The colors in the Grand Canyon of the Yellowstone derive both from minerals and from living organisms. There are infinite shadings of yellow and orange, and also reds and pinks, off-whites, browns, greens, and black. Most of these colors result from the weathering of the rocks and from the upward passage of hot water and steam. Rainwater and the oxygen in the air break down the rhyolite that is the predominant rock of the canyon. At the same time, hot water and steam react with minerals in these rocks. Both processes convert some of the iron and other metals (such as manganese) in the rock to oxides or hydrous oxides. These new minerals most often are the common brick red of rust, but some are black, and some hydrated iron oxides are bright yellow. Some of the black shadings are probably magnetite, a jet black iron oxide, while some of the black is lichen growing on the rocks. In moist places, such as near the hot springs at the base of the canyon, algae and moss grow and lend a lush green color to the rock surfaces.
There may also be colorful microorganisms present around the few hot springs, but the living ones make a modest contribution to the riot of color in the canyon. Dead microorganisms leave no residual color. Although you might think the Yellowstone River got its name from the yellow of this canyon, historians believe that the Native American name was for the yellow sandstone cliffs lining the river in several stretches for hundreds of miles downriver from Billings to the river’s mouth. The Hidatsa (or Min-netaree) tribe called it “Mi Tsi A-Da-Zi.” French fur trappers translated that to “Roche Jaune” and English speakers to “Yellowstone.” The early Native Americans who named the river probably never saw this canyon. j From the parking area, you can also reach Crystal Falls on Cascade Creek. Walk back along the side road, crossing over a small creek, to the North Rim Trail. Then walk an easy 200 yards Few visitors to Canyon see Crystal Falls at close range.