Concentric Circles at 3CN17

Concentric circles pecked into a sandstone wall using a hammerstone at site 3CN17 at Petit Jean. Arkansas astronomer Dr. P. Clay Sherrod theorized that this petroglyph was the target of a shadow produced at sunrise on only one day each year—the summer solstice.

Cave wall with concentric circles chiseled into it

Courtesy of Don Higgins