Buddhist monk meditating in a crop formation at Cheesefoot Head in Hampshire, England. Crop formations or crop circles are patterns of flattened plants in crops such as wheat or barley. They started appearing frequently in the mid-1980s in south-west England. Their cause is unknown. Many theories exist, ranging from science-based physical explanations such as the plasma vortex" theory based on the phenomenon of electrohydro- dynamics (EHD) to suggestions that they are created by extraterrestrial intelligences. Some people believe they are due to an unknown physical or mystical earthly force."