Forest physiography; physiography of the United States and principles of soils in relation to forestry . ^^d the Vallcy of the Red Rivcr.^and distribution of moraines oE the Dakota glacial . , ,. , (Wiiiard, u. s. PostglaciaJ Stream dissection hasfurther diversified the topography,the Missouri River having cut a trench several hundred feet deep whosesides are for the most part steep. DRAINAGE MODIFICATIONS One of the interesting effects of glaciation was the diversion of streamsfrom northward to southward courses; an instance of this is the Mis-sissippi in the southwestern corner of the Driftl
Forest physiography; physiography of the United States and principles of soils in relation to forestry . ^^d the Vallcy of the Red Rivcr.^and distribution of moraines oE the Dakota glacial . , ,. , (Wiiiard, u. s. PostglaciaJ Stream dissection hasfurther diversified the topography,the Missouri River having cut a trench several hundred feet deep whosesides are for the most part steep. DRAINAGE MODIFICATIONS One of the interesting effects of glaciation was the diversion of streamsfrom northward to southward courses; an instance of this is the Mis-sissippi in the southwestern corner of the Driftless Area below valley maintains an even width of ij miles for about 12 miles,then widens gradually, and in a stretch of about 60 miles its width in-creases, except for a slight local contraction near the mouth of theWisconsin River, and finally becomes 3! miles. This decided wideningof a low-gradient valley upstream suggests that in preglacial time thevalley was occupied by a northward-flowing river. > J. E. Todd, Aberdeen-Redfield Folio U. S. Geol. Surv. No. 165, igog, pp. 7 et lobe, North and South DakotaGeol. Surv.) PRAtRIE PLAINS 475 Other cases of stream diversions are discussed in connection with theAppalachian Plateaus, page 685, the Great Plains, page 405, and theConnecticut Valley, page 638. More general and quite as con-spicuous are the influences ofglaciation upon the drainage sys-tems laid out upon the surfacesof the various till sheets or dis-posed along their margins. TheOhio and the Missouri havecourses in marked sympathy withthe glaciated tract, as if they hadbeen pushed bodily out of pre-glacial courses, and such indeed isthe case at many points on bothstreams. The Ohio in particularexhibits a valley whose most strik-ing characteristics are open-broadstretches alternating with rock-walled gorges which closely con-fine the stream; and abandonedchannel stretches are exhibited atmany points. Many less con-spicuous illustrations of stream divers
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectforestsandforestry
