Seirer_180110_8500908.jpgPrairie Mushroom A rock of Dakota sandstone, some 27 feet in diameter, is one of several formations in the aptly named Mushroom Rock State Park in eastern Ellsworth County. The formation, estimated at some 100 million years old, is what geologists call a concretion and was created through non-uniform erosion. The 5-acre park, just north of Kanopolis Reservoir, was given to the state more than a half-century ago. It's likely there are many more such features at the site. But they're still buried by soil.

A rock of Dakota sandstone, some 27 feet in diameter, is one of several formations in the aptly named Mushroom Rock State Park in eastern Ellsworth County. The formation, estimated at some 100 million years old, is what geologists call a concretion and was created through non-uniform erosion. The 5-acre park, just north of Kanopolis Reservoir, was given to the state more than a half-century ago. It's likely there are many more such features at the site. But they're still buried by soil.