View of the Inner Gorge of the Grand Canyon

Peering down into the Grand Canyon, you can barely see the Colorado River cutting its way through the Inner Gorge made of what is called the Vishnu Basement Rocks or Granite Gorge, named by the explorer John Wesley Powell. These rocks date from the Precambrian and early Proterozoic ages of the Earth's history. They are made up of very old granite and pegmatite metamorphic rocks; primarily Vishnu schist, Brahma schist, Rama schist, Orthoamphibole-bearing gneiss and Elves Chasm pluton or quartz diorite.