This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
The Grand Canyon is often described by its width and its exposed rock layers, but the Colorado River that cut it is the more interesting half of the story, because the canyon is really a record of a river winning a very slow argument with rising land. The Colorado Plateau, the broad tableland the river crosses through northern Arizona, has been slowly uplifted over millions of years by tectonic forces unrelated to the river itself; as the plateau rose, the Colorado, already established on its course, cut downward to keep pace rather than being pushed aside, carving through nearly two billion years of rock in the process, some of the oldest exposed rock anywhere on the continent. That kind of canyon, called an entrenched or superimposed river, only forms when the uplift is slow enough for the river to keep eroding faster than it is displaced, and the Grand Canyon's own nearly one mile of depth is the visible record of the Colorado managing exactly that balance for roughly five to six million years, a modest span in geological time for a mile of solid rock.