5.9 - Mining

Question 1

Mining Basics

Answer 1

• Ore: commercially valuable deposits of concentrated minerals that can be harvested and used as raw materials
• Metals: elements that conduct electricity, heat, and have structural properties for building (found within ores)
• Reserve: The known amount of a resource left that can be mined.
  Usually measured in years left of extraction.
• Overburden: Soil, vegetation, & rocks that are removed to get to an ore deposit below
• Tailings & slag: leftover waste material separated from the valuable metal or mineral within ore (often stored in ponds @ mine site)

Question 2

Surface Mining

Answer 2

• Removal of overburden to access ore near surface
• Different types: open pit, strip, mountaintop removal, placer
  - Mnt. top removal = esp. damaging to landscape & habitats, streams nearby
• As ore near surface becomes more scarce, mining moves deeper underground to subsurface mining (more dangerous & expensive)

Problems:
- Removal of vegetation & soil
- Topsoil erosion
- Habitat loss
- Increased stream turb
- Increase PM in air

Question 3

Subsurface Mining

Answer 3

• More expensive due to higher insurance & health care costs for workers
• Risks: poor ventilation leading to toxic gas exposure, mine shaft collapse, injury from falling rock, lung cancer, asbestos, fires, explosions
• Vertical “shaft” drilled down into ground
  - Elevator to carry down workers & transport out resource
  - Often used for coal
• Increasingly used as surface coal deposits are depleted

Question 4

Environmental Impacts of Mining

Answer 4

• Acid mine drainage: rainwater leaks into abandoned mine tunnels & mixes with pyrite, forming sulfuric acid
• Rainwater carrier sulfuric acid into nearby streams, or infiltrates ground water
• Lowers pH of water, making toxic metals like mercury & aluminum more soluble in water sources (killing aquatic org.)
• Methane Release: coal mining releases methane gas (CH4) from rock around coal
  - Vented out of mine to prevent explosion & continues seeping out after mine closes
  - GHG → climate change
  - Topsoil erosion
  - Habitat loss
  - Increased stream turb.
• PM Release: coal mining especially, releases lots of soot and other particulates that can irritate human & animal lungs

Question 5

Mine Relamation

Answer 5

• Process of restoring land to original state after mining has finished
  Includes:
  1. Filling of empty mine shafts/hole
  2. Restoring original contours of land
  3. Returning topsoil, with acids, metals, and tailings removed
  4. Replanting of native plants to restore community to as close to original state as possible