drift mining

Drift mining is a method of accessing valuable geological material, such as coal, by cutting into the side of the earth, rather than tunneling straight downwards (see shaft mine). Drift mines have horizontal entries into the coal seam from a hillside. Drift mines are distinct from slope mines, which have an inclined entrance from the surface to the coal seam. If possible, though, drifts are driven at just a slight incline so that removal of material can be assisted by gravity.
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