Transcript Chapter 26 - Cobb Learning

Chapter 27
Minerals and the
Environment
Mining
• Removal of minerals & fossil fuels from the
Earth’s crust.
Mining methods depend on:
• Depth of resources
• Amount of stability of material that must be
removed (overburden) to reach the mineral
• Topography
• Safety
• economics
Surface (strip) mining
• Removes deposits that lie in horizontal
bed’s close the earth’s surface
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Land is clear-cut
Overburden removed
Deposit is removed
Overburden replaced
• Long term environmental damage
Mountaintop Removal
• Type of surface mining – Coal
• Coal seams are exposed by removing the
tops of mtns., using explosives and/or heavy
equipment
• Overburden dumped into adjacent valleys
• Coal removed
• Fed. Law requires reclamation
– Topography is never really restored
Open Pit Mining
• Huge hole dug using explosives & heavy
equipment
• Deposit is removed
• Pit is often filled with water that becomes
acidic or polluted with heavy metals from
mine waste
Open Pit – Uranium Mining
Subsurface Mining
• Deep vertical mine shafts with horizontal
tunnels branching off
• Used when deposits are too far underground
to be reached by surface mining
• Less habitat destroyed
• Much more dangerous
– Cave-in, collapse, explosions, poisonous gases
– flooding
Drilling
• To remove liquids and gases
• Deep shafts drilled into the earth to reach
geologic formations
• Pressure usually forces the liq. Or gas to
surface
– If no pressure, water or steam is injected
Environmental problems with
drilling
• Platforms destroy habitat at surface
• Liquids are susceptible to leaks & spills
• Pipelines that carry liquids or gas result in
habitat loss
US Mining Laws
• The General Mining Law of 1872
– Encourages the exploration & mining of
mineral resources
– Allows corporations to acquire large tracts of
public land below market value
– Corporations can remove valuable mineral
without paying adequate royalties or sufficient
cleanup
The Surface Mining Control &
Reclamation Act of 1977
• Mined land must be restored to pre-mined
state
– Disposal of waste
– Re-contouring land to get back topography
– Replant native vegetation
How Mineral Deposits Are
Formed
• Ore Deposits – formed when metals are
concentrated in anomalously high amounts
by geological processes
• Mineral resources are usually extracted
from ore deposits
Resources and Reserves
• Minerals are classified as:
– 1. Mineral Resources
• Elements, chemical compounds, minerals or rocks
that can be extracted to obtain a usable commodity
• The combination of reserve.
– 1. Mineral Reserves
• The portion of the resource that is identified and
from which usable materials can be legally and
economically extracted at the time of evaluation
Availability of Mineral
Resources
• When the availability of a mineral becomes
limited, there are 4 possible solutions:
1. Find more sources
2. Recycle and reuse what has already been
obtained
3. Reduce consumption
4. Find a substitute
Impacts of Mineral Development
• Environmental Impacts
– Depends on many factors – mining procedures,
climate, rock type, etc.
• Social Impacts
– Increased demand for housing and services in
mining areas
Minimizing Environmental
Impact of Mineral Development
• Environmental regulations at the federal,
state and local levels
• On-site and off-site treatment of waste
• Practicing the 3 R’s of waste management
Minerals and Sustainability
• R-to-C Ratio
– A measure of the time available for finding the
solutions to depletion of nonrenewable
resources
– R = known reserves
– C = rate of consumption