Geology and Nonrenewable Minerals Chapter 12
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.
Answer of the Day • U.S. 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 General Mining Law of 1872 Fig. 12-1, p. 269
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.
General Structure of the Earth Oceanic crust Continental crust Atmosphere Biosphere Vegetation and animals 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
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
Plate Tectonics Spreading center Oceanic tectonic plate Oceanic tectonic plate 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 Hot material rising through the mantle Mantle convection cell Mantle Two plates move towards each other. One is subducted back into the mantle on falling convection current. Hot outer core Inner core Inner core Fig. 12-3, p. 272
Plate Tectonics • Tectonic plates • Lithosphere - outer most part of the mantel • Plate tectonics and biological evolution • - Populations became isolated and speciation occurred.
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
Divergent Move apart Convergent Pushed together Transform Grind past one another Types of Plate Boundaries Fig. 12-5, p. 274
Types of Plate Boundaries Lithosphere Asthenosphere Oceanic ridge at a divergent plate boundary Fig. 12-5a, p. 274
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
Types of Plate Boundaries Fracture zone Transform fault Lithosphere Asthenosphere Transform fault connecting two divergent plate boundaries Fig. 12-5c, p. 274
External Earth Processes • Erosion • - material is dissolved, loosened, or worn away • Physical (mechanical) weathering: frost wedging • Chemical weathering • Biological weathering
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?
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.
Question of the Day • What two pieces of information do you need to figure the Richter Magnitude of an earthquake.
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.
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.
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 (1638-1687)
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)
Crosscutting Relations • Any rock unit or fault that cuts acrosss other rock units is younger than the rock units through which it cuts.
Faunal Succession • Plant and animal fossils succeed one another in a recognizable order. • William Smith (1769-1839)
Question of the Day As the Tsunami crest approaches shore, the wave height _________, the velocity __________, and the period _____. Choices: Decreases Increases Remains constant
Answer of the Day As the Tsunami crest approaches shore, the wave height increases, the velocity decreases, and the period remains constant.
The Rock Cycle 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
Mineral Resources • Generally nonrenewable • Metallic, nonmetallic, and energy resources • Ores - rock containing enough of one or more metallic minerals to be mined profitably.
Where do your possessions come from? • List some popular and valuable item and list the materials of which it is made.
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.
Identified Undiscovered Reserves Other Categories of Mineral Resources Fig. 12-7, p. 276
Finding Mineral Resources • Aerial and satellite images • Radiation detectors • Magnetometers • Gravimeters • Seismic surveys • Chemical analyses
Extracting Mineral Deposits • Surface mining • Subsurface mining • Overburden - soil and rock • Spoils - discarded overburden or waste material
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
Open-pit Mine Fig. 12-8, p. 277
Spoil from an Unrestored Area Strip Mine Fig. 12-9, p. 277
Contour Strip Mining Undisturbed Land Overburden Highwall Coal seam Overburden Pit Bench Coal seam Spoil Banks Fig. 12-10, p. 277
Mountaintop Mining Fig. 12-11, p. 278
Environmental Effects of Using Mineral Resources • Disrupting the land surface • Subsidence • Toxic mining waste • Acid mine drainage • Air pollution • Toxic holding ponds
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 Noise; ugliness; thermal water pollution; pollution of air, water, and soil; solid and radioactive wastes; safety and health hazards; heat Use transportation or trans-mission to individual user, eventual use, and discarding Fig. 12-12, p. 279
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
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. 12-13, p. 279
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
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
Depletion Curves for a Nonrenewable Resource Mine, use, throw away; no new discoveries; rising prices A 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. 12-14, p. 280 Time
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
Question of the Day The change of rocks from one type to another is known as the ________?
Answer of the Day The change of rocks from one type to another is known as the Rock Cycle?