A controversial method of coal mining is mountaintop removal, in which the entire top of a mountain is blasted away to expose a coal seam that runs through the mountain or the ridge. As with other surface mining, there is a significant amount of overburden placed in nearby valleys and valley streams ...

The most economical method of coal extraction from coal seams depends on the depth and quality of the seams, and also the geology and environmental factors of the area being mined.

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