Smoky Hills—Introduction

drawing of outline of this region on Kansas map

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Download fact sheet on the rocks and minerals of the Smoky Hills.

The region known as the Smoky Hills occupies the north-central part of the state. It is delineated by outcrops of Cretaceous-age rocks and takes its name from the early morning haze that often gathers in the valleys.

During the Cretaceous Period (that interval of geologic time from about 144 to 66 million years ago), Kansas was once again under water. Unlike the relatively shallow seas of the Pennsylvanian and Permian, the seas that advanced and retreated during the Cretaceous were deeper and more widespread. Three principal rock outcrops characterize the Smoky Hills--the sandstones of the Dakota Formation, the limestones of the Greenhorn Limestone, and the thick chalks of the Niobrara Chalk.

The Dakota Formation sandstones crop out in a wide belt from Rice and McPherson counties, in the south, to Washington County, in the north. They are the remains of beach sands and sediments dumped by rivers draining into the early Cretaceous seas. The hills and buttes in this part of the Smoky Hills, such as Coronado Heights in Saline County, are capped by this sandstone and rise sharply above the surrounding plains.

color photo of outcrop on side of hill

Outcrop of the Dakota Formation at Wilson Lake, Russell County.

The next outcrop belt to the west is the Greenhorn Limestone, which is made up of thin (usually less than 6 inches) chalky limestones beds alternating with thicker beds of grayish shale. The Greenhorn Limestone was deposited in a relatively shallow part of the Cretaceous sea. Near the top of the Greenhorn is a limestone bed called Fencepost limestone. Because timber was scarce in this part of the state, limestone was used extensively by early settlers for buildings and fenceposts.

The third and westernmost range of hills in the Smoky Hills developed on the thick chalks of the Niobrara Chalk. These chalk beds, which were deposited in the deeper part of the Cretaceous ocean, are exposed in bluffs of the Solomon, Saline, and Smoky Hill rivers and in an irregular belt from Smith and Jewell counties to Finney and Logan counties. The Niobrara is known for the pinnacles, spires, and odd-shaped masses formed by chalk remnants, such as Castle Rock and Monument Rocks in Gove County. It is also known for fossils of swimming reptiles such as plesiosaurs and mosasaurs that lived in the ocean while dinosaurs roamed the land.

Text by Liz Brosius, Kansas Geological Survey. Unless noted otherwise, illustrations by Jennifer Sims, Kansas Geological Survey; photographs by John Charlton, Kansas Geological Survey.

Smoky Hills--Intro | Smoky Hills--Rocks and Minerals
Smoky Hills--Places to Visit | Other regions