Existing comment:
Gorge and Platform:
The rugged, V-shaped Inner Gorge rises darkly from the Colorado River. The broad shelf above it is the Tonto Platform, which spreads like a soft green blanket across both sides of the canyon.
The Inner Gorge begins here, where other Pre-Cambrian rocks are first exposed. These rocks, which include the dark-colored Vishnu Schist and pink Zoroaster Granite, are the oldest rocks exposed at Grand Canyon. West of here (downstream), the Inner Gorge achieves a depth of over 1200 feet.
The Tonto Platform is formed where exposures of the relatively soft, easily eroded Bright Angel Shale retreat to the base of the Redwall cliff. It is one of the few expanses of relatively flat terrain in the canyon. The Tonto Trail meanders across this platform for 92 miles in an east-west direction.
The Tonto Platform is sparsely vegetated with blackbrush, sage, and desert scrub, and owes its color partly to vegetation, and partly to the pale green color of the Bring Angel Shale. |