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AS Geography > 3. Rocks and Weathering > Flashcards

3. Rocks and Weathering Flashcards

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1
Q

Continental crust

A

35-70km thick
Very old
Lighter
Granitic

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2
Q

Oceanic crust

A

6-10km
Very young
Heavier
Mainly basaltic

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3
Q

The layers of the Earth

A 
Surface
Lithosphere
Asthenosphere
Mesosphere
Outer core
Solid inner core
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4
Q

Lithosphere

A

cool, rigid, brittle
crust and upper mantle
70km deep

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5
Q

Crust

A

2 types, continental and oceanic

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6
Q

Evidence for plate tectonics

A

Earthquakes
Changes in the magnetic field of the Earth
Paleomagnetism, the different magnetising of emerging magma
Fossil remains
Rock distribution
Fit of the continents

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7
Q

Types of plate of boundary

A

conservative, convergent, divergent

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8
Q

Conservative plate boundary

A

Plate boundary sliding past each other

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9
Q

Divergent plate boundary

A

New crust is formed from the moving away of two plates

Often in the middle of oceans

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10
Q

Convergent plate boundary/collision

A

When a continental and a oceanic plate converge, one plate will be subducted.
Forms fold mountains when 2 continental plates collide
Earthquakes

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11
Q

Why do plates move?

A

Convection currents of rising and falling magma because of radioactive decay in the core
Plates are dragged by their edges which have become cold and heavy

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12
Q

What is sea floor spreading

A

The movement of continents in response to the growth of oceanic crust between them

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13
Q

Mid-ocean ridges

A

Giant submarine mountain chains. New lithosphere is created here. Formed at divergent boundaries

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14
Q

Slab pull

A

Slab pull is the pulling force exerted by a cold, dense oceanic plate plunging into the mantle due to its own weight. The theory is that because the oceanic plate is denser than the hotter mantle beneath it, this contrast in density causes the plate to sink into the mantle.

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15
Q

Volcanic island arcs

A

Magma rises up out of the oceanic crust and forms volcanic island arcs parallel to the ocean trench. Formed when oceanic lithosphere is subducted under oceanic lithosphere

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16
Q

Ocean trenches

A

Formed at convergent boundaries by slabpull and subduction

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17
Q

Subduction zones

A

When oceanic lithosphere collides with another plate.
It is easily pushed down into the upper mantle. Subducted oceanic plate is cooler and denser so continues to go deeper. The older the crust the steeper it dips.

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18
Q

Benioff zone

A

Earthquakes occur here

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19
Q

How are mountains built by plate tectonics

A

They are built at convergent plate boundaries. Sedimentary rocks are folded up into an accretionary wedge

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20
Q

Weathering

A

the decomposition and disintegration of rocks in situ

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21
Q

Physical weathering

A

the disintegration of rock into smaller, angular fragments of the same rock, such as scree

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22
Q

Chemical weathering

A

the decomposition of rock, creating altered rock substances, such as kaolinite from granite

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23
Q

Biological weathering

A

when plants and animals chemically alter rocks and physically break them thorough their growth and movement

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24
Q

Freeze-thaw/frost shattering

A

when water in joints or cracks freezes at 0°C and expands by 10% exerting pressure on the rock

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25
Q

Granular disintegration

A

alternate expansion and contraction of minerals in rocks causes the rock to break down into small pieces

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26
Q

Block disintegration

A

when rocks split along joints into large rectangular shaped blocks

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27
Q

Disintegration

A

found in hot desert areas where there is a large diurnal temperature range.

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28
Q

Exfoliation

A

a type of disintegration where the outer layers of rock peel off due to stresses caused by heat

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29
Q

Wetting and drying

A

Physical weathering process where rocks are mechanically disintegrated by the accumulation of successive layers of water molecules in between the mineral grains of a rock

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30
Q

Salt crystallisation

A

the decomposition of rock by solutions of salt

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31
Q

Pressure release

A

overlying rocks are removed by erosion causing underlying rocks to expand and fracture

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32
Q

Hydrolosis

A

occurs on rocks with orthoclase feldspar

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33
Q

Hydration

A

the process whereby certain minerals absorb water expand and change

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34
Q

Oxidation

A

when iron compounds react with oxygen to produce a reddish brown coating

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35
Q

Humic acids

A

acids derived from the decomposition of vegetation

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36
Q

Chelation

A

the process in which plant roots can absorb relatively insoluble minerals

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37
Q

Limestone

A

a rock consisting of calcium carbonate, therefore susceptible to carbonation-solution

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38
Q

Carbonation

A

occurs on rocks with calcium carbonate e.g chalk or limestone

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39
Q

Granite

A

a rock prone to hydrolysis because of the presence of feldspar

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40
Q

Regolith

A

superficial and unconsolidated material found at the Earth’s surface.
Prone to downslope movement
Clay-rich regolith is particularly unstable because of their ability to retain water

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41
Q

Aspect

A

the direction in which a slope faces

42
Q

Mass movement

A

any large-scale movements of the Earth’s surface that is not accompanied by a moving agent such as a river, glacier or ocean wave

43
Q

Shear strength

A

the internal resistance of the slope

44
Q

Shear stress

A

the forces attempting to pull a mass downslope

45
Q

Heave/creep

A

a slow, small-scale process of mass movement that occurs mostly in winter

46
Q

Talus creep

A

the slow movement of fragments on a scree slope

47
Q

Falls

A

mass movement that occurs on steep slopes, especially bare rock faces where joints are exposed

48
Q

Slides

A

mass movement that occurs when an entire mass of material moves along a slip plane

49
Q

Van’t Hoff’s Law

A

The rate of chemical weathering increases 2-3 times for every increase of temperature of 10 degrees to a maximum of 60

50
Q

What influences the rate and type of weathering

A

Joints and bedding planes, nature of the sedimentary rocks, chemical composition

51
Q

What will increase chemical weathering

A

Increase in moisture and heat

52
Q

What influences freeze thaw, salt crystallisation and insolation

A

critical temperature changes
frequency of cycles
diurnal and seasonal variations in temperature

53
Q

What types of weathering are common and occur in Glacial/Periglacial regions

A

Frost is important in disintegration. Slow chemical weathering, Hydration weathering common from high moisture

54
Q

What types of weathering are common and occur in Temperate regions

A

Fluctuations in precipitation and evaporation. Both mechanical and chemical weathering occur. H

55
Q

What types of weathering are common and occur in Arid/Semi arid regions

A

Evaporation exceeds precipitation. High temperatures. High amounts of mechanical weathering, disintegration

56
Q

What types of weathering are common and occur in Humid/Tropical regions

A

High seasonal rainfall. High amounts of moisture. Intense deep weathering

57
Q

What causes rates and types of weathering to vary

A

Climate

58
Q

Characteristics of Limestone

A

Permeability

Solubility

59
Q

characteristics of granite

A

Igneous
Resistant to erosion
Susceptible to freeze-thaw and hydrolysis
Impermeable

60
Q

Exogenic factors affecting slope processes

A 
Climate
Temperature
Precipitation
Vegetation
Weathering
Runoff
61
Q

Soil

A

Part of the regolitih. Clay soils can hold more water than sandy soils

62
Q

How are slopes open systems

A

Recieve inputs such as energy, mass, water and sediment
Produce outputs: energy(reradiated heat) and mass
Slopes also store kinetic energy which is converted into mass movement and erosion

63
Q

Slope form

A

the shape of the slope in cross section

64
Q

Slope processes

A

Activities acting on the slope

65
Q

Slope evolution

A

The changes in slope over time

66
Q

Types of mass movement

A

very slow: soil creep
Fast: avalanches
dry movement: rockfalls
Fluid: mudflows

67
Q

What causes mass movement

A

gravity
slope angle
pore pressure

68
Q

How does gravity cause mass movement

A

It moves the material (slide) and sticks its.

69
Q

How does water cause mass movement

A

water lubricates the particles and fills the empty space between them

70
Q

What causes slope failure

A

reduction in shear strength of the slope or increase in shear stress

71
Q

Shear stress

A

increase in the forces trying to pull a mass downslope

72
Q

shear strength

A

the internal resistance of the slope

73
Q

Factors that contribute to increased shear stress

A

removal of lateral support
Removal of underlying support
Slope loading
Lateral Pressure

74
Q

How might lateral support be removed

A

undercutting by rivers, wave action, faulting, rockfalls

75
Q

What is slope loading

A

weight of water, vegetation, accumulation of debris

76
Q

what is lateral pressure

A

water freezing, swelling of clays, pressure release

77
Q

Factors that contribute to reduced to reduced shear strength

A

weathering effects: disentegration, hydration, dissolution of cementing minerals
Changes in pore pressure: saturation
changes in structure: fissures in clay
organic effects: burrowing of animals

78
Q

how might water weaken a slope

A

Increase shear stress and decrease shear resistance
Increase the weight of a mobile mass
reduces the cohesion between particles

79
Q

How can downslope movement be opposed

A

Friction
cohesive forces
pivoting
vegetation

80
Q

What is surface wash

A

when the soil’s infiltration capacity is exceeded, and water drains across saturated or frozen ground following heavy downpours or melting of snow

81
Q

Sheetwash

A

unchanneled flow of water over a soil surface

82
Q

Types of heaves

A

soil creep

solifluction

83
Q

Soil creep/solifluction

A

soil particles are heaved to the syrface by heating/wetting/freezing of water. Freeze thaw causes the soil the soil to expand and srink. the soil “rolls”

84
Q

Types of slides

A

rotational slip
slumping
landslides

85
Q

What causes slumping

A

when a mass of regolith detaches from it’s substrate along a spoon-shaped sliding surface. Regolith driven. Lubricated by a fluid

86
Q

Angle of repose

A

maximum angle that a slope is stable

87
Q

Rotational slip

A

slump mass is permable and is lubricated by liquid. slump mass is unconsolidated regolith. Slump mass detaches from headscarp and moves downslope

88
Q

Types of falls

A

avalanches
rockfall
debris fall

89
Q

What are falls

A

When material falls under the influence of gravity after being detached

90
Q

talus

A

apron of debris sloping away from the cliff

91
Q

what causes rockfalls

A

undercutting

92
Q

Types of flows

A 
mudflows
lahar
debris flow
debris avalanche
landslide
93
Q

Mudflows

A

caused by heavy rain and flooding. required a 25 degrees+ gradient. mixture of water, mud and loose rocks

94
Q

Lahar

A

when volcanic ash mixes with water/snow.

95
Q

debris flow

A

mudflow mixed with large rock fragments

96
Q

what causes flows

A

regolith sliding off bedding plain

97
Q

Negative human impacts on slope stability

A

undercutting slopes, increasing slope angle
removal of vegetation
loading of slopes
addition of water

98
Q

Preventative measures against mass movement

A 
identification of regions at risk
use netting
barriers
pinning
terracing
99
Q

Slope stabilisation

A

adding vegetation
peforated pipes to allow water to pass through and flow out
afforestation
retaining walls

100
Q

Rainsplash erosion

A

erosive effect raindrops have on hillslopes. compact and dislodge particles in all directions

AS Geography (10 decks)

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