Disputes about the Grand Canyon

To celebrate the century (1869 -1909) a bold study of the Grand Canyon, J. Powell, the U.S. issued a postage stamp. Indeed, some geologists believe that it was enough just a few million years. Others, however, carry canyon incision to the beginning of the Tertiary period, then held for several tens of millions of years. K. Hapt suggests that by the beginning of the Quaternary canyon hit by at least 3 / 4 of its current depth, and that during the Quaternary glaciations in the valley deepened still more than 430 m. But in order for such erosion realized, the work of a river is not enough need another condition, namely the corresponding height of the mountains, there is also a corresponding fall. Originally a vast Colorado Plateau was not mountainous (more precisely, there was no mountains, rugged canyons). The surface layers of sedimentary rocks which form the plateau, as variegated leaves of the book, originally stretched approximately at sea level, almost, where these layers were deposited once. Prakolorado and other river crossing is a low plateau in the wrong big meanders, what we see today in lowland rivers (Fig. 5.6). Decisive, or should I say "stick", meaning there has been a gradual lifting of the plateau by tectonic forces, which began in the Tertiary period. The river could not remain indifferent to it and crashed into a plateau, as gnaws a circular saw in the log, which brings to her bottom. Meanders deepened more and more. Extraordinarily impressive, this stage of the river incision is reflected in the picturesque «Goosenecks» («goose necks") loops Valley San - Juan, a tributary of the Colorado. In this case, meanders partially adapted to the structures of the bedrock. Now the surface of the plateau is located at an altitude of 1500 -3000 m. Thus, most of the river compensated lifting, crashing into a plateau, but it most, rather than the entire value uplift. This is evidenced by the rapids and rapids of Colorado, as well as its longitudinal profile: it is much steeper than that of most major rivers near their mouths.