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A Level Physical Geography > Coasts- Landforms & Landscapes > Flashcards

Coasts- Landforms & Landscapes Flashcards

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1
Q

Concordant coastlines

A

Rocks on these coastlines run parallel to the sea

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2
Q

Discordant coastlines

A

Rocks on these coastlines fun perpendicular to the sea

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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
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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
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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

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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)
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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)
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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
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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
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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)
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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
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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
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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

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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

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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
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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
Q

How could you determine the age of a sand dune?

A
  • 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
Q

Embryo dune

A
  • 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
Q

Fore dune

A
  • 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
Q

Yellow dunes

A
  • 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
Q

Grey dunes

A
  • 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
Q

Dune slacks

A
  • found between mature dunes and where the water table reaches the surface
  • plants adapted to damp and shelter
  • peaty soil
31
Q

Mature dunes

A
  • 100m from shore
  • if undisturbed can support shrubs, trees etc.
  • humans may plant fast growing conifers
32
Q

Pioneer species

A

The first plants that colonise an area, usually with special adaptations

33
Q

Halophytes

A

Salt tolerant species eg. glasswort and cordgrass

-they can also tolerate the periodic soaking of the sea caused by tides

34
Q

What are the required conditions for mudflat formation?

A
  • sheltered areas where deposition occurs
  • where salt and freshwater meet
  • low energy coastline
35
Q

Salt marsh succession

A
  • 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
Q

How might sea level rise threaten salt marshes?

A
  • 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
Q

What are mudflats?

A

Created by the deposition of fine salts and clays in sheltered, low energy coastal environments (eg. estuaries)

38
Q

What is a salt marsh?

A

An area of coastal grassland that is regularly flooded by sea water eg. Darwin, Australia

39
Q

What human threats are there to salt marshes?

A
  • 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

A Level Physical Geography (26 decks)

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