Geology and Nonrenewable Minerals Chapter 15

Environmental Effects of Gold Mining Gold producers South Africa Australia United States Canada Cyanide heap leaching Extremely 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 crust  Oceanic 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 PLATE PACIFIC PLATE COCOS PLATE SOUTH AMERICAN PLATE NAZCA PLATE AUSTRALIAN PLATE SOMALIAN SUBPLATE SCOTIA PLATE ANTARCTIC PLATE Transform faults Divergent 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 cracks Oceanic 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 mantle Subduction 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 processes Weathering : driven directly or indirectly by energy from the sun(mostly in the form of flowing water and wind) Physical, Chemical, and Biological : soil Erosion Wind Flowing water Human activities Glaciers

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: <4.0 Minor: 4.0–4.9 Damaging: 5.0–5.9 Destructive: 6.0–6.9 Major: 7.0–7.9 Great: >8.0 Earthquake Seismic waves Focus Epicenter Magnitude Amplitude Foreshocks and aftershocks Primary 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, 2004Before :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  Rockslides  Avalanches  Mudslides : 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 formation Sedimentary Igneous Sandstone Granite Shale Lava rock DolomiteMetamorphic Slate Anthracite Lignite Slate Bituminous 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, and what are their environmental effects?  Some naturally occurring materials in the earth’s crust can be extracted and made into useful products in processes that provide economic benefits and jobs.  100 minerals: naturally occurring material  fossil fuels(coal);  metallic(aluminum, iron, copper);  non-metallic(sand, gravel,limestone)  Ore: large concentration of a particular mineral, often a metal  High-grade ore – large amount of desired non-renewable resource  Low-grade ore – small amount of the resource

Mineral Use Has Advantages and Disadvantages  Mine and convert minerals into useful products  Disadvantages: enormous amounts of energy, disturbs land, erode soil, produce solid waste, air and water pollution Life cycle of a metal resource

Extracting, Processing, Using Nonrenewable Mineral and Energy Resources

There Are Several Ways to Remove Mineral Deposits  Surface mining : shallow deposits removed  mechanized equipment strips away overburden(soil and rock overlay), discarded as waste called  Used to extract 90% of the nonfuel mineral and rock resources and 6-% of the coal Type of surface mining used depends on Resource Local 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 Australi a

Fig , p. 357 Undisturbed land Overburden Highwall Coal seam Overburden Pit 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  Loss of rivers and streams – 1900 km have been buried  Subsidence :collapse of land Mining has harmful effects…….

Mining Has Harmful Environmental Effects  Major pollution of water and air: toxin-laced mining waste deposited in areas other than mining site. Acid Mine Drainage  Effect on aquatic life :ph change,40% of all US watersheds contaminated  Large amounts of solid waste  3/4 th of all US solid waste  mining gold Illegal Gold Mine

Removing Metals from Ores Has Harmful Environmental Effects  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 ores to release metals.  Without proper equipment, releases sulfur dioxide and suspended particles, damage vegetation and acidify soils  Water pollution: highly toxic cyanide salts to extract gold from it’s ore. Leave behind cyanide laden water  Summitville Gold Mining, Co

Summitville Gold Mining Site in Colorado, U.S.

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

How Long Will Supplies of Nonrenewable Mineral Resources Last?  All nonrenewable 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 metals China 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 ave to switch to nano materials

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

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

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

I s Mining Lower-Grade Ores the answer?  Factors limit the mining of lower grade ores  increased cost of mining  limited availability of fresh water, specially in arid areas  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, that 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 styroform 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 metals from ores  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