East Tennessee State University geoscientist Dr. Eileen Ernenwein walks the Cane Notch archaeological site with her Bartington Grad 601-2 Magnetic Gradiometer, which includes two magnetometers. Photo courtesy Nolpix Media
By Jeff Keeling
(This is the sixth in a series on the Cane Notch archaeological site and subsequent studies. The site is located in Washington County in 12 acres of bottomland along the Nolichucky River. Its first field school and dig occurred in December 2015 and January 2016. What is anticipated to be years of research is just commencing. This article highlights role of geoscientific technology – particularly magnetometry and ground penetrating radar – in the project.)
A data readout from the magnetometer showing the location of three houses in the Cane Notch village. Courtesy Eileen Ernenwein.
When the time came for archaeologists to map out where they would dig at the Cane Notch site, ETSU professor Dr. Jay Franklin wanted to take advantage of the best science has to offer. Fortunately for Franklin, he didn’t have to look far.
Franklin turned to Dr. Eileen Ernenwein, a colleague who teaches in ETSU’s Department of Geosciences. People the world over turn to Ernenwein for her knowledge and skill in applying magnetometry and ground penetrating radar to archaeological projects.
The availability of Ernenwein, whose interdisciplinary PhD work at the University of Arkansas combined archaeology and geosciences, changed the game at the 12-acre site along the banks of the Nolichucky River.
“Without the technology that I use, you’re going to do one of two things when you discover a site,” Ernenwein said last week from her office at ETSU’s Ross Hall. “You could decide simply based on what you’ve found on the surface, or you could dig random little pits with a shovel – shovel test pits is what we call them.”
Data from ground penetrating radar with accompanying explanatory text.
Because Cane Notch is a plowed field with quite a bit of surface material – and any preserved material beneath the “plow zone” – the standard approach would have involved walking the field and mapping out areas where there were concentrations of material.
Instead, Ernenwein was happy to apply her methods close to home. She started with her own magnetometer device, which includes two actual magnetometers carried out from the user’s shoulders. Once she realized the size and potential of the site, she borrowed a walk-behind machine with five magnetometers on it.
The magnetometry data helped Ernenwein and company to pinpoint in two dimensions where houses were likely to be in the village at Cane Notch.
“Humans, what we do on the landscape is we push dirt around, and we rearrange everything and we set fire to a lot of things,” Ernenwein said. “Both those things leave a signature in the magnetic property of the soil.”
Those “signatures” helped the Cane Notch team make its decisions on the dig areas for this winter’s field school, though the magnetometry and its cousin, ground penetrating radar, have provided a much greater depth of information than just suggesting where to dig.
Ground penetrating radar data showing the same 20-meter-square area at three separate depths, with a house near the bottom right corner. Courtesy Eileen Ernenwein.
Ground penetrating radar – the MRI to magnetometry’s x-ray
Magnetometry can be completed faster than ground penetrating radar (GPR), Ernenwein said. But whereas magnetometry reveals disturbances just in two-dimensional format – “sort of like an x-ray,” Ernenwein said – GPR, “is really powerful because it’s three-dimensional.”
GPR sends radio waves into the ground and measures the magnitude of reflections from buried archaeological features, such as house floors. The waves also reflect off of natural features under the surface – water tables, natural strata in rock, flood deposits and other soil layers.
The original data are collected as reflection profiles, which are often stacked together and “sliced” horizontally to make slice maps. Parts of one such map are shown on page 1, and reveal different features of a house found within a 20-by-20-meter pit, at depths of 37-45 centimeters, 45-52 centimeters and 52-60 centimeters.
“GPR is much slower, so we tend to use the magnetometer more broadly, simply because we can,” Ernenwein said. “But there are lots of house floors that don’t even exist in the magnetometry that the GPR can see, so what that means is there are houses that weren’t burned.”
Ernenwein has some GPR data on those houses, but is still working on processing it. “GPR is an advantage because it can see those houses that are not burned, and tell you how deep they are.”
Eileen Ernenwein, left, with graduate student Cayla Cannon at Cane Notch.
Photo courtesy Nolpix Media.
Providing context after the dig
With artifacts being studied after the winter dig, Ernenwein can take her own data and extrapolate in a way that helps the overall project. This makes the geoscience element of the project about far more than just finding where to dig.
“We have another half dozen or so houses, probably the exact same type, same depth, same size and shape.
A gorget found at Cane Notch.
Photo courtesy Sean Kelly
Once you dig up one anomaly, you can say,‘this is probably true of all the other ones that are the same’ (with respect to the geoscience data).
“The two together, the archaeological excavations and the geophysics, is the synergy to the final thing. Even though we don’t have every single artifact, we have a village plan map now.”
Ernenwein’s been on televised documentaries involving sites at Petra in Jordan and Machu Picchu in Peru, and worked on five continents because of how specialized her skill set is. Yet she’s looking forward enthusiastically to continued work at Cane Notch.
“I would say the site here is a world class site, because it’s got the potential to tell us about what’s going on in what is a black hole in archaeology for this area in this time period (1400s to early 1600s),” Ernenwein said. “I’ve got a lot more to do there, and I’m really excited about it.”
