The little 'Grand Canyon of the Toutle River' is a one-fortieth scale model of the real Grand Canyon. To claim that this little canyon is a scale model of the Grand Canyon is entirely misleading. The Grand Canyon is made of 5000 feet of multiple lithologies. The layers there are limestone, dolomite, sand, shale each of which vary in hardness and erodability. Each layer has different fossils in it.
Some layers have footprints of vertebrates on their surfaces.
There are erosional channels in the Esplanade and collapsed caves in the Redwall limestone. Some of the collapsed caves contain pieces of Chinle formation. This is the top most horizon in the Grand Canyon area but is only found in two places at two small hills on the south side of the canyon. The entire area has been denuded of Chinle. The remnants found in Redwall Limestone cave breccia throughout the region is evidence of a lot of erosion off the top of the canyon.