Is There Gold in Them Thar Crossbreeding Hills? Darrh Bullock University of Kentucky.
Thars Gold in Them Thar Hills
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Transcript of Thars Gold in Them Thar Hills
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Thars Gold in Them
Thar Hills
AP Environmental Science
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Earth's three major concentric zones• Core
• Mantle• asthenosphere• Lithosphere
• Crust
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Fig. 15-3, p. 337
Spreading center Ocean
trench
Plate movement
Subduction zone Oceanic crust
Continental crust
Continental crust
Material cools as it reaches the outer mantle
Cold dense material falls back through
mantle
Hot material
rising through
the mantle
Mantle convection
cell
Two plates move towards each other. One is subducted back into the mantle on a falling convection current.
Mantle
Hot outer core Inner
core
Plate movement
Collision between two continents
Tecto
nic
plate
Oceanic tectonic plate Oceanic tectonic plate
Oceanic crust
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Three types of plate boundaries
• Divergent plate boundaries– Plates move apart from one another
• Convergent plate boundaries– Internal forces push two plates together
• Transform faults– Plates slide and grind past one another along a fault line
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Divergent plate boundaries
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Convergent plate boundaries
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Transform fault
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Natural geologic hazards
• Earthquakes
• Volcanoes
• Tsunamis
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How tsunamis occur
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External processes shaping the earth
• Weathering• Physical or mechanical weathering• Chemical weathering• Biological weathering
• Erosion • Flowing streams and rain• Wind• Glaciers
• Mass wasting• Rockslides, landslides, mudslides
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Rocks shaped by glaciers
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Yosemite Valley shaped by a glacier
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Valley of Fire in New Mexico created by lave seeping out of the
ground
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Three types of rock• Igneous
– Granite, lava rock
• Sedimentary– Sandstone, shale, dolomite, limestone, lignite, bituminous coal
• Metamorphic– Anthracite, shale, marble
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Igneous rock
Forms below earth’s surface, when molten
rock comes up from the upper mantle, cools, and hardens
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Sedimentary rock
Forms from sediments deposited
in layers which accumulate over time – the weight
and pressure “cements” these layers together
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Metamorphic rock
Forms when preexisting rock is subjected to high
temperatures, high pressures, chemically
active fluids, or a combination of these
agents
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Rock cycle• Interaction of physical and chemical processes
• Recycles the earth three types of rocks
• Slowest of earth’s cyclic processes
• Concentrates the planet’s nonrenewable minerals
• Without it we would not exist
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Mineral resource – concentration of naturally occurring material in or on the Earth’s crust that can be extracted
and processed into useful materials at an affordable cost
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Nonrenewable Mineral Resources
• Metallic mineral resources• Iron, copper, and aluminum
• Nonmetallic mineral resources• Salt, gypsum, phosphates, water, and soil
• Energy resources• Coal, oil, natural gas, and uranium
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Ore – rock containing enough of one or more metallic minerals to be mined profitably
High-grade ore vs. low-grade ore
Reserves – identified resources from which a usable nonrenewable mineral can be extracted profitably at
current prices
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Global Outlook: Mineral Resource Distribution
• United States, Canada, Russia, South Africa, and Australia supply most of the nonrenewable mineral resources used by modern societies
• United States, Germany, and Russia consume about 75% of the world’s most widely used metals
• Japan virtually has no metal resources
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Nonrenewable Mineral Resources in the United States
• Depleted some of its metal resources – lead, aluminum, and iron
• Depends on imports of 24 of its 42 most important nonrenewable mineral resources
• No manganese, cobalt, chromium, and platinum reserves –essential for economy and military (without these there are no planes, jet engines, automobiles, satellites, sophisticated weapons, and home appliances)
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SUPPLIES OF MINERAL RESOURCES
• The future supply of a resource depends on its affordable supply and how rapidly that supply is used.
• A rising price for a scarce mineral resource can increase supplies and encourage more efficient use.
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SUPPLIES OF MINERAL RESOURCES
• Depletion curves for a renewable resource using three sets of assumptions. – Dashed vertical
lines represent times when 80% depletion occurs.
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Ores
(result of several internal and external geologic processes)
• Plate tectonics
• Magma
• Hydrothermal process
• Manganese nodules
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Manganese Nodules• Potato-size• Contain 30 – 40%
manganese by weight• Also contain iron, copper,
and nickel• Cover about 25 – 50% of the
Pacific Ocean floor• Can be sucked up or
scooped up – what are the environmental impacts?
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How are buried mineral deposits found?
• Remote sensing – aerial photos and satellite images• Planes with radiation measuring equipment and
magnetometer• Drilling deep wells• Sensors in already dug wells• Seismic surveys• Chemical analysis
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Mining Extraction Techniques
• Surface mining – equipment strips away the overburden of soil and rock and discards as spoil
• Subsurface mining – underground• In-situ leaching –flush out desired mineral
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Bucket-wheel Excavator
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Types of Surface Mining
• Open-pit mining• Dredging• Area strip mining• Contour strip mining• Mountaintop removal
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Open-pit diamond mine
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Open-pit diamond mine in Canada – have you seen Ice Road Truckers
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Open-pit copper mine in Silver City, New Mexico
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Strip mining
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Strip mining
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Contour strip mining for coal
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Dredging
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Mountaintop Removal
• Machinery removes the tops of mountains to expose coal.
• The resulting waste rock and dirt are dumped into the streams and valleys below.
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Subsurface mining disturbs less than one-tenth as much land as surface
mining and usually produces less waste material.
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Hazards of Subsurface Mining
• Collapse of roofs and walls• Explosions of dust and natural gas• Lung diseases
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Hazards of mining coal – dust of coal can ignite
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In-situ leaching – small holes are drilled and a water-based chemical solvent is used to flush out desired minerals
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In-situ Leaching
• Waste rock is minimal• Safer for miners• Less expensive• Shorter lead times to production• Less surface ground disturbance• Less required remediation• Toxic chemicals enter groundwater supply
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Environmental Impacts
• Scarring and disruption of the land surface• Collapse of land above underground mines• Wind- or water-caused erosion of toxin laced
mining water• Acid mine drainage• Emissions of toxic chemicals into the
atmosphere• Exposure of wildlife to toxic mining waste
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Natural Capital Degradation
Extracting, Processing, and Using Nonrenewable Mineral and Energy Resources
Steps Environmental effects
Mining Disturbed land; mining accidents; health hazards, mine waste dumping, oil spills and blowouts; noise; ugliness; heat
Exploration, extraction
ProcessingSolid wastes; radioactive material; air, water, and soil pollution; noise; safety and health hazards; ugliness; heat
Transportation, purification, manufacturing
UseNoise; 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
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Acid mine drainage
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Acid Mine Drainage – occurs when rainwater seeping through a mine or mine
wastes carries sulfuric acid to nearby streams and
groundwater
According to the EPA – mining has polluted about
40% of western watersheds
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Acid mine drainage
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Guess what?
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Sinkholes caused by mine collapse
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Ore extracted from the Earth’s crust typically has 2 components:
1. Ore mineral containing desired metal
2. Waste material called gangue
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Removing the gangue from ore produces piles of
waste called tailings
Particles of toxic metals blown or leached from tailings by rainfall can
contaminate surface water and groundwater
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After gangue has been removed,
smelting is used to separate the metal
from the other elements in the ore
mineral
Iron Slag
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Smelting
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Smelters emit enormous quantities of air pollutants which damage vegetation
and soils in the surrounding area
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Ducktown Copper Basin in Tennessee – result of copper smelting
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It takes decades for vegetation to be restored by secondary succession and expensive restoration efforts
Copper Basin, TN
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Smelters also cause water pollution and produce liquid and solid
hazardous waste
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Environmental Drawback to Mining
The refinement of these minerals often require extensive energy input
About 15.7kW of electricity is used to produce 1 kg of pure aluminum from its ore
Recycling aluminum requires only 5% of the energy required to smelt it and generates only 5%of the greenhouse gases
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We need to Recycle those
Aluminum Cans!
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Cyanide heap leaching – gold ore is heaped into a large pile and a cyanide solution is sprayed on top of the pile
As the cyanide percolates downward, the gold leaches out
The gold extracted may only be about 0.01% of the total ore processed
Liquid waste and other toxins kept in tailing ponds, which eventually leak and enter groundwater supplies
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Using cyanide to mine gold
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Solutions
Sustainable Use of Nonrenewable Minerals
• Do not waste mineral resources.
• Recycle and reuse 60–80% of mineral resources.
• Include the harmful environmental costs of mining and processing minerals in the prices of items (full-cost pricing).
• Reduce subsidies for mining mineral resources.
• Increase subsidies for recycling, reuse, and finding less environmentally harmful substitutes.
• Redesign manufacturing processes to use less mineral resources and to produce less pollution and waste.
• Have the mineral-based wastes of one manufacturing process become the raw materials for other processes.
• Sell services instead of things.
• Slow population growth.
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Relevant Environmental Laws
• U.S. Clean Water Act• Surface Mining Control and Reclamation Act of
1977• General Mining Law
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