Iowa DOT's policy is to be
sensitive to the environment
and foster and enhance
environmental stewardship.

IOWA DEPARTMENT OF TRANSPORTATION

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Unit 1: Geology of Iowa

D. How Geology Affects Iowa's Landscapes

Many factors affect Iowa's landscapes. Depending on where you are in Iowa, you will see a variety of landscapes.

Western Iowa Landscape - Several different landscapes are found in western Iowa. In the northwest we see a landscape shaped by very thick, uniform glacial deposits. The glacial deposits are on top of bedrock deposits far below ground. This provides for a landscape dominated by very gently rolling low hills.

Along the western edge of Iowa, Missouri River deposits dominate the landscape. Alongside these river deposits is a unique deposit known as the Loess Hills. These were formed by the wind carrying very small sediments to the Missouri River valley where they fell to the ground and formed the Loess Hills. The result is a narrow band of loess deposits alongside the river deposits.

illustration courtesy of "Landforms of Iowa" by Jean C. Prior

In west central and southwest Iowa, glacial deposits again dominate the landscape. The difference between these deposits and those in the northwest is that they are much older. Because they are so much older, more erosion has taken place, creating deep valleys and high hills.

Central Iowa Landscape - The landscape that dominates central Iowa is called the Des Moines Lobe. The Des Moines Lobe is a product of the last glaciers in Iowa. These are thick deposits of gravel that sit on top of rock deposits deep below the ground's surface. These gravel deposits form shallow aquifers. Aquifers are layers of sediment that carry and hold water. The aquifers provide a source of water for many central Iowa towns.

In south central Iowa we see the same landscapes that we see in southwest Iowa. These are the oldest glacial deposits that have deeper valleys and higher hills.

Eastern Iowa Landscape - Two different landscapes are found in northeast Iowa. The first type of landscape is a middle-aged glacial surface dominated by low, gentle hills. These contain an abundance of field stones. Some of them are quite large.

The second type of landscape in this area is along the Mississippi River. Here there are tall cliffs and bluffs. Very thick limestone and dolomite deposits formed these. These cliffs can be more than 100 feet high! Almost no glacial deposits are on top of the limestone and dolomite.

In the very southeastern-most part of the state, again we find river deposits from several of the Mississippi River's old courses. Remember how rivers can change courses?

Southern Iowa Landscape - The deposits explained in the previous paragraphs form an U-shaped region. This region spans from west central to east central Iowa. Again, these are the oldest glacial deposits in Iowa. The deposits have undergone many years of erosion. This created deeper valleys and higher hills when compared to other younger glacial deposits found elsewhere in Iowa.

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