geology and nonrenewable minerals chapter 15. environmental effects of gold mining gold producers...
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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