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2 . 04 . 6 Page 16 <br /> The immediate mine roof consists of thinly laminated shales <br /> and sandstones . These beds rise up to the base of the Cliff <br /> House Sandstone an average of twenty feet above the coal seam. <br /> The thick Cliff House Sandstone provides a great deal of ground <br /> stability and prevents subsidence from reaching the surface after <br /> pillars are extracted by second mining . <br /> STRATIGRAPHIC CROSS-SECTION <br /> See 2 . 04 .6 pages 2 , 3 , 4 and 5 . <br /> 1/10/90 <br />