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Geology and Nonrenewable Minerals
Chapter 12
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Question of the Day What law has allowed some people to get rich at the expense of the U.S. people and their public lands.
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Answer of the Day U.S. General Mining Law of 1872.
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General Mining Law of 1872 Original purpose of the law
Impact on US public lands Benefits to mining companies Costs to the public Environmental issues Laws in other countries Was Designed to encourage mineral exploration and the mining of hardrock minerals (gold, silver, copper, zink, nickel, and uranium) on U.S. public lands and to help develop the then sparsely populated West. p. 267 Fig. 12-1, p. 269
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Internal Geologic Processes
What is geology? - the study dynamic processes occurring on the Earth’s surface and in it’s interior. Earth’s internal structure Core - solid inner part, surrounded by a liquid core of semisolid material. Mantle - surrounds the core. Solid rock over the asthenosphere. Crusts (continental and oceanic) Plate tectonics - convection cells cause about 15 plates to move across the earth’s surface.
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General Structure of the Earth
Oceanic crust Continental crust Atmosphere Vegetation and animals Biosphere Lithosphere Soil Upper mantle Crust Asthenosphere Rock Lower mantle Core Mantle Crust (soil and rock) Biosphere (living and dead organisms) Hydrosphere (water) Lithosphere (crust, top of upper mantle) Atmosphere (air) Fig. 3-5, p. 38
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Earth’s Major Tectonic Plates
EURASIAN PLATE ANATOLIAN PLATE NORTH AMERICAN PLATE JUAN DE FUCA PLATE CHINA SUBPLATE CARIBBEAN PLATE PHILIPPINE PLATE ARABIAN PLATE AFRICAN PLATE PACIFIC PLATE SOUTH AMERICAN PLATE NAZCA PLATE INDIAN-AUSTRLIAN PLATE SOMALIAN SUBPLATE ANTARCTIC PLATE Convergent plate boundaries Divergent boundaries Transform faults Fig. 12-4, p. 273
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Plate Tectonics Fig. 12-3, p. 272 Spreading center Oceanic tectonic
Ocean trench Collision between two continents Plate movement Plate movement Tectonic plate Oceanic crust Oceanic crust Subduction zone Continental crust Continental crust Material cools as it reaches the outer mantle Cold dense material falls back through mantle Mantle convection cell Hot material rising through the mantle Two plates move towards each other. One is subducted back into the mantle on falling convection current. Mantle Hot outer core Inner core Inner core Fig. 12-3, p. 272
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Plate Tectonics Tectonic plates
Lithosphere - outer most part of the mantel Plate tectonics and biological evolution - Populations became isolated and speciation occurred.
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Earth’s Crust and Upper Mantle
Abyssal hills Folded mountain belt Abyssal floor Oceanic ridge Abyssal floor Trench Craton Volcanoes Continental rise Oceanic crust (lithosphere) Continental slope Abyssal plain Continental shelf Abyssal plain Continental crust (lithosphere) Mantle (lithosphere) Mantle (lithosphere) Mantle (asthenosphere) Fig. 12-2, p. 271
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Types of Plate Boundaries
Divergent Move apart Convergent Pushed together Transform Grind past one another Fig. 12-5, p. 274
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Types of Plate Boundaries
Lithosphere Asthenosphere Oceanic ridge at a divergent plate boundary Fig. 12-5a, p. 274
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Types of Plate Boundaries
Volcanic island arc Trench Lithosphere Rising magma Asthenosphere Subduction zone Trench and volcanic island arc at a convergent plate boundary Fig. 12-5b, p. 274
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Types of Plate Boundaries
Fracture zone Transform fault Lithosphere Asthenosphere Transform fault connecting two divergent plate boundaries Fig. 12-5c, p. 274
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External Earth Processes
Erosion - material is dissolved, loosened, or worn away Physical (mechanical) weathering: frost wedging Chemical weathering Biological weathering
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Question of the Day What are the two types of seismic waves?
Which one of these two can travel through the interior of the earth? How do we know the earths outer core is molten/ liquid?
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Answers of the Day The two seismic waves are P waves and S waves.
The P waves are able to travel through the earths interior. S waves cannot travel through liquid, so only the P wave would pass through the outer core if it was liquid.
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Question of the Day What two pieces of information do you need to figure the Richter Magnitude of an earthquake.
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Answer of the Day The S - P time interval and the maximum amplitude of the seismic wave is required to determine the magnitude of an earthquake.
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Fundamental Laws of Geology
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Uniformaitarianism states that the present is the key to the past.
James Hutton in 1795 was popularized in 1830 by Charles Lyell in the textbook Principles of Geology.
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Original Horizontality
Sedimentary rocks are formed by particles which, under the influence of gravity, settle to the bottom of rivers, lakes, and oceans and form essentially horizontal layers. Steno ( )
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Superposition In any undisturbed sequence of strata the oldest or first-deposited layer would be on the bottom and that the youngest or last-deposited layer would be on the top. Steno (later seventeenth century) Demonstrated by Hutton (1795)
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Crosscutting Relations
Any rock unit or fault that cuts acrosss other rock units is younger than the rock units through which it cuts.
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Faunal Succession Plant and animal fossils succeed one another in a recognizable order. William Smith ( )
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Question of the Day As the Tsunami crest approaches shore, the wave height _________, the velocity __________, and the period _____. Choices: Decreases Increases Remains constant
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Answer of the Day As the Tsunami crest approaches shore, the wave height increases, the velocity decreases, and the period remains constant.
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The Rock Cycle Fig. 12-6, p. 275 Erosion Transportation Weathering
Deposition Igneous Rock Granite, pumice, basalt Sedimentary Rock sandstone, limestone Heat, pressure Cooling Magma (molten rock) Heat, pressure, stress Melting Metamorphic Rock Slate, marble, gneiss quartzite Fig. 12-6, p. 275
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Mineral Resources Generally nonrenewable
Metallic, nonmetallic, and energy resources Ores - rock containing enough of one or more metallic minerals to be mined profitably.
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Where do your possessions come from?
List some popular and valuable item and list the materials of which it is made.
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Environmental Impact How is this material taken from the Earth?
How might extraction this material affect the environment and the people who live where the material occurs and the people who work to extract it.
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Categories of Mineral Resources
Identified Undiscovered Reserves Other Fig. 12-7, p. 276
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Finding Mineral Resources
Aerial and satellite images Radiation detectors Magnetometers Gravimeters Seismic surveys Chemical analyses
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Extracting Mineral Deposits
Surface mining Subsurface mining Overburden - soil and rock Spoils - discarded overburden or waste material
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Mining Methods Open-pit (surface mining) Bingham Utah
Area strip mining (surface) Contour strip mining (surface) Mountaintop removal (surface) The Surface Mining Control and Reclamation Act of 1977 Subsurface mining Hazards and environmental tradeoffs of subsurface mining
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Open-pit Mine Fig. 12-8, p. 277
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Spoil from an Unrestored Area Strip Mine
Fig. 12-9, p. 277
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Contour Strip Mining Undisturbed Land Overburden Highwall Coal seam
Pit Bench Coal seam Spoil Banks Fig , p. 277
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Mountaintop Mining Fig , p. 278
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Environmental Effects of Using Mineral Resources
Disrupting the land surface Subsidence Toxic mining waste Acid mine drainage Air pollution Toxic holding ponds
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Environmental Effects of Mineral Use
Natural Capital Degredation Extracting, Processing, and Using Nonrenewable Mineral and Energy Resources Steps Environmental Effects Disturbed land; mining accidents; health hazards; mine waste dumping;oil spills and blowouts; noise; ugliness; heat Mining Exploration, extraction Processing Solid wastes; radioactive material; air, water, and soil pollution; noise; safety and health hazards; ugliness; heat Transportation, purifi- cation, manufacturing Use Noise; ugliness; thermal water pollution; pollution of air, water, and soil; solid and radioactive wastes; safety and health hazards; heat transportation or trans- mission to individual user, eventual use, and discarding Fig , p. 279
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Processing of Mineral Resources
Ore mineral - the desired metal Gangue - (“gang”) the waste material Tailings - piles of waste produced by processing Smelting - separates the metal from other elements in the ore mineral Products Disposal or recycling
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Typical Life Cycle of a Metal Resource
Surface mining Metal ore Separation of ore from gangue Smelting Melting metal Conversion to product Discarding of product (Scattered in environ-ment) Reuse Recycling Fig , p. 279
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Environmental Limits to Resource Extraction
Environmental damage: a major mining problem which will limit their availability, not exhaustion of supplies Ore grade - higher-grade ores exploited first Including environmental costs in products
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Supplies of Mineral Resources
Available supply and how rapidly it is used Minerals become “Economically depletion” not “totally depleted” Five choices after depletion Recycle or reuse Waste less Use less Find a substitute Do without Depletion time is how long it takes to use 80% of the reserves Economics determines what part of the known supply is extracted and used Finding alternatives
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Depletion Curves for a Nonrenewable Resource
Mine, use, throw away; no new discoveries; rising prices Recycle; increase reserves by improved mining technology, higher prices, and new discoveries B Production Recycle, reuse, reduce consumption; increase reserves by improved mining technology, higher prices, and new discoveries C Present Depletion time A Depletion time B Depletion time C Fig , p. 280 Time
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Economics and Supplies of Nonrenewable Resources
Roll of economics in mining Standard economic theory = supply and demand Limited free market in developed countries Government subsidies of mining 1872 US General Mining Law Economic problems of developing new mines
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Question of the Day The change of rocks from one type to another is known as the ________?
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Answer of the Day The change of rocks from one type to another is known as the Rock Cycle?
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Mining Lower-grade Ores
New extraction technologies are needed Factors that limit mining lower-grade ores Costs Supplies of freshwater Environmental impacts Biomining: microorganisms and in-situ mining
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Nanotechnology Revolution
Buckyballs Molecular economy Possible achievements of nanotechnology Possible environmental and health threats Likely need for guidelines and regulations
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Ocean Mining Ore deposits in the ocean Minerals from seawater
Minerals in ocean sediments Hydrothermal deposits Manganese-rich nodules Mining issues in international waters Environmental issues
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Hydrothermal Ore Deposits on the Ocean Floor
White smoker Black smoker Sulfide deposit Magma Tube worms White crab White clam Fig , p. 283
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Finding Substitutes for Scarce Mineral Resources
Materials revolution Ceramic substitutes High-strength plastics and composites Finding some substitutes may be impossible Some substitutes are inferior
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