3.1.3.3 Coastal landscape development Flashcards
What are the stages of sand dune development
- Embryo
- Fore
- Grey
- Dune heath
What happens in the embryo dune stage
- driftwood or litter traps sediment
- accumulation occurs
- pioneer plants create stability
What happens at fore dunes
An increase in humus causes an increase in vegetation
What happens at grey dunes
- the sand is grey
- there is an organic layer
Define dune slacks
- deep dips
- below the high water mark
What is a dune heath
Marks the end of the successional landform, generally a woodland area.
What are the steps of salt marshes (halospheres)
1) algae
2) less hostile conditions allows for pioneer plants to settle such as Spartina grass
3) an increase in vegetation
4) as the land rises above sea level, less flooding occurs and less salt tolerant vegetation occurs
Why is algae beneficial to the development of salt marshes
- survives high salinity
- survives high turbidity
- survives being inundated and low oxygen levels
- slows currents which allows for deposition
Why is Spartina well suited to the salt marsh environment
- the two root system (one horizontal and one vertical)
- one root binds to the mud
- the other anchors it in place
- Spartina traps more mud than any other British plant
What is a salt marsh
Tidal space where flocculated mud is caught in roots of halophytes (salt loving plants)
This builds up and dries out
Define a swash aligned beach
- where waves move up the beach
- parallel to incoming wave crests
- minimal longshore drift
Define a drift aligned beach
- parallel to the direction of dominant LSD
- sediment can be transported long distances
Define a spit
Narrow piece of land with one end joined to the mainland and another projected out to sea
How is a spit formed
When longshore drift occurs an the coastline changes direction
Provide an example of a spit
Spurn Head, Holderness
What can spits lead to the formation of
Salt marshes
Define a bar
When a spit connects two headlands
Define a tombolo
A spit which joins an island
Provide an example of a tombolo
Chesil beach, Dorset
- 30km long
- links to the isle of Portland
4 conditions necessary for the development of sand dunes
- high tidal range
- abundant supply of sand
- gentle beach profile
- vegetation which can stabilise
4 conditions necessary for the development of salt marshes
- low energy, sheltered environment
- high supply of fine material
- mixing of fresh water and salt water for flocculation
- roots of vegetation to hold the sediment
Define flocculation
Where salt water meets fresh water and fine particles combine and aggregate
Define a discordant coastline
Where lines of rock run perpendicular to the shoreline
Why do headlands and bays form on discordant coastlines
Because the soft rock is eroded faster than the hard rock
Explain wave refraction
- bending of waves to mirror the shape of the coast
- as waves reach headlands, the water shallows and friction cause the wave to slow
- the waves in deeper waters continue unimpeded
- this bends the wave
Factors effecting erosion of cliffs
- lithology of rock
- the angle of dip
Define a wave cut notch
Where erosion caused a cliff to be undercut
Define a wave cut platform
- a wave cut notch puts stress on the cliff which collapses
- increased retreat causes wave cut platform
Define eustatic change
Change in the volume of water
Define isostatic change
Change caused by vertical movement of the land
What are the main causes of eustatic change
- tectonic change (sea floor spreading increases the volume of the basin)
- changes in temperature
What are the main causes of isostatic change
- tectonic uplift or depressions
- accumulation and melting of ice sheets compresses or decompresses the land
Which areas of the UK are at risk from sea level rise
Hull, London and Middlesbrough
What are rias
- submerged river valleys
- wide and deep at the mouth
What are fjords
- submerged glacial valleys
- shallow at the mouth and deep inland
- Sognefjorden, Norway is over 1000m deep in places
What are dalmatian coastlines
- where flooded valleys are parallel to the coastline
- leaving islands
How can sea level rise affect freshwater
Saltwater intrusion in aquifers
How has the rate of sea level rise changed
Moved from 1-2mm per year to 4-5mm per year
Kiribati context
- 100,000 population
- 50,000 on the main atoll Tarawa
- low lying mangrove atolls
- 1m above sea levels in places
How is Kiribati in danger
- many of the atolls could disappear within 50 years
Social defences to rising sea levels
- residents are proud of the country so they build many of the defences
- ‘migration with dignity’ campaign allowing for residents to apply for jobs in neighbouring countries if the islands are submerged
Environmental defences in Kiribati
- over 50,000 mangroves planted to protect against storm surges
What has president Tong done in response to salinisation of water and farmland
Bought 20km squared of land in Fiji
How does Kiribati maintain economic stability
- people make palm sugar to sell
