Mushroom Rock State Park and Rock City are, as a duo entry, one of the 8 Wonders of Kansas Geography because...both sites showcase rare Dakota sandstone concretions, up to 27 feet in diameter, deposited 100 million years ago and since exposed by the relentless forces of erosion.  

Both are found in the Smoky Hill physiographic region of Kansas.

The rocks at Mushroom Rock State Park are made of sandstone from the Dakota Formation, deposited along the edge of a Cretaceous sea about 100 million years ago. Over time, circulating water deposited a limey cement between the sand grains, creating harder bodies of sandstone called concretions. Concretions are often spherical. The softer sandstone of the stem has eroded more rapidly, creating the mushroom-shaped rock.  This unique geological oddity has drawn people including Indians, mountain men, soldiers, and present day visitors. Kit Carson was to have said that the area was his favorite little place.

Concretions are often spherical. The softer sandstone of the stem has eroded more rapidly, creating the mushroom-shaped rock.

This unique geological oddity has drawn people including Indians, mountain men, soldiers, and present day visitors. Kit Carson was to have said that the area was his favorite little place.

BECOMING A STATE PARK 

Until 1963, the only way to see these spheres was by traveling a rough trail on privately-owned land. Ellsworth County constructed a road that year through the heart of the area, allowing access by automobile. The Ellsworth County Historical Society secured these 5 acres, owned by two different parties, to be deeded to the Kansas Park and Resources Authority, now Kansas Department of Wildlife and Parks. On April 25, 1965, with over 300 people in attendance, Mushroom Rock State Park was officially presented to the state and dedicated as a state park. Mushroom Rock State Park is a satellite park of Kanopolis State Park.

For KDWP Mushroom Rock state park website, click here. 

Directions to Mushroom Rock State Park:  Two miles south and two-and-a-half miles west of the intersection of K-140 and K-141.

ROCK CITY near Minneapolis 

Source:  http://www.kgs.ku.edu/Extension/KSplaces/visit25.html   Thanks to Von Rothenberger for additional information.

A few miles south of Minneapolis in Ottawa County is an area covered by huge sandstone spheres, known as Rock City. About two hundred of these unusual rocks, some with diameters up to 27 feet, occupy an area roughly the size of two football fields.  They range in diameter from 10-20 feet with the average diameter being 12 feet.  

Called concretions by geologists, the spheres weathered out of the sandstone in the Dakota Formation, deposited about 100 million years ago during the Cretaceous Period. Over time, ground water circulated through the sandy rock and deposited a calcium carbonate that grew outward in all directions from calcite crystals or limy fossil fragments scattered throughout the sandstone. As the softer uncemented portions of the sandy rock weathered away, these spheres of cemented sandstone remained. The concretions show signs of crossbedding,  angled lines that formed in the sand as it was deposited, probably by water currents.  

The site, owned and operated by a non-profit corporation, has a visitor center and picnic tables and has been designated as a National Natural Landmark.  

Directions to Rock City:  3.6 miles south of Minneapolis on K-106, then 1/2 mile west on Ivy Road (1051 Ivy Road).  Rock City is operated as a public park from May 1 to September 1 and is open daily 9 a.m.-5 p.m. A small admission fee is charged.  It can be seen all year.