The Grand Canyon of the Colorado River cuts more than one mile into the earth’s crust and two billion years into earth’s past. The Canyon reveals one of the oldest and most time-complete geological records. From metamorphosed deposits of Archean sand, silt, mud, and volcanic ash at the River’s surface to mid-Permian limestone capping the highest Canyon rim, its layered walls delineate the repeated advance and retreat of tropical seas, the spread of non-marine swamps and river deltas, and the windblown advance of great sand dunes. But despite the age of its rocks, the Grand Canyon itself is relatively young. When the Gulf of California opened roughly six million years ago, the River’s base dropped, causing rapid headward erosion. Most of the Canyon was downcut in just the past two million years.The Grand Canyon Suite presents three views from Toroweap, situated at roughly 4000 feet in elevation, within the Canyon on the Esplanade – a broad shelf of Supai sandstone that is oxidized bright red. Above the Esplanade rise Permian layers of shale, sandstone, and limestone. Three thousand nearly vertical feet below the Esplanade, at the bottom of the Inner Gorge, flows the Colorado River.

The Colorado Plateau - A Geologic History, Donald L. Baars, University of New Mexico Press, 1983.

Geology of the National Parks, Ann G. Harris, Esther Tuttle, and Sherwood Tuttle, Kendall/Hunt Publishing, 1997.