Iowan erosion surface

The Iowan Erosion Surface (IES) is a geographic region located mostly in northeastern Iowa and extends into southeastern Minnesota. The IES has been a center of controversy for Quaternary workers due to its topographic relief and other elements . ). Early workers proposed the notion that the surface was a glacial deposit between the early Wisconsin and Illinoian stages. In 1968, Ruhe proposed that this area underwent a dramatic erosive event during the Late Wisconsin. Most of the region is underlain by pre-Illinoian till, with an age of greater than 0.5 Ma. A thin blanket of Late Wisconsin aged loess covers the till in some places. The relief of the IES is a generally subdued with broad interfluves and over-sized valleys. Elliptical hills called paha stand above the landscape and have an orientation of NW-SE (northwest to southeast).