1
Q
Formation of beaches
A
- large sediment is found towards the top of the beach where it has been left from storms
- backwash is often weaker than the Swash as the water quickly percolates into the sand
- as backwash isn’t as powerful, larger sediment remain at the top of the beach
- scree near the cliff as a result of mass movement + weathering means that angularity increases towards the cliff
2
Q
Formation of a storm beach
A
- formed during storms - material deposited above high water mark
- semi-permanent, can become vegetated
3
Q
Formation of cusps
A
- semi-circular depressions formed by a collection of waves reaching the same point
- once the curving shape is created, Swash is concentrated in the small bay that forms in the centre of the cusp
- this creates a stronger backwash that removes material down the beach
- act like headlands + bays once formed
- few cms high, few metres across (up to 60m)
4
Q
Formation of anastomosing drainage basins
A
- mini drainage basins formed by water flowing down the beach often from runnels
5
Q
Formation of runnels (ripples)
A
- formed by turbulence + wave action
- the spreading out of wave energy across a wide area of beach creating ridges + intervening depressions
- common on sandy, shallow beaches
6
Q
Formation of breached ridge
A
- raised area on beach
- cause water pools to form (runnels) which drain over time by breaching the ridge
7
Q
Formation of Swash-aligned beaches
A
- form in low energy environments e.g. bays
- waves approach parallel to the shore, so there is limited LSD
- sediment doesn’t travel far along the beach where it
- wave refraction may reduce the speed of high energy waves, leading to the formation of a shingle beach with larger sediment
8
Q
Formation of drift-aligned beaches
A
- forms when waves approach at an angle
- so LSD causes sediment to travel far along the beach = may lead to the formation of a spit at the end of a beach
- generally larger sediment is found at the start of the beach + weathered sediment moves further down the breach through LSD (smaller sediment at the end)
9
Q
What is a spit?
A
A long narrow strip of land which is formed when LSD causes the beach to extend out to sea due to changes in direction of coastline
10
Q
Spit formation
A
- LSD transfer material along the coastline following the direction of prevailing winds as Swash
- if a chnage in direction of coastline occurs, material continues to be transported following the direction of LSD
- deposition of sediment occurs when there is a drop in velocity, commonly at estuaries as the flow into the sea is stronger than the LSD
- this causes the build up of sediment + therefore the extension of land out to search due forming a spit
11
Q
What can influence the shape of a spit?
A
- changes in direction of prevailing winds will influence wave direction + therefore cause the change in direction of transported material
- wave refraction can also create a recurved tip as material is carried round into the more sheltered water behind the spit
12
Q
How may a spit change over time?
A
- the recurved end may be abandoned as a new spit will be formed on the old recurved end + so on
- this creates a spit with multiple recurved ends = compound spit
13
Q
Formation of offshore bars
A
- also known as sand bars
- submerged or partly exposed ridges of sand created by waves offshore
- destructive waves erode sand from the beach with their strong backwash + deposit it offshore
- offshore bars act as both sediment sinks + input stores
- they can absorb wave energy thereby reducing the impacts of waves on the coastline
14
Q
Formation of a tombolo
A
- a beach or ridge of sand + shingle that has been formed between a small island + mainland
- deposition occurs where waves lose energy due to wave refraction off the island + the tombolo begins to build up
15
Q
Formation of barrier beaches
A
- where a beach or spit extends across a bay to join two headlands
- this traps water behind it leading to the formation of a lagoon which is separated from the sea
- some barrier beaches may have been formed due to rising sea level after the last glacial period = meltwater from glaciers deposited sedimentary in the coastal zone
16
Q
Sand dune formation
A
- occur when prevailing winds blow sediment to the back of the beach
- the formation of dunes therefore require large quantities of sand + large tidal range
- this allows the sand to dry, so it is light enough to be picked up + carried by the wind to the back of the beach
- dunes develop as a process of a vegetation succession
17
Q
Vegetation succession for sand dunes
A
- pioneer species such as sea rocket are resistant to+ able to survive in the salty sand, with it’s roots helping to bind the dunes together
- decaying organic matter adds nutrients + humus to the soil allowing marram grass to grow
18
Q
Dune structure
A
- embryo dunes = upper beach area where sands starts to accumulate around a small obstacle
- yellow dunes = more sand accumulates + dune grows - vegetation may develop to stabilise the dune - tallest of succession
- grey dunes = sand develops into soil with lots of moisture + nutrients, as vegetation dies enabling more varied plant growth
- dune slack = water table rises closer to surface allowing the development of moisture loving plants
- mature dunes = sandy soils develop due to greater nutrient content, trees will grow (willow, oak etc.) = woodland area becomes windbreak to mainland behind
19
Q
What are salt marshes?
A
- in sheltered bays or behind spits, salt + minerals will build up
- vegetation may establish, further stabilising the salt marsh
- like sand dunes, salt marshes can stabilise through vegetation succession
20
Q
Formation of mangroves
A
- trees that are adapted to grow in saline, low oxygen conditions
- they develop in coastal swamp areas
- they can stabilise shorelines with roots + protect areas from erosion as well as providing an environment for wildlife
21
Q
Tidal sedimentation in estuaries
A
- estuary = point where river meets sea
- when the flow of water from the river meets the incoming tides + waves from the sea, the water flow ceases so sediment is deposited
- flocculations also causes rapid deposition
- pioneer plants colonise the area leading to more sediment being trapped
- mudflats + salt marshes may develop as a result
22
Q
Embryo Dunes
A
- sand couch grass
- pH 8-8.5
- humus <1%
- 20-50m inland
23
Q
Fore Dunes
A
- marram grass colonises = binding soil together + provides organic matter
- pH 8
- humus 1-2 %
- 50 + years
- 50-80m inland
24
Q
Yellow dunes
A
- marram/ sea sedge = more organic material
- pH 7-7.5
- humus 2.5%
- 100+ years
- 150m inland
25
Grey dunes
- creeping willow
- pH 6.5
- humus 5%+
- 150 years old
- 300m inland
26
Dune Slack
- orchids
- 6.5 pH
- humus 10%
27
Mature Dunes
- trees = eventually pine trees
- 4.5 pH
- humus 10%+
- 2000m inland
28
Formation of salt marshes
- salt marsh begins when mud + silt are deposited along a sheltered part of the coastline = lack of energy means rate of deposition is greater than transportation
- the deposition builds up over time = mud breaks the surface to form mudflats
- some plants begin to grow e.g. cordgrass = pioneer plants, tolerant to seawater + long roots bind mud + sediment together
- due to sediment accumulating it gets covered by the tide less = this leaches out some of the salt + means plants can grow in more fertile soil
- over time bigger plants will grow until marsh uplands form that has trees as well as plants
29
Where do salt marshes form?
- low energy coastlines
- behind spits + barrier islands
- in estuaries + harbours
8.2 Coastal Landforms
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