No one knows what creates the thousands of fairy circles dotting southern Africa, but we now know that after mysteriously springing up, they live for approximately 41 years. Via ScienceNOW:
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Tens of thousands of the formations—bare patches of soil, 2 to 12 meters in diameter—freckle grasslands from southern Angola to northern South Africa, their perimeters often marked by a tall fringe of grass. Locals say they’re the footprints of the gods. Scientists have thrown their hands up in the air. But now Walter Tschinkel, a biologist at Florida State University, has discovered something no one else has.
By comparing photos taken over a 4-year period, he confirmed something other scientists had suspected: The circles were alive—or at least they were dynamic. A number of circles appeared and disappeared over this time period. Extrapolating from the data, Tschinkel calculated that most smaller circles arise and vanish every 24 years, whereas larger circles last up to 75 years.