Archeology Toolbox: Geophysics

Big Stock Photos

Big Stock Photos

Archeologists are known for digging in soil to find forgotten or lost artifacts, buildings, cities, and even human remains. But a shovel is only one of the tools archeologists use, and it is not always the best one.

Sometimes archeologists use tools and techniques that allow them to “see” underground without digging.

This past Sunday, Steven DeVore, a geophysicist for the National Park Service, spoke at a Sioux Falls-chapter of the South Dakota Archaeological Society program at Augustana College. Since one of my characters in the novel I’m writing is an archeologist who uses various geophysical techniques at a South Dakota dig site, I attended the program to learn more.

I learned there are about five or six different techniques that can be used, and archeologists might use just one or a combination of all of them, depending on the ground conditions and the goal of the surveying. Some of the techniques use probes that insert electricity or microwave energy into the ground and can get readings from various depths. Then the results can be compared to each other and aerial photos or old maps to help identify things like structures, hearths, pits, fence lines, trails, utility pipes, and graves.

The fascinating thing is how the archeologists can understand the mapped results of the tests. DeVore showed slides of a number of sites where geophysical techniques were used. I saw lots of blobs and dots, but I could also see straight lines which are usually man-made. Other times, I could see circles with a dark spot in the center. Those were probably outlines of Native American earth lodges with the remains of a central hearth.

DeVore mentioned that the equipment they use is expensive to buy, but with them archeologists can map out large areas of land in very little time. Plus, geophysics can give a big-picture view and understanding to an entire site, where digging can give great detail in very small areas. Another advantage to using geophysics is that whatever is buried doesn’t have to be exposed by digging, which in turn, “destroys” the site. It’s also very useful in finding graves without disturbing the human remains.

I learned two specific details I hadn’t known before. The first one is a common-sense thing. In a resistance survey, the archeologist sends electricity through the ground. They can’t do this one if the ground is too wet! Common-sense, but I hadn’t thought about it, and I certainly don’t want my character electrocuting himself or anyone else!

The other cool thing I learned is that archeologists sometimes use remote controlled model airplanes or drones, outfitted with cameras, to take aerial photos. Doesn’t that sound like fun? I may have to add that detail to my story!


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