Circle in progress
This forming fairy circle illustrates how these barren spots arise naturally. In this circle, weathering is still in progress, so a few hardy plants survive in the barren spot. But the patterns of water flow and weathering will likely spell doom for these interlopers; the conditions favor the deeper-rooted grasses at the edges. Water has trouble penetrating the barren crust within the circle, so plants that take root there will struggle to survive. Instead, the water rolls over the crust, draining toward the plants at the edges of the circles. With time, the result is larger, hardier plants surrounding the fairy circle and bare ground inside.
