Transcript Chapter 15
Chapter 16 Nonrenewable Mineral Resources – Part 2 Key Questions What are nonrenewable mineral resources and how are they formed? How do we find and extract nonrenewable mineral and energy resources from the earth’s crust? How fast are mineral supplies being used up? What are Mineral Resources? Concentration of naturally occurring material in or on the earth’s crust that can be extracted and processed into useful materials Classified as nonrenewable resources because they take so long to produce We know how to find and extract 100+ nonrenewable minerals from the earth’s crust We can extract… Metallic mineral resources (iron, copper, aluminum) Nonmetallic mineral resources (salt, clay, sand, phosphates, soil) Energy resources (coal, oil, natural gas, uranium) Ore Rock containing enough of 1+ metallic minerals to be mined for profit We convert 40 metals extracted from ores into everyday items that are either 1) used and thrown away OR 2) reused or recycled Categories of nonrenewable mineral resources 1. 2. 3. 4. US Geological Survey divides nonrenewable mineral resource into categories: Identified resources: deposits of nonrenewable mineral resource with a known location and quantity Undiscovered resources: potential supplies assumed to exist in theory Reserves: identified resources from which resource can be extracted for profit Other resources: identified and discovered but not classified as reserves How do ores form from magma? Ores form as a result of internal and external geologic processes Plate tectonics shape the earth’s crust and determine where the richest mineral deposits are found As magma cools, it crystallizes into mineralcontaining igneous rocks Ore deposits form through hydrothermal processes Upwelling magma solidifies into black smokers Shoots out mineral-rich hot water on the seafloor Minerals accumulate as hot and cold water contact Form ore deposits rich in copper, lead, zinc, silver, and gold Finding nonrenewable resources Aerial photos and satellite images Planes that detect deposits of radioactive metals Gravimeter to measure differences in density (ore differs from surrounding rock) Drilling deep well and extracting core samples Seismic surveys by explosions and analyzing shock waves Chemical analysis of water and plants (absorb minerals) Mining techniques (once resources have been found) Surface mining: equipment strips outer layer of soil and rock; in US, used to extract 90% nonfuel resources and 60% coal Open-pit mining: machines dig holes and remove ores Dredging: chains scrape underwater mineral deposits Area strip mining: parallel strips made in flat land; power shovels used Contour strip mining: terraces cut into side of hill; power shovels used Mountaintop removal: explosives used to remove top of mountain and expose coal underneath Open Pit Mine Dredging Area Strip Mining Contour Strip Mining Surface Mining Control and Reclamation Act of 1977 Requires mining companies to restore surface-mined land so that it is usable again Although surface-mined land can be restored, it is expensive and not done in many countries Subsurface mining Used to remove coal and other metal ores that are too deep to be extracted by surface mining Blast tunnels to get to deposit, use machinery to transport ore to the surface Disturbs 1/10 as much land as surface mining, produces less waste More dangerous and expensive Environmental Effects of Extracting Mineral Resources Fig. 15-6 p. 343 Subsurface Mine Opening Acid drainage from reaction of mineral or ore with water Percolation to groundwater Surface Mine Runoff of sediment Spoil banks Leaching of toxic metals and other compounds from mine spoil Acid mine drainage-pollution and degradation by acid runoff and toxic chemicals from mining -can kill fish and other aquatic life Leaching may carry acids into soil and groundwater supplies Smelting Melting metal Separation of ore from machine Conversion to product Metal ore Recycling Surface mining Discarding of product Scattered in environment Processes involved in extraction Smelting: used to separate metal from other elements in the ore Enormous amount of pollution which damages surrounding vegetation and soil Smelters also produce liquid and hazardous waste that must be disposed of safely Are there environmental limits? Resource experts believe that the greatest danger from increasing consumption of nonrenewable resources is environmental damage caused by extraction and processing. More accessible and high-grade ores are exploited first It takes more $ to exploit the deeper ores, causing more environmental effects Will there be enough mineral resources? Future of nonrenewable minerals depends on: actual supply and rate at which supply is used Economic depletion: cost more to find, extract, transport and process than it’s worth Depletion time: time it takes to use up a certain proportion of NM Supplies of mineral resources Reserve-to-production ratio: number of years that reserves of a NM will last Materials revolution: new materials (ceramics and plastics) are being developed as replacements for metals Substitutes cannot be found for many mineral resources