Forest physiography; physiography of the United States and principles of soils in relation to forestry . the extremelocalized deformation of the mountains has so warped the ancientsurface, and intense erosion by both water and ice has so completelydissected it, as to make its determination very difficult if not impos-sible. It is truly remarkable how abruptly the wxU-developed and butlittle dissected peneplain of the Great Plains of Montana terminates atthe foot of the front ranges. The line is almost as definite as a long-continued erosion which the peneplain represents must haveaff
Forest physiography; physiography of the United States and principles of soils in relation to forestry . the extremelocalized deformation of the mountains has so warped the ancientsurface, and intense erosion by both water and ice has so completelydissected it, as to make its determination very difficult if not impos-sible. It is truly remarkable how abruptly the wxU-developed and butlittle dissected peneplain of the Great Plains of Montana terminates atthe foot of the front ranges. The line is almost as definite as a long-continued erosion which the peneplain represents must haveaffected the present mountainous area west of it, but was probablyoffset by repeated deformation terminating or culminating in the greatoverthrust to which the present mountain height and the deep dissectionare largely due. In the Galton range the old surface may be safely in-ferred; the older features have not been so completely destroyed owingto the relatively small amount of local deformation and the less intenseaction of water and ice. For the Galton range, although bounded by ROCKY MOUNTAINS. 311. 1 Yi 0 10 12 3 15 KilometersContour interval 500 feet Fig. 94. — Map of a part of the Lewis Mountains, western Montana, representing typical glacial featuresof the range. (Chief Mountain quadrangle, U. S. Geol. Surv.) 312 FOREST PHYSIOGRAPHY structural limits, is internally, but a simple uplifted block whose minorflexures or faults are not sufficiently pronounced to interrupt the ancientsurface. GLACIAL FORMS Some of the most remarkable erosion features produced by alpineglaciers are to be found in the Lewis range on the continental divide inwestern Montana. They are represented on the Chief Mountain quad-rangle, Montana, Fig. 94, one of the most interesting topographic sheetsyet published, not only because of the exceptional nature of the regionbut also because of the unusual faithfulness with which the topographerhas represented the landscape. The strata of the Lewis Mountains a
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectforestsandforestry
