Archaeologist Reveals Hidden Earthworks with Latest Geophysical Technology

by Jennifer Spiegel

Archaeologist Jarrod Burks started out as a pre-med student at the University of Illinois when a class taken in Egyptology piqued his interest in archaeology. When he realized there was archaeology to be done right here in the Midwest, he changed his major. Graduate school brought him to Ohio, right to the Hopewell heartland. Today, he’s using the latest in remote sensing technology to reveal that heartland’s hidden secrets.

The earliest form of remote sensing – using survey tools at the surface to map archaeological sites – was done with compasses and chains. It was this approach taken by Ephraim Squier and Edwin Davis when they published Ancient Monuments of the Mississippi Valley in 1848. Their detailed maps of Ohio’s prehistoric mounds and earthworks document hundreds of complex earthen designs written across the landscape. 

Most of these earthworks have been obliterated by time and human development. But through the use of 21^st century remote sensing techniques, known as geophysics, Burks is rediscovering these ancient monuments. In fact, he’s uncovered some that had already been erased from the land by the time Squier and Davis began their work. 

“The ‘aha’ moment came while I was working at the Hopewell Mound Group in 2001, and our instruments detected an earthwork beneath the surface which had never been known before. I realized it was possible to find new discoveries even at sites that were very well known and studied.” 

A few years ago he was surveying an area in Ross County where Squier and Davis had mapped two small circles; Burks found 11. He’s made similar discoveries at several sites. The most surprising may be what has come to be known as the Moorehead Circle at Fort Ancient.  

Geophysical survey involves the use of several kinds of technologies that enable the archaeologist to see beneath the surface of the earth without ever picking up a shovel. The magnetometer, for instance, detects differences in the earth’s magnetic field that are often the result of human activity. Burned dirt is permanently magnetized, so cooking pits show up clearly against the uniformity of the surrounding subsoil.

Ground penetrating radar transmits electromagnetic waves into the earth, which bounce back when they encounter something. This is useful in detecting gravel, stone, and dense clay, used by humans as building materials. The resulting image that is created is a block of data that can be peeled away layer by layer, much like a CT scan.

The electrical resistance meter is another geophysical tool often employed today. It injects electricity into the ground then measures the conductivity of the earth, looking for differences that indicate the existence of subsurface features.

Using all of these tools together often yields the best survey results. The accuracy of the technology allows us to see the original footprint of earthworks, including those that are completely invisible on the surface.

Having these tools at his disposal, Burks realized he could use them to identify and preserve more of Ohio’s ancient earthworks. It was with this goal in mind that he and Bruce Lombardo, interpretative ranger at the Hopewell Culture National Park, founded Heartland Earthworks Conservancy in 2010. 

 

Established as a non-profit for the purpose of identifying and preserving native earthworks, HEC is actively working to identify and nominate sites to the National Register of Historic Places. They are also committed to educating the public about the importance of the sites and the need to protect them. 

Dr. Burks and Mr. Lombardo will be speaking at a public lecture on November 3^rd at The Ohio State University Newark campus. Beginning at 2 p.m. Mr. Lombardo will speak on “Geometric Earthwork Complexes of the Hopewell Culture” and at 2:45 Dr. Burks will present “What’s New with Ohio’s Earthworks: an Update on Geophysical Surveys in Ohio”. 

The free lectures will be held in the Christine Warner Student Center and Library located at 1179 University Drive, Newark, Ohio.