Page 15--Landforms and Landscapes, continued

Flint Hills

The Flint Hills region, which runs north and south through east-central Kansas, is one of the few large areas of native prairie grassland left in the United States. The grassland that covers the Flint Hills once covered most of central and western Kansas and the surrounding states. When people moved in, the prairie in other areas became covered with farms and cities. Away from the roads and buildings, the Flint Hills region looks much as it did 10,000 years ago.

Although the Flint Hills region is known for its rolling grasslands, it is named for flint, a type of rock that is found embedded in the limestone that forms the hills. Flint, also called chert, doesn't erode as easily as the softer limestone. When the limestone at the surface is eroded by wind and water, it eventually breaks down into soil. The exposed flint is broken down into gravel, which mixes with the soil and makes the ground rocky.

Smoky Hills

The Smoky Hills change from east to west. The eastern hills are capped with sandstone. This means the top layer of rock is sandstone with other layers, or beds, of rock underneath. The sandstone was formed from sediment carried by rivers into the shallow seas from the east.

The hills in the middle are capped with limestone. This area of the Smoky Hills is known as post-rock country. Because wood was scarce, early farmers quarried limestone to use as fence posts. Although most of the newer posts are made of steel or wood, limestone fence posts can still be seen along many roads in the area. Limestone and sandstone in the Smoky Hills also are used for building.

Limestone in the Smoky Hills was formed from deposits in fairly shallow areas of the Cretaceous sea. Fossils of seashells and even sharks' teeth are frequently found in this area.

When the seas dried up in the western part of the Smoky Hills region, thick layers of sediment were left behind. The sediment was later buried between 1,000 and 2,000 feet underground and formed into chalk. Some areas of the chalk bed were later exposed by erosion. Today, much of the chalk at the surface has been eroded away by water. In some areas, tall, steep-sided chalk formations were left standing after the surrounding chalk eroded away. In Gove County, the Smoky Hill River carved out a large formation called Castle Rock and a series of formations called Monument Rocks. Chalk bluffs also can be found along the Smoky Hill River in Logan, Trego, and Gove counties.

Figure 38. This opening in Monument Rocks was formed over millions of years by erosion.

Chalk, like the post-rock limestone, contains marine fossils. Clams, small plants, sharks' teeth, and seashell fossils are fairly common. Fossils of large fish, giant swimming and flying reptiles, and swimming birds also have been found, but they are much rarer.