. Elements of geology : a text-book for colleges and for the general reader. Geology. RAVINES, CANONS, GORGES. 17 way downward, forming narrow cations with almost perpendicular walls several thousand feet deep, so that in many parts we have the singular phenomenon of a whole river-system running almost hidden far below the surface of the country, and rendering the country entirely impass- able in certain directions (see Frontispiece). Nor is the erosion con-. Fig. 10.—Canon of the Colorado and its Tributaries tf'rom a Drawing by Newberry). fined to canons; for the rain-erosion has been so thor
. Elements of geology : a text-book for colleges and for the general reader. Geology. RAVINES, CANONS, GORGES. 17 way downward, forming narrow cations with almost perpendicular walls several thousand feet deep, so that in many parts we have the singular phenomenon of a whole river-system running almost hidden far below the surface of the country, and rendering the country entirely impass- able in certain directions (see Frontispiece). Nor is the erosion con-. Fig. 10.—Canon of the Colorado and its Tributaries tf'rom a Drawing by Newberry). fined to canons; for the rain-erosion has been so thorough and general that much of the upper portion of the plateau has been wholly carried away, leaving only isolated turrets (buttes) or isolated level tables with cliff-like walls (mesas) to indicate their original height. All these facts are well shown in Fig. 10. The explanation of these deep and narrow cafions is probably to be found in the predominance of stream-erosion over general disintegration and rain-erosion, which is characteristic of an arid climate (Gilbert). Chief among these canons is the Grand Canon of the Colorado, 300 miles long and 3,000 to 6,200 feet deep, forming the grandest natural geological section known. Into this the tributaries enter by side-ca- nons of nearly equal depth, and often of extreme narrowness. Fig. 11 represents the natural proportions of such a canon. Time.—These remarkable canons have evidently been cut wholly by the streams which now occupy them, and which are still continuing the work. The work, probably commenced in the early Tertiary with. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original LeConte, Joseph, 1823-1901. New York : D. Appleton and Co.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectgeology, bookyear1892
