A study of the streams of the western slope of the Missouri Valley in South Dakota and northern Nebraska presents some striking contrasts. These are the more notable because the histories of the streams since the Tertiary have been much the same. At the opening of the Pleistocene, their courses were uniformly eastward from the mountains on the west to the master stream in the James River Valley. The Glacial Period resulted in the shifting of the latter westward to the present line of the Missouri above Yankton and it rapidly cut down to a grade of about one foot per mile. This quickened or rejuvenated all the streams considered.
Proceedings of the Iowa Academy of Science
©1907 Iowa Academy of Science, Inc.
Todd, J. E.
"Effects of Certain Characteristics of Rocks on Their Erosion,"
Proceedings of the Iowa Academy of Science, 14(1), 267-270.
Available at: https://scholarworks.uni.edu/pias/vol14/iss1/23