It may seem that Philippe De Smedt is mowing the grass when he rides his quad around Stonehenge, but, really, he is investigating what lies beneath it. This “archeologist without a spade” uses electromagnetic induction (EMI) tools to investigate layers of soil without disturbing natural landscapes — or heritage sites like Stonehenge.
“Electromagnetic induction survey is a sensing technique that allows you to look at both the electrical and magnetic variations of the soil,” De Smedt explains at TEDxGhent. “The electrical properties tell you something about the composition of soil — for example, organic matter or clay content — while the magnetic variations tell you about the mineralogy of the soil … and human actions — for example if you burn something, this would leave a magnetic trace.”
In 2013, De Smedt and colleagues used EMI in his home country of Belgian to investigate the site of the 12th-century Boudelo Abbey outside of Ghent. Both the electric and magnetic variations in soil detected suggested former human architecture, De Smedt says, and after an excavation, remains of the abbey were found — complete with brick foundations.
But at some sites, like at Stonehenge, digging is not ideal. Which is why De Smedt rides his quad around the landmark, working with the Stonehenge Hidden Landscapes Project, an archaeological survey that uses only non-invasive technologies (like EMI) to uncover masses of information about the area, including “previously unknown ritual monuments …. [and] dozens of burial mounds,” reports the University of Birmingham.
Says De Smedt: “Through combining soil science and archaeology, with electromagnetic induction survey we can scan our way into the soil starting from the present all the way down — offering a new perspective on our buried past.”
To learn more, watch his entire talk below: