Topic 5.9 Notes – Impacts of Mining

What Mining Is

Mining means extracting economically valuable minerals, ores, and geologic fuels from Earth. An ore is rock that contains a valuable substance in a high enough concentration to be worth extracting.

Whether a deposit counts as a usable reserve depends on a mix of factors:

• Ore grade which means how concentrated the valuable material is
• Depth and accessibility of the deposit
• Overburden which is the soil and rock above it
• Extraction and processing costs
• Available technology
• Market price of the resource
• Regulations and cleanup requirements

Mining has a built-in trade-off. It provides low-cost energy and raw materials for things like electricity, buildings, electronics, and transportation. But getting those materials usually means land clearing, excavation, crushing rock, using lots of water and energy, and producing a lot of waste.

The big APES pattern is simple. As the high-grade, easy-to-reach ores get used up, mining shifts to lower-grade or harder-to-reach deposits.

Ore Grade and Mining Methods

A lower ore grade means there is less valuable material in each amount of rock. So to get the same amount of copper, gold, or coal, you have to mine and process more material.

That cause-and-effect chain shows up a lot on tests:

• Lower ore grade
• More rock mined and processed
• More water and energy used
• More waste and pollution
• Higher cost

As shallow, accessible deposits are depleted, companies move to deposits that are deeper, poorer, or both.

Keep that pattern in mind as you compare surface and subsurface mining.

Surface mining

Surface mining removes vegetation, soil, and rock to reach shallow deposits. The material above the deposit is overburden.

Surface mining is usually cheaper than underground mining, but it causes major land disturbance.

Strip mining

Strip mining is used for shallow horizontal deposits, especially coal seams. Miners remove vegetation and overburden in long strips.

• The named impact you should know is erosion
• When vegetation is removed, roots no longer hold soil in place
• That makes the land much more vulnerable to erosion and sediment runoff

Other surface methods

• Open-pit mining digs a large pit to remove broadly distributed metal ores.
• Mountaintop removal blasts away the top of a mountain to reach coal, and waste may be dumped into valleys.
• Heap leaching uses chemical solutions to pull metals from low-grade ore piles.

The coal diagram below gives you a quick visual of several surface methods, especially contour mining, area mining, highwall or auger mining, and mountaintop mining.

Coal mining methods

Subsurface mining

Subsurface mining uses shafts and tunnels to reach deeper deposits.

In that same diagram, the shaft, slope, and drift mines are the subsurface examples.

It disturbs less land at the surface, but it is more expensive and more dangerous than surface mining. Hazards include:

• Collapse
• Explosions
• Dust
• Toxic gases
• Subsidence which is sinking of the ground surface

For coal, this matters a lot. As shallow coal runs out, companies rely more on subsurface mining, which raises extraction costs. Coal seams can also release methane, which is both an explosion hazard and a greenhouse gas.

Mining Waste

Mining produces much more waste than useful product. You need to know the three major categories together.

Environmental and Economic Impacts

Mining can destroy habitat and reduce biodiversity because it removes vegetation, changes land shape, builds roads, and creates waste piles. Strip mining is especially tied to erosion and sedimentation because removing plant cover exposes loose soil.

Water pollution is another major issue:

• Groundwater and surface water can be contaminated by exposed rock, mine waste, and chemicals
• Acid mine drainage happens when sulfide minerals are exposed to oxygen and water, producing sulfuric acid
• That acidic water can dissolve and carry toxic metals

Acid mine drainage

This kind of iron-stained, acidic runoff is a common visible sign of acid mine drainage. Mining also creates dust and particulate matter during blasting, crushing, hauling, and storage. Coal mining is especially linked to four impacts you should be ready to name:

• Habitat destruction
• Groundwater contamination
• Dust particles
• Methane release

Economically, mining provides:

• Jobs
• Tax revenue
• Low-cost energy
• Raw materials for products

But there are long-term costs too, including pollution control, cleanup, health effects, reclamation, and abandoned-mine management. Over time, depletion makes mining both more environmentally intensive and more expensive.

Ways to Reduce Mining Damage

Reclamation means restoring mined land to a stable, usable condition. Common steps usually happen in this order:

1. Backfilling excavated areas
2. Regrading land to stable contours
3. Replacing topsoil
4. Controlling erosion
5. Replanting vegetation
6. Restoring drainage

Progressive reclamation helps by restoring land in sections instead of leaving the whole site disturbed at once.

Other damage-reduction methods include:

• Lined storage and engineered tailings containment
• Monitoring wells, protective covers, and runoff control
• Treating acid mine drainage with limestone or sometimes constructed wetlands
• Reducing dust by wetting roads and covering trucks
• Capturing methane where possible
• Reducing demand for virgin ore through reuse, recycling, repair, and recovering metals from electronics