Plate Tectonics, Minerals, Rocks & Mining Terrestrial Earth Plate Tectonics, Minerals, Rocks & Mining

Plate tectonics shapes the Earth Plate tectonics = process that underlies earthquakes and volcanoes and that determines the geography of the Earth’s surface Crust = lightweight thin component of Earth’s surface Mantle = malleable layer on which the crust floats Core = molten heavy center of Earth made mostly of iron 2

Pangaea: the supercontinent Pangaea = at least twice in Earth’s history, all landmasses were joined in one supercontinent 3

Earth’s crust is constantly created and destroyed Divergent plate boundaries = magma surging upward to the surface divides plates and pushes them apart, creating new crust as it cools and spreads Transform plate boundary = two plates meet, slipping and grinding alongside one another Friction spawns earthquakes along slip-strike faults

Tectonic plates can collide Convergent plate boundaries = where plates collide Subduction = one plate of crust may slide beneath another Magma erupts through the surface in volcanoes Two colliding plates of continental crust may lift material from both plates Resulted in the Himalaya and Appalachian mountains Boundary Interactive Boundary Animations 5

The Earth has 15 major tectonic plates Movement of these plates influences climate and evolution

Minerals and Rocks What is a mineral? naturally occurring, inorganic, solid element or compound with a definite chemical composition and a regular internal crystal structure What is rock? solid, cohesive, aggregate of one or more minerals Each rock type has a characteristic mixture of minerals What is an Ore? Rock with large concentration of a particular maineral to make it profitable High and low grade ores NON- Metalic Mineral Sand, gravel, limestone Metalic Aluminum, Steel, manganese, cobalt, chromium, Copper, Gold

Minerals

Rock Cycle Sedimentary Rock Heat, Pressure Heat, Igneous Rock Shale, Sandstone, Limestone Deposition Transport Erosion Rock Cycle Heat, Pressure Weathering Heat, Pressure Igneous Rock Granite, Pumice, Basalt Metamorphic Rock Slate, Quartzite, Marble Magma (Molten Rock) Fig. 16-9 p. 339

Mining: Extract Ore from Ground Types of Mining: Surface Mining: Scoop ore off surface or earth. cheap. safe for miners. large environmental destruction. Sub-Surface or Underground Mining: Use of shafts to reach deeply buried ores. expensive. hazardous for miners. less environmental damage.

Surface Mining open pit mining: circular hole in ground, with ramp circling down along sides, allows deeper ore to be reached.

Surface Mining- Strip Mining strip-mining: scoop off rock overburden, and then scoop off ore material. Economics of strip mining depend on stripping ratio Large land area can be involved, especially for coal and bauxite. Results of Mining utube

Bauxite Mine In the Earth's Crust, in every million atoms, around 82 000 of them are Aluminum, (82 000 ppm1), by weight. This is around 8 % or almost one in every 12 atoms. This places aluminum amongst the world's most abundant elements. Despite being present of Earth in such incredibly vast quantities on Earth, the metal never occurs on it's own in nature. Instead of existing free like Gold and Silver, due to its higher level of reactivity, it is always chemically bonded in compounds when it normally occurs. The most common of these compounds is Bauxite, or Aluminum Ore which contains large quantities of Aluminum Oxide.

Mountain Top Removal Removing Overburden

spoils Overburden Coal seem bedrock Appalachian Voices http://www.youtube.com/watch?v=aiSzOiGFa-0

Gold in Quartz https://www.youtube.com/watch?v=ohrrE1rjzLo A large quartz boulder with a lot of visible gold. Usually, the gold is much finer and hard to see.

Placer Deposition Panning for gold in a placer deposit Weathering liberates particles of heavy metal containing minerals Minerals and gangue (waste) are transported by water As water velocity decreases, heavy metals sink first, accumulating in protected parts of a stream bed Much of the early gold removed from the Sierra Nevada was found in placer deposits RESISTANT PLACERS Minerals resistant to weathering and erosion may also accumulate in this manner Examples include diamonds, sapphires and rubies (varieties of corundum), and emeralds Photo Source: http://www.emporia.edu/earthsci/amber/go336/daniel/goldpag2.html

Aeolian Placers The "diamond crawl" in a deflation basin, Diamond Area No 1, Namibia Diamond concentrations were increased by wind erosion

Environmental Impact of Mining

Waste water/sludge dams

Underground Mining A technology originating in antiquity. A variety of configurations, depending upon conditions

Acid Mine Drainage AMD results from the oxidation of sulfide minerals at the earth’s surface. This form of chemical weathering generates sulfuric acid, a very powerful acid. The sulfuric acid quickly reacts, dissolving other minerals and often releasing poisonous metal cations into surface waters.

Environmental Impact of Mining Scaring the land surface- result spoils banks Soil poor, windblown .. Primary succession slow Toxic wastewater stored in sludge dams. Toxins include slenium, arsenic, and mercury

Cassiterite tin oxide ore mineral, SnO2. It is generally opaque but is translucent in thin crystals. Its luster and multiple crystal faces produce a desirable gem. Cassiterite has been the chief tin ore throughout ancient history and remains the most important source of tin today TinSoldiers

Non-renewable Mineral Resource Depletion Curves Source: Miller, G. Tyler, Living In The Environment. (2000) Wadsworth Publishing. New York.

Non-renewable Mineral Resource Depletion Curves Source: Miller, G. Tyler, Living In The Environment. (2000) Wadsworth Publishing. New York.

US Non-renewable Resource Reserves Source: Miller, G. Tyler, Living In The Environment. (2000) Wadsworth Publishing. New York.

Mining is an Economic Activity The decision to mine (or not to mine) a particular ore deposit depends upon: an analysis of costs, benefits and risks tangible (i.e. dollar profit) intangible (i.e. hopes of stimulating the economy, fears of environmental damage)

Gradual shift toward surface mining

Mining around the world Hungary’s disaster China’s rare earth minerals Minining Law http://www.youtube.com/watch?v=ofN1aLMwcUI Mining around the world Hungary’s disaster China’s rare earth minerals US rare earth mineral info ad Proposal for New Massive Mine in Romania Goldmining Mining ore Bauxite mining Mountaintop removal

Mining Issues surface Mine Safety: In U.S., stringent mining regulations have lead to a reduction in fatalities, both in terms of total deaths per year, deaths per person-hour worked, and deaths per ton mined. surface

Acid Mine Drainage AMD results from the oxidation of sulfide minerals at the earth’s surface. This form of chemical weathering generates sulfuric acid, a very powerful acid. The sulfuric acid quickly reacts, dissolving other minerals and often releasing poisonous metal cations into surface waters.

Health Problems collapse of mine. fire (methane, coal dust, etc.). asphyxiation (methane, carbon monoxide, etc.). pneumoconiosis (from inhaling coal dust). asbestosis (from inhaling asbestos fibers). silicosis (from inhaling silicate dust). heavy metal poisoning (e.g. mercury). radiation exposure (in uranium mining).

Environmental Damage 4FeS2 + 14H2O = 4Fe(OH)3 + 8H2SO4 Gaping holes in ground (old open pit mines). Piles of mine tailings (non-ore removed from mines). Accidental draining of rivers and lakes. Disruption of ground water flow patterns. Loss of topsoil in strip-mined regions (350 to 2,700 km2 in US alone). Contamination from sulfuric acid (H2SO4) produced through weathering of iron sulfide (FeS2, pyrite) in tailings. 4FeS2 + 14H2O = 4Fe(OH)3 + 8H2SO4 Contamination from heavy metals (e.g. arsenic, mercury) in mine tailings.

Smelting and Refining: Environmental Problems Production of huge piles of slag. Emission of CO2, a greenhouse gas, into the atmosphere. Pollution associated with the generation of electricity needed in anode furnaces (especially aluminum). Sulfur dioxide emissions from the refining of sulfide ores are a major source of air pollution. The sulfur dioxide combines with water to produce sulfuric acid. Release of heavy metals (As, Cd, Hg), present in trace quantities in sulfide ores, into the atmosphere.

Cost Trends copper Cents per pound Amount of commodities mined per year has generally increased. Commodity prices can take big swings, but average prices during the last century often declined or remained constant. Cents per pound copper Ore grades have all decreased as milling technology has improved