Preliminary report of the United States Geological Survey of Wyoming, and portions of contiguous territories : (being a second annual report of progress), under the authority of the Secretary of the Interior . tinent. We supposethat the channels of all the streams on the eastern slope of the KockyMountains were at one time occupied with water from hill to hill, andthat the drainage was toward the sea. But in the Great Basin, which,so far as we kuow, has no outlet, the drainage must have been by evap-oration, for the evidence points to the conclusion that it was entirelyfilled with water high u
Preliminary report of the United States Geological Survey of Wyoming, and portions of contiguous territories : (being a second annual report of progress), under the authority of the Secretary of the Interior . tinent. We supposethat the channels of all the streams on the eastern slope of the KockyMountains were at one time occupied with water from hill to hill, andthat the drainage was toward the sea. But in the Great Basin, which,so far as we kuow, has no outlet, the drainage must have been by evap-oration, for the evidence points to the conclusion that it was entirelyfilled with water high up on the sides of the mountains. There isoTcater uniformity in the terraces in the Great Basin than in the valleyof the Missouri, which indicates a far more equable drainage. Still,those along the flanks of the Wasatch Mountains number two or threeprincipal ones, but these formations separate into five or six; and Stans-bury mentions one locality where there are ten or twelve of them. Inthe Missouri Valley, and along the eastern slope generally, the terracesvary much in height and importance. Fig. 18 shows the peculiar form of the main terrace as shown on theI^Iissouri Eiver, just above Omaha. Fig. The distant hills are composed of the yellow marl or loess, and thesurface has been weathered into the rounded, conical hills. This por-tion is often covered with the drift or stray rocks, or what I have calledin a former report the erratic block deposit. On the terraces these erraticmasses are scarcely ever found, and in the broad bottoms of the MissouriKiver seldom if ever. This fact strengthens the opinion that the terracesare really one of the latest features, and that they were formed duringthe drainage of the waters toward the sea after the temperature hadreached nearly its present state. Oscillations of level may have contrib-uted somewhat to the formation of the terraces, but I am inclined tobelieve that the drainage or the contraction of the waters is the maincause. Thi
Size: 2244px × 1114px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1870, bookpublishe, booksubjectgeology
