low energy environments, in bays, with a large beach profile often with berms and sand dunes
drift aligned beaches require….
a regular supply of sediment to sustain them. without human management these lead to the formation of spits, bars, tombolos and barrier islands
features of a beach (sea to sand)
ridges and runnels
ripples
cusps
berms
storm beaches
what are berms
low hills of sand or gravel that forms at the upper limit of the swash. They
are short-term features and are removed by successive tides and storms
what are cusps
crescent-shaped embayment developed on beaches of mixed sediment, formed where sand meets shingle
what are simple spits
a long SINGULAR narrow extension of sand or shingle which has one end attached to the coastline and one out into the sea, formed by longshore drift
what are recurved spits
those shaped by the effects of tides or local changes in wind direction
what are compound spits
those with multiple protrusion from the spit, often from storms
what are tombolos
when spits extend from a coast to an island
howare esturane mudflats created
created by flocculation in sheltered low energy coastlines
what are saltmarshes
mudflats with the addition of vegetation, areas of flat silty sediments around esturies or lagoons
list the three environments which saltmarshes can form in
sheltered areas where deposition occurs
where salt and fresh water meet
where there are no strong tides or currents to remove deposited silts
salt marsh succession:
starts below high tide
only needs a loss of energy for flocculation to occur
pioneer species grow between high and low tide (sward zone)
gradually mud rises above high tide and the low marsh develops
soil conditions improve and meadows are formed
climatic climax is reached in the uplands
threats to saltmarshes
sea level rise
development along a coastline
storms
sand dune development
sand bounced along the beach by saltation
trapped by physical obstacles e.g driftwood
embryo dunes are suitable for colonisation of pioneer species
these provide stability, binding the sand together to create foredunes/mobile dunes
as more plants grow these become fixed dunes
over time dunes mature and reach climatic climax
dune slacks
vs
creeks
near the water table on a sand dune
develop to remove water, within the intertidal zone
why are mangroves important
important for ecosystems and wildlife such as the manatee, lizards and Bengal tigers
natural coastal protection from storm surges, coastal erosion and
characteristics of mangroves:
found in tropical and sub-tropical areas
between 20degrees N-S
found along the coasts of Africa, Australia, Asia and the Americas
conditions required for mangrove growth
permanently waterlogged soil
in areas with a limited supply of freshwater
hot weather
intense sunlight
gently sloping coastline with mudflats
the values of mangroves
ocean tsunami of 2004, where the mangroves had been removed 6000 died, only 2 deaths where they still were
tourism provides 75% GDP
threats to mangroves
human clearance - tourist development
agricultural land
settlement
infrastructure
overfishing
pollution
climate change
UN figures on mangrove clearance
estimates 20% lost since 1980. Thailand lost 50% since 1960 and Philippines 70% since 1920
