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OCR A level Geography > Coasts KQ2- How are coastal landforms developed? > Flashcards

Coasts KQ2- How are coastal landforms developed? Flashcards

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1
Q

Define weathering

A

The in-situ decomposition of rock by chemical, biological, and physical processes

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2
Q

What is the effect of an increase of surface area of rock due to physical weathering?

A

-allows other weathering processes to take place

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3
Q

What climatic conditions mean physical weathering has more of an effect?

A

Large temperature fluctuations

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4
Q

Name 4 types of physical weathering

A
  • freeze-thaw
  • pressure release
  • thermal expansion
  • salt crystallisation
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5
Q

What causes freeze-thaw weathering?

A
  • water enters cracks in the rock and when it freezes it expands
  • the expansion puts pressure on the rock and can enlarge existing joints
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6
Q

What is the effect of freeze-thaw weathering?

A
  • even resistant rocks are split

- pieces of rock break off

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7
Q

What causes pressure release?

A
  • Overlying rocks are removed by weathering and erosion

- the release of pressure means underlying rock expands and fractures

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8
Q

What is the effect of pressure release?

A

-Parallel fractures are formed

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9
Q

What causes thermal expansion?

A
  • rocks experience repeated cycles of temperature change
  • when heated rock expands
  • when cooled rock contracts
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10
Q

What is the effect of thermal exapansion?

A

Outer layers of rock may crack and flake off

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11
Q

What causes salt crystallisation?

A
  • solutions of salts get into rock pores
  • salts precipitate and form crystals in pore spaces in rocks
  • this causes pressure within the rock
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12
Q

What is the effect of salt crystallisation?

A

Rock disintegrates

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13
Q

Which 2 salts are particularly effective at salt crystallisation?

A

Sodium sulfate and sodium carbonate

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14
Q

Name 5 types of chemical weathering

A 
Oxidation
Carbonation
Solution
Hydrolysis
Hydration
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15
Q

What causes oxidation?

A

minerals in rock react with oxygen in air or water

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16
Q

What effect does oxidation have?

A

The original structure of rock is destroyed and disintegrates

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17
Q

Which element and type of rock is particularly susceptible to oxidation?

A

Iron and sandstone

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18
Q

What causes carbonation?

A
  • rainwater reacts with dissolved carbon dioxide, forming weak carbonic acid
  • The weak acid reacts with calcium carbonate to form calcium bicarbonate
  • calcium carbonate is soluble in water
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19
Q

What is the effect of carbonation?

A

Rocks containing CaCO3 are dissolved

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20
Q

What causes solution?

A

-some salts are soluble in water or under specific conditions (e.g iron is only soluble in very acidic water)

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21
Q

What is the effect of solution?

A

Rock minerals dissolve, reducing the size of the rocks. This can sometimes undermine structural integrity

22
Q

Name a type of solution

A

Carbonation

23
Q

What causes hydrolysis?

A

Silicates combine with water, reacting chemically to produce clays

24
Q

What is the effect of hydrolysis?

A
  • the secondary minerals formed are softer than the original minerals
  • these means the rock is more easily eroded
25
Q

What causes hydration?

A
  • When water molecules react with rocks new minerals
  • these have a larger volume
  • this exerts pressure
26
Q

What is the effect of hydration?

A

surface flaking of rock occurs

27
Q

Name two causes of biological weathering

A

Tree roots and organic acids

28
Q

How does tree root weathering occur?

A
  • tree roots grow into cracks and exert pressure

- if these trees topple they act as a lever

29
Q

What is the effect of tree roots on rocks?

A
  • pressure exerted on cracks can expand fissures in the rock

- trees toppling bring soils and rock to the surface allowing them to be weathered further

30
Q

How does organic acid weathering (chelation) occur?

A
  • Molluscs secrete acids
  • The decomposition of plant an animal litter can cause soil water to become acidic
  • Blue-green algae can also have a weathering effect
31
Q

What is the effect of organic acid weathering?

A
  • Molluscs create small surface hollows in the rock
  • this increases surface area for other weathering processes
  • acidic soil reacts with some minerals
32
Q

How does high permeability of rock affect weathering?

A
  • can increase weathering

- as it allows weathering fluids to flow through the rock

33
Q

Does salt crystallisation result from the evaporation of sea water?

A

Yes

34
Q

Define mass movement

A

The downslope transportation of material under gravity

35
Q

What is soil creep?

A
  • results from the repeated contraction and expansion of individual soil particles
  • causes them to very slowly move downwards under gravity
36
Q

What is Mudflow?

A
  • Movement of material downslope in the form of a fluid

- Material on a slope becomes saturated with water, making it much heavier

37
Q

Under what conditions do mudflows usually occur?

A
  • after a period of intense rainfall

- areas that have thin soils overlying impermeable bedrock

38
Q

Under what conditions do rock slides usually occur?

A

-rocks that have jointing or bedding planes roughly parallel to the angle of the slope

39
Q

Under what conditions do rock falls usually occur?

A

-on slopes in excess of 40 degrees

40
Q

What can prompt rock falls to occur?

A
  • extreme physical or chemical weathering
  • storm action
  • Earthquakes
41
Q

What signs can point to rock falls having occurred on a cliff?

A

A tallus/scree slope at the foot of the cliff

42
Q

Under what conditions does rotational slumping usually occur?

A

-When weaker rocks/clays overlie more resistant impermeable rocks

43
Q

What signs can point to slumping having occurred on a cliff?

A

The presence of a recurved slip plane

44
Q

Name the 5 wave action processes

A 
Abrasion
Attrition
Hydraulic action
Pounding
Solution
45
Q

Which are the two most significant processes?

A

Pounding and hydraulic action

46
Q

What is abrasion?

A

Water containing rock particles scour the coastline (rock rubbing against rock)

47
Q

What is attrition?

A

Rock particles transported by wave action, collide with each other and become worn away, smaller, and rounder

48
Q

What is hydraulic action?

A
  • When waves break against the cliff face air and water trapped in cracks and crevices becomes compressed
  • as the water recedes pressure is released and the air and water expands
  • this widens the crack
49
Q

What is pounding?

A

The mass of a breaking wave exerts pressure on the rock, weakening it

50
Q

What is solution?

A

Minerals are dissolved by water, this is limited by the quantity of minerals in the rock

51
Q

Give an example of a mineral dissolved in sea water

A

Magnesium carbonate

OCR A level Geography (31 decks)

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