Coal mining is removal of coal from ground. Depending on the depth of coal, from the earth's surface, a number of methods may be used to mine or extract it. If the coal is near surface, strip mining or mountaintop removal mining may be performed. For deeply buried coal, longwall mining or blast mining may be used. Strip mining removes layers of soil above the coal seam or strip and then mines for the coal. In comparison, mountaintop mining makes use of the steep slope or valleys to deposit the soil removed from top of coal bed (known as overburden) and the cleared coal seams are extracted. In longwall mining, a machine moves back and forth in the coal bed and deposits the loosened coal onto a pan, which takes it to a conveyor belt, from it is taken for processing. Blast mining was the older technique (and is still used in many parts of the world), in which the coal seam is broken using explosives (such as dynamite), which looses the coal and is removed from site using trucks and carts.
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