Cannonball Concretions

Two large, round stones take up the majority of the image, with more behind, and a butte in the back
Cannonball Concretions

NPS Photo/J. Zylland

Quick Facts
Cannonball Concretion Pullout, North Unit of Theodore Roosevelt National Park
These unusual stone formations are a fascinating look into the geological processes of the North Dakota badlands.

Historical/Interpretive Information/Exhibits, Parking - Auto, Parking - Bus/RV, Scenic View/Photo Spot, Trash/Litter Receptacles

What are cannonball concretions? Jutting out from the landscape, these large, round stones don’t appear to properly fit into the badlands. The secret lies in the large butte located nearby.

When mineral rich water seeps down through the porous layers that make up the badlands, it can deposit those minerals in spaces or gaps in the sediments. The minerals act as a kind of glue, holding these sediments together, often forming around a core. As more and more layers are deposited, the concretion builds outward like a pearl, before being exposed by erosion.

Who knows how many concretions are still waiting to be exposed, deep inside the butte?

It is illegal to remove any resource from a national park. Leave any flower, stone, or other object where you find it so that other visitors can enjoy it as well. 

It is illegal to carve, paint, or otherwise alter anything in a national park. 

Theodore Roosevelt National Park

Last updated: November 7, 2021