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Unformatted text preview: APES notes chapter 14 Core Case Study: Environmental Effects of Gold Mining o Mineral resources extracted from the earths crust are processed into an incredible variety of products that can make life easier and provide economic benefits and jobs o But extracting minerals from the ground and converting them to such products have a number of harmful environmental effects o For example, gold miners typically remove enough rock to equal the weight of 50 automobiles to extract an amount of gold that would fit inside your clenched fist. o The waste left piled near mine sites can pollute the air and nearby surface water o Between 1980 and 2007, global gold production more than doubled o In 2007, South Africa, Australia, the United States, and Canada were, in order, the worlds top producers of gold o In Australia and North America, cyanide heap leaching is used by mining companies to level entire mountains of rock containing only small concentrations of gold o To extract the gold, miners spray a solution of highly toxic cyanide salts (which react with gold) onto huge open-air piles of crushed rock. The solution then drains into storage ponds o After the solution is circulated a number of times, the gold is removed from the ponds o This cyanide is extremely toxic to birds and mammals drawn to these ponds in search of water o The ponds can also leak or overflow, posing threats to underground drinking water supplies and fish and other forms of life in nearby lakes and streams. Special liners in the collection ponds can prevent leaks, but some have failed o In 2000, snow and heavy rains washed out an earthen dam on one end of a cyanide leach pond at a gold mine in Romania. The dams collapse released large amounts of water laced with cyanide and toxic metals into the Tisza and Danube Rivers flowing through parts of Romania, Hungary, and Yugoslavia o People were told not to fish, drink or withdraw water from affected rivers or from wells along the rivers. Food industries and paper mills were shut down. o This accident could have been prevented by if the mining company had installed a stronger containment dam and a backup collection pond to prevent leakage into nearby surface water Geology o Study of dynamic processes occurring on the earths surface and in its interior o As the earth cooled over eons its interior separated into the core , the mantle and the crust o The core Earths innermost zone Extremely hot and has a solid inner part surrounded by a liquid core of molten or semisolid material o The mantle Surrounds the core Most of the mantle is solid rock Under its rigid outermost part is the asthenosphere Asthenosphere A zone of hot, partly melted rock that flows and can be deformed like soft plastic o The crust Outermost and thinnest zone of the earth Continental crust Underlies the continents (including continental shelves extending into the oceans) Oceanic crust Underlies the ocean basins and makes up 71% of the...
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- Spring '08