Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments / by Sir Charles Lyell.

  • Lyell, Charles, Sir, 1797-1875.
Date:
1865
Catalogue details

Licence: Public Domain Mark

Credit: Elements of geology, or, The ancient changes of the earth and its inhabitants as illustrated by geological monuments / by Sir Charles Lyell. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

    84/822 (page 62)
    FAULTS. [Ch. V. Vaults. A B perpendicular, C D oblique to the horizon. faults A B, C D, continue parallel to one another; in other cases, the strata on each side are inclined, as in a, b, c, d (fig. 86.), though Fig. 8G. E F, fault or fissure filled with rubbish, on each side of which the shifted strata are not parallel. their identity is still to be recognized by their possessing the same thickness and the same internal characters.”* In Coalbrook Dale, says Mr. Prestwich -f, deposits of sandstone, shale, and coal, several thousand feet thick, and occupying an area of many miles, have been shivered into fragments, and the broken remnants have been placed in very discordant positions, often at levels differing several hundred feet from each other. The sides of the faults, when perpendicular, are commonly separated several yards, but are sometimes as much as 50 yards asunder, the interval being filled with broken debris of the strata. In following the course of the same fault it is sometimes found to produce in different places very unequal changes of level, the amount of shift being in one place 300, and in another 700 feet, which arises, in some cases, from the union of two or more faults. In other words, the disjointed strata have in certain districts been subjected to renewed movements, which they have not suffered elsewhere. We may occasionally see exact counterparts of these slips, on a small scale, in pits of loose sand and gravel, many of which have doubtless been caused by the drying and shrinking of argillaceous and other beds, slight subsidences having taken place from failure of support. Sometimes, however, even these small slips may have been produced during earthquakes ; for land has been moved, and its level, relatively to the sea, considerably altered, within the period when much of the alluvial sand and gravel now covering the surface of continents was deposited. * Playfair, Illust. of Hutt. Theory, t Geol. Trans, second series, voi. v, § 42. ' p. 452.