patterned ground

Patterned ground is a geologist’s term of art for the conspicuously symmetrical distribution of stones on the surface of areas subject to intensive frost. The patterns formed can take the shape of circles, polygons, or stripes. Circles and polygons form on relatively flat ground, stripes on sloping ground. The term was coined by A. L. Washburn, a geologist at the University of Washington at Seattle. Several processes of freezing and thawing, saturation and drying out, produce the patterns, and there is a considerable literature on the subject. They are frequent in periglacial regions, that is, areas where a cold climate has contributed to the morphology of the landscape.

Robert Hass