Unit 7 Geology & Mining Resources Chapter 14

Mantle Core Crust Lithosphere Asthenosphere Low-velocity zone Solid Outer core (liquid) Inner core (solid) 35 km (21 mi.) avg., 1,200˚C 2,900km (1,800 mi.) 3,700˚C 5,200 km (3,100 mi.), 4,300˚C 10 to 65km 100 km 200 km 100 km (60 mi.) 200 km (120 mi.) Lithosphere Asthenosphere (depth unknown)

INDIAN-AUSTRLIAN PLATE EURASIAN PLATE CHINA SUBPLATE PHILIPINE PLATE INDIAN-AUSTRLIAN PLATE PACIFIC JUAN DE FUCA PLATE COCOS CARIBBEAN NORTH AMERICAN SOUTH EURASIAN ANATOLIAN ARABIAN AFRICAN Carlsberg Ridge Southwest Indian Ocean Ridge ANTARCTIC PLATE Transform fault East Pacific Rise Mid- Indian Ocean Southeast Indian Atlantic Reykjanes Divergent ( ) and transform fault ( ) boundaries Convergent plate boundaries Plate motion at convergent at divergent

Theory of Plate Tectonics 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

Plate Tectonics and Evolution Continental Drift helps to explain how populations become separate species as the continents move apart

Oceanic ridge at a divergent plate boundary Lithosphere Asthenosphere Oceanic ridge at a divergent plate boundary

Trench and volcanic island arc at a convergent plate boundary Lithosphere Rising magma Asthenosphere Subduction zone Trench and volcanic island arc at a convergent plate boundary

Transform fault connecting two divergent plate boundaries Fracture zone Transform fault Lithosphere Asthenosphere Transform fault connecting two divergent plate boundaries

Erosion Materials are dissolved, loosened, or worn away from one part of the Earth’s surface to another

Weathering Process that breaks down rocks into smaller pieces that can be eroded Mechanical (frost weathering) Chemical Biological

Minerals Inorganic Occurs naturally Solid Regular crystalline structure

Rocks Combination of minerals May be organic Can contain fossils

Igneous Rock Forms when magma or lava cools and hardens Intrusive form INSIDE the crust Extrusive form on/ outside the crust Ex: granite, lava rock

Sedimentary Rock Formed from sediments that become compacted Ex: coquina, sandstone, shale

Metamorphic Rock Rock is subjected to high pressure, temperature, or chemicals Ex: anthracite, marble, slate

Volcanoes Earthquakes

Earthquakes Liquefaction of Two adjoining plates 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

Earthquakes Caused by movement of tectonic plates P-waves and S-waves see earthquake activity

Richter Scale

Volcanoes extinct volcanoes central vent magma magma reservoir conduit Solid lithosphere Upwelling magma Partially molten asthenosphere Volcanoes

3 Types of Volcanoes Composite volcanoes Cinder cones Shield volcanoes

General Mining Law of 1872 To encourage mineral exploration and mining out West Anyone can buy public land (except parks or wilderness) by patenting it

General Mining Law of 1872 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

General Mining Law of 1872 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!

General Mining Law of 1872 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

Environmental Concerns Don’t sell the land Lease it for up to 20 years Pay royalties on whatever they remove Stricter clean up requirements

Nonrenewable Mineral Resources 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

Nonrenewable Mineral Resources 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

How do we find resources? 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

Underground Methods Seismic surveys Chemical analysis

Tailings – gangue that has been separated from the desired mineral 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

Ore Deposits 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

Removing Mineral Resources 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

Environmental Impacts of Mining 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

Environmental Impacts of Mining 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

Restoration & Reclamation 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 Environmental Effects Mining Processing Use 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, purification, manufacturing Use Noise; ugliness thermal water pollution; pollution of air, water, and soil; solid and radioactive wastes; safety and health hazards; heat transportation or transmission to individual user, eventual use, and discarding

Percolation to groundwater Leaching of toxic metals Subsurface Mine Opening Surface Mine Runoff of sediment Acid drainage from reaction of mineral or ore with water Spoil banks Percolation to groundwater Leaching may carry acids into soil and ground water supplies Leaching of toxic metals and other compounds from mine spoil

Scattered in environment Smelting Separation of ore from gangue Melting metal Conversion to product Metal ore Recycling Surface mining Discarding of product Fig. 14.8, p. 327 Scattered in environment

Supplies of Mineral Resources 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

Recycle; increase reserves by improved mining 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 Time