It is commonly understood that the Raccoon River, where it flows through Des Moines, lies just south of the southern limit of the Wisconsin drift sheet in Iowa. North of this river the upland of Wisconsin drift presents the character of a youthful ground moraine, marked by gentle sags and swells, with undrained depressions here and there, features that are conspicuous even in so short a distance as that from Des Moines to Ankeny. South of Raccoon River the level of the old Kansan drift plain is still marked by the level of the upland; but the land is well dissected by erosion and the upland in the area of Kansan drift is thoroughly drained by the numerous ramifying ravines. These contrasts are evident, even within the area of a single topographic sheet, that of the Des Moines quadrangle.
Proceedings of the Iowa Academy of Science
©1914 Iowa Academy of Science, Inc.
Tilton, John L.
"An Area of Wisconsin Drift Further South in Polk County, Iowa, Than Hitherto Recognized,"
Proceedings of the Iowa Academy of Science, 21(1), 219-220.
Available at: https://scholarworks.uni.edu/pias/vol21/iss1/32