Geology and Nonrenewable

Minerals

Chapter 15

Environmental Effects of Gold Mining

Gold producersSouth AfricaAustraliaUnited StatesCanada

Cyanide heap leachingExtremely

toxic to birds and mammals

2000: Collapse of a dam retaining a cyanide leach pond

Black Hills, S. Dakota

Earth’s Major Geological Processes and Hazards

Gigantic plates in the earth’s crust move very slowly atop the planet’s mantle, and wind and water move the matter from place to place across the earth’s surface.

Natural geological hazards such as earthquakes, tsunamis, volcanoes, and landslides can cause considerable damage.

The Earth Is a Dynamic Planet

What is geology? Three major concentric zones of the earth

Core: solid inner part surrounded by a liquid core

Mantle: mostly solid rock Including the asthenosphere: hot,partly melted

rock that flows and can be deformed like plastic Crust

Continental crustOceanic crust: 71% of crust

Major Features of the Earth’s Crust and Upper Mantle

The Earth beneath your feet is moving…….

Convection cells, or currents : move large volumes of rock and heat in loops within the mantle like gigantic conveyer belts

Tectonic Plates: dozen or so huge rigid plates move extremely slowly atop the denser mantle on hot, soft rock in the underlying asthenosphere

Lithosphere: continental and oceanic crust and the rigid, outermost part of the mantle

The Earth’s Crust Is Made Up of a Mosaic of Huge Rigid Plates: Tectonic Plates

Fig. 14-4, p. 347

EURASIAN PLATE

NORTH AMERICAN PLATE

ANATOLIAN PLATE

JUAN DE FUCA PLATE

CARIBBEAN PLATE

PHILIPPINE PLATE

CHINA SUBPLATE

AFRICAN PLATE ARABIAN PLATE INDIA

PLATEPACIFIC PLATE PACIFIC PLATECOCOS

PLATESOUTH AMERICAN PLATE

NAZCA PLATEAUSTRALIAN

PLATESOMALIAN SUBPLATE

SCOTIA PLATE

ANTARCTIC PLATE

Transform faultsDivergent plate boundaries Convergent plate boundaries

The Earth’s Major Tectonic Plates

The Earth beneath your feet is moving ….

Three types of boundaries between plates Divergent plates –plates move apart

Magma – flows up through the resulting cracksOceanic ridge – some of which have higher peaks and

deeper canyons than earth’s continents Convergent plates – oceanic plate collides with a continental

plate, Subduction: the latter rides up over the denser oceanic

plate and pushes it down into the mantleSubduction zone: area where collision and subduction takes

place Trench : forms at the boundary between the 2 converging

plates Transform fault e.g. San Andreas fault: where plates slide

and grind past one another along a fracture. Most located on the ocean floor

The San Andreas Fault as It Crosses Part of the Carrizo Plain in California, U.S.

Some Parts of the Earth’s Surface Build Up and Some Wear Down Internal geologic processes

Generated by heat from the earth’s interior ,generally build up the earth’s surface in the form of continental and oceanic crust including mountains and volcanoes

External geologic processesWeathering : driven directly or indirectly by

energy from the sun(mostly in the form of flowing water and wind)Physical, Chemical, and Biological : soil

ErosionWindFlowing waterHuman activitiesGlaciers

Weathering: Biological, Chemical, and Physical Processes

Volcanoes Release Molten Rock from the Earth’s Interior

Volcano: magma reaches the earth’s surface through a.. Fissure: central vent or a long crack Magma Lava: magma that reaches the earth’s surface. Debris

ranging from large chunks of larva rock to glowing hot ash, liquid lava and gases such as water vapor, carbon dioxide and sulfur dioxide . Much of the world’s volcanic activity is concentrated along the boundaries of the earth’s tectonic plates

1980: Eruption of Mount St. Helens

1991: Eruption of Mount Pinatubo: cooled the earth’ average temperature for 15 months

Benefits of volcanic activity: highly fertile soil, creates outstanding landforms (Crater Lake in Oregon)

Creation of a Volcano

Earthquakes Are Geological Rock-and-Roll Events

Richter scale Insignificant: <4.0Minor: 4.0–4.9Damaging: 5.0–5.9Destructive: 6.0–6.9Major: 7.0–7.9Great: >8.0

EarthquakeSeismic wavesFocus EpicenterMagnitudeAmplitude

Foreshocks and aftershocksPrimary effects of earthquakes: shaking, permanent vertical or horizontal displacement of the ground

Major Features and Effects of an Earthquake

Areas of Greatest Earthquake Risk in the United States

Areas of Greatest Earthquake Risk in the World

Earthquakes on the Ocean Floor Can Cause Huge Waves Called Tsunamis

Tsunami, tidal wave : generated when part of the ocean floor suddenly rises or drops. Usually occurs offshore in subduction zones.

Detection of tsunamis: by ocean buoys, pressure recorders on the ocean floor which measures changes in water pressure as the waves pass over it; data relayed via satellites tsunami warning systems

December 2004: Indian Ocean tsunami Magnitude of 9.15 Role of coral reefs and mangrove forests in

reducing death toll

Formation of a Tsunami and Map of Affected Area of Dec 2004 Tsunami

Shore near Banda Aceh,Gleebruk in Indonesia before and after tsunami

After: December 28, 2004 Before :June 23, 2004

Gravity and Earthquakes Can Cause Landslides Mass wasting: detached or loose rock, soil

and mud to slide down steep slopes near the shores of oceans or lakes Slow movement Fast movement

RockslidesAvalanchesMudslides : 1970 – Peru, buried the town

of Yungay and killed 17,000 people Effect of human activities on such geological

events: forest clearing, road building , crop

growing, building houses

Earth’s Rocks are Recycled……..

The three major types of rocks found in the earth’s crust—sedimentary, igneous, and metamorphic—are recycled very slowly by the process of erosion, melting, and metamorphism.

There Are Three Major Types of Rocks

Earth’s crust• Composed of minerals and rocks

Three broad classes of rocks, based on formationSedimentary Igneous

Sandstone GraniteShale Lava rockDolomite Metamorphic Slate AnthraciteLignite SlateBituminous coal Marble

The Earth’s Rocks Are Recycled Very Slowly

Rock cycle: the interaction of physical and chemical processes that change rocks from one type to another. Slowest of the earth’s cyclic processes

What Are Mineral Resources? Naturally occurring materials in the earth’s crust that can

be extracted and made into useful products in processes that provide economic benefits and jobs.

100 minerals: fossil fuels(coal) metallic(aluminum, iron, copper) non-metallic(sand, gravel, limestone, salt, precious gems)

Mineral deposit – area in which a particular mineral is concentrated. Ore – metal-yielding material; contains 2 parts: the ore mineral

(metal) and waste mineral material (gangue) High-grade ore – large amount of desired metal Low-grade ore – small amount of the desired resource

Removing Metals from Ores

Nonrenewable – takes so long to be produced

Ore extracted by mining Ore mineral = desired metal Gangue - waste material. Removing the gangue

from the ores produces tailings. Particles of toxic metals blown by the wind or leached by rainfall can contaminate surface water and groundwater.

Smelting – heating ore in order to separate desired metals. Without proper equipment, releases sulfur dioxide and suspended particles, damage vegetation and acidify soils

Extracting, Processing, Using Nonrenewable Mineral and Energy Resources

Life Cycle of a Metal Resource

Mineral Use Has Advantages and Disadvantages

Ads: Mine and convert minerals into useful products

Disads: uses enormous amounts of energy, disturbs land, erodes soil, produces solid waste, air and water pollution

Ways to Remove Mineral Deposits Surface mining : shallow deposits

removed mechanized equipment strips away

overburden(soil and rock overlay), discarded as waste called spoils

Used to extract 90% of the nonfuel mineral and rock resources and 6% of the coal

Type of surface mining used depends onResourceLocal topography

Subsurface mining Deep deposits removed Used to extract coal and metal ores

Types of Surface Mining

Open Pit Mining - machines dig hole and remove ore

Strip Mining - earth movers strip overburden and power shovels remove deposit

Contour Mining - mine coal on hilly terrain. Wall of dirt left in front of a highly erodible bank of soil and rock called highwall

Mountain Top Removal - Appalachian Mountains , draglines, explosives remove top of mountain to expose seams

Open-Pit Mine in Western Australia

Fig. 14-17, p. 357

Undisturbed land

Overburden

HighwallCoal seamOverburdenPit

Bench

Coal seam

Spoil banks

Contour Strip Mining in hilly areas

Mountaintop Coal Mining in West Virginia, U.S.

Scarring and disruption of the land surface E.g., spoils banks

Large amounts of solid waste (3/4th of all US solid waste)

Toxin-laced mining waste deposited in areas other than mining site .

Loss of rivers and streams – 1900 km have been buried

Subsidence - collapse of land

Mining has Harmful Environmental Effects…….

Harmful Environmental Effects

Major pollution of water – Acid mine drainage Leaching of heavy metals Oil and chemical spills Highly toxic cyanide salts

are used to extract gold from its ore; leave behind cyanide laden water

Effect on aquatic life – pH change, 40% of all US watersheds

contaminatedIllegal Gold Mine

Environmental Effects of Gold Mining

Gold producersSouth AfricaAustraliaUnited StatesCanada

Cyanide heap leachingExtremely

toxic to birds and mammals

2000 - Collapse of a dam retaining a cyanide leach pond

Black Hills, S. Dakota

Summitville Gold Mining Site in Colorado, U.S.

The U.S. General Mining Law of 1872

Encouraged mineral exploration and mining of hard-rock minerals on U.S. public lands

Developed to encourage settling the West (1800s)

Until 1995, land could be bought for 1872 prices

Companies must pay for clean-up now

LEGISLATION

Date Name of

Legislation What it Did

1872 Mining Act Governed prospecting and mining of minerals on publicly owned land

1920 Mineral Leasing Act

Permitted the Bureau of Land Management to grant leases for development of deposits of coal, phosphate, potash, sodium, sulfur, and other leasable minerals on public domain lands.

1976 Resource Conservation and Recovery Acts (RCRA)

Regulated some mineral processing wastes

LEGISLATION (cont.)

Date Name of Legislation

What it Did

1977 Surface Mining Control And Reclamation Act

Established a program for regulating surface coal mining and reclamation activities. It established mandatory standards for activities on state and federal lands, including a requirement that adverse impacts on fish, wildlife, and related environmental values be minimized. It requires mining companies to restore most surface-mined land.

1980 Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA); Superfund Act

Regulated damage done by mining

POSSIBLE REMEDIES FOR MINIMIZING EFFECTS OF TOXINS Buffer/neutralize with alkaline(basic) substances

such as limestone (calcium carbonate), sodium hydroxide (NaOH), or ammonia.

Cover tailings to reduce contact with precipitation.

Sedimentation ponds/retention basins or ponds.

Bioremediation by sulfate-reducing bacteria.

Ecological Restoration of a Mining Site in New Jersey, U.S.

POSSIBLE STEPS TO RESTORING SURFACE-MINED LAND

Re-contouring/regrading land to its original topography.

Replacing and/or adding topsoil/nutrients as needed to improve soil quality or structure

Replanting native vegetation fast-growing species early successional species

Monitor for 5 to 10 years

How Long Will Supplies of Nonrenewable Mineral Resources

Last? All mineral resources exist in finite amounts, and

as we get closer to depleting any mineral resource, the environmental impacts of extracting it generally become more harmful.

Relatively abundant deposits of iron and aluminum (bauxite)

Scarce - manganese, chromium, cobalt, platinum An increase in the price of a scarce mineral

resource can lead to increased supplies and more efficient use of the mineral, but there are limits to this effect.

Uneven Distribution of Minerals

Most of the nonrenewable mineral resources supplied by Canada United States Germany Russia South Africa - self sufficient in all key

minerals, largest producer of gold, chromium and platinum

Australia

8% of world population, consume 75% of the world’s key metalsChina increasing

consumption

Four Strategic Metal Resources….

Manganese Cobalt Chromium Platinum US has little or no reserves of these metals

which are essential for the country’s economy and military strength

May have to switch to “nano” materials

MINERAL PRODUCTION OF SOME NON-FUEL MINERAL RESOURCES

Mineral 2004 Production

(thousands of metric tons)

Bauxite (aluminum ore) 159,000

Copper 14,600

Iron ore 1,340,000

Phosphate rock (for fertilizer) 141,000

Zinc 9,600,000

*High production rates lead to eventual depletion of the resources.

The Nanotechnology Revolution Nanotechnology (tiny tech) - use carbon,

oxygen and silicone atoms to create everything from medicines, solar cells to automobile bodies

Currently used in more than 400 items - odor eating socks, wrinkle –free clothes, cosmetics, sun screens

Nanoparticles Are they safe?

Investigate potential ecological, economic, health, and societal risks

Develop guidelines for their use until more is known about them

Future supply depends on Actual or potential supply of the mineral Rate at which it is used

When it becomes economically depleted Recycle or reuse existing supplies Waste less Use less Find a substitute Do without

Economic Depletion of Non- renewable Mineral Resources

MINERAL ORES AND YEARS OF SUPPLY

Mineral Years of Supply

Bauxite (aluminum ore) 152

Copper 32

Iron ore 105

Nickel 41

Zinc 22

*The increased demand for manufactured goods means we need to extract more and more raw materials from the Earth.

Depletion Curves for a Nonrenewable Resource

Depletion time - time it takes to use up approximately

80% of the reserves of a mineral at a given rate of use

Market Prices Affect Supplies of Nonrenewable Minerals

Subsidies and tax breaks to mining companies keep mineral prices artificially low

Does this promote economic growth and national security?

Scarce investment capital hinders the development of new supplies of mineral resources

Is Mining Lower-Grade Ores the answer?

Factors limit the mining of lower grade ores increased cost of mining limited availability of fresh water environmental impacts of increased land disruption,

waste material and pollution produced during mining and processing

Use microorganisms that can extract minerals “in-place” or “in-situ” mining.Biomining - genetic engineering techniques used to produce bacteria that can be used to extract a particular metal without disturbing the surrounding environment

Extend Supplies by Getting More Minerals from the Ocean…

Mineral resources dissolved in the ocean-very low concentrations, requires more energy and money than they are worth

Only magnesium, bromine and sodium chloride are abundant enough to be extracted profitably

Deposits of minerals in sediments along the shallow continental shelf and near shorelines - sand, gravel,phosphates,sulfur,tin,copper,iron,tungsten,silver,titanium,platinum,diamonds

Extend Supplies by Getting More Minerals from the Ocean

Hydrothermal ore deposits : sulfides, zinc, silver, copper precipitate out and build up as mineral deposits currently costs too much to extract, disputes over ownership

Metals from the ocean floor - potato sized manganese nodules, cover 25-50% of the Pacific ocean floor Effect of mining on aquatic life Environmental impact - sea bed mining ,less impact than

land (??)

How Can We Use Mineral Resources More Sustainability?

Find substitutes for some scarce mineral resources materials revolution : silicon, ceramics, plastics houses made of styrofoam sprayed with ceramic spray

called Grancrete, reduces use of timber high strength plastics and composite materials

strengthened by light weight carbon and glass fibers are transforming the automobile and aerospace industries

making plastics requires fossil fuels and oil

Substitution may not always be possible : platinum, industrial catalyst chromium : stainless steel

We Can Recycle and Reuse Valuable Metals

Recycling Lower environmental impact than mining

and processing virgin materials Reuse - gold, silver, iron, copper, steel,

aluminum, platinum Recycling aluminum beverage cans and

scrap aluminum produces 95% less air pollution, 97% less water pollution and uses 95% less energy

There Are Many Ways to Use Mineral Resources More

Sustainability

How can we decrease our use and waste of mineral resources?

Pollution and waste prevention programs 3M : Pollution Prevention Pays (3P) Cleaner production : air pollution 70%

lower, saved $750 million in waste disposal and material costs

Sustainable Use of Nonrenewable Minerals

Industrial Ecosystems: Copying Nature

Mimic nature: recycle and reuse most minerals and chemicals : waste outputs of one organism becomes the nutrient inputs of another

Resource exchange webs : wastes of one manufacturer becomes the raw materials for another

Ecoindustrial parks on brownfields, which are abandoned industrial sites

Industrial forms of biomimicry Benefits : come up with new environmentally

beneficial and less resource-intensive chemicals Better image among consumers

An Industrial Ecosystem in Denmark Mimics Natural Food Web