How do Archaeologists Find Sites?

Archaeologists have many tools that help them locate archaeological sites. They use old maps and other historical documents to see where people used to live. Archaeologists talk to people who remember where buildings, cemeteries, barns, roads, fences, and graves used to be. They study the land because people often live on high ground near a water source. New research techniques such as GIS (Geographic Information Systems) help them create environmental models that can predict where archaeological sites might be located.

Archaeologists use equipment such as ground penetrating radar (GPR) to find walls, foundations, and graves beneath the ground surface. GPR uses radio waves to locate anomalies in the soil. Variations in soil texture and chemistry and variations in materials (for example, sand versus clay or soil versus brick or stone) reflect the radio waves differently. The operator can see these variations on the machine’s screen as the equipment passes over the ground. Anomalies are flagged for mapping and further investigation. The GPR collects information along narrow bands or slices. The GPR analyst uses computer software to compile the slices and interpret the depth and extent of the anomalies, providing additional information to guide further archaeological research.

Archaeologists use metal detectors to find nails, buttons, and other metal artifacts that may be associated with former buildings, military encampments, battlefields, and any other sites where metal artifacts are expected. The metal detector emits electromagnetic waves that reflect off metal artifacts. Iron and steel reflect the waves differently than other metals such as brass, copper, silver, and gold. The metal detector emits a sound to the operator when it passes over a metal object. Archaeologists must dig at each locale where the metal detector signals an artifact to determine what object is present. Metal detecting was an important part of the investigations at Monroe’s Crossroads conducted by the National Park Service. Go to the History page to learn more. Remember, it is illegal to metal detect on federal property without a permit.

Underwater archaeologists use magnetometry (electromagnetic signals) and side-scan sonar (sound) to find shipwrecks and other submerged resources. Like GPR, the magnetometer or sonar signals reflect differently as they encounter variations in materials or bottom of the sea, lake, or river under investigation. The operator can see these variations on a computer screen that compiles the information generated by the magnetometer or sonar. Locations or anomalies are mapped precisely so archaeologists can return to the location. Divers must investigate each anomaly to see what is present.

All of these techniques produce clues to where sites may be located. Archaeologists must visit potential locations and conduct field investigations to know for certain whether an important site is present.

At Fort Bragg archaeologists use a systematic survey method to find sites. They inspect areas by walking straight lines called transects. They examine the ground surface and dig small holes called shovel test pits at regular intervals along each transect, usually every 100 feet. Investigators record the location where they dig each shovel test, the kinds of soils they see, local vegetation, nearby water sources, and whether they find artifacts or not. Areas that contain artifacts or cultural features are given archaeological site numbers.

All archaeological sites found in the United States are given a site number. Site numbers are made up of three parts that identify where they are found — two numbers that represent the state, two letters that represent a county in that state; and a last set of numbers determined by the number of sites already found in that county. Consider the site number 31HK1641. The 31 tells us the site is in North Carolina, the 31st state alphabetically. The HK stands for Hoke County. The final number tells us this is the 1,641st site found in Hoke County. In North Carolina, site numbers are assigned by the Office of State Archaeology. As of 2011, there are nearly 5,700 archaeological sites at Fort Bragg.