What's That in Kansas

Rock City Canonball Concretions

Cannonball formations in Rock City Park, Kansas
Picture from: Nationalparks  

These roughly round boulders are called "cannonball formations," although they'd be mighty big cannonballs.

They're in Rock City, a park just south of Minneapolis, Kansas

They're made of sandstone that's been cemented together by calcite.  Geologists call them calcite-cemented concretions.  Concretions are sedimentary rocks cemented together by a mineral (like calcite).

Here's what happened. This was originally a layer of Dakota sandstone.  It was porous, so water could flow through it fairly easily through spaces between the individual grains of sand that make up the sandstone.  Some of the water had calcite dissolved in it.

Calcite, you may know, is used to make cement because it can bind together grains of sand and gravel.  As the calcite-containing water was flowing through the Dakota sandstone, something caused the calcite to precipitate out.  It could have been a change in the water temperature, or it's chemical composition.

As the calcite precipitated, it cemented the sand grains around it together.  This created spherical areas of tightly-cemented sandstone within the layer of less-well-cemented sandstone.

When erosion started, it wore away the regular Dakota sandstone faster than the parts that were cemented with calcite.  Eventually, the sandstone on top of, on the sides of, and on the bottom of the concretions wore away, leaving cannonball concretions looking like some strange rocks that rolled onto the landscape.

Kansas Underground Salt Museum

Giant underground room in the Hutchinson Salt Mine

"Back to the salt mine" usually doesn't mean fun, but dropping down into the old salt mine in Hutchinson, Kansas is actually pretty nice.

To get to the mine, an elevator drops you 650 feet down in about a minute and a half.

When the mine opened in 1923, the owner hailed it as the "most modern in the world."  Miners used what was then new technology to excavate vast "rooms" in the salt vein.  They would drill into a wall of salt, place explosives, then blast off a layer.  Big machines would crush it into gravel, then elevators would haul it to the surface.

Picking up souvenir chunks of rock salt

The method is called room-and-pillar for reasons that are pretty obvious once you're in the mine.  It's a series of enormous rooms with big pillars of salt left standing between them to hold up the roof.

The size of the rooms is amazing.  They're also cold, so if you go, even in summer, take a sweatshirt or coat.

Down in the mine, you can see where equipment scraped salt from the walls, the equipment miners used for blasting and crushing the salt, the underground rail line that hauled crushed salt to the elevators and you can pick through a pile of salt rocks for specimens to take home with you.  It's all pretty interesting.

No one is producing commercial salt from the mine anymore, but it's still in use. It's now a secure, constant-temperature, underground storage site.  It holds everything from corporation records props and prints of old Hollywood movies.