Mining methods are often dictated by the type and location of the coal deposit. Coal is mined either by underground tunneling or by removing or "stripping" the covering rocks, which are known as overburden. When the deposit is more than 150 feet below the surface the underground method is used.
Bell Pit: The name of this early underground method comes from the shape of the excavation, with a narrow vertical shaft sunk into the coal or iron ore seam, which was then opened out into a small chamber. Little timber was used, so once the roof became unsafe, the pit was abandoned and another shaft sunk nearby. Coal was cut by using picks and shovels.
Room-and-Pillar Mining: Entails the excavation of a series of "rooms" into the coalbed, leaving "pillars" or columns of coal to help support the mine roof. The coal is broken up by explosives, loaded onto a vehicle by a mechanized loading machine.
Longwall Mining: This method is popular because of the greater safety and efficiency it affords. In this method, a rotating shear on the mining machine shaves from blocks or panels of coal in a back-and-forth motion, similar to that of a meat slicer, and dumps the broken coal onto a conveyor belt that extends across the longwall. As the mining machine advances, the roof behind it caves in.
Surface, or open pit: This mining of coal is done where the overburden is relatively shallow. Large earth-moving equipment, draglines , or shovels are used to remove the fractured overburden from the coal. The coal is then typically broken up by blasting it with explosives. The coal is loaded into special haulage trucks.
Mountaintop removal mining: This method is a variant of surface mining. In order to reach coal seams the top of the mountain or the "overburden" is broken up and removed by blasting. Once the rock surrounding the coal is blasted off, in what is known in the industry as "shoot and shove," the excess rock and earth is dumped over the side of the mountain into the valleys below, often burying the streams that run through them.