A crop circle or crop formation is a pattern created by flattening a crop, usually a cereal. Crop circles have been described as all falling “within the range of the sort of thing done in hoaxes” by Taner Edis, professor of physics at Truman State University. Although obscure natural causes or alien origins of crop circles are suggested by fringe theorists, there is no scientific evidence for such explanations, and human causes are consistent for all crop circles. A commentary in The Guardian noted that “[i]t is still open to dispute whether some are caused by natural phenomena or all created by human hand.”
The number of crop circles has substantially increased from the 1970s to current times. There has been little scientific study of them. Circles in the United Kingdom are not spread randomly across the landscape but appear near roads, areas of medium to dense population and cultural heritage monuments, such as Stonehenge or Avebury. In 1991, two hoaxers, Bower and Chorley, made disputed claims to have created many circles throughout England after one of their circles was described by a circle investigator as impossible to be made by human hand.
Formations are usually created overnight, although some are reported to have appeared during the day. In contrast to crop circles or crop formations, archaeological remains can cause cropmarks in the fields in the shapes of circles and squares, but they do not appear overnight, and they are always in the same places every year.