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Environmental Science > Lithosphere > Flashcards

Lithosphere Flashcards

1
Q

What is an In Situ resource?

A

a resource that is extracted from where it is made

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2
Q

What happens to an In Situ resource as it is extracted

A

it is depleted UNLESS they are made rapidly

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3
Q

How long do most geological, resource making processes take?

A

thousands/millions of years

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4
Q

Give examples of In Situ resources that are:
a) formed slowly
b) formed faster

A

a) fossil fuels
metal ores
rocks

b) sand
gravel

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5
Q

What are the three main rock types and how can we generally identify them?

A

Sedimentary - has layers/fossils/clasts

Igneous - crystalline

Metamorphic - changed by heat and/or pressure, also has layering/folding

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6
Q

Give two example metals extracted from the crust, their global annual production in tonnes, and examples of their major uses

A
  1. Iron
    1700 million tonnes
    Buildings: girders
    Transport: ships
    Appliance casing: fridges
  2. Copper
    19 million tonnes
    Electric cables, water pipes
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7
Q

Give two examples of minerals/materials extracted from the crust, their global annual production in tonnes, and examples of their major uses

A
  1. Limestone
    600 million tonnes
    Cement
    Building blocks
  2. Aggregates (sand/gravel)
    40 billion tonnes
    Concrete
    Building mortar
    Glass
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8
Q

What are igneous processes?

A

the processes by which rocks and minerals are created by the cooling and hardening of magma or molten

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9
Q

What can igneous processes create?

A

mineral veins

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10
Q

Give an example of an igneous process

A

Hydrothermal deposition

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11
Q

How does hydrothermal deposition work?

A
  1. Igneous intrusion produces pressurised superheated water at high temps
  2. That water dissolved many minerals from the surrounding rock
  3. The mineral-rich solutions travel along fissures away from the igneous batholith, and cool
  4. As they cool, dissolved minerals come out of solution (crystallise) in order of solubility
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12
Q

Why is hydrothermal deposition useful?

A

Before solution and crystallisation, it is just a mixture of minerals that cannot be exploited
- soon after the batholith forms, minerals separate and deposit, and exploitation becomes possible

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13
Q

Give some examples of metal ores deposited by hydrothermal processes

A

tin
copper
lead
silver
gold
arseinc

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14
Q

What is an ore?

A

naturally occurring solid material from which a metal or valuable mineral can be profitably extracted

a rock that contains a significant quantity of ore minerals/rock with a relatively high concentration of a particular metal

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15
Q

Give an example of a valuable mineral in a vein

A

Gold
Silver
Lead ore

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16
Q

What are metamorphic processes?

give examples

A

when igneous processes and tectonic movements of crustal plates alter existing igneous/sedimentary rocks with high temp and/or pressure

e.g. limestone to marble, mudstone to shale

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17
Q

What are sedimentary processes?

A

Where minerals settle and build up to produce layers of sediment

The deposition and cementation at the Earth’s surface and in water bodies creates sedimentary rocks/minerals

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18
Q

What are the four sedimentary deposits?

A
  1. Proterozoic Marine Sediments (banded iron deposits)
  2. Alluvial deposits
  3. Biological sediments
  4. Evaporites
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19
Q

What are Proterozoic Marine Sediments?

A
  • Where iron ore deposits form when dissolved iron compounds became oxidised by oxygen released
  • due to the abundance of photosynthesising organisms
  • between 2.5 and 1.8 million years ago
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20
Q

What are Alluvial deposits?
Give some examples

A
  • ancient ore veins eroded by flowing water (e.g. rivers) and deposited in river sand and gravel
  • the ability of the water to carry solids depends on velocity of water and density of solids
  • gold, diamonds, tin ore
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21
Q

What are Evaporites?
Give an example

A
  • when ancient seas become isolated, water evaporates leaving crystallised minerals
  • also forms in inland seas in desert areas due to river evaporation
  • halite (sodium chloride)
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22
Q

What are biological sediments?

A
  • where living organisms form the mineral deposits e.g. shells, guano, plankton, dead plants
  • the processes concentrate minerals that are then deposited in sedimentary rocks
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23
Q

What biological material forms:
a) limestone and chalk
b) coal
c) crude oil and natural gas

A

a) shells of marine organisms
b) terrestrial vegetation
c) marine organisms

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24
Q

What is secondary enrichment?

A
  • if the initial mineral was soluble, it may dissolve from one rock, and move through the groundwater to a new place
  • the groundwater leaches and oxidises primary ores, adding O2, OH, CO2
  • as oxidation state changes, it gets deposited
  • creates ores 10x richer than the original
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25
Q

Give some secondary ores created by secondary enrichment that are prized

A

Turquoise
Malachite
Azurite

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26
Q

What is weathering?

A

The break down of rocks in situ by ice, water, temperature and organisms

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27
Q

What are the types of weathering?

A

Physical/Mechanical
Biological
Chemical

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28
Q

What is physical/mechanical weathering?

A

the disintegration of rocks into smaller pieces by mechanical processes without any change in the chemical composition

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29
Q

What are the types of weathering?

A

Frost shattering (FTA) in cold environments

Exfoliation in environments with temperature extremes

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30
Q

What is biological weathering?

A

the disintegration of a rock due to biological action

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31
Q

Give examples of biological weathering

A
  1. biota (e.g. rabbits, earthworms, birds) burrow into the soil which exposes a larger surface area of the rock - leaves vulnerable for more weathering
  2. large roots penetrate and force their way through - forces cracks in the rocks to get bigger and increases surface area for water to enter - breaks up the edge of a cliff
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32
Q

What is chemical weathering?

A

the disintegration of a rock via chemical reactions as a result of either the input of water or humic acid

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33
Q

What influences chemical weathering?

A

climate - extreme temp/high levels of rainfall can increase chemical weathering

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34
Q

Outline an example of chemical weathering

A
  1. Rainwater contains dissolved CO2 - makes carbonic acid (H2CO3)
  2. Weak acid reacts with rocks composed of calcium carbonate (limestone)
  3. Limestone dissolves
  4. Calcium carbonate is removed in solution
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35
Q

What are the two types of igneous rock?

A

Intrusive
Extrusive

36
Q

How do intrusive rocks form?
Give an example

A

magma cools slowly underground, there is more time for crystals to grow
e.g. granite

37
Q

How do extrusive rocks form?
Give an example

A

magma cools quickly on the surface of the Earth’s crust (in a lave flow), then there is no time for crystals to grow so the crystals are very small
e.g. Basalt

38
Q

How is sedimentary rock formed?

A
  1. previous rock is weathered and eroded and the particles are transported and deposited
  2. as the loose sediment is buried, the layers are under a huge pressure and this binds them together to form a rock

physical pressure fusing grains together = compaction

if minerals are precipitated into spaces = cementation

39
Q

How do metamorphic rocks form?

A
  1. sedimentary rock = buried
  2. intense heat/pressure exerted
  3. rock recrystallises to form a new metamorphic rock
40
Q

How do rocks recrystallise?
What differences will there be?
Give examples

A

They become semi molten, then the minerals recrystallise and interlock

They will be much stronger than they were before

e.g. marble = metamorphosed limestone
e.g. slate = metamorphose clay/mudstone

41
Q

What is a resource?

A

All of the material theoretically available for exploitation
Includes reserves plus those that cannot yet be exploited
- FINITE

42
Q

What is a stock/resource base?

A

All of the material in the lithosphere - including the minerals that can be exploited now/may be exploited in the future/never be economically exploitable

43
Q

What is a reserve?

A

The amount of resource that can be economically exploited now using existing technology
- frequently changes

44
Q

Give three examples of reasons why reserves may fluctuate

A

Market price - increase=increase
Extraction tech - economically viable = increase
COOG - increase=decrease

45
Q

How can reserves be categorised?

A

Inferred reserves
Probable reserves
Proven reserves

46
Q

What is an inferred reserve?

A

Where the presence of the mineral can be predicted from knowledge of present geological structures but you don’t know enough to estimate the economically extractable amount

47
Q

What is a probable reserve?

A

Where sufficient information about the deposit is known so you can sufficiently accurately estimate the amount that can be economically extracted, justifying further exploitation

48
Q

What is a proven resource?

A

Where you have already carried sufficient exploration (including trial drilling) to accurately estimate the amount of mineral to be economically extracted

49
Q

What factors influence the viability of exploitation? (3)

A

absence of tech to exploit it
financial cost = too much
env. impact = unacceptable

50
Q

What is Lasky’s principle?

A

As the purity of a mineral decreases, the amount of the mineral present increases exponentially

51
Q

What is the problem for future reserves?

A

We need to develop better tech/exploitation methods, the quantity of the ore is not the issue

52
Q

Why do we use arbitrary units?

A

Whatever the units, the trend will be the same

Allows comparison

53
Q

What are the two types of mineral exploitation graphs?

A

linear-linear
logarithmic-linear

54
Q

Which graph is more accurate, lin-lin or log-lin?

A

Log-lin
We can read more accurate data points, and be more specific (accurate)

55
Q

What are the mineral exploitation methods?

A

Infrared spectroscopy
Gravimetry
Magnetometry
Seismic surveys
Resistivity
X-ray fluorescence
Trial drilling
Chemical analysis

56
Q

How does IR spectroscopy work?

A

Images taken by satellite/plane in the IR spectrum can give info about surface geology, as different minerals emit different wavelengths of IR

57
Q

Pros and cons of IR spectroscopy?

A
  • Fast
  • Non-destructive
  • Limited - cannot provide full structural info
  • Water skews it
58
Q

How does gravimetry work?

A

measures small changes in gravity caused by changes in density in the rock

carried out by hand/plane

ign rocks more dense than sed rocks

59
Q

Pros and cons of gravimetry

A
  • Allows specific identification of geological features
  • Determines purity
  • Time consuming/difficult to master
  • Expensive
60
Q

How does magnetometry work?

A

measures changes in the ambient magnetic field caused by contrasts in magnetic susceptibility

sensitive to more magnetic rocks/ferrous metals like ones containing magnetite, tungsten, cobalt

carried out by hand/plane

61
Q

What is magnetic susceptibility?

A

the ability of a substance to take on an induced magnetism caused by it’s immersion in Earth’s magnetic field

directly proportional to iron content e.g. haematite/magnetite

62
Q

Why is magnetometry a staple in mining exploration?

A

Iron is often present in accumulations of non-ferrous ores (because it’s risen from the core etc)

63
Q

Pros and cons of magnetometry?

A
  • Equipment easy to use/transport
  • Not impacted by interference that other
    geophysical methods are
  • Difficult to estimate depth
  • Skilled people are needed to use the data and configure results etc
64
Q

How do seismic surveys work? (general)

A

reliant on sound waves produced by controlled explosions or a seismic vibrator on the surface

uses the echos to give info on depth, density, shape of rock strata

65
Q

Describe the process of seismic surveys

A
  1. Loud noise/vibration produced by striking the surface/explosives
  2. Vibration passes through the rock and is reflected by changes in density
  3. Returning vibrations are detected by geophones
  4. converted into voltage which is then recorded at a recording station

Can also be done under the sea by survey ships/hydrophones

66
Q

Pros and cons of seismic surveys

A
  • Gives many useful data in just one survey
  • gives superior results where large velocity contrasts exist
  • cannot image a low-velocity layer e.g. sand below clay
  • cannot image thin, high-velocity layers
67
Q

How does resistivity measuring work? (general)

A

It measures the resistance of the rocks or ground beneath electrodes to show changes in the rock strata

some rocks are less resistant to electrical current e.g. if they contain water or iron

sed rocks have a lower resistance than ig rocks because they have higher water contents

68
Q

Describe the process of resistivity measuring

A

electrodes are placed in a transect and a current is passed between each electrode and the resistance is recorded for each one

69
Q

What is resistivity?

A

the measurement of the difficulty with which electricity passes through material

70
Q

Pros and cons of resistivity measuring

A
  • low cost due to speed and efficiency
  • minimal ground disturbance/non invasive
  • condition dependent: space, cables etc
  • can be easily complicated by external factors e.g. noise
71
Q

How does X-ray fluorescence work?

A

an X-ray is emitted towards a rock sample, causing the atoms in the rock to become excited and release an X-ray back

by measuring the returning X-rays you can calculate the composition of the rock

72
Q

Pros and cons of X-ray fluorescence

A
  • high resolution means it can analyse complex samples
  • fast and non destructive
  • limitations on measuring lighter elements
  • high accuracy requires a similar and suitable reference standard to be compared to
73
Q

How does trial drilling work?

A

Where a core sample of he rock is taken and the purity of the ore found can be removed and measured in a laboratory

74
Q

Pros and cons of trial drilling

A
  • only way to confirm exactly how big and rich a deposit is
  • work can be carried out relatively quickly
  • high level of surface disturbance and potential for wall collapse
  • most expensive form of mineral deposit detection
75
Q

How does chemical analysis work?

A

Laboratory tests confirm the chemical composition and purity of the mineral in rock samples

76
Q

Pros and cons of chemical analysis

A
  • ID of minerals
  • quite accurate
  • cost
  • need for specific expertise and a lab, so time consuming in that way`
77
Q

What factors affect mining viability?

A

Mining costs: depth, overburden, hydrology
Processing costs
Transport costs
Land costs
Chemical form
Purity
COOG
Market economics

78
Q

How do mining costs affect mining viability?

A

Depth:
- depth doubles, cost more than doubles
- mine sides cannot be vertical due to collapse
- depth increases = water runoff increases = pumping costs increases

Overburden:
- Hard = needs blasting
- Loose = landslide risk = gentle gradient mine = larger area
- ALL INCREASE COST

Hydrology:
- drainage costs increase if high precipitation or impermeable rock below the mine

Is the deposit concentrated or disseminated? That will affect the cost due to area

79
Q

How do processing costs affect mining viability?

A

Removal of:
- waste rock
- overburden
increases costs depending on volume

80
Q

How does chemical form affect mining viability?

A
  • affects ease of abstraction
    e.g. Aluminium from bauxite = easy
    Aluminium from clay = hard but more abundant
  • crushing requirements
  • electrolysis requirements
81
Q

How does purity affect mining viability?

A
  • affects extraction cost and environmental impacts
  • greater purity = comparatively low processing costs
  • low purity:
    more rock needed
    more waste/spoil generated
    more energy required for mining/processing
    more pollution generated
82
Q

How do land costs affect mining viability?

A

State: derelict will be cheaper than prime agricultural land
Buying: whos land is it?

83
Q

How do transport costs affect mining viability?

A
  • distance
  • bulk/weight, has it been reduced by processing
  • presence of existing infrastructure
  • ease of bulk transport

(both ore and waste rock)

84
Q

How does COOG affect mining viability?

A

MINING MUST BE PROFITABLE
- has to be a balance between production cost and income

  • COOG changes as technology improves/becomes available and prices fluctuate

Higher market price: COOG decreases
Lower market price: COOG increases
Improved extraction technology: COOG decreases
Higher energy cost: COOG increases

85
Q

What is COOG?

A

Cut-Off Ore Grade

The lowest ore purity that can be mined economically, using existing technology

Mineral reserves include deposits above the COOG

86
Q

How does market economics affect mining viability?

A
  • controls specific exploitation viability
  • controlled by demand, volume produced, cost of extraction/processing
  • demand rises/falls quickly
  • supply increases slowly
  • no match = wild price fluctuation = difficult to predict future markets
  • exploiting places is beneficial is they already have:
    infrastructure
    tech
    transport
    energy
    equip supplies
    a trained workforce

Environmental Science (5 decks)

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