Cleared circles: Anthropogenic or Biogenic? Use of non-invasive geophysical techniques to determine origin

Caldwell, T. G., McDonald, E. V., Bacon, S. N., Cleared circles: Anthropogenic or Biogenic? Use of non-invasive geophysical techniques to determine origin, The Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP), Abstracts with Program, April 10, 2011-April 14, 2011