Monument Rocks (Chalk Pyramids), Kansas

Located 4 miles east of US 83 and about 25 miles south of Oakley, Kansas

Chalk Pyramids and Monument Rocks are names for the same group of rock outcroppings, near US-83 in western Kansas. There are signs at the turn-off (6 miles of gravel roads). You can see the rocks in the distance from the highway if you know where to look. Like the Castle Rock Badlands, Monument Rocks are on private range land, but thanks to the owners, they are open to the public. The United States Department of the Interior has designated this site as a National Natural Landmark.  These 70 feet tall sedimentary formations of Niobrara Chalk were created 80 million years ago when this area was part of a vast inland sea.


How Did Chalk Pyramids Form?


The "Badlands" of Kansas, famous for its fossils, is an area of chalk bluffs, chalk flats, and chalk pinnacles.  80 million years ago this region was an open ocean brimming with calcium-shelled microscopic animals (foraminera), giant oysters, sharks, bony fish, and reptiles swimming and flying overhead. The tests (little shells) of trillions of foraminera fell like snow to the bottom as they died, forming thick limey ooze (see picture above!), which enveloped the corpses of larger animals. Through time the ooze was covered by other sediments and pressed into chalk (a soft limestone). Thousands of years of sculpting by the Smoky Hill River have left what you see today. This geological formation is the Niobrara Chalk, named after bluffs of the same chalk on the Missouri River near the mouth of the Niobrara River in northeast Nebraska.

Information from: Kansas Nature-Based Tourism Alliance


More Information About the Geology of Western Kansas

Smoky Hill River Valley and Lake Scott State Park

The Smoky Hill river valley and its tributaries in western Kansas contain numerous chalk outcroppings or "badlands". They were all part of an ancient inland seaway which extended from the present Gulf of Mexico to Alaska. The placid, semitropical sea averaged 500 ft. deep. Its silty bottom was ideal for fossilization. This prehistoric seabed was drained by the slow uplift of the Rocky Mountains at the end of the Cretaceous period.

Map of Western Interior SeawayThese thick chalk beds have been named the Niobrara formation of the late Cretaceous geologic period and date from 80 to 70 million years old. Chalk is a soft limestone composed mainly of microscopic bits of compacted shells (coccoliths). The Niobrara formation is over 500 feet thick and includes the Fort Hays Limestone at the base and the Smoky Hill Chalk at the top.

Subsequent sediment was deposited during the Tertiary period that followed the Cretaceous. The best known formation of this period is the Ogallala, composed of sandy limy rocks often exposed as bluffs like those at Lake Scott State Park in northern Scott County. The Ogallala formation also provides the majority of groundwater for western Kansas.

During the more recent Pleistocene epoch, glaciers and torrential rains formed most of the present day rivers and streams. It was at this time that the Smoky Hill chalk beds were cut out and continue to erode today, forming pinnacles, spires and unique-shaped forms. Two spectacular examples are Castle Rock in eastern Gove county and Monument Rocks (also known as Chalk Pyramids) in western Gove county. Both sites are inspirational historic landmarks.

Western Kansas is known world-wide for its diverse fossils. The Niobrara formation is famous for its abundance of extinct fossil fish, swimming reptiles (mosasaurs and plesiosaurs), flying reptiles (pteranodons) and ancient birds with teeth (Hesperornis and Ichthyornis). The Ogallala formation yields fossil specimens of rhinoceros, camels, and land tortoises.

Information, courtesy of Chuck Bonner, taken from the Keystone Gallery website.

Here's a great site that tells you about the wildlife you can find in this magnificent area!


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