Depositional Landforms Flashcards
How are bars formed?what do they do?
A spit that joins together 2 headlands
Obvious at low tide
Makes the water shallow at high tide
Causes waves to break early
Lagoon may be formed within a bay as a result of a bar
How are spits formed?
Sediment carried by longshore drift
A change in the shape of the coastline leads to more deposition
Hooked end can form if there is a change in wind direction (prevailing wind blowing at an angle)
Waves are unable to get past spit so water behind is very sheltered silts
Spit=spun head, holderness coast
How are tombolo’s formed?
Where a spit links the mainland and an island
How are sand dunes formed?
Formed and shaped by sand deposits that get blown off of the beach
Sufficient sand is deposited and dries in the intertidal zone
Sand is transported by saltation by the blowing wind
Sand dunes only form when the deposition is greater than erosion
Dried sand reaches top of beach and is trapped by debris eg driftwood, dead seaweed, rocks,pebbles
Sand becomes colonised by small plants
Small plants trap more sand
Ph of sand becomes alkaline and online hardiest plants survive eg Lyme grass
What are embryo dunes?
1st stage
Contain plants such as Lyme grass and marram grass
Species survive by growing upwards
Grow to around 1m
What are foredunes?
2nd stage
Initially yellow but darken as organic matter adds humus to soil
Dunes slightly alkaline
Grow to 5m
Around 20% of sand exposed
What are grey dunes?
3rd stage
More fixed
Acidic soil
Humus forms increasing water retention
New species eg creeping willow
Less than 10% sand exposed
8-10m high
What are wasting dunes?
4th stage
Little sand accumulates
Soil is more acidic, water retentive, high humus
Vegetation is heather and gorse
6-8m high
