Mining of Ores (College Board AP® Environmental Science) : Study Guide

Alistair Marjot

Written by: Alistair Marjot

Reviewed by: Jacque Cartwright

Updated on

Impacts of mining lower grade ores

What are lower grade ores?

  • Lower grade ores contain smaller concentrations of valuable minerals

    • This means they require more extensive processing to extract usable material

  • As high-grade ores become depleted, mining companies must turn to lower quality deposits

Environmental impacts of mining lower grade ores

Increased resource consumption

  • More energy is required to extract and process lower-grade ores

  • Higher water usage is needed for chemical separation processes, increasing strain on local water sources

Greater waste production

  • Mining lower-grade ores generates larger amounts of waste rock and tailings

  • Tailing ponds hold toxic slurry, which can leak into surrounding ecosystems

Higher pollution levels

  • More fossil fuels are burned to power mining equipment and ore processing

    • This contributes to higher CO₂ emissions

  • The use of chemicals like cyanide and sulfuric acid in ore extraction increases the risk of soil and water contamination

Economic and social impacts

Rising mining costs

  • Extracting minerals from lower-grade ores increases operational costs, as more ore must be processed to obtain the same yield

    • These higher costs can lead to increased consumer prices for metals and minerals

Land degradation and habitat destruction

  • Larger mining operations are required to process more ore, leading to expanded deforestation, habitat destruction, and soil erosion

    • Example: In regions like the Amazon rainforest, lower-grade gold mining contributes to widespread deforestation

Surface mining

What is surface mining?

  • Surface mining involves the removal of large sections of soil and rock (known as overburden) to access minerals near the Earth’s surface

  • It is used for extracting coal, gold, copper, and other valuable minerals

  • More common than underground mining because it is cheaper and safer, but it has significant environmental impacts

Types of surface mining

Strip mining

  • Removes long strips of land to extract minerals located close to the surface

  • Destroys vegetation and topsoil, leading to increased erosion and habitat loss

Open-pit mining

  • Excavates large, deep pits to access ore deposits

  • Used for gold, copper, and iron ore mining

  • Generates massive amounts of waste rock, altering landscapes permanently

Environmental impacts of surface mining

Habitat destruction

  • Deforestation and removal of vegetation disrupt ecosystems and wildlife populations

  • Loss of biodiversity as species are displaced from their natural habitats

Soil erosion and degradation

  • Exposed soil after mining is prone to erosion, leading to loss of fertile land

  • Mining spoils (waste materials) are often acidic and prevent plant regrowth

Water pollution

  • Heavy metals and chemicals from mining runoff contaminate rivers and groundwater

  • Acid mine drainage (AMD) occurs when exposed rock reacts with air and water, releasing toxic sulfuric acid

Case Study

Berkeley Pit, Montana: Water pollution from mining waste

  • Location:

    • Berkeley Pit is an abandoned open-pit copper mine in Butte, Montana.

  • Issue:

    • After mining ceased in 1982, groundwater began flooding the pit

    • This lead to the accumulation of highly acidic water (pH ~2.5) mixed with heavy metals such as arsenic, lead, and cadmium

  • Environmental impacts:

    • The toxic water poses a serious threat to local water systems if it overflows or seeps into surrounding groundwater

    • In 1995, a flock of snow geese landed in the pit and over 300 of the geese died from exposure to the contaminated water

  • Management:

    • After the 1995 incident, officials implemented bird deterrent measures

      • These include loud noises, lasers, and trained personnel using shotguns to fire non-lethal rounds to scare birds away

    • The pit is part of the Superfund cleanup program, with water treatment efforts in place to prevent contamination spread

    • Pumps and treatment plants help remove heavy metals and neutralize acidity before releasing water into the environment

Mining wastes

  • Mining wastes are the unwanted materials left behind after extracting valuable minerals from ore

  • These wastes include overburden, tailings, and slag, each of which poses environmental risks

Types of mining wastes

Overburden

  • Soil and rock layers removed to reach ore deposits

  • Often piled into spoil heaps, which can lead to habitat destruction

Tailings

  • Finely ground rock and chemical byproducts left after ore processing

  • Contain heavy metals, cyanide, and sulfur compounds, which can leach into water sources

  • Stored in tailing ponds, which risk leakage, dam failure, and water contamination

Slag

  • Residue left after smelting ores, mainly composed of metal oxides

  • Can contain toxic elements like arsenic and lead, contaminating soil and groundwater

Managing and reducing mining waste

  • Recycling mine waste: Some tailings and slag can be reused in construction materials or road-building

  • Land reclamation: Restoring mined lands by planting vegetation and stabilizing waste piles

  • Better waste storage: Improved tailing dam designs reduce the risk of spills and contamination

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Alistair Marjot

Author: Alistair Marjot

Expertise: Biology & Environmental Systems and Societies Content Creator

Alistair graduated from Oxford University with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems & Societies. Alistair has continued to pursue his interests in ecology and environmental science, recently gaining an MSc in Wildlife Biology & Conservation with Edinburgh Napier University.

Jacque Cartwright

Reviewer: Jacque Cartwright

Expertise: Geography Content Creator

Jacque graduated from the Open University with a BSc in Environmental Science and Geography before doing her PGCE with the University of St David’s, Swansea. Teaching is her passion and has taught across a wide range of specifications – GCSE/IGCSE and IB but particularly loves teaching the A-level Geography. For the past 5 years Jacque has been teaching online for international schools, and she knows what is needed to get the top scores on those pesky geography exams.