The formation of the Grand Canyon of the Yellowstone

At Artist Point, the Grand Canyon of the Yellowstone shows its spectacular natural painting of pastel-colored canyon walls and the impressive Lower Fall waterfall.
The Yellowstone River originates in the Absaroka Range in southeastern Yellowstone, flows through Yellowstone Lake and drains northward into the 20 miles (32 km) long Grand Canyon of the Yellowstone. The steep walls of this narrow canyon are cut into fairly soft ryolithic lava and tuff that is chemically weathered by hot ground water. Numerous hot springs in the canyon area still alter the color of the deep grayish ryolithe into the famous yellow, brown and red hues that give Yellowstone its name. At Lower Falls, an average of 37400 gallons (141800 l) drop per second 308 feet (93 m) into the canyon over an unaltered edge of resistant gray ryolithe lava. The explosive past of this supervolcano changed the canyon’s appearance during the last 484000 years by repeated filling by ash and volcanic debris and re-cutting by the flowing water. During the ice ages the drainage system was repeatedly blocked by ice caps, creating a long lake in the canyon. About 12000 years ago the ice melted and since the river deepened the canyon into today’s V-shape by removing even the glacial sedimentary layers.
The evening sun casts an enchanting light on the pastel-colored volcanic rocks of the Grand Canyon of the Yellowstone and Lower Fall.