A fluxgate magnetometer sounds like something that could send you back through time, but really it measures the magnetic properties of soil. This technology has been used on the Shriver Circle, an ancient earthwork in Ohio that is now invisible from ground-level.
Earthworks generally are quite large, and building one involved the rearrangement of large amounts of soil. Wherever soil has been disturbed, the baseline magnetic field is disrupted, and the magnetometer can detect these anomalies. The magnetic “signature” of earthworks usually is highly visible and distinctive.
A case in point is the Shriver Circle, one of the largest circular enclosures ever built in the Ohio Valley. It was mapped by Smithsonian surveyors and was known to be located about 2.5 miles north of Chillicothe. But decades of farming and other development had largely obliterated it from the landscape.
Story: Bradlet T. Lepper, The Columbus Dispatch | Photo: Jarrod Burks