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AS Geography > 3. Rocks and Weathering > Flashcards

3. Rocks and Weathering Flashcards

(100 cards)

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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
Granular disintegration
alternate expansion and contraction of minerals in rocks causes the rock to break down into small pieces
26
Block disintegration
when rocks split along joints into large rectangular shaped blocks
27
Disintegration
found in hot desert areas where there is a large diurnal temperature range.
28
Exfoliation
a type of disintegration where the outer layers of rock peel off due to stresses caused by heat
29
Wetting and drying
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
30
Salt crystallisation
the decomposition of rock by solutions of salt
31
Pressure release
overlying rocks are removed by erosion causing underlying rocks to expand and fracture
32
Hydrolosis
occurs on rocks with orthoclase feldspar
33
Hydration
the process whereby certain minerals absorb water expand and change
34
Oxidation
when iron compounds react with oxygen to produce a reddish brown coating
35
Humic acids
acids derived from the decomposition of vegetation
36
Chelation
the process in which plant roots can absorb relatively insoluble minerals
37
Limestone
a rock consisting of calcium carbonate, therefore susceptible to carbonation-solution
38
Carbonation
occurs on rocks with calcium carbonate e.g chalk or limestone
39
Granite
a rock prone to hydrolysis because of the presence of feldspar
40
Regolith
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
41
Aspect
the direction in which a slope faces
42
Mass movement
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
Shear strength
the internal resistance of the slope
44
Shear stress
the forces attempting to pull a mass downslope
45
Heave/creep
a slow, small-scale process of mass movement that occurs mostly in winter
46
Talus creep
the slow movement of fragments on a scree slope
47
Falls
mass movement that occurs on steep slopes, especially bare rock faces where joints are exposed
48
Slides
mass movement that occurs when an entire mass of material moves along a slip plane
49
Van't Hoff's Law
The rate of chemical weathering increases 2-3 times for every increase of temperature of 10 degrees to a maximum of 60
50
What influences the rate and type of weathering
Joints and bedding planes, nature of the sedimentary rocks, chemical composition
51
What will increase chemical weathering
Increase in moisture and heat
52
What influences freeze thaw, salt crystallisation and insolation
critical temperature changes frequency of cycles diurnal and seasonal variations in temperature
53
What types of weathering are common and occur in Glacial/Periglacial regions
Frost is important in disintegration. Slow chemical weathering, Hydration weathering common from high moisture
54
What types of weathering are common and occur in Temperate regions
Fluctuations in precipitation and evaporation. Both mechanical and chemical weathering occur. H
55
What types of weathering are common and occur in Arid/Semi arid regions
Evaporation exceeds precipitation. High temperatures. High amounts of mechanical weathering, disintegration
56
What types of weathering are common and occur in Humid/Tropical regions
High seasonal rainfall. High amounts of moisture. Intense deep weathering
57
What causes rates and types of weathering to vary
Climate
58
Characteristics of Limestone
Permeability | Solubility
59
characteristics of granite
Igneous Resistant to erosion Susceptible to freeze-thaw and hydrolysis Impermeable
60
Exogenic factors affecting slope processes
``` Climate Temperature Precipitation Vegetation Weathering Runoff ```
61
Soil
Part of the regolitih. Clay soils can hold more water than sandy soils
62
How are slopes open systems
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
Slope form
the shape of the slope in cross section
64
Slope processes
Activities acting on the slope
65
Slope evolution
The changes in slope over time
66
Types of mass movement
very slow: soil creep Fast: avalanches dry movement: rockfalls Fluid: mudflows
67
What causes mass movement
gravity slope angle pore pressure
68
How does gravity cause mass movement
It moves the material (slide) and sticks its.
69
How does water cause mass movement
water lubricates the particles and fills the empty space between them
70
What causes slope failure
reduction in shear strength of the slope or increase in shear stress
71
Shear stress
increase in the forces trying to pull a mass downslope
72
shear strength
the internal resistance of the slope
73
Factors that contribute to increased shear stress
removal of lateral support Removal of underlying support Slope loading Lateral Pressure
74
How might lateral support be removed
undercutting by rivers, wave action, faulting, rockfalls
75
What is slope loading
weight of water, vegetation, accumulation of debris
76
what is lateral pressure
water freezing, swelling of clays, pressure release
77
Factors that contribute to reduced to reduced shear strength
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
how might water weaken a slope
Increase shear stress and decrease shear resistance Increase the weight of a mobile mass reduces the cohesion between particles
79
How can downslope movement be opposed
Friction cohesive forces pivoting vegetation
80
What is surface wash
when the soil's infiltration capacity is exceeded, and water drains across saturated or frozen ground following heavy downpours or melting of snow
81
Sheetwash
unchanneled flow of water over a soil surface
82
Types of heaves
soil creep | solifluction
83
Soil creep/solifluction
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
Types of slides
rotational slip slumping landslides
85
What causes slumping
when a mass of regolith detaches from it's substrate along a spoon-shaped sliding surface. Regolith driven. Lubricated by a fluid
86
Angle of repose
maximum angle that a slope is stable
87
Rotational slip
slump mass is permable and is lubricated by liquid. slump mass is unconsolidated regolith. Slump mass detaches from headscarp and moves downslope
88
Types of falls
avalanches rockfall debris fall
89
What are falls
When material falls under the influence of gravity after being detached
90
talus
apron of debris sloping away from the cliff
91
what causes rockfalls
undercutting
92
Types of flows
``` mudflows lahar debris flow debris avalanche landslide ```
93
Mudflows
caused by heavy rain and flooding. required a 25 degrees+ gradient. mixture of water, mud and loose rocks
94
Lahar
when volcanic ash mixes with water/snow.
95
debris flow
mudflow mixed with large rock fragments
96
what causes flows
regolith sliding off bedding plain
97
Negative human impacts on slope stability
undercutting slopes, increasing slope angle removal of vegetation loading of slopes addition of water
98
Preventative measures against mass movement
``` identification of regions at risk use netting barriers pinning terracing ```
99
Slope stabilisation
adding vegetation peforated pipes to allow water to pass through and flow out afforestation retaining walls
100
Rainsplash erosion
erosive effect raindrops have on hillslopes. compact and dislodge particles in all directions

AS Geography (10 decks)

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