Seams openings near

A clastic dike is typically a vertical or near-vertical seam of sedimentary material that fiUs a crack in and cuts across sedimentary strata—the dikes are found in sedimentary basin deposits worldwide. Clastic dikes form rapidly by fluidized injection (mobilization of pressurized pore fluids) or passively by water, wind, and gravity (sediment swept into open cracks). Dike thickness varies from millimeters to meters and the length is usually many times the width. 

A drift mine (Figure 5.4) is one in which a horizontal (or nearly horizontal) seam of coal outcrops to the surface in the side of a hill or mountain, and the opening into the mine, can be made directly into the coal seam. Thus, drift mines are used in cases where a coal seam outcrops on a hill or mountainside. A drift mine consists of a single passageway that follows the coal seam back into the mountain. Drift mines eliminate the need to tunnel through overlying rock to reach a coal deposit. 

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