Coasts part 3
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Describe the characteristics of a salt marsh and explain their formation
Saltmarshes are intertidal mudflats of stagnant water, exposed at low tide.The form in sheltered areas along the coast, such as behind a spit, plants begin to colonise the area and make the salt marsh difficult to erode once it is established
What type of vegetation grows in marshes?
halophytic vegetation (salt tolerant)
What conditions are needed to form dunes? (4)
- onshore winds
- large foreshore area of sand
- space behind high tide mark
- presence of coloniser plants
What factors affect a salt marsh? (4)
- sediment supply
- human action
- wave type
Give an example of a pioneer species in a salt marsh
Describe the characteristics of pioneer plants on a salt marsh
- Withstand long periods submerged by salt water
- cope with a high pH
- hollow stems to allow oxygen to the roots from the air
- can secrete salt through leaves
- roots anchor it to the mud
What plants may develop as a salt marsh becomes more established?
- Sea lavender
- Sea aster
What plants grow when a salt marsh has reached its climax?
How might humans interfere with salt marshes? (3)
- destroying it to make space for something else eg oil refinery
- draining it for agriculture
- managing it so it doesn't progress as part of a wildlife scheme
- eutrophication from fertiliser outwash changes composition of land
Why does sea level change threaten salt marshes?
salt marshes are low lying and may be flooded
Name the benefits of salt marshes
- natural coastal defence
- wildlife habitat
- able to adapt in response to sea level change
Describe salt marshes as a sea defence
- only useful in areas of low lying land that can be given up to the sea
- prone to disease and pollution can kill them
- used in managed retreat (soft engineering)
What are the different salt marsh zones? (6)
- Pioneer Zone
- Low-mid marsh zone
- mid-upper marsh zone
- drift zone
- upper marsh swamps
- transition zone
Name the dune types in order from smallest to biggest
- Embryo dune
- Fore dune
- Yellow dune
- Grey dune
- Mature dune
Define: coastal sand dunes
accumulations of sand shaped into mounds by the wind, which develop on beaches that have a large tidal range
Give an example of a plant found on an embryo dune
marram grass (deep rooted)
Give an example of a plant found on a fore dune
Give an example of a plant found on a yellow dune
Give an example of a plant found on a grey dune
Give an example of a plant found on a mature dune
Give an example of a plant found in a dune slack
willow (loves water)
What is the pH of an embryo dune?
pH = 8
What is the pH of a fore dune?
What is the pH of a yellow dune?
What is the pH of a grey dune?
What is the pH of a mature dune?
how are embryo dunes formed?
- sand is picked up by onshore winds
- transported by saltation
- becomes trapped behind an obstacle
- more sand becomes trapped
What are the conditions in a embryo dune?
- no water
- alkaline conditions
- can only be colonised by pioneer species like marram grass
What is a psammosere?
ecological succession that began life on newly exposed coastal sand. Ranges from small grasses to large trees.
What are dune slacks?
Lower areas in between mature dune ridges
How do humans threaten sand dunes? (5)
- removal of sand for mineral extraction
- trampling it
- levelling of land for development purposes
- water abstraction
- conversion into agricultural land
Why does organic matter decay as dunes age?
dunes move further away from the sea as they age which reduces sand supplies and causes decay
Which type of dune is also known as a fixed dune and why?
Grey dunes are also known as fixed dunes because they are unlikely to move and have become completely colonised
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