Cultural Resources & Archeology Research & Projects: February-March, 2009
Magnetic houses? Using the earth's magnetic field to date archeological sites
Archeologists finished their dig of a Cherokee Winter House in early February, just in time for other Park employees to complete a paving project on Newfound Gap Road. The road does not cover the site, but digging close to the road could undermine the stability of the roadbed. During the dig, archeologists did archeomagnetic dating of burned material they found in the Cherokee house hearth. This method allows archeologists to date artifacts more precisely (within 20 years of the actual event) than the carbon dating that’s been the only method available before. It works by comparing how the magnetic particles in material found at the site—say, burned wood—line up with a record of the earth’s magnetic fields in the past. The earth’s magnetic field changes slowly but regularly, and we have a reliable record of when and how it changed. When wood or other material burns, the metallic elements inside it line up with the magnetic field at the time, thereby “recording” the date for archeologists to compare to read later. This lets archeologists look for patterns of movement and production, because they know when ceramics were fired or when people last cooked in a particular house.
Artifacts that archeologists found on their bitter cold dig included not only hearth materials but beads, animal bones (including deer, frogs, and toads), ceramics, and at least three projectile points that will likely turn out, in analysis, to be arrowheads as well.