Where on Earth? - October 2013

Clues for October 2013:
1. One of five National Natural Landmarks in its host state, this site boasts more giant sandstone “cannonball” concretions — roughly 200, ranging in diameter from about three to six meters — than anywhere else in the world.
2. The sand in the concretions was deposited in a river channel near the edge of the Western Interior Seaway as part of the Late Cretaceous Dakota Formation. Later precipitation of calcite from groundwater flowing through the rock cemented portions of the sandstone together, preserving riverbed features such as cross-bedding (as seen in the photo) and imparting durability to the concretions while the surrounding rock gradually eroded away.
3. Not to be confused with a mountainous locale of the same name in a peachy southern state, this site is located on relatively flat land just kilometers from a small town that shares its moniker with the largest city in a state known for its lakes.
Name the site and its host state.
Scroll down for the answer
Answer: The “cannonball” concretions at Rock City, Kan., are made of sand — deposited near the edge of the Western Interior Seaway during the Late Cretaceous — that was later cemented together with calcite. Other sites host higher concentrations of such concretions, like Canada’s Red Rock Coulee (as noted by EARTH reader Ken Turnbull), but those at Rock City are among the world’s largest at 3 to 6 meters in diameter. Photo is by Jimmy Emerson.

October winners:
Brian Allison (Cologne, Minn.)
Marilyn Hurst (Madison, Wis.)
Frank Snyder (Anchorage, Alaska)
Edith Starbuck (Rolla, Mo.)
Margaret Wessel (Vashon Island, Wash.)
To submit your photographs to our Where on Earth? contest, send them via e-mail to


01 Oct 2013