Effects of prescribed fire on archaeological artifacts

collecting fire effects data
Research team collecting data during burn experiments.

The National Park Service has completed a research study that analyzed the effects of prescribed fire in their Midwest Region on archaeological artifacts. Researchers placed artifacts in areas to be burned in six park units in South Dakota, Arkansas, Iowa, Minnesota, and Kansas. Using thermocouples and data loggers, they measured the temperature every five seconds as fire moved through the plots containing the artifacts, while human Fire Effects Monitors recorded the type of fire spread (head, backing, or flanking) and the flame length, flame depth, and rate of spread.

Their major findings include:

  • The majority of artifacts subjected to fire during the six prescribed burns did not experience any significant impacts.
  • The adherence of combustive residue to artifacts was the most frequent impact observed on artifacts. Between 48 and 75 percent of each assemblage exhibited low to high amounts of combustive residue. With effort, combustive residue was removed from the more durable classes of artifacts, such as glass and stone.
  • Artifacts after grass fire
    Experimental artifacts in situ following a prescribed burn at Effigy Mounds National Monument.
  • Cleaning and weathering experiments on archeological materials demonstrated that most impacts to surface artifacts were of a non-permanent nature and could be removed with light to moderate cleaning.
  • Serious impacts to artifacts such as scorching, fracturing, or melting were observed in only 5-10 percent of the assemblages.
  • The incidence of serious or significant impacts to the artifact assemblages was a combination of fuel type/fuel load and artifact material. Artifacts such as bone, shell, leather, wood, and lead exhibited more frequent serious impacts when compared to materials such as ceramic, stone, metal, and glass.
  • Experimental prescribed burns demonstrated a significant amount of variability in fire conditions resulting from non-uniform fuel types and loads, particularly in wooded environments.

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Author: Bill Gabbert

After working full time in wildland fire for 33 years, he continues to learn, and strives to be a Student of Fire.