Slices of the Past

When archaeologists suspect that an important find lies buried beneath the earth, they reach for their shovels, hoping to hit some clue of a buried city or important burial site; sometimes they even call in backhoes and trenching machines. But now, a University of Denver anthropology professor has come up with a ground-breaking alternative that may turn traditional archaeology upside down.

Lawrence B. Conyers and his colleague, Dean Goodman, have adapted a technology known as "ground penetrating radar" to pioneer a new era of "non-invasive" archaeology. By pumping radar pulses into the ground and creating images of the radar reflections on a computer, they can obtain detailed pictures of a potentially important site before the first shovel of dirt is lifted. Then, the researchers can decide whether to dig--and where to dig--while doing the least damage to important artifacts.

"Archaeologists tend to be very low-tech people," Conyers says. "They have a tendency to be more comfortable digging in the dirt than working with computers. But this radar can help to locate sites and objects that you can't see on the surface. It can help us save sites that could be destroyed with traditional excavation techniques."

Ground-penetrating radar has been used for decades for everything from locating buried family treasures hidden from the Nazis to finding the engines of the ValuJet crashed in the Everglades. Conyers has used the technology, and the software written by Goodman, to: map a Mayan village buried under 15 feet of volcanic ash in Ceren, El Salvador; create images of a Mayan ceremonial center buried in a sugar cane field in Coatzalmaguapa, Guatemala; locate 1,700 year old kiln sites and a large village buried in wind-blown sand between two ceremonial pyramids in Peru; and disclose details of ancient burial sites in Japan

Closer to his home base in Denver, Conyers has employed the new technique to reveal the history of the ancient Anasazi people of the American West. Because of their sacred nature, the issue of whether to disturb these sites is crucial to their descendants.

Near Bluff, Utah, Conyers and his colleagues pinpointed a subterranean kiva, used in ceremonial rites by the Anasazi people. "Even though the people that constructed this kiva have been dead for more than 900 years, these sites are still very sacred," says Conyers. "So radar was a method that we could use to first image what was there and then adjust out excavation procedures to dig only in certain spots to test our scientific ideas."

Nearby, Conyers and his colleagues also found a field littered with sherds of pottery that dated to 1100 AD. By searching the area with radar, they located a village of Anasazi "pit houses. "Archaeologists usually use this type of evidence to locate sites, but of course have no idea where they are under the ground," says Conyers. "The typical way of finding the buried houses of this sort is to randomly dig test pits or drill auger holes--or even worse use backhoe trenchers that really destroy the site."

Mapping these sites using traditional excavation methods would have cost millions of dollars and taken many years. Conyers, using ground-penetrating radar and 3-D imaging software developed by Goodman, can map a site for a fraction of the cost in as little as three weeks. Many buried sites would not have been discovered without the ground-penetrating radar technology and would be potentially at risk from construction and erosion.

The next step for Conyers is the creation of moving 3-D images that will allow people to take video "tours" of archaeological sites that have not been unearthed. Maybe those people who Conyers refers to as "dirt archaeologists" will soon retire their shovels.

Related Reading:

"Ground-penetrating Radar: An Introduction for Archaeologists," by Lawrence B. Conyers and Dean Goodman, Altamira Press, Walnut Creek, California, 1997.