Cat Steps in the Loess Hills

The Loess Hills of western Iowa are a unique landform. While loess soil is found in many places, the depth of the western Iowa deposits make it unique to this area and one area of China. The loess particles are uniform in size, smooth sided and angular which makes them stable when dry, but prone to sloughing when wet. This results in the characteristic steep stair-like cat steps of the hills.

• What is causing the hillsides in the Loess Hills to form a stair-step formation?

• Looking at the first photo, what do you notice on the hillside?
• Why do you think the hillside was cut flat on the side of the roadway?

Students could:

• Construct a model using loess soil. Challenge students to get the soil to hold its shape with a curved shape and then with a flat side.
• Observe what happens when you add water. Look at the soil under a microscope and try to distinguish the shape of the particles.