The Loess Hills of Iowa

Don't know much about the Loess Hills of Western Iowa? This section explores the makeup of loess soil, the ecosystem, the unique qualities of the area, and threats to the hills.

The issues facing working landscapes are especially evident in the fragile Loess Hills of western Iowa.

What is Loess?
Loess (pronounced "luss") is a German word meaning "loose" and it is the name of a type of soil. Loess is a deposit of fine, yellowish-gray, clay-like sediment which can be found from north central Europe to eastern China and in the American Midwest. Loess deposits are especially common at the edges of large river basins and are generally thought to be made up of material carried by winds that went through the area during and after glacial periods.

What Are the Loess Hills of Iowa?
The story of the Loess Hills of Iowa started more than 25,000 years ago when a large glacier began to retreat from the area. As the glacier melted, water filled the Missouri River valley. When the water level dropped, large amounts of silt were left behind. Much of that silt was swept up by winds and dropped to the east of the Missouri River Valley. Most of the loess piled up within 2–10 miles of the river in a corridor running about 200 miles north to south along the river valley, creating the Loess Hills of Iowa.

One-of-a-Kind Qualities
What makes the Loess Hills of Iowa a unique landscape is the depth of the loess. Only one other location in the world, near the Yellow River in China, has loess deposits greater than the 100 to 200 foot depths in the Loess Hills of Iowa. This makes the Loess hills unique and globally significant. Endangered animals and rare prairie grasses can be found on these lands. These hills are very fragile and are vulnerable to water erosion. Human activity and tree invasion are also a concern. They cause the Loess Hill's prairie ecosystem to shrink—several species are in danger of extinction.

Threats to the Hills
Small towns, big cities, farmers, business owners, parks and preserves combine to make the Loess Hills a huge working landscape. Even though humans have worked this land for hundreds of years, its unique qualities have only come into the spotlight in the last 30 years. Current threats include erosion, mining, urban sprawl, poor conservation practices, and bad land-use decisions.

Explore More: Working Landscapes
Copyright 2004, Iowa Public Television
The Explore More project is supported by funds from the
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How the Loess Hills Were Formed
Twelve to thirty thousand years ago glaciers were moving and melting over parts of the Iowa landscape and the states to the north. Due to changes in temperature, the front of the glaciers would melt in the summer and huge amounts of meltwater would flow down the Missouri River valley. More

The Prairie Ecosystem in the Loess Hills
Prairies are landscapes where the soil, weather, and other conditions favor grasses over trees. Although prairie areas can be found anywhere along the Loess Hills, they dominate the southern and western slopes. More

The Wetland Ecosystem of the Loess Hills
Wetlands are places where the soil is saturated with water for at least several weeks during the year. Many wetlands have shallow standing water throughout the year, but others have water only during the spring when heavy rainstorms or melting snow increases the amount of water in the area. More

The Woodland Ecosystem of the Loess Hills
Woodlands are one of three distinct ecosystems found in the Loess Hills of Iowa. Trees and woodland areas in Iowa’s original landscape were limited to places where fires were unlikely to occur and had plenty of water. More

Loess Hills Safari
Check out some of the plants, animals, and insects you might find in the Loess Hills More