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 –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