Monument Rocks

These pillars are the Smoky Hill Chalk, an ooze of microscopic shells that settled on the floor of an inland sea about 80 million years ago at roughly a third of a millimeter every ten years, and built up hundreds of feet. Most of the chalk later wore away. These blocks survived because harder, cemented beds on top shielded the softer layers below. In their sides you can see thin gray seams of gypsum and the shells of the oyster Ostrea congesta, and cliff swallows plaster mud nests on the walls.

The rocks are not finished changing. A spire called the Sphinx, or Old Chief Smoky, that showed a human face from the side fell in 1986. The Keyhole Arch grows wider every year, and local lore says it began when someone shot a bullet through a thin spot. Travellers on the Butterfield Overland Despatch used the formations as a landmark, and a Fort Monument stood nearby to guard that road. On October 31, 1968, the site became the first National Natural Landmark in Kansas.

The rocks stand on private ranch land, and the owners let visitors drive the county road between them and walk around them. The rules are posted and enforced: no climbing, since the chalk breaks, no digging for fossils, no fires, and no wandering into the surrounding pasture. There are no restrooms, fuel or food nearby, and the roads turn to mud after rain. Keystone Gallery on U.S. 83 hands out maps.