This is a photo of a scratch circle taken by David Marvin:
However, the lack of snow and ice on the beaches has allowed unique features called scratch circles, or Scharrkreise, to form on the sand. Etched by windblown, dried dune grasses, the circles take shape when the wind causes a bent stalk of grass to pivot around on its axis, scratching out an arc or full circle in the sand.
This is delightful, a perfect geometric form made by nature in a seemingly random way. (via @BadAstronomer)