Mineral Extraction Take notes! Not all of this material is in your textbook!
Partner talk • From an ENVIRONMENTAL lens, what are the pros and cons of driving a hybrid electric vehicle like the Toyota Prius? That is, are hybrid electric cars environmentally friendly? Unlike internal combustion engines, hybrid vehicles require lanthanum, neodymium, and lithium and other minerals. These have to be extracted from the ground by mining. To answer the question, we need to know a bit about mining practices…
VOCABULARY TERMS • Ore- metal or mineral containing material extracted from the mine. Includes both metal and waste material that must be separated from the metal • Overburden- layer of rock and material lying over the ore. Surface mining removes this layer. • Spoils-Unwanted rock and other waste material produced during mining, dredging, quarrying, or excavation
Vocabulary con’t • Gangue – Unwanted material mixed in with the ore that will be removed during refining. • Tailings – The gangue residue after it has been separated from the ore. • Smelting-process of refining an ore when desired metal is separated from other components of ore usually involving heat
Uneven distribution of Minerals • Minerals are unevenly distributed over the crust • Ores consist of concentrated accumulation of economically valuable minerals and metals
Partner talk • Are mineral resources considered renewable or non-renewable? Why? • What are the implications of this uneven distribution of minerals and resources?
Mining Economics • Minerals are NON-RENEWABLE. They can be recycled sometimes, but there is a limited amount of these resources available. • Countries must trade with one another to obtain important and valuable minerals and metals that are not found within its territories
Types of mining • Two kinds of mining take place on land: • SURFACE MINING • Strip Mining • Open-pit Mining • Mountaintop Removal • Placer Mining • SUBSURFACE MINING
Area Strip Mining • Earth movers strip away overburden, and giant shovels remove the mineral deposit. • Leaves highly erodible hills of rubble called spoils • Often used in coal and sand mining
Contour Strip Mining • Used on hilly or mountainous terrain. • Unless the land is restored, a wall of dirt is left in front of a highly erodible bank called a highwall.
OPEN-PIT MINING • Creates a large pit or hole in the ground. • Used when resource is close to the surface but extends beneath the surface horizontally and vertically (ex. Copper mine)
Partner Talk • Based on the pictures you have seen, what problems do you think might occur with open pit mining?
Kennecott Bingham Canyon Mine near Salt Lake City, UT one of the largest open-pit mines in the world Collapse Disaster April 2013 http://www.ksl.com/?sid=24748916
Mountaintop Removal • Machinery or blasting removes the tops of mountains (overburden) to expose coal. • The resulting waste rock and dirt are dumped into the streams and valleys below. (Spoils) Figure 15-14
Surface mining • PLACER MINING • The process of looking for metal nuggets and precious stones in river sediments. • River water is used to separate heavier items like diamonds, tantalum, and gold, from lighter items like sand and mud. (ex. California gold rush)
SUBsurface mining • Used when resources are more than 100 meters below Earth’s surface. • Vertical and horizontal shafts • Can be VERY deep (some are more than 2 miles deep) • (ex. Coal, diamonds, and gold)
Partner Talk • What issues do you think might occur with subsurface mining?
Impacts • Subsurface mining accidents are extremely dangerous to miners, and long term exposure to gases and particles are known to cause serious respiratory diseases. • In 2010, 33 miners in Chile were trapped for 69 days in a 540 square foot shelter until a small tunnel could be dug down to pull them out. It took 17 days to even confirm they were still alive! • Mine accidents are often fatal – April 2010 W. Virginia coal mine explosion kills 25 • Fatal coal mine accidents have been occurring several times a year (sometimes up to 100 people!) in China this decade alone
Mining Impacts • Metal ores are smelted with toxic chemicals (such as Arsenic or Cyanide) to extract the desired metal. These chemicals may leech out into the surrounding area. Figure 15-15
Impacts • Deposit of spoils and tailings could cause contamination and the blocking of the flow of rivers.
Impacts • Mining companies may not restore mining sites back to their original states. It then falls under CERCLA and federal superfund dollars might be used
Impacts • Surface and Subsurface mining can cause acid mine drainage, where lower pH water from the mine is stored above ground, and leakage can lower the pH of nearby soils and streams.
Mining legislation • The Mining Law of 1872 (General Mining Act) • regulates the mining of silver, copper, and gold ore as well as fuels, including natural gas and oil, on federal lands. • Written to encourage development in the western United States, it says federal land is open to mining claims by any citizen. • it contains very few environmental protection provisions.
General Mining Act • Mining claim can give legal ownership of land • Abused: land used for other purposes • Very low royalties to federal government
Law • The Surface Mining Control and Reclamation Act of 1977– • regulates surface mining of coal and the surface effects of subsurface coal mining. • land be minimally disturbed during the mining process • Land must be restored after mining is completed. • It does NOT regulate all the harmful effects of mining operations
Restoration Work(Reclamation) 1. Fill in the hole or depression in the landscape. 2. Fill material must be relatively free of metals, acids, and other compounds and shaped to follow the preexisting contours. 3. The land must be replanted to re-create the ecosystem that existed before mining. 4. Properly completed reclamation makes the soil physically stable so that erosion does not occur and water infiltration and retention can proceed.