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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 The Earth’s Major Tectonic Plates EURASIAN PLATE JUAN DE FUCA PLATE NORTH AMERICAN PLATE CARIBBEAN PLATE ANATOLIAN PLATE CHINA SUBPLATE AFRICAN PLATE PACIFIC PLATE COCOS PLATE NAZCA PLATE Divergent plate boundaries PACIFIC PLATE SOUTH AMERICAN PLATE SOMALIAN SUBPLATE SCOTIA PLATE PHILIPPINE PLATE ARABIAN PLATE INDIA PLATE AUSTRALIAN PLATE ANTARCTIC PLATE Convergent plate boundaries Transform faults Fig. 14-4, p. 347 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 Earthquake Seismic waves Focus Epicenter Magnitude Amplitude 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 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 Before :June 23, 2004 After: December 28, 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 Dolomite Metamorphic 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? 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 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 Australia Undisturbed land Overburden Pit Contour Strip Mining in hilly areas Bench Spoil banks Fig. 14-17, p. 357 Mountaintop Coal Mining in West Virginia, U.S. Mining has Harmful Environmental Effects……. 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 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 contaminated Illegal Gold Mine 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 Summitville Gold Mining Site in Colorado, U.S. The U.S. General Mining Law of 1872 Encouraged mineral exploration and mining of hardrock 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 1872 Mining Act 1920 Mineral Leasing Act 1976 Resource Conservation and Recovery Acts (RCRA) What it Did Governed prospecting and mining of minerals on publicly owned land 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. Regulated some mineral processing wastes LEGISLATION (cont.) Date Name of Legislation 1977 Surface Mining Control And Reclamation Act 1980 Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA); Superfund Act What it Did 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. 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 8% of world population, consume 75% of the world’s key metals Germany China increasing consumption Russia South Africa - self sufficient in all key minerals, largest producer of gold, chromium and platinum Australia 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 Bauxite (aluminum ore) Copper Iron ore Phosphate rock (for fertilizer) Zinc 2004 Production (thousands of metric tons) 159,000 14,600 1,340,000 141,000 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 Economic Depletion of Nonrenewable Mineral Resources 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 MINERAL ORES AND YEARS OF SUPPLY Mineral Bauxite (aluminum ore) Copper Years of Supply 152 32 Iron ore Nickel Zinc 105 41 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 “insitu” 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