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Coal mining is the mining of coal. Colliery refers to the mine, and the associated buildings and machinery.
How coal is extracted from coal seams depends on how deep the seams are, and also the geology and geography of the area it's being mined in.
If the coal seams are near the surface, the coal is extracted by either:
- open pit mining, in some countries, synonymous with a quarry
- strip mining, coal is extracted by large machines in strips; the strata on top of the coal are allowed to fall back to where the seam was, once the mining has finished.
Most open cast mines in the USA extract lignite. In South Wales opencasting for steam coal and anthracite is practised.
However most coal seams are too deep underground for open cast mining. Most coal is extracted by either:
- deep mining, The shaft is dug vertically deep into the ground. These tend to be the most productive pits and often contain high quality coals. Coal is lifted to the surface with hoists.
- slope mining, The shaft is dug at an angle of about 45 degrees to the coal seam. Coal is moved to the surface with a conveyor belt.
- drift mining, The shaft is dug into the side of a mountain. Drift mines are smaller than deep mines and are common in South Wales - also in West Virginia. Coal is transported from the mine to the treatment plant via conveyor belts or mine railway cars.
Mining can be very dangerous and although in the West disasters are now rare, pit collapses, explosions and flooding are still common in parts of the world. China tries to keep its mining disasters hidden, but news leaks out.
The industry has been subject to sometimes violent labor relations in the U.S. (for example, see Ludlow Massacre); union organizers were sometimes murdered by management.
Now coal mining is highly unionized, and the unions are sometimes militant. Mining communities are often close-knit and very religious with a strong sense of community spirit. They also tend to be strongholds of left-wing Britain and possibly the world is Tower Colliery at the northern end of the south Wales valleys. This colliery was started in 1805 and at the end of the 20th century it was bought out by its miners rather than allow it to be closed.
Coal mining frequently causes significant adverse environmental impacts. Strip mining typically destroys most environmental value in the land through which it passes. However open-cast mining can be almost as severe in its impact. All forms of mining are likely to generate areas where coal is stacked and where the coal has significant sulphur content, such coal heaps generate highly acidic metal rich drainage when exposed to normal rainfall. These liquors can cause severe environmetal damage to receiving water-courses.
See also
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