Mining and Quarrying Impacts
Mining and Quarrying Impacts
Mining and quarrying extract a wide range of useful materials from the ground such as coal, metals, and stone. These substances are used widely in building and manufacturing industry, while precious stones have long been used for adornment and decoration. Mining and quarrying involve investigating potential sites of extraction, then getting the required material out of the ground, and finally processing with heat or chemicals to get out the metal or other substance of interest. All these operations may use large amounts of water.
Mining and quarrying can be very destructive to the environment. They have a direct impact on the countryside by leaving pits and heaps of waste material. The extraction processes can also contaminate air and water with sulfur dioxide and other pollutants, putting wildlife and local populations at risk. More careful use of natural resources, including recycling, and also restoration efforts after mining and quarrying can help limit these environmental impacts.
Historical Background and Scientific Foundations
People have always extracted useful materials from the ground. The Stone, Bronze, and Iron Ages were underpinned by knowledge of how to obtain these materials. Archaeological studies have shown evidence for copper mining in Africa around 6,000 years ago and, a little later, in ancient Egypt and North America. Meanwhile, the Romans developed many mining techniques to make the process more efficient. Today practically every manufactured item contains material that has been mined or quarried.
Mining involves taking an economically useful material from the ground. Substances that are mined include ores, coal, evaporites, and precious stones and metals. Quarrying is the cutting or digging of stone, and related materials, from an excavation site or pit and it usually leaves behind a large hole in the ground. An ore is a deposit containing an economically viable amount of a mineral, which itself is a crystalline inorganic compound, usually containing a metal. It is the metal that is of value. The main groups of minerals that are mined are oxides, sulfides, and silicates. Economically, the most significant metals are aluminum, manganese, copper, chromium, and nickel.
The evaporites are materials that are deposited in the ground from evaporation of chemical solutions. They include rock salt, used for culinary purposes and in water softening, and gypsum, which is used to make plasterboard. Substances like diamond, precious metals, and stones are always in great demand for decorative purposes, including jewelry. Meanwhile, gravel, clay, sand, and limestone are quarried in vast quantities for use in building materials like concrete, cement, and glass. Crushed stone from quarries is used in large amounts to build roads. A mile of a motorway could require nearly a quarter of a million tons of crushed stone. Sulfur deposits are mined mainly to make sulfuric acid, which is a mainstay of the chemical industry.
Mining and quarrying involve three distinct stages. First there is exploration and assessment to see whether a resource is worth exploiting. This might involve a certain amount of drilling into the ground. Then the substance is extracted by whatever technique is most appropriate to its location. This is often dictated by the depth of the resource under the surface. Open pit and shallow strip mining are commonly used to extract resources up to 600 ft (180 m) below ground. The mining process removes the source and the rock and soil, known as overburden, on top of it. The overburden is stacked up into a so-called spoil heap close by. Deeper resources will be extracted by underground mining that can go to about 8,000 ft (2,440 m). Beyond this, temperatures increase to a level that makes mining impracticable. Rock removed to create tunnels for mining is generally added to the spoil heap. Finally, the ore or other resource must be processed to extract the metal or material of interest. This usually involves some kind of heat or chemical treatment. For example, smelting is a common form of processing and involves roasting an ore to release the metal it contains.
Impacts and Issues
Mining and quarrying have often been criticized for their social and environmental impact. Far fewer lives are claimed by the industry in modern times, thanks to improved technology and safety measures. However, mining was a difficult and dangerous job. Valuable materials like gold and diamonds have often helped finance corrupt regimes, crime, and terrorism while inhuman labor conditions have often been employed in their extraction.
The environmental impacts of mining and quarrying are several. While the extractions are underway, the landscape is visibly disfigured and habitat loss can be extensive. The mining operations themselves and the accompanying spoil heaps cause a drastic change in the location with direct destruction of habitat and blocking or burying nearby bodies of water. Mining can often affect local hydrology, causing changes in the water flow as well as quality. The pits left behind by large mining operations often fill with groundwater, which then
WORDS TO KNOW
ACID RAIN: A form of precipitation that is significantly more acidic than neutral water, often produced as the result of industrial processes.
EVAPORITES: Salts deposited by the evaporation of aqueous solutions.
ORE: Rock containing a significant amount of minerals.
STRIP MINING: A method for removing coal from seams located near Earth’s surface.
becomes polluted. Mining companies now acknowledge that they need to invest in restoring land they have exploited. This involves leveling spoil heaps, filling in holes and re-grassing the area. However, it can take many years for vegetation to become re-established at a former mine site. There are also many abandoned mines where environmental impact is ongoing.
Emissions from mining and quarrying can contaminate both air and water. The U.S. Environmental Protection Agency (EPA) lists as many as 100 different air pollutants issuing from the nation’s mining industry, including dust particles and sulfur dioxide, which can create acid precipitation. Meanwhile, the Mineral Policy Center in Washington, D.C., says that 12,000 mi
(19,312 km) of rivers and streams in the United States are polluted by abandoned and current mining operations. The problem is that a great deal of water is used in extraction of ores, especially those containing only low concentrations of metals, and this leaches heavy metals and sulfur from the rocks so that it enters the water supply. Ore processing can sometimes be more polluting than the extraction itself For example, smelting often releases sulfur dioxide into the atmosphere to create acid precipitation, including acid rain.
Fires occurring in underground mines are another environmental impact. These can be difficult to extinguish and may actually burn for many years. There are hundreds of such mine fires around the world, in China, the United States, Russia, and India, for example. They emit a substantial amount of methane and carbon dioxide into the atmosphere, thereby adding to the greenhouse effect.
The polluting nature of mining and quarrying is underlined by work carried out by the Blacksmith Institute, which is focused on solving pollution problems in the developing world. Each year they publish a list of the world’s most polluted sites. In 2007, six of the top ten most polluted sites were mines or smelter facilities.
Mining and quarrying are, by their very nature, destructive to the environment. As the global population grows and many countries improve their standards of living, demand for industrial materials is sure to grow. This creates increasing pressure on existing mineral resources, which are finite. Prospectors will go further afield in search of new supplies. There have even been discussions about trying to exploit the pristine environment of Antarctica. However, there is a growing awareness that mineral resources are indeed finite and that they should be conserved. Efforts to recycle metals and other materials could help prevent the depletion of resources.
Cunningham, W.P., and A. Cunningham. Environmental Science: A Global Concern. New York: McGraw-Hill International Edition, 2008.
Bioethics Education Project. “Pollution: Mining and Quarrying.” http://www.beep.ac.uk/content/231.0.html (accessed April 30, 2008).
Blacksmith Institute. “The World’s Worst Polluted Places 2007.” http://www.blacksmithinstitute.org/ten.php (accessed April 30, 2008).