Landforms Of Depostition Flashcards
Spit
Longshore drift moves material along the coastline. A spit forms when the material is deposited.
Bar
A ridge of sand or shingle which forms across the mouth of a river or entrance to a bay or harbour. Longshore drift transports sediment and deposits it.
Tombolo
Change in the shape of the headland results in the formation of a spit.
The spit grows out from the mainland and joins to an island creating a tombolo.
Storm beach
At the back of the beach, very powerful waves during storm conditions may deposit larger material forming a storm beach.
Cuspate foreland
Formed when longshore drift comes from both ways.
Breakpoint bar
Ridges of sediment with crests generally running parallel to the coast which form where steep destructive waves break.
Berm
Smaller ridges that develop at the position of the average high tide marks resulting from deposition.
Ridges and runnels
Occur in sand. They form parallel to the shore in the foreshore zone. Ridges are raised above the shore, either side of a runnel. They form as a simple drainage route for water.
Cusps
Beach cusps are made up of various grades of sediment in an arc pattern. The horns are made up of coarser materials and the embayment contains all the finer grade sediment.
Barrier islands
Narrow nearshore or offshore deposits of sand or sediments that are parallel to the coastline. The islands are separated from the mainland by a shallow lagoon. They are often found in chains and are separated by narrow tidal inlets. Glaciers melted after the last ice age, the sea levels rose and the contained sediment from the ice was released. Rising water pushed the sediment towards the land and was deposited in shallow areas just off the coast. Waves then continued to bring in sediment and build up the islands.
What 5 things do you need to form a sand dune?
- large supply of dry sand
- large tidal range (sand has longed to dry/ wet sand cannot be picked up)
- gently sloping beach
- onshore winds that are 15kph + (sand picked up and blown by wind- saltation)
- object/obstacle (forms a windbreak, slowing down sand)
How is a sand dune formed?
Sand piles up by and object and turns into an ever increasing wind break.
Sand piles into a dune at the back of the beach.
Sand is pushed over the dune crest, falling down the steeper windward slope.
The dune moves steadily inland.
Pioneer plants colonise the dunes.
Roots eventually hold sand in place.
New sand dunes build up behind the first dune.
3 features of new/embryo dunes
- continually moving sand (covers up pioneers, no anchor points for roots, very abrasive to plant tissue)
- very little freshwater (rainwater rapidly percolates through coarse sand, no organic matter to retain water, salt from sea spray makes it hard for plants to absorb water)
- very few nutrients (there is no dead organic matter being recycled in the sand)
Name 2 pioneer species for sand dunes
Sand couch grass
Lyme grass
How are pioneer species adapted to live on sand dunes? 3 adaptions
- tolerant of salt (live closer to sea)
- waxy leaf coating (retains water)
- rolled leaves (reduces transpiration)
Give 2 adaptions of marram grass for living on sand dunes
- can grow up to 1m per year (doesn’t get covered by new sand)
- can spread sideways up to 3m per year (helps to trap sand and keep it in one place)
4 ways that conditions change moving inland on sand dunes
- exposure (wind) decreases
- less salt water, more fresh water so plants don’t have to be specialist
- more nutrients inland as more organic matter in soil
- very little sand movement as vegetation covers the dune
Name the main plant on a mobile dune
Marram grass
Name the plants found on semi fixed dunes
Many plants beside marram grass
Name the plants found on fixed dunes
Marram grass is sparse
Many species of plants are present
What plants are found in dune slacks
Short vegetation due to rabbits
What plants are found in the climax of a sand dune?
Scrub and woodland
What is succession?
Where primary succession takes place, only a few species can cope (pioneer species). Gradually over time conditions change and become more favourable to a wider range of vegetation types. The end stage is the climatic climax community, it is a community of vegetation adapted to the climate of the area.
How is a salt marsh formed?
- Salt marshes start as mud flats
- in areas of sheltered water, sediment clumps together and sinks (flocculation)
- as plants arrive, their roots make mudflats more stable
- as the mudflats build up, plants can grow there and create a salt marsh habitat
Where do salt marshes develop?
On depositional coasts where tidal action is fairly gentle.
E.g. Estuaries, enclosed bays, behind barrier islands, low energy coastlines
There must be very little wave action or fine particulate cannot build up.
What sort of plants are salt marshes dominates by?
Halophytic (salt tolerant) plants
Give 3 examples of salt marsh pioneer species
Glasswort
Cord grass (spartina)
Eel grass
Give examples of how pioneer species are adapted to live in a salt marsh
Roots help to consolidate and bind mud
Spartina roots are 2m long and anchor the sediment
The upper parts trap more sediment 1-2cm/yr
When plants die the roots stay in the mud and hold it together
What sort of plants are found in a salt marsh when mud height increases
Salt marsh grass
Sea aster
As mud grows even higher on the salt marsh what is the vegetation like?
More species taking up more space and less bare ground. The muddy shore spends more time emersed (out of water). The plants grow bigger and exist is greater abundance.
What plants are found at the top of the salt marsh?
(Damp) Rush Sedge (Dry) Red fescue If there's freshwater at the top of the marsh, it can develop into scrub and eventually forest.
