Visit the Iowa / Missouri Loess Hills This Summer

Locating Loess Deposits. Looking at dirt may not seem like an exciting way to spend a vacation trip, but the Iowa/Missouri Loess Hills are interesting from the viewpoint of geology, if nothing else. My wife and I were leaving Sioux City, Iowa, after attending a wedding for a relative. Not too far south of Sioux City, on Interstate 29, we saw a sign that read "Loess Hills Scenic Byway." A stop at a rest area provided some informational literature, and we were on our way to see some loess hills.

Loess (it's pronounced "luss") is a type of soil found in most places around the world, but only in China are loess deposits as high (up to 200 feet) as they are along the western border of Iowa and Missouri. The loess deposit area is approximately 15 miles wide and 200 miles long, extending from near Sioux City, Iowa, to St. Joseph, Missouri. Council Bluffs, Iowa, named for the loess bluffs where Native American Indians used to hold councils, is included in the deposit area.

The Formation of Loess. Wikipedia gives some helpful background about the soil. The word "loess" comes ultimately from a Swiss German word which means "loose," which perfectly describes the loess soil. The hills are the by-products of the end of an ice age. Runoff from melting glaciers created what would become known as the Missouri River. Rocks in the river were ground to fine powdery particles called loess. After the river had done its work and receded to a lower level, the wind took over, blowing the loess particles to the east bank of the river, piling the particles into the hills they are today. At the end of a long process, topsoil was formed, and animal and human life began to inhabit the hills. Archaeological artifacts indicate that humans have lived in the hills for approximately 6000 years.

The Fragile Nature of Loess. Because of its composition, loess erodes easily and can be shifted dramatically by nothing more than the wind. As Wikipedia notes, even well-managed farms of loess soil can lose large amounts of soil each year through erosion.