Locating Sites

Depending on the conditions and the vegetation cover, different methods are used to locate sites.

Surface Survey

Surface or "pedestrian" survey is the most common way to find sites in plowed fields. Artifacts are exposed by plowing, and are visible on the surface. Crews, often made up of volunteers, line up and sweep across fields looking for artifacts. Surface survey works best where there is little vegetation covering the ground, such as in the spring.

Many sites are also found this way by farmers who find artifacts on their fields. When they keep track of where things were found, and tell an archaeologist about the finds, they're making an important contribution to archaeology.

Volunteers participate in a field survey to document sites.
A local resident with several of the projectile points he has found on his land. He has shared the information with archaeologists and reported the sites.

Shovel Testing

In grassy or wooded areas, sites can be found by digging small holes (roughly 50 cm diameter) at regular intervals (usually 10-15 meters apart). The soil is screened to look for artifacts. Each hole is mapped, and any artifacts are mapped by hole and bagged separately. Because this digging destroys a portion of the site, it should be supervised by trained archaeologists who have a good reason for investigating an area.

Recording the artifact finds on a topographic map for the permanent record.
Area middle-schoolers help shovel test a city park to learn what might be under the ground. This information will be used to help the community plan future development in the parks. By knowing which areas contain sensitive archaeological materials, the city planners can design activities and construction that will not disturb the cultural resources.

Examining Creek Banks

Sites may also be found by examining eroding stream banks. These sites have often been buried by flood deposits that have preserved the archaeological material. Many times these sites form a layer cake representing a series of occupations in the same area. The site's stratigraphy can then be recorded from the eroded bank.

Artifacts 1500 years old were found eroding from this streambank cut. They were found in the dark soil horizon visible below the string line.
Two layers of prehistoric shell middens are being exposed by erosion along the banks of the Mississippi River near Prairie du Chien. Testing at this site showed that the bottom layer was 2000 years old.


Accidental Discoveries

Sometimes sites or artifacts are discovered by accident, as when a construction project cuts through a previously unknown site. Some cave art has been found by explorers examining the caves and observing art on the wall.

Indirect Methods

New technologies are making available a wide range of remote sensing techniques. Archaeologists have found sites through examination of air photos, various kinds of radar, including ground penetrating radar, and other indirect methods. Remote sensing techniques work best on sites that have features such as walls or deep pits that are distinctly different from the surrounding soil. Radar or pulses of electricity are systematically sent into the ground. Distinct features will provide a different reading from that of the surrounding soil. These techniques have not had as much application in the Midwest as in other parts of the world such as the southwestern United States or the Middle East, where archaeological features such as buried walls provide more readily identifiable patterns.

A geomorphologist works with archaeologists to conduct a "resistivity" survey of a site before excavation. The archaeologists can then compare the results to those obtained during the excavation, and can learn how different archaeological features show up on the resistivity survey. This will allow for better interpretation of remote sensing results in the future.