Geology, Minerals, and Mining - agricanto.org · Geology, Minerals, and Mining ... • The...
Transcript of Geology, Minerals, and Mining - agricanto.org · Geology, Minerals, and Mining ... • The...
Chapter
11
Lecture Presentations prepared byReggie Cobb
Nash Community College© 2015 Pearson Education, Inc.
Geology, Minerals, and Mining
© 2015 Pearson Education, Inc.
This lecture will help you understand:
• Earth’s internal structure and plate tectonics • Rocks and the
rock cycle • Geologic hazards • Mineral resources • Mining methods • Impacts of mining • Reclamation and
mining policy • Sustainable use of minerals
© 2015 Pearson Education, Inc.
Central Case Study: Mining for … Cell Phones? (cont’d)• Cell phones and other high-tech products contain
tantalum • Coltan: columbite + tantalum
• Since 1998, the war in the Democratic Republic of the Congo has killed 5 million
© 2015 Pearson Education, Inc.
Central Case Study: Mining for … Cell Phones?
• Soldiers controlled mining operations and forced farmers and others to work, while taking most of the ore
• People entered national parks, killing wildlife and clearing rainforests, causing ecological havoc
• Profits from coltan sales financed the war
• Most tantalum from the Congo goes to China
© 2015 Pearson Education, Inc.
Geology: the physical basis for environmental science• We extract raw minerals from beneath our planet’s
surface • Turn them into products we use everyday
• Geology • The study of Earth’s physical features, processes, and
history • A human lifetime is just the blink of an eye in geologic
time • Our planet consists of many layers
• Most geologic processes occur near the surface
© 2015 Pearson Education, Inc.
Earth consists of layers
• Core • Solid iron in the center • Molten iron in the outer core
• Mantle • Less dense, elastic rock • Asthenosphere
• Very soft or melted rock
• Lithosphere • Harder rock that contains
the mantle and crust • Crust
• The thin, brittle, low-density layer of rock
© 2015 Pearson Education, Inc.
Plate tectonics shapes Earth’s geography
• Plate tectonics: movement of lithospheric plates • Heat from inner Earth drives convection currents • Pushes the mantle’s soft rock up (as it warms) and down
(as it cools) like a conveyor belt • The moving mantle drags the lithosphere
• Continents have combined, separated, and recombined over millions of years
• Pangaea: all landmasses were joined into one supercontinent 225 million years ago
© 2015 Pearson Education, Inc.
Plate tectonics shapes Earth’s geography (cont’d)
• Earth has 15 major tectonic plates • Movement of these plates influences climate and
evolution
© 2015 Pearson Education, Inc.
• Divergent plate boundaries • Rising magma (molten rock)
pushes plates apart, creating new crust
• Transform plate boundaries • Two plates meet, slipping and
grinding • Friction spawns earthquakes
along strike-slip faults • Fault
• A fracture in the crust
There are three types of plate boundaries
© 2015 Pearson Education, Inc.
There are three types of plate boundaries (cont’d)
• Convergent plate boundaries • Where plates collide
• Subduction • One plate slides beneath another • Molten rock erupts through the surface in volcanoes • Ocean crust slides beneath continental crust
• Two plates of continental crust collide, lifting material
• Built the Himalaya and Appalachian Mountains
© 2015 Pearson Education, Inc.
Tectonics produces Earth’s landforms
• Tectonics builds mountains • Shapes the geography of oceans, islands, and continents • Some large lakes formed in immense valley floors
• Topography created by tectonics shapes climate • Alters patterns of rain, wind, currents, heating, cooling,
which …. • Affect rates of weathering and erosion and the location of
biomes, which … • Affect evolution and extinction
© 2015 Pearson Education, Inc.
The rock cycle alters rock
• Rock cycle • The heating, melting, cooling, breaking, and reassembling
of rocks and minerals • Rock
• Any solid aggregation of minerals • Mineral
• Any element or inorganic compound • Has a crystal structure, specific chemical composition, and
distinct physical properties • Rocks help determine soil characteristics
• Which influence the region’s plant community • Helps us appreciate the formation and conservation of
soils, minerals, fossil fuels, and other natural resources
© 2015 Pearson Education, Inc.
Different types of rocks
• Magma • Molten, liquid rock • Lava
• Magma released by a volcano
• Igneous rock • Formed when magma cools
© 2015 Pearson Education, Inc.
Different types of rocks (cont’d)
• Sediments • Rock particles formed by
physical erosion or chemicallyfrom precipitation of substances
• Sedimentary rock • Formed as sediments are
pressed together and bound by dissolved materials
• Compaction and transformation also create fossils • Metamorphic rock
• Rock deep underground is subjected to great heat or pressure, changing its form
© 2015 Pearson Education, Inc.
Geologic and natural hazards
• Some consequences of plate tectonics are geologic hazards
• Earthquakes and volcanoes • Circum-Pacific belt, or the “ring of fire”
• An arc of subduction zones and fault systems • Most of Earth’s volcanoes
and earthquakes occur along the “ring of fire”
© 2015 Pearson Education, Inc.
Earthquakes result from movement at plate boundaries and faults• Earthquake
• A release of pressure along plate boundaries and faults • Some can do tremendous damage to life and
property • Especially with loose
or saturated soils • Cities built on landfills
are vulnerable • Building can be built
or retrofitted to decrease damage
© 2015 Pearson Education, Inc.
Volcanoes arise from rifts, subduction zones, or hotspots• Volcano
• Molten rock, hot gas, or asherupts through Earth’s surface
• Can cool and create a mountain • Lava can exit in rift valleys,
ocean ridges, subduction zones, or hotspots (holes in the crust)
• Lava can flow slowly or erupt suddenly • Pyroclastic flow
• Fast-moving cloud of gas, ash, and rock • Buried Pompeii in A.D. 79
© 2015 Pearson Education, Inc.
Volcanoes exert environmental impacts
• Ash blocks sunlight • Sulfur emissions lead to sulfuric
acid • Block radiation and cool the
atmosphere • Large eruptions can decrease
temperatures worldwide • Mount Pinatubo in Philippines (1991) • Mount Tambora’s eruption caused
the 1816 “year without a summer” and killed 70,000
© 2015 Pearson Education, Inc.
Landslides are a form of mass wasting
• Landslide • A severe, sudden mass wasting • Large amounts of rock or soil flow downhill
• Mass wasting • The downslope movement of soil and rock due to gravity • Occurs naturally but can be caused by humans when soil
is loosened or exposed • Mudslides
• Soil, rock, and water movement caused by saturated soil from heavy rains
• Lahars • Extremely dangerous mudslides caused when volcanic
eruptions melt snow
© 2015 Pearson Education, Inc.
Landslides are a form of mass wasting (cont’d)
• The town of Oso, Washington, was buried in 2014 by a massive landslide
© 2015 Pearson Education, Inc.
Tsunamis can follow earthquakes, volcanoes, or landslides • Tsunami
• Huge volumes of water are displaced by: • Earthquakes, volcanoes, landslides
• Can travel thousands of miles across oceans • Damages coral reefs, coastal forests, and wetlands
• Saltwater contamination makes it hard to restore them
• Agencies and nations have increased efforts to give residents advance warning of approaching tsunamis
• Preserving natural vegetation (e.g., mangrove forests) decreases the wave energy of tsunamis
© 2015 Pearson Education, Inc.
Tsunamis can follow earthquakes, volcanoes, or landslides (cont’d) • On March, 2011, an earthquake off Japan triggered
a massive tsunami • The earthquake and tsunami killed 9000 people and
caused hundreds of millions of dollars in damage • Radioactive material escaped from a nuclear power plant
© 2015 Pearson Education, Inc.
We worsen or lessen the impacts of natural hazards
• We also face other natural hazards • Floods, coastal erosion, wildfire, tornadoes, hurricanes
• Overpopulation • People must live in susceptible areas
• We choose to live in attractive but vulnerable areas • Coastlines, mountains
• Engineered landscapes increase frequency or severity of hazards
• Damming rivers, suppressing fire, clear-cutting, mining • Changing climate through greenhouse gases changes
rainfall patterns, increases drought, fire, flooding, storms
© 2015 Pearson Education, Inc.
We worsen or lessen the impacts of natural hazards (cont’d)• We can decrease impacts of hazards through
technology, engineering, and policy (informed by geology and ecology)
• Building earthquake-resistant structures • Designing early warning systems (tsunamis, volcanoes) • Preserving reefs and shorelines (tsunamis, erosion) • Better forestry, agriculture, mining (landslides) • Regulations, building codes, insurance incentives
discourage development in vulnerable areas • Mitigating climate change may reduce natural hazards
© 2015 Pearson Education, Inc.
Earth’s mineral resources
• We mine and process mineral resources for countless products
© 2015 Pearson Education, Inc.
We obtain minerals by mining
• We obtain minerals through the process of mining • Mining
• In the broad sense, it is the extraction of any nonrenewable resource
• Fossil fuels, groundwater, and minerals • Mining
• In relation to minerals, it is the systematic removal of rock, soil, or other material
• To remove the minerals of economic interest • Because minerals occur in low concentrations,
concentrated sources must be found before mining is begun
© 2015 Pearson Education, Inc.
Frequently Asked Question
• How do geologists “see” mineral deposits below the ground?
© 2015 Pearson Education, Inc.
We use mined materials extensively
• We don’t notice how many mined resources we use
• The average American uses 37,000 lb of new minerals and fuels every year
• This level of consumption shows the potential for recycling and reuse
A child born today is predicted to use 3 million lb of minerals
over his/her life
© 2015 Pearson Education, Inc.
Metals are extracted from ores
• Metal • An element that is
lustrous, opaque, and malleable and can conduct heat and electricity
• Ore • A mineral or grouping of
minerals from which we extract metals
© 2015 Pearson Education, Inc.
Metals are extracted from ores (cont’d)
• Economically valuable metals from ore include:
• Copper • Iron • Lead • Gold • Aluminum • Tantalum
• Used to manufacture electronics
© 2015 Pearson Education, Inc.
We process metals after mining ore
• Most minerals must be processed after mining • After the ore is mined, rock is crushed, and the
metals are isolated by chemical or physical means • The material is processed to purify the metal
• Alloy • A metal is mixed, melted, or fused with another metal or
nonmetal substance • Steel is an alloy of iron and carbon
• Smelting • Heating ore beyond its melting point, then combining it
with other metals or chemicals • Modifies the strength, malleability, etc., of metals
© 2015 Pearson Education, Inc.
We process metals after mining ore (cont’d)
• Processing minerals exerts environmental impacts • Most methods are water- and energy-intensive • Chemical reactions and heating to extract metals from
ores emit air pollution and toxic wastes • Tailings
• Ore that is left over after metals have been extracted • Pollute soil and water • Contain heavy metals or chemicals (cyanide, sulfuric
acid) • Surface impoundments
• Store slurries of tailings • Accidents release pollutants into the environment
© 2015 Pearson Education, Inc.
We also mine nonmetallic minerals and fuels
• Sand and gravel provide fill and construction materials
• Phosphates provide fertilizer • Limestone, salt, potash, etc., are also mined • “Blood diamonds” are mined and sold to fund,
prolong, and intensify wars in Angola and other areas • Poor people are exploited for mine labor
• Substances are mined for fuel • Uranium is used in nuclear power • Coal, petroleum, natural gas, oil sands, oil shale, methane
hydrate are not minerals (they are organic)
© 2015 Pearson Education, Inc.
Minerals we use come form all over the world
© 2015 Pearson Education, Inc.
Mining methods and their impacts
• Mining provides jobs and money for communities • It provides raw materials for products we use
• Mining has environmental and social impacts • Large amounts of material are removed during mining,
disturbing lots of land • Different mining methods are used to extract
different minerals • The method used depends on economic efficiency
© 2015 Pearson Education, Inc.
Strip mining removes surface layers of soil and rock
• Strip mining • Removal of layers of soil and
rock to expose the resource just below the surface
• For coal, oil sands, sand, gravel • Overburden
• Soil and rock that is removed by heavy machinery
• After extraction, each strip is refilled with the overburden • Causes severe environmental impacts
• Destroys natural communities over large areas and triggers erosion
© 2015 Pearson Education, Inc.
Strip mining removes surface layers of soil and rock (cont’d)• Acid drainage
• Sulfide in newly exposed rock reacts with oxygen and rainwater, producing sulfuric acid
• Sulfuric acid leaches toxic materials from rock
• Flows into streams, killing fish and other organisms
• Pollutes groundwater used for drinking and irrigation • Although acid drainage is natural, mining greatly
accelerates it by exposing many new rock surfaces at once
© 2015 Pearson Education, Inc.
The Science Behind the Story
• Can Acid Mine Drainage Reduce Fracking’s Environmental Impact?
• Hydraulic fracturing injects water laden with drilling chemicals into layers of shale rock deep
• Along with natural gas, fracking wells pull up wastewater • Water mixed with dissolved salts, toxic metals, radioactive radium
isotopes • Release of the wastewater pollutes the streams
© 2015 Pearson Education, Inc.
The Science Behind the Story (cont’d)
• In parts of Pennsylvania, active hydraulic fracturing operations are very near streams affected by acid mine drainage
© 2015 Pearson Education, Inc.
The Science Behind the Story (cont’d)
• Dr. Vengosh and his team developed a process to treat the wastewater using acid mine drainage
• Removed most pollutants • Resulting water can
be reused in drilling applications
© 2015 Pearson Education, Inc.
In subsurface mining, miners work underground
• Accesses deep pockets of a mineral through tunnels and shafts up to 2.5 miles deep
• Zinc, lead, nickel, tin, gold, diamonds, phosphate, salt, coal
• The most dangerous form of mining
• Dynamite blasts, collapsed tunnels
• Toxic fumes and coal dust • Collapsed tunnels
cause sinkholes
© 2015 Pearson Education, Inc.
Frequently Asked Question
• Why would anyone choose to work in a mine when it’s such dangerous work?
© 2015 Pearson Education, Inc.
Open pit mining creates immense holes
• Open pit mining • Used with evenly distributed minerals • Terraced, so workers and machines can move about • Copper, iron, gold, diamonds, coal
• Quarries • Open pits for clay, gravel, sand, stone (limestone, granite,
marble, slate) • Huge amounts of rock are removed to get small
amounts of minerals • Habitat loss, aesthetic degradation, acid drainage
• Abandoned pits fill with water • Acid drainage forms if sulfur is present
© 2015 Pearson Education, Inc.
Open pit mining creates immense holes (cont’d)
• The world’s largest open pit mine • This Utah mine is 2.5 mi across and 0.75 mi deep; almost
half a million tons of ore and rock are removed each day
© 2015 Pearson Education, Inc.
Placer mining uses running water
• Placer mining • Using running water, miners sift through material in
riverbeds • Used for gold, gems
• Debris washes into streams
• They become uninhabitable for wildlife
• Disturbs stream banks • Causes erosion • Harms plant communities
© 2015 Pearson Education, Inc.
Mountaintop removal reshapes ridges and can fill valleys• Mountain removal mining
• Entire mountaintops are blasted off
• “Valley filling”: dumping rock and debris into valleys
• For coal in the Appalachian Mountains of the eastern U.S.
• Degrades and destroys vast areas
• Pollutes streams • Deforests areas • Causes erosion, mudslides, flash
floods, biodiversity loss
© 2015 Pearson Education, Inc.
Mountaintop removal reshapes ridges and can fill valleys (cont’d)• Mine blasting cracks foundations and walls • Floods and rockslides affect properties • Coal dust and contaminated water cause illness
• Lung cancer, heart and kidney disease, pulmonary disorders, hypertension, death
• The poor people of Appalachia suffer while we benefit from coal-produced electricity
• Critics argue that valley filling violates the Clean Water Act
• In 2010, the EPA introduced rules to limit damage
© 2015 Pearson Education, Inc.
Solution mining dissolves resources and extracts resources in place• Solution mining (in-situ recovery)
• Resources in a deep deposit are dissolved in a liquid and sucked out
• Water, acid, or other liquids are injected into holes • Used for salt, lithium, boron, bromine, magnesium,
potash, copper, uranium • Less environmental impact than other methods
• Less surface area is disturbed • But acids, heavy metals, uranium can accidentally leak or
leach out of rocks and contaminate groundwater
© 2015 Pearson Education, Inc.
Some mining occurs in the ocean
• We extract minerals (e.g., magnesium) from seawater
• Minerals are dredged from the ocean floor • Manganese nodules: small, ball-shaped ores
scattered across the ocean floor • These reserves may exceed all terrestrial reserves
• Logistical difficulties in mining have kept extractions limited, so far
© 2015 Pearson Education, Inc.
Restoring helps reclaim mine sites
• Governments in developed countries require companies to reclaim (restore) surface-mined sites
• Reclamation • Aims to bring a site to a condition similar to its pre-mining
condition • Involves removing structures, replacing overburden,
replanting vegetation • The U.S. Surface Mining Control and Reclamation
Act (1977) mandates restoration • Companies must post bonds to cover restoration costs
© 2015 Pearson Education, Inc.
Restoring helps reclaim mine sites (cont’d)
• Even on restored sites, impacts may be severe and long-lasting
• Complex communities are simplified • Forests, wetlands, etc., are replaced by grasses
• Essential symbioses are eliminated and often not restored
• Water can be reclaimed • Moderate the pH • Remove heavy metals
© 2015 Pearson Education, Inc.
An 1872 law still guides U.S. mining policy
• The General Mining Act of 1872 • Encourages metal and mineral mining on federal land
• Any citizen or company can stake a claim on, or buy (for $5 per acre), any public land open to mining
• The public gets no payment for any minerals found • Supporters say it encourages a domestic industry that is
risky and requires investment to locate vital resources • Critics say it gives valuable public land basically free to
private interests • People have developed the land for uses (e.g., for
condominiums) that have nothing to do with mining • Efforts to amend the act have failed in Congress
© 2015 Pearson Education, Inc.
Weighing the Issues
• Restoring Mined Areas • Mining has severe environmental impacts, and restoring a
mined site to a condition similar to its state before mining is costly and difficult
• How much do you think we should require mining companies to restore a site after a mine is shut down?
• What criteria should we use to guide restoration? • Should we require complete restoration? No restoration? • Explain your recommendations
© 2015 Pearson Education, Inc.
Minerals are nonrenewable resources in limited supply• Many minerals are rare and could become
unavailable • Once known reserves are mined, minerals will be
gone • For example, indium, used in LCD screens, might last
only 30 more years • Gallium (for solar power) and platinum (fuel cells) are also
scarce • Estimating how long a reserve will last is hard
• New discoveries, technologies, consumption patterns, and recycling affect mineral supplies
• As minerals become scarcer, prices rise
© 2015 Pearson Education, Inc.
Years remaining for selected minerals
• Minerals are nonrenewable resources, so supplies are limited
© 2015 Pearson Education, Inc.
Major reasons why nonrenewable resource availability estimates may increase or decrease over time• Discovery of new resources • New extraction technologies • Changing social and technological dynamics • Changing consumption patterns • Recycling
© 2015 Pearson Education, Inc.
We can use minerals sustainably
• Recycling minerals addresses • Finite supplies • Environmental damage
• 35% of metals are currently recycled from U.S. solid waste
• 33% of our copper comes from recycled sources • Recycling decreases energy use
• It also lowers greenhouse gas emissions
© 2015 Pearson Education, Inc.
We can recycle metals from e-waste
• Electronic waste (e-waste) from computers, printers, cell phones, etc., is rapidly rising
• Recycling keeps hazardous wastes out of landfills while conserving mineral resources
© 2015 Pearson Education, Inc.
We can recycle metals from e-waste
• Cell phones can be refurbished and resold in developing countries
• Or their parts can be dismantled or refurbished • Today, only 10% of cell phones
are recycled • Recycling reduces demand
for virgin ores and reduces pressure on ecosystems
© 2015 Pearson Education, Inc.
Conclusion
• Geologic processes shape Earth’s terrain and form the foundation for living systems
• We depend on minerals and metals to make our products
• Mineral resources are mined by various methods • Contribute to material wealth • But cause extensive environmental damage
(habitat loss, acid drainage, etc.) • Restoration and regulations help minimize the
environmental and social impacts of mining • Recycling and sustainable use prolong mineral
resources