A fairy ring, also known as a fairy circle, elf circle, elf ring or pixie ring, is a naturally occurring ring or arc of mushrooms.  These are created through the growth of the fungus growing outward from a central point.  The fungus grows outward expanding the circle and dies off from the nutrient exhausted central area resulting in the creation of a ring.

h4. See also

"Wikipedia - Fairy Ring":[https://en.wikipedia.org/wiki/Fairy_ring]
fairy ring