Geology, Minerals, and Mining - agricanto.org · Geology, Minerals, and Mining ... • The downslope movement of soil and rock due to gravity ... • Soil, rock, and water movement

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


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


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


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


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


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


Plate tectonics shapes Earth’s geography (cont’d)

• Earth has 15 major tectonic plates • Movement of these plates influences climate and

evolution


• 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


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


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


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


Different types of rocks

• Magma • Molten, liquid rock • Lava

• Magma released by a volcano

• Igneous rock • Formed when magma cools


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


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”


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


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


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


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


Landslides are a form of mass wasting (cont’d)

• The town of Oso, Washington, was buried in 2014 by a massive landslide


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


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


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


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


Earth’s mineral resources

• We mine and process mineral resources for countless products


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


Frequently Asked Question

• How do geologists “see” mineral deposits below the ground?


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


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


Metals are extracted from ores (cont’d)

• Economically valuable metals from ore include:

• Copper • Iron • Lead • Gold • Aluminum • Tantalum

• Used to manufacture electronics


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


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


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)


Minerals we use come form all over the world


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


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


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


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


The Science Behind the Story (cont’d)

• In parts of Pennsylvania, active hydraulic fracturing operations are very near streams affected by acid mine drainage


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


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


Frequently Asked Question

• Why would anyone choose to work in a mine when it’s such dangerous work?


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


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


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


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


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


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


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


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


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


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


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


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


Years remaining for selected minerals

• Minerals are nonrenewable resources, so supplies are limited


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


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


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


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


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

Geology, Minerals, and Mining - agricanto.org · Geology, Minerals, and Mining ... • The downslope movement of soil and rock due to gravity ... • Soil, rock, and water movement

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