Surface Mining Techniques

In addition to the forms of underground mining previously described on this blog, there are also several forms of aboveground mining used in some areas because of the increased convenience.

Strip mining is a technique used when the seam of coal is very near the surface or when the "overburden," or earth above the seam, is too unstable to mine under. As mining progresses, the removed overburden fills in the coal cavity. Any increased safety afforded by strip mining is offset, however, by the damage done to the natural landscape. The land surrounding the coal seam must be destroyed, and recovery of the area is often not attempted.

Contour mining is functionally very similar to strip mining, with the same problems and advantages. The only difference is that it follows the contours of the mountains being mined, creating "terrace" levels on the mountainside.

Mountaintop removal is by far the most controversial form of surface mining, wherein the tops of hills are removed to access coal seams. The overburden from this is put into surrounding valleys. This technique is extremely damaging to forest ecosystems and to mountainous water sources, and it damages the landscape as well, because the original mountain shape is not restored. Though like all surface mining, mountaintop removal is financially effective for the companies and safer for the miners, many think the ecological destruction is not worth the coal gained.

Sources: http://en.wikipedia.org/wiki/Mountaintop_removal_mining