Gorge and Platform
The rugged, V-shaped Innter 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 older
Precambrian rocks are first exposed. These rocks,
which include the dark colored Vishnu Shist and
pink Zoroaster Granite, are the oldest rocks
exposed at the Grand Canyon. West of here (down-
stream), the Inner Gorge achieves a depth of over
1200 feet (366m).
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 (148km) in an east-
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 Bright Angel Shale.
The Inner Gorge is a canyon within
a canyon. Dwarfed by the mile-deep
vastness of Grand Canyon, the
1000-foot deep Inner Gorge would,
in turn, dwarf most other canyons
in the world.