The explosion breaks up the dirt and rock called overburden. The overburden is then removed by giant earth- moving machines called draglines. When the coal is uncovered smaller shovels scoop up the coal and load it into trucks. Once the coal is mined the overburden and topsoil are replaced. Then the site is returned to the way it was before mining.
Underground mining is used when the coal lies in the deeper layers of the Earth.
When the coal seam is fairly close to the surface yet too deep to use surface mining, a slope mine can be built, with the mine entrance being a tunnel which slants down from the surface to the coal seam. A drift mine is a mine in which the entry is directly into a horizontal coal seam exposed at or near the surface. The most common type is the shaft mine. These mines may be 400 to 1,000 feet deep. Miners remove the coal by drilling a hole, or shaft, in the ground until they reach the layer of coal.