. Elements of geology. Geology. 82 LYELL'S ELEMENTS OF GEOLOGY. Denudation. Fig. Faults and denuded coal strata. de la Zouch. one side of which the coal beds abed rise to the height of 500 feet above the corresponding beds on the other side. But the upHfted strata do not stand up 500 feet above the general surface; on the contrary, the outline of the country, as expressed by the line z z, is uniform and unbroken, and the mass indicated by the dotted outline must have been washed away.* There are proofs of this kind in some level countries, where dense masses of strata have been cleared aw
. Elements of geology. Geology. 82 LYELL'S ELEMENTS OF GEOLOGY. Denudation. Fig. Faults and denuded coal strata. de la Zouch. one side of which the coal beds abed rise to the height of 500 feet above the corresponding beds on the other side. But the upHfted strata do not stand up 500 feet above the general surface; on the contrary, the outline of the country, as expressed by the line z z, is uniform and unbroken, and the mass indicated by the dotted outline must have been washed away.* There are proofs of this kind in some level countries, where dense masses of strata have been cleared away from areas several hundred square miles in extent. In the Newcastle coal district, it is ascertained that faults occur in which the upward or downward movement could not have been less than 140 fathoms, which, had they affected equally the con- figuration of the surface to that amount, would produce mountains with precipitous escarpments near 1000 feet high, or chasms of the like depth ; yet is the actual level of the country absolutely uni- form, affording no trace whatever of subterraneous The ground from which these materials have been removed, is usually overspread with heaps of sand and gravel, formed out of the ruins of the very "rocks which have disappeared. Thus, in the districts above alluded to, rounded and angular fragments occur of hard sandstone, limestone, and ironstone, with a small quan- tity of the more destructible shale,' and even rounded pieces of coal, the form of these relics pointing to water as the denuding agent. In geological descriptions we often read of "alluvium" and " diluvium," as opposed to " regular strata," or " fixed rocks," or " rocks in ; It will be useful, therefore, to explain these terms. At the surface there is commonly a layer of vegetable mould, derived partly from decayed plants, and partly caused by the castings of earth-worms, which are continually sifting
Size: 2346px × 1065px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlyellcharlessir17, bookcentury1800, booksubjectgeology
