A peculiar method of surface decay by which granite or granite gneisses are left with a corrugated or fluted surface. In a large subangular fragment of granite, one side contains a dozen of these little channels, from 1 to 4 in (2.5 to 10.2 cm) deep and from 3 to 10 in (7.6 to 25.4 cm) apart from center to center. These channels run straight down the face of the rock.