How to look into soil without digging into it

2014-07-30_(05.56h)__D300s__0018_f.jpg

TEDxGhent’s Philippe De Smedt tows electromagnetic induction tools to reveal hidden objects underground near Stonehenge (Photo: Ludwig Boltzmann Institute for Archaeological Prospection and Virtual Archaeology)

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.

The hidden abbey is revealed by soil variation detected by the  electromagnetic induction survey (Photo: Philippe De Smedt)

The hidden abbey is revealed by soil variation detected by the electromagnetic induction survey (Photo: Philippe De Smedt)

The magnetic variations in soil suggest the former presence of buildings (Photo: Philippe De Smedt)

The magnetic variations in soil suggest the former presence of buildings (Photo: Philippe De Smedt)

An excavation shows evidence of the abbey and a ditch system (Photo: Philippe De Smedt)

An excavation shows evidence of the abbey and a ditch system (Photo: Philippe De Smedt)

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:

Leave a Reply

Your email address and name are required fields marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>