For ten years it has been well known to geologists that all of the State of Iowa was at one time or another covered by Pleistocene ice. The northeastern corner of the State is usually mapped as unglaciated - a part of "the unglaciated area" which includes adjacent corners of Illinois, Wisconsin and Minnesota. At no time was this area an island in a sea of ice as the maps suggest. It was once swept on the west by a glacier that extended far to the south. At another time the area was swept by ice on the east. The drifts of these two glaciations overlap south of the area, leaving a triangular patch that never was glaciated. Along the western border of the unglaciated land, that is, along the eastern border of the Nebraskan Glacier, a drainage stream flowed. This stream is now the Mississippi River. Thus west of the River there is no unglaciated land, according to Iowa geologists (Kay & Apfel 1929).
Proceedings of the Iowa Academy of Science
©1940 Iowa Academy of Science, Inc.
Conard, Henry S.
"Liverworts of the So-Called Unglaciated Area of Iowa,"
Proceedings of the Iowa Academy of Science, 47(1), 91-95.
Available at: https://scholarworks.uni.edu/pias/vol47/iss1/13