Chapter 14
Geology and Nonrenewable
Minerals
Core Case Study
Environmental Effects of Gold Mining
• Gold Mining typically removes large quantities of rock to
extract tiny amounts of gold.
• Cyanide Heap Leaching – spraying of highly toxic cyanide salts
(which react with gold) on large piles of rock, and catching the
toxic runoff into storage ponds. The ponds are circulated a
number of times and the gold is removed from the ponds.
• Extremely toxic to wildlife
• Romania suffered major water contamination in 2000 and in
2001, when snow and heavy rains washed out an earthen
dam on one end of a cyanide leach pond.
Earth’s Major Geological Processes
Primitive earth cooled into 3 major concentric zones.
Core – earth’s inner most zone
(solid inner part, surrounded by liquid core of molten rock)
Mantle – thick, solid rock zone surrounding the core
ASTEHNOSPHERE – hot partly melted rock that flows and
can be deformed like soft plastic
Crust – outermost & thinnest zone.
(continental crust & oceanic crust – 71%)
LITHOSPHERE – outermost part of the mantle and continental crust
oceanic crust.
Earth’s Major Geological Processes
• Convection cells or currents move large
volumes of rock and heat in loops within the
mantle like giant conveyer belts.
• Tectonic Plates – huge rigid plates where much
of earth’s geologic activity takes place as they
separate, collide or slide past one another
When these plates move they produce tremendous forces
that cause mountain ranges to form, earthquakes to shake
parts of the crust, and volcanoes to erupt.
Earth’s Major Geological Processes
Divergent Boundary – when ocean plates move apart
allowing molten material to flow up though the cracks creating
oceanic ridges.
Convergent Boundary - ocean plates collide with
continental plates. The continental plate rides up over the cooler,
denser, oceanic plate and pushes it down into the mantle by a
process called subduction. Trenches ordinarily form here, but
when two continental plates collide they form mountains along
the collision boundary.
Transform Fault – continental or ocean plates slide past
one another
Tectonic Plates
Geologic Convection Cells
Earth’s Major Geological Processes
Some parts of earth build up, while others wear
down.
• Internal geologic processes generated by the heat
from the earth’s interior, build up the earth’s surface via
continental and oceanic crust.
• External geologic processes are driven directly by or
indirectly by the energy from the sun and include wind,
flowing water, and glaciers which all contribute to
erosion and are influenced by gravity.
• WEATHERING – major external influence containing
three types, Chemical, Biological, and Physical. It is the
first step in soil formation.
Volcanoes
Volcanoes are formed when magma reaches the surface via fissures. When
the magma reaches the earth’s surface it is then called lava.
Volcanic activity can release debris ranging from large chunks of lava rock to
glowing hot ash, liquid lava, and gases such as H2O vapor, CO2, and SO2.
Most activity is concentrated around tectonic plate boundaries. Example: Ring
of Fire
Mount Pinatubo 1991 largest stratospheric disturbance in 20th century
http://www.youtube.com/watch?v=K7NnLO5NNb8
Mount St. Helens 1980 worst in U.S. history
http://www.youtube.com/watch?v=BaRAGzjSkzo
Volcanoes
Volcanism produces scenic views and produces fertile soils
formed by weathering of lava.
This draws attention from humans as settlement locations.
We can reduce human lives lost and property damage in these
areas by the following:
• Use historical records and geologic measurements to
prevent people from living in these areas.
• Monitor volcanic activity to warn of eruptions.
• Develop evacuation routes and plans for those who live in
areas prone to volcanic activity.
Earthquakes
Forces inside the earth’s mantle cause rocks to
suddenly shift or break producing transform faults
or fractures in the crust.
Abrupt movement causes energy to be released in
the form of vibrations called seismic waves. These
waves move through surrounding rock and this
process is called an earthquake.
Most occur at boundaries of tectonic plates.
Earthquakes
Focus – place where an earthquake begins below the
earth’s surface.
Epicenter – found directly above the focus on the earth’s
surface.
Magnitude – measure of ground motion indicated by the
size of the seismic waves. Used to measure severity of an
earthquake.
Richter Scale – used to measure earthquake intensity. Each
unit has amplitude 10 times greater than the next smaller
unit.
Aftershocks/Foreshocks – tremors after or before an
earthquake
Earthquakes
1989 California Earthquake
1994 California Earthquake
2011 Japan Tsunami
Tsunamis
Tsunami – series of large waves generated when part
of the ocean floor suddenly rises or drops.
Tsunamis are caused by underwater earthquakes,
volcanic eruption, or thrust faults in the ocean floor.
Between 1900 and late 2007 tsunamis killed
approximately 278,000 people in the Pacific Ocean
region.
Tsunamis
2004 Tsunami
Landslides
Gravity and earthquakes can cause landslides by
detaching loose soil, rocks, and mud to slide
down steep slopes.
This movement is called mass wasting.
Landslide Video
French Alps Landslide
Earth’s Rocks and how They’re
Recycled.
The earth’s crust consists mostly of minerals and rocks.
Minerals – elements or inorganic compounds that occur naturally in the
earth’s crust as a solid and with a regular internal crystalline structure.
Single element examples: Gold, Silver, and diamonds (carbon).
Most of the more than 2000 identified minerals exist as inorganic compounds:
Salt (NaCl) Quartzite (SiO2)
Rocks – solid combination of one or more minerals found in the earth’s crust.
Single mineral rocks: Limestone (CaCO3), Quartzite (SiO2)
Two or more mineral rocks: Things like Granite which is made of feldspars, micas, and quartz
crystals.
(From Left to Right: Gold, Silver, Salt, Quartzite, Limestone, Granite)
Three Major Rock Types
Sedimentary – made of sediments- dead plant and animal
remains and existing rocks that are eroded and weathered
into tiny particles.
Igneous - forms below the earth’s surface when magma
wells up from the earth’s upper mantle or deep crust and
then cools and hardens.
Metamorphic – forms when preexisting rock is subjected
to high temperatures, high pressures, chemically active
fluids, or a combination of these, which
Can you guess what this means?
cooling
melting
Weathering and
Erosion
Heat and
Pressure
SEDIMENTS
melting
Weathering and
Erosion
Compaction and
cementation
Weathering and
Erosion
Heat and
Pressure
Mineral Resources and the
Environmental Effects of Using Them
Mineral Resource – concentration of naturally
occurring material from the earth’s crust that can be
extracted and processed into useful products and raw
materials at an affordable cost.
EXAMPLES:
Fossil Fuels – Coal
Metallic Minerals – Al, Fe, and Cu
Nonmetallic Minerals – Sand, Gravel, Limestone
*Because they take so long to form, these components of the earth’s natural
capital are classified as NONRENEWABLE MINERAL RESOURCES.
Mineral Resources and the
Environmental Effects of Using Them
Ore – rock that contains large concentrations of
a particular mineral (often metal).
High-grade Ore – contains large amount of
desired nonrenewable resource.
Low-grade Ore – contains small amount of
desired nonrenewable resource.
Important Metals
Aluminum – packaging, structural material
Steel – alloy of Fe, and other elements such as
Mn, Co, Mo, and Cr. Used in all types of
products.
Copper – electrical and communications
Platinum – electronics, catalyst in industry, and
in automobile pollution control
converters
Gold – electrical equipment, jewelry, coins, medical
implants, and as a catalyst to speed up
certain chemical reactions
Important Nonmetals
Most widely used nonmetals are sand and gravel.
Sand is primarily SiO2 or silicon dioxide. It is used to make glass, bricks, and
concrete.
Gravel is used for roadbeds and to make concrete.
Limestone is mostly CaCO3 or calcium carbonate. It is crushed to make road
rock, concrete, and cement.
Phosphate salts are mined and used in inorganic fertilizers and some
detergents.
Reserves – identified resources from which the mineral can be extracted
profitably at current prices
Mineral Use Advantages
Mining and processing minerals does have benefits.
• Generates Significant income
• Provides Local, State, and National revenues from
taxes, fees, and royalties.
• Provides Employment directly and indirectly
Mineral Use Disadvantages
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Use enormous amounts of energy
Disturb Land
Produce Solid Waste
Pollute the Air, Water, and Soil
The environmental impacts of mining an ore are affected by it’s percent
of metal content, or grade. Mining lower grade ores takes more money,
energy, water, and other materials and increases land disruption, mining
waste, and pollution.
Why?
Because lower grade ores are harder to extract and you need more
volume of material to compare with the high percent of material
available in high grade ores, which are easier to extract.
Mining Techniques
Surface Mining – used to harvest shallow deposits
Subsurface Mining – used to harvest deep deposits
Open Pit Mining – Machines dig massive holes and remove ores
Strip Mining – used for extracting deposits that lie close to the earth’s
surface and lie in horizontal beds.
Area Strip Mining – used where terrain is fairly flat
Contour Strip Mining – used where terrain is hilly or mountainous
Mountaintop Removal – use of explosives, large power shovels, and
huge machines to remove tops of mountains
Hydraulic Mining – using water cannons to wash entire hillsides into
collection boxes. (outlawed in U.S.)
Waste/Spoil Piles
Mountain Top Removal
Open Pit Mining
Subsurface Mining
Mining Terms
Overburden – soil and rock overlying a useful
mineral deposit.
Spoils – overburden discarded as waste material
Tailings – the unused materials left on land
from dredging ore deposits from streams
Life Cycle of a Metal Resource
Surface Mining
Metal ore
Separation of ore from gangue
(waste material pronounced gang)
Recycling
Smelting
Melting Metal
Conversion to Product
Discarding of Product
Natural Capital Degradation
STEPS
Environmental Effects
Mining
Exploration, Extraction
Disturbed Land; mining accidents; health
hazards; mine waste dumping; oil spills
and blowouts; noise; ugliness; heat.
Processing
Transportation, Purification
Manufacturing
Solid wastes; radioactive material; air,
water, and soil pollution; noise; safety
and health hazards; ugliness; heat.
Use
Transportation or transmission
to individual user, eventual use
and discarding
Noise; ugliness; thermal water pollution;
pollution of air, water, and soil; solid and
radioactive wastes; safety and health
hazards; heat.
Mining Harmful Environmental
Effects
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Scarring and Disruption of the Land Surface
Destroys biodiversity
Chemical Weathering and Erosion of spoils and tailings
Production of Toxic waste water
Production of large amounts of solid waste
Clean up is Costly and mining areas may not be
Subsidence – collapse of land above underground
mines
• Acid Mine Drainage – rainwater seeping through a
mine or mine waste pile carries H2SO4 into streams or
groundwater.
Smelting Harmful Environmental
Effects
• Emits enormous amounts of air pollutants and
suspended particles
• Damage vegetation and acidify soils in the
surrounding area
• Cause water pollution
• Produces toxic liquid and solid waste that
requires safe disposal
Mineral Resources are Distributed
Unevenly
• Some areas have rich mineral deposits while
others have few or none.
• US imports 50% or more of 24 of its most
important nonrenewable resources.
• Four Strategic Metal Resources include
Manganese, Cobalt, Chromium, and Platinum
which are essential for US economics and military
strength.
• Nanomaterials may eventually be a substitute for
some of these materials.
Nonrenewable Mineral Resources can
be Economically Depleted
• Future Supply of Nonrenewable Minerals
depends on the ACTUAL or POTENTIAL Supply
and the RATE at which it is used.
• Minerals become Economically Depleted when it
costs more than it is worth to find, extract,
transport, and process the remaining deposits.
• At this point we can recycle or reuse, waste less,
use less, find a substitute, or do without
• Depletion Time – the time it takes to use up a
certain portion of reserve at a given rate of use.
Typically 80%.
Depletion Curves
Curve A – shortest
depletion time
Curve B – longer
depletion time
Curve C – longest
depletion time
Economics and Mining
• Geological processes determine the quantity and
location of a mineral resource.
• Economics determines what part is extracted and used.
• Standard economic theory states that in a competitive
market a plentiful mineral resource is cheap when it’s
supply exceeds demand and when a resource becomes
scarce it’s price rises.
• Rising prices can help encourage exploration, develop
better technology, promote resource conservation,
search for substitutes, and make it profitable to mine
lower-grade ores.
Economics and Mining
• Some Economists say this price effect may no longer occur
in developed countries since Industry and government use
subsidies, taxes, regulation, and import tariffs to control
supplies, demands, and prices of minerals.
• An artificially low price helps to promote economic growth
and national security.
• Most consumers are unaware of real costs being higher
than the market price, since they are paying taxes that
provide government subsidies and tax breaks to mining
companies and to environmental effects of mining.
Note:
Between 1982 and 2007, U.S. Mining companies received
more than $6 billion in government subsidies.
Economics and Mining
Critics of Mining
Add hidden extra costs to
market prices so harmful
environmental effects of
mining will be drastically
reduced, would increase
recycling and reuse
dramatically, and allow for
many minerals to be
replaced with less
environmentally harmful
substitutes.
Mining Companies
Need taxpayer subsidies and
low taxes to keep the prices
of minerals low for
consumers. Subsidies also
help keep companies local
instead of taking their
business to other countries
where they will not face
such high taxes and
regulation.
U.S General Mining Law of 1872
• Designed to encourage mineral exploration and the mining of hardrock minerals such as Au, Ag, Cu, Zn, Ni, and U on public US lands to
help develop the then sparsely populated West.
• Under this law claims could be made on US public lands, except
National parks and wilderness, for $500 to improve for mineral
development, and $120/year/20 acres whether or not mining is in
operation.
• Until 1995 when a freeze on such land transfers was declared by
Congress. However at that time, the price per hectare dropped to
$6 - $12 or $2.50 -$5. per acre.
• Once land was transferred the transferee could then lease, build,
sell, or use for essentially any purpose.
• According to a 2004 study $285 billion worth of publicly owned
mineral resources have been transferred to private companies. 1/5
of them to foreign companies – at 1872 giveaway prices.
U.S General Mining Law of 1872
• Mining companies remove approximately $400 billion
in hard rock minerals per year from U.S. Public Lands.
• Companies pay taxpayers 2.3% of mineral value
compared to 13.2% for fossil fuels and 14% for grazing
rights on public land.
• Companies have abandoned severely degraded and
polluted mining sites leaving expensive clean up to the
taxpayers.
• U.S. Department of the Interior estimates that the
clean up of more than 500,000 abandoned sites will
cost taxpayers approximately $32-72 billion.
The Politics
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Critics of Mining
Money given up for subsidies offsets
the lower prices
Ban such public land sales or propose
20 year leases
Stricter environmental controls and
cleanup
Set up fund paid for by royalties to
clean up abandoned sites
Mining companies would pay 8-12%
royalty off of the gross income
Canada, Australia, South Africa, and
other countries require higher royalty
payments and have laws that make
mining companies fully responsible
for environmental damage
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Mining Companies
Have to invest large sums of money
to develop a site before profits can
be made
Government subsidized land costs
help provide high paying jobs for
miners.
Supply vital resources for Industry
Stimulate economies
Reduce trade deficits
Keep mineral products affordable
Mining Lower-grade Ores
• In 1900 average copper ore mined was 5% copper by weight. Today
it is 0.5%.
• New technologies are being developed to extract low-grade ores.
• Limitations to the mining of low-grade ores include increased cost
of mining, the limited availability of freshwater, and the
environmental impacts.
In-place or in situ mining – use of microorganisms to extract minerals.
This process is referred as Biomining, which removes desired metals
from ores while leaving the surrounding environment undisturbed.
This process is extremely slow and can take decades to remove the
same volume of material that conventional methods can remove in
months or years.
Mining Minerals from the Ocean
Some ocean minerals are dissolved in sea water. However, most are in
very low concentrations which require more energy and money than
they are worth.
• Only Mg, Br, and NaCl are abundant enough to be extracted
profitably.
• Sediments along the continental shelf are significant sources of
sand, gravel, phosphates, sulfur, tin, copper, iron, tungsten, silver,
titanium, platinum, and diamond.
• Other sources include Hydrothermal Ore Deposits around thermal
vents in which minerals precipitate out, and Manganese Nodules
that litter the ocean floor of the Pacific.
Problems with utilizing these sources fall to high costs, ownership, and
environmental impacts on aquatic ecosystems.
Using Mineral Resources More
Sustainably
• Materials Revolution – elements like silicon and compounds like plastic
and ceramic being substituted for metals. Examples include glass fiber
optic cables for communications and Grancrete (styrofoam sprayed with
ceramic)for building materials
• Use of Nanotechnology (molecular level engineering)
• Use of High-strength plastics and composite materials strengthened by
lightweight carbon and glass fibers
Why would using plastics still cause environmental issues?
• Chemists are learning how to make some plastics from plant materials
• Recycle and Reuse valuable metals (recycling aluminum produces 95% less
air pollution and 97% less water pollution and uses 95% less energy than
mining and processing it.
• Ask how can we decrease our use and waste of minerals opposed to how
we can increase our supplies of nonrenewable minerals
Solutions
Sustainable Use of Nonrenewable
Minerals
• Do Not Waste Mineral Resources
• Recycle and Reuse 60-80% of mineral resources
• Include the harmful environmental costs of mining and processing
minerals in the prices of items (full-cost pricing)
• Reduce mining subsidies
• Increase subsidies for recycling, reuse, and finding substitutes
• Redesign manufacturing processes to use less mineral resources
and to produce less pollution and waste (cleaner production)
• Use mineral resource wastes of on manufacturing process as raw
materials for other processes
• Slow population growth
Industrial Ecosystems