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Chapter 14 Crust 35 km (21 mi.) avg., 1,200˚C Low-velocity zone 100 km (60 mi.) 200 km (120 mi.) Crust Mantle Lithosphere Solid 10 to 65km 2,900km (1,800 mi.) 3,700˚C Outer core (liquid) Core Inner core (solid) 100 km Asthenosphere (depth unknown) 200 km 5,200 km (3,100 mi.), 4,300˚C Reykjanes Ridge EURASIAN PLATE JUAN DE FUCA PLATE CHINA SUBPLATE Transform fault PHILIPINE PLATE PACIFIC PLATE MidIndian Ocean Ridge Transform fault INDIAN-AUSTRLIAN PLATE Southeast Indian Ocean Ridge NORTH AMERICAN PLATE COCOS PLATE East Pacific Rise MidAtlantic Ocean Ridge EURASIAN PLATE ANATOLIAN PLATE CARIBBEAN PLATE ARABIAN PLATE AFRICAN PLATE SOUTH AMERICAN PLATE Carlsberg Ridge AFRICAN PLATE Transform fault Southwest Indian Ocean Ridge ANTARCTIC PLATE Convergent plate boundaries Plate motion at convergent plate boundaries Divergent ( ) and transform fault ( boundaries ) Plate motion at divergent plate boundaries Explains and unifies many geologic theories 1960’s Basically describes how the Earth’s crust is made of plates that move around on top of the upper liquid portion of the mantle Continental Drift helps to explain how populations become separate species as the continents move apart Lithosphere Asthenosphere Oceanic ridge at a divergent plate boundary Trench Volcanic island arc Rising magma Subduction zone Lithosphere Asthenosphere Trench and volcanic island arc at a convergent plate boundary Fracture zone Transform fault Lithosphere Asthenosphere Transform fault connecting two divergent plate boundaries Materials are dissolved, loosened, or worn away from one part of the Earth’s surface to another Process that breaks down rocks into smaller pieces that can be eroded Mechanical (frost weathering) Chemical Biological 1. Inorganic 2. Occurs naturally 3. Solid 4. Regular crystalline structure Combination of minerals May be organic Can contain fossils Forms when magma or lava cools and hardens Intrusive form INSIDE the crust Extrusive form on/ outside the crust Ex: granite, lava rock Formed from sediments that become compacted Ex: coquina, sandstone, shale Rock is subjected to high pressure, temperature, or chemicals Ex: anthracite, marble, slate Volcanoes Earthquakes Liquefaction of recent sediments causes buildings of sink Two adjoining plates move laterally along the fault line Earth movements Cause flooding in Low-lying areas Landslides may occur on hilly ground Shock waves Epicenter Focus Earthquakes Caused by movement of tectonic plates P-waves and S-waves see earthquake activity extinct volcanoes central vent magma conduit magma reservoir Solid lithosphere Upwelling magma Partially molten asthenosphere Volcanoes 3 Types of Volcanoes • Composite volcanoes • Cinder cones • Shield volcanoes To encourage mineral exploration and mining out West Anyone can buy public land (except parks or wilderness) by patenting it Must say they think there are minerals there and that they will spend at least $500 to improve the land for mineral development Pay $2.50- $5.00 an acre Then they can do whatever they want with it Mining companies (F & D) remove $2-3 BILLION in resources each year from land they got this way! About 20% of companies with mining rights on US public lands are FOREIGN! Modified in 1992 to require companies to post bonds to cover the full amount of a clean up in case the company goes bankrupt Clean up would cost taxpayers $33-72 Billion Lobbyists are trying to weaken these laws Don’t sell the land Lease it for up to 20 years Pay royalties on whatever they remove Stricter clean up requirements Concentration of naturally occurring material in or on the crust that can be extracted & processed at a reasonable cost Take a long time to produce Metallic and nonmetallic Energy Identified Resources- we know where they are and how much there is Reserves- resources we can extract at a reasonable price Undiscovered Resources- potential supplies, don’t know for sure it is there or how much there is Other- discovered or undiscovered but not a reserve Aerial photos and satellite images Detect radiation from radioactive deposits (Uranium) Magnetometer to detect changes in magnetic field (Iron ore) Gravimeter to detect changes in gravity caused by different densities of rock Seismic surveys Chemical analysis Ore – a rock containing enough metallic minerals to be mined profitably Mineral + unwanted gangue Tailings – gangue that has been separated from the desired mineral Reserves – identified resources from which nonrenewable minerals can be extracted profitably The most common way that ore deposits form is through hydrothermal processes: especially at divergent boundaries superheated seawater dissolves metals hydrothermal vents support marine ecosystems based on chemosynthesis sedimentary sorting based on density (panning for gold) evaporite mineral deposits water evaporates leaving minerals residual deposits left when soluble minerals are washed away thereby concentrating insoluble minerals nonrenewable Overburden of soil and rock is removed and discarded as spoil Types of Surface Mining: Open-pit Dredging of underwater mineral deposits Area strip mining Contour strip mining Subsurface mining disturbs less than 1/10 as much land as surface mining more hazardous, more expensive, less productive Open Pit Mine Dredging Area Strip Mining Contour Strip Mining Subsurface: Underground Coal Mine Tailings are the waste materials left over after removing the minerals from ore. Tailings are sometimes reprocessed. Common contents of tailings: Arsenic Barite Calcite Cyanide Fluorite Mercury Pyrite Quartz Disruption of land Subsidence of land Wind or water erosion of mineral waste Acid mine drainage sulfuric acid released Emission of toxic chemicals into the air Leakage of toxic wastes into waterways Smelting separates the metals from other substances made into products which are used and then recycled or discarded this process emits huge quantities of air pollutants (without effective pollution controls) water pollution produces hazardous wastes Reclamation – make land suitable for another purpose (agriculture, recreation, etc) Restoration – restore native habitat Regrading the land to original topography Replacing topsoil Planting native vegetation Steps Mining exploration, extraction Processing transportation, purification, manufacturing Use transportation or transmission to individual user, eventual use, and discarding Environmental Effects Disturbed land; mining accidents; health hazards; mine waste dumping; oil spills and blowouts; noise; ugliness; heat Solid wastes; radioactive material; air, water, and soil pollution; noise; safety and health hazards; ugliness; heat Noise; ugliness thermal water pollution; pollution of air, water, and soil; solid and radioactive wastes; safety and health hazards; heat Subsurface Mine Opening Acid drainage from reaction of mineral or ore with water Surface Mine Runoff of sediment Spoil banks Percolation to groundwater Leaching of toxic metals and other compounds from mine spoil Leaching may carry acids into soil and ground water supplies Smelting Separation of ore from gangue Melting metal Metal ore Conversion to product Recycling Discarding of product Surface mining Scattered in environment Fig. 14.8, p. 327 Economic depletion Mining lower grade ores, mining ocean floor. seawater extraction expensive! Mining is subsidized in US government tax deductions, depletion allowances, Mining Law of 1872 Sagebrush Rebellion in the 80’s miners, ranchers, etc. pushed for opening up federal public lands for use 72% of US Public lands are in Alaska; 22% are in western states Using alternative products ceramics, plastics A Mine, use, throw away; no new discoveries; rising prices Recycle; increase reserves by improved mining technology, higher prices, and new discoveries Production B Recycle, reuse, reduce consumption; increase reserves by improved mining technology, higher prices, and new discoveries C Present Depletion time A Depletion time B Time Depletion time C