In a visually striking sequence from "Raiders of the Lost Ark," the first film in the Indiana Jones series, the camera frames a line of diggers in Egypt, silhouetted against the setting sun, whose pick axes and shovels rhythmically rise and fall as centuries of rock and dirt are hacked away to reach a fabled lost city buried beneath the sands.

Roughly a century ago, at such famous excavations as the Tomb of the Pharaoh Tutankhamen, such heavy pick-and-shovel labor would indeed have been the norm of archaeology.

In the movies, often what suffices to find the outline of a hidden entrance to a tomb is to gently brush away a remaining handful of sand that neatly follows the shape of the door.

In the movies, often what suffices to find the outline of a hidden entrance to a tomb is to gently brush away a remaining handful of sand that neatly follows the shape of the door.

Even if there is a germ of truth in the celluloid reality for large-scale, relatively modern man-made features, for archaeologists who study the very small-scale and often deeply buried evidence of a prehistoric past, this just isn't the case.

Rinita Dalan, an NSF-funded archaeologist at Minnesota State University, Moorhead, whose background is in archaeology and geophysics, says that while the days of physical labor of excavation, whether with a shovel or a trowel, are far from at end, the electronics revolution that has touched practically every field of science and most walks of life in the past half-century now allows archaeologists to work smarter, not harder.

These advances harness the science of geophysics to help explore a world often invisible to the naked eye.

Dalan should know whereof she speaks, having come into geophysical archaeology from, as it were, the ground up. She got a start in the field, before turning to academia, with a geotechnical and cultural-resource management consulting firm that employed both archaeologists like her and geophysicists.

"I was trained as an archaeologist but I also helped out on geophysical projects where I started out at the bottom of the ladder," she recalls. "I started out as ‘powder monkey'; I carried the dynamite around. That was exciting for me. I moved up from there to be the person who stuffs dynamite in the hole and wires the blasting caps to the person who oversees the fieldwork to the person who interprets and writes up the data. When the company got out of archaeological work, I stayed on and did geophysics."

But her love of archaeology ultimately prevailed, and she came full circle and started applying this technology to learn about the past.

Obviously, she doesn't shrink from the intellectual challenges of archaeology, but she is also quick to admit that what drew her to the field was the excitement, not all of it cerebral. Among the many exciting places her previous work took her was the "red zone" atop Mount St. Helens, where she helped to site a new visitor's center.

But today, more experienced, and perhaps wiser, she is less likely to seek out the physical challenge and more likely to be interested in developing and refining these sensors that enhance the human senses to detect the presence of magnetic, electrical and chemical signatures in the soil left by human activity.

In collaboration with Bartington Instruments, an English firm that specializes in magnetometers and other specialized electronics, Dalan worked on the development of an electronic sensor that detects variations in soil magnetic properties to infer past human presence.

Bartington Instruments is now marketing a version of the device.

Because the meticulous care required in archaeological excavation is time-consuming, labor-intensive and expensive, methods like Dalan's that allow researchers to identify sites and to focus their efforts on the most promising areas within them can contribute significantly to the amount of information obtained from a given location.

Her technique rests on the assumption that human activities, even hunting and gathering, change the content of magnetic minerals in surface soils and that by examining variation in magnetic susceptibility, which depends on the concentration, composition and size of these magnetic minerals, promising excavation sites can be pinpointed.

Rather than a large-scale disturbance, the sensor requires the boring of a vertical core through the soil to produce a small hole, and then lowering a sensor into it.

"That's one of the advantages of this technology: you learn a lot about a site without having to disturb it," she notes. "Geophysical techniques in general allow us to cover entire sites and get a lot of information in a relatively short time with minimal disturbance."

"That's one of the advantages of this technology: you learn a lot about a site without having to disturb it," she notes. "Geophysical techniques in general allow us to cover entire sites and get a lot of information in a relatively short time with minimal disturbance."

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Several surface geophysical techniques already exist that permit archaeologists to look, in effect, below the surface and locate underground structures and features, such as the remains of buildings, hearths and burial pits. They are very useful for work aimed at specific periods of geologic time when human impacts on the landscape were large and tend to have left substantial traces.

But for most of prehistory, the physical markers of human presence consist of stone tools and animal bones, that are too small to produce remotely sensed signatures.

Dalan's sensor, on the other hand, provides a tool that can work at a fine level of detail, even far below the surface, and contrast against the geophysical background "noise" of a specific location.

"Geophysical remote-sensing techniques are not a direct substitute for physical excavation," Dalan notes. "Excavation gives you tons of information about a small space. With geophysics, you have the coverage and it can give you a much broader picture about a settlement plan. They work in combination and there is certainly less need for excavation if you do geophysics."

While there are still advances to make in interpretation of geophysical data, she adds, as a technique in the archaeologists' toolbox, "I think geophysics is moving forward by leaps and bounds, finally."

Dalan added that since its initial development, the sensing device has been continually improved, in part through her work with the undergraduate students in her archaeology courses who helped test the prototypes.

She plans this summer to do more development work with the technique of "down-hole geophysical technology." Part of these efforts will involve students and instructors that participate in an annual training course in geophysics offered by the National Park Service. This training course, at which Dalan annually volunteers, provides the public with an opportunity to experience this technology firsthand.

"We're going to do some comparison tests with multiple sensors and see what happens," she said.

She noted that NSF's funding of the work allowed her not only to focus on refining the technique, but also to use the newly developing technology to help teach.