Appalachian coal lies underground in thin seams, too thin for underground mine shafts. The only way to extract the coal profitably is with surface mining.
Surface mining involves the removal of soil and rock (overburden in mining terminology) with explosives and heavy machinery to get at the coal. As much as 200–300 meters of overburden is removed. The removed material, also called mine spoils, is used to reconstruct the area after mining operations are done. The removed material takes up more volume and cannot simply be replaced (try digging a hole in your backyard and filling it back in and you’ll discover how this works).
The “excess spoils” must be dumped elsewhere. In Appalachian mountaintop mining, the excess is deposited into valleys. These valley fills are usually located next to—often downstream from—surface mines, burying headwater streams completely. The groundwater and surface waters from the mine often flow through these valley fills before discharging into streams.
Disturbed land is pink in these close-up images of a large mine about 20 miles southwest of Charleston, West Virginia. The natural color image from Sentinel-2 shows more detail in the same area. Active mining is bright in this Sentinel-2 image, and lighter green shades show some reclaimed land.