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19 Chapter Two: Mining Coal

Coal tended to form in horizontal layers, called coal seams, deep below the surface. Over millions of years since, great earth movements have lifted up rocks and coal seams to build mountains, cracked them open with earthquakes, and tilted them at angles; they have also been worn down by sun, rain, and other forces. So coal is now found at all kinds of depths, from thousands of feet down to exposed at the Earth’s surface. There are basically two ways of mining it, surface and underground. Finding Coal There are several ways to locate an area with plentiful coal, called a coalfield. Most simply, it is seen at the surface as a hard, dark rock. Walking or driving across an area, or flying overhead, may be enough to locate surface coal seams. Satellite photographs can also show their dark bands and patches. These areas are known as exposed coalfields. There are several ways to find coalfields hidden under the surface. One of the most effective and least costly is the seismic survey. Shock waves or seismic vibrations

The black band in this photo is a coal seam in a bank of soil.