The minimum durations of the glacial ages in Iowa have been estimated from present-day consensus of opinion as to the rates of advance and retreat of ice sheets. For the retreat of the late Wisconsin from Iowa the rate of one mile in ten years was adopted. The same rate was assumed for the advance of this ice sheet into Iowa and also for the advances and retreats of earlier ice sheets. The minimum duration of glacial time in Iowa was calculated to be about 30,000 years.
Proceedings of the Iowa Academy of Science
©1931 Iowa Academy of Science, Inc.
Kay, George F.
"Minimum Durations of the Glacial and Interglacial Ages in the Pleistocene of Iowa,"
Proceedings of the Iowa Academy of Science, 38(1), 204-205.
Available at: https://scholarworks.uni.edu/pias/vol38/iss1/47