APES 5.9 — Impacts of Mining

Section 01

Mining Basics

⛏ Ore

A commercially valuable deposit of a specific mineral — often a metal. Metals have valuable heat- and electricity-conducting properties and are used as raw building materials. Example: iron ore → steel.

📊 Reserve

The known amount of a material left in the ground, measured in years of supply at current extraction rates. All mined metals are non-renewable — they will eventually run out.

🪨 Overburden

The soil, vegetation, and rocks removed to access an ore deposit near the surface. It is excavated and piled around the mine site using large dump trucks.

☠️ Tailings & Slag

Tailings are non-valuable rock components separated from the mined resource. Slag is a liquid waste mixture of chemicals used to separate valuable ore. Both are stored in on-site pools and can contaminate nearby groundwater if they overflow.

Section 02

Surface Mining

Used when ore deposits are near the surface. Overburden must be removed and stockpiled. All surface mining causes environmental disruption — but some methods are far worse than others.

Surface · Type 1

Open Pit

A large pit is dug into the ground, getting deeper and deeper as ore is extracted. Overburden is piled on the sides of the pit. Used for copper, gold, iron, and more.

Moderate Impact

Surface · Type 2

Placer Mining

Done on a smaller scale — typically in streams and riverbeds. Uses a sieve to shake out sediments and recover dense, valuable materials like gold. This is what happened during the California Gold Rush!

Lower Impact

Surface · Type 3

Strip Mining

Overburden is peeled back in parallel strips, exposing the ore beneath. Commonly used for coal near the surface. The stripped land is very vulnerable to erosion.

Significant Impact

Surface · Type 4

Mountaintop Removal

Dynamite blows the top of a mountain off to expose coal seams beneath. The most destructive form of surface mining. Causes massive habitat loss, erosion, stream turbidity, and air particulates.

⚠ Most Destructive

⚠ Mountaintop Removal — Environmental Consequences

🌲 Habitat Loss — Trees and vegetation destroyed; animal homes eliminated

🌊 Increased Erosion — No root structures left to hold topsoil in place

💧 Stream Turbidity — Sediments wash down into rivers and streams

🌫 Air Particulates — Explosive blasts release large amounts of dust and particulate matter

Section 03

Subsurface Mining

Used when ore deposits are too deep for surface methods, OR when surface deposits are exhausted. Primarily used for coal. Much more expensive and dangerous than surface mining.

Why So Expensive?

💰 Workers require higher pay due to health risks

🏥 High insurance costs for worker health and accident coverage

⚙️ Complex machinery and shaft infrastructure needed

📉 As surface deposits exhaust, deeper mining becomes inevitable

Dangers to Workers

☁️ Toxic gas buildup — Poorly ventilated mines accumulate methane

🪨 Mine collapse — Shaft walls can cave in, trapping miners

🫁 Asbestos & dust — Lead to lung cancer and respiratory disease

🔥 Fires & explosions — Methane ignition inside the mine

Mine Anatomy

A vertical miner's elevator shaft carries workers straight down into the earth. From there, workers spread horizontally through tunnels to reach coal seams. A separate coal elevator transports extracted coal back up to the surface. As surface reserves are exhausted, these shafts must be dug progressively deeper.

Section 04

Environmental Impacts

🧪

Acid Mine Drainage

When a mine is abandoned, rainwater seeps into the open shaft and mixes with naturally occurring pyrite in the exposed rock. This reaction forms sulfuric acid. Rainwater then washes this acid into nearby rivers and streams — and potentially groundwater — lowering pH. This makes toxic metals like mercury, lead, and aluminum more soluble, poisoning aquatic life.

💨

Methane Release

Coal deposits are surrounded by methane gas. During mining, methane must be vented out of the mine to prevent explosions and worker fatalities. However, methane is a highly potent greenhouse gas — its release directly contributes to climate change and global warming.

🌫

Particulate Matter

Coal mining produces large amounts of soot and fine dust particles that enter the air. Miners are especially at risk for lung cancer and other respiratory diseases. Mountaintop removal is particularly bad — explosions send enormous dust clouds into surrounding communities.

🌱

Topsoil Erosion & Habitat Loss

Surface mining removes vegetation and topsoil. Without root structures to anchor the soil, rapid erosion occurs. This destroys habitat for plants, animals, and soil organisms. Lost topsoil cannot easily be replaced.

🐟

Increased Stream Turbidity

Disturbed sediments and soil particles flow into rivers and streams, making the water murky and cloudy (high turbidity). This blocks sunlight from aquatic plants, clogs fish gills, and degrades the aquatic ecosystem.

Surface vs. Subsurface — Quick Compare

Factor	Surface Mining	Subsurface Mining
Cost	Lower	Much higher
Worker Safety	Safer (relatively)	Many serious hazards
Habitat Disruption	High (visible, large-scale)	Lower on surface
Acid Mine Drainage	Both affected	Both affected
Methane Release	Less	Significant venting required
When Used	Shallow deposits	Deep deposits; exhausted surface reserves

Section 05

Mine Reclamation

Once a mine is no longer in use, mine reclamation is the process of attempting to restore it to its original state. It doesn't undo all the damage — but it's a critical step toward healing the land.

Reclaimed surface mine with restored vegetation

Reclaimed Mine Land — Eagle Butte, WY

Acid mine drainage in stream showing environmental impact

Native Grass Restoration

Fill the Hole

Rock and soil are placed back into the excavated pit or shaft, closing off the mine opening to prevent acid mine drainage and eliminate physical hazards.

Restore Land Contours

The surface is reshaped to match the original elevation, slope, and drainage patterns of the landscape — returning it to roughly its pre-mining form.

Return Clean Topsoil

Topsoil is replaced after being treated to remove acids, tailings, and residual heavy metals. Clean soil is essential for plant growth and soil organism health.

Replant Native Vegetation

Native plant species — not invasives — are planted to stabilize the soil with their root systems and to restore habitat for native animal species. This is the most ecologically critical step.

Why Native Plants?

Native plants have co-evolved with the local ecosystem. Their root structures are best adapted to prevent erosion, and their presence signals to native animals that a habitat is safe to return to. Non-native species can become invasive and further disrupt the recovering ecosystem.

Section 06

Check Your Knowledge

1. What is the most environmentally destructive form of surface mining?

2. Acid mine drainage forms when rainwater mixes with which naturally occurring mineral?

3. Which of the following is TRUE about subsurface mining compared to surface mining?

4. What is the LAST and most ecologically critical step in mine reclamation?

5. Acid mine drainage lowers the pH of nearby water. Which of the following is a direct consequence of this?

Section 07 · Skill 7.E

FRQ Practice

Practice the AP Exam skill of proposing a solution to an environmental problem in an applied context.

Scenario: An abandoned coal mine site has been found to have very high sulfur levels in the tailings and overburden left at the site.

Part A: Describe ONE environmental impact of the high sulfur content found in the tailings and overburden at the abandoned mine site.

Model Answer: The high sulfur content in the tailings and overburden at the abandoned coal mine site can lead to acid mine drainage. When rainwater percolates through the sulfur-rich tailings, it reacts with the sulfur (in the form of pyrite, FeS₂) and oxygen to produce sulfuric acid (H₂SO₄). This acidic water then leaches into nearby streams, rivers, and groundwater, significantly lowering the pH of those water bodies. The lower pH makes toxic heavy metals such as lead, mercury, and aluminum more soluble, increasing their concentrations in the water to levels that are lethal to fish and other aquatic organisms.

Part B: Propose ONE solution to reduce or remedy the environmental impact you described in Part A. Explain how your solution addresses the problem.

Model Answer: One solution would be to conduct mine reclamation at the site, specifically treating and removing the sulfur-rich tailings before replacing topsoil. The tailings could be neutralized by adding limestone (calcium carbonate) to the site, which reacts with the sulfuric acid to raise the pH back to a neutral level. The neutralized material can then be safely buried or removed from the site. After treatment, native vegetation should be replanted over the reclaimed land. The root systems of native plants will stabilize the soil, preventing further erosion and reducing the runoff of contaminated material into nearby waterways. This approach directly addresses the source of acid mine drainage and helps restore the surrounding aquatic ecosystem.

IMPACTS OFMINING