Marron (1982) reported the first map of the areal distribution of hollows mantled with colluvium in an area underlain by graywacke and shale in Redwood National Park near Orick, California. By inspection of a dense network of logging road-cuts, she found about 76 in 3.8 km2, which is close to the density of 22/km2 reported as a minimum by Dietrich and Dunne (1978)for an area in central coastal Oregon.