Coasts- Landforms & Landscapes Flashcards
1
Q
Concordant coastlines
A
Rocks on these coastlines run parallel to the sea
2
Q
Discordant coastlines
A
Rocks on these coastlines fun perpendicular to the sea
3
Q
Wave cut platform formation
A
- waves breaking at the foot of a cliff produce a wave-cut notch (due to erosion by waves)
- as the cliff is undercut, the rock above collapses and so the cliff gradually retreats
- a sloping rocky platform (wave cut platform) is left behind, which is covered at high tide
4
Q
How do wave cut platforms impact rates of erosion?
A
- as the platform grows the waves have further to travel in shallower water
- this means they tend to break earlier and dissipate their energy
- the rate of erosion of the headland is therefore reduced
- this limits further growth of the wave cut platform
5
Q
What is a cliff profile?
A
The cliff profile refers to his steep the cliff face is at its meeting point with the sea
6
Q
Impact of different bedding planes on cliff stability
A
- of bedding planes are horizontal then the cliff profile will be stable with a steep cliff face
- rock that has been lifted (due to tectonic movement) with its bedding planes tilted downwards away from the coast create very stable cliffs
- bedding planes that tilt upwards have a cliff profile similar to the angle of tilt- due to the frequency of mass movements that occur at the base of the cliff (from wave action)
7
Q
How does a headland erode to form a stack?
A
- a headland is attacked by waves along lines of weakness
- this frequent erosion (eg. hydraulic action) forms a cave
- if the weakness runs through the headland, two caves may form back to back- eventually forming an arch
- wave attack continues at the base of the arch while sub-aerial weathering (eg.freeze thaw) attacks the roof
- eventually this roof collapses leaving a stack (an isolated column of rock)
8
Q
What is a spit?
A
- a long narrow piece of land joined to the mainland which projects out to sea/across a river estuary
- a depositional landform made of sand and shingle
- form at drift-aligned beaches
9
Q
Formation of a spit
A
- longshore drift moves material along the coastline in the direction of the prevailing wind
- as the coastline changes direction the finer material will continue to be transported out to sea
- this will build outwards and upwards and form a permanent feature
- material can’t extend to meet the mainland due to river currents in the estuary and increasing water depth
- wave refraction and secondary wind forces the material to move in a different direction-results in s curved end
10
Q
Beach formation
A
- beaches form in a low energy environment where sediment must be present
- deposition must be the dominant feature where effects of waves are reduced
- beaches form when there is insufficient energy to move sediment further so it is deposited
- occur in the littoral zone (between low and high tide)
11
Q
Beach profiles in the summer
A
- steeper in the summer
- waves are more constructive
- energy dissipates and deposits sediment over a wider area
12
Q
Beach profile in winter
A
- destructive waves more common
- beaches eroded by high-energy waves
- sometimes backwash exerts a rip current dragging sediment back as the next wave arrives over the top
- so the beach profile flattens
13
Q
Ridges and runnels
A
Ridges- sand accumulations at the lower edge of the beach (form longshore bars)
Runnels- channels through which backwash goes out to sea
14
Q
What is sediment at the top of the beach like?
A
- larger pebbles
- backwash weaker than swash so large sediment can’t be dragged back into the sea
15
Q
What is sediment at the bottom of the beach like?
A
- smaller pebbles
- more rounded due to constant actions of waves causing abrasion and attrition
- scree falling from cliff face can explain more angular sediment
16
Q
Properties of swash aligned beaches
A
- form in low energy environments eg. bays
- waves arrive roughly parallel to the shore
- beach may consist of sand or shingle
- beach is self contained and length will not change as no longshore drift is taking place
17
Q
Properties of drift aligned beaches
A
- form where the waves approach the coast at an angle
- longshore drift moves sediment along the beach- often accumulating in the form of a spit
- finer shingle particles likely to be carried further along the beach and become increasingly rounded
18
Q
Compound spits
A
Spits with hooks on their land ward side
19
Q
Simple spits
A
Bars of sand without barbs or hooks
20
Q
Formation of tombolos
A
- formed when spits extend from the coast to an island
- may form in the ‘shadow’ of wave refraction caused by an offshore island
- can only form along low energy coastlines (constructive waves means deposition is dominant process)
- must be a supply of sediment to deposit
- must be a drift aligned coastline
21
Q
Formation of bars
A
- when waves approach a gently sloping coast, friction between waves and the sea bed cause waves to break some distance from the coast
- overtime more material builds up parallel to the coast to form ridges called offshore bars
22
Q
Lagoon
A
- form when a bar connects to headlands on either side of a bay and is large enough to be above sea level
- this bar is called a barrier beach
23
Q
What are sand dunes?
A
Accumulations of sand blown into mounds by the wind (aeolian landforms)
24
Q
Sand dune formation
A
- sand accumulates on the beach from longshore drift
- at low tide, the sand dries out allowing the prevailing winds to move the loose sand up the beach
- large inter tidal zone for sand to be dry (time between high and low tide)
- sand transported by saltation
- debris on beach traps sand (called strand line)
- grass grows which stabilises the dunes
25
How could you determine the age of a sand dune?
- size of the dune
- type of plants growing
- amount of vegetation
- luminescent dating (measure radiation to see when sand was last exposed to the Sun)
26
Embryo dune
- sand continuously moving
- high pH over 8
- high wind speed
- no more than 1m high
- 80% of sand exposed
- plant type: sea twitch and Lyme grass
27
Fore dune
- drought resistant plants colonise eg. Lyme grass and marram grass
- root systems bind sand together
- as they grow, more sand is trapped and dunes increase in height (up to 5m)
- 20% of sand exposed
28
Yellow dunes
- more diversity of plants
- humus layer builds
- pH slightly alkaline
- marram grass dominates other vegetation
- dunes 5-10m high
- 80% of sand vegetated
- rabbits and other mammals enrich soil
29
Grey dunes
- 100% vegetation
- 50-100m from sea
- sheltered from winds
- humus darkens allowing soil to form
- pH more acidic
- water content low
- 10m high and wider
30
Dune slacks
- found between mature dunes and where the water table reaches the surface
- plants adapted to damp and shelter
- peaty soil
31
Mature dunes
- 100m from shore
- if undisturbed can support shrubs, trees etc.
- humans may plant fast growing conifers
32
Pioneer species
The first plants that colonise an area, usually with special adaptations
33
Halophytes
Salt tolerant species eg. glasswort and cordgrass
| -they can also tolerate the periodic soaking of the sea caused by tides
34
What are the required conditions for mudflat formation?
- sheltered areas where deposition occurs
- where salt and freshwater meet
- low energy coastline
35
Salt marsh succession
- as tidal currents slow, mud and small particles are deposited close to high tide line
- floccuation-particles of clay stick together to form a mass that can sink into the seabed
- pioneer plants colonise which trap further deposits of mud
- mud level rises above high tide and salt marsh developed- and a wider range of plants develop
- soil conditions improve and vegetation succession continues
- shrubs and trees colonise
- by this time the upper levels of the marsh are rarely covered by sea
36
How might sea level rise threaten salt marshes?
- land is of relatively low value so that have been declared areas of managed retreat
- the salt marsh will act as a buffer against erosion of the mainland
37
What are mudflats?
Created by the deposition of fine salts and clays in sheltered, low energy coastal environments (eg. estuaries)
38
What is a salt marsh?
An area of coastal grassland that is regularly flooded by sea water eg. Darwin, Australia
39
What human threats are there to salt marshes?
- industrial pollution eg. oil pollution- may harm marsh species
- dredging- removes sediment which may reduce mudflat accumulation and disrupt marsh ecosystem
- commercial and recreational shipping- erodes marshes
- grazing- causes trampling of species
