Located in the Adams-Highland-Pike tri-county area in southern Ohio is one of only 28 confirmed impact craters in the United States. Known as the Serpent Mound Impact Structure, this feature is about 9 miles in diameter and is the result of an impact by an asteroid or comet that struck Ohio between 256 and 330 million years ago. The structure is named after a prehistoric Native American effigy mound shaped like a snake found in the southwestern portion of the impact crater.
For decades the nature of the Serpent Mound Impact Structure was disputed, owing to its geologic complexity. Early Ohio geologists interpreted it as a “sunken mountain.” Later, it was thought to be the site of an ancient volcanic eruption. However, modern advancements in technology have aided geologic studies of the area. Among other factors, the presence of zinc minerals and surface exposures of rocks normally found only in the subsurface in the area have played a key role in determining its origin as an impact site.
The promotional video below offers a brief look at Guidebook 22: Guide to the Serpent Mound Impact Structure, South-Central Ohio. Download the PDF in the "Explore Further" section below. To order a printed copy, contact our Geologic Records Center.