This area, known as both Tuweep
and Toroweap, is on the northwest rim of the Grand Canyon in the remote
Arizona Strip. The Kanab Plateau rises sharply to the east, while the
volcanic
Pine/Uinkaret Mountains form the western margin of Toroweap Valley.
The view from Toroweap Overlook, 3000 vertical feet above the Colorado
River, is breathtaking; the sheer drop, dramatic! Equally impressive
are the volcanic features, cinder cones and lava flows, which make this
viewpoint unique in Grand Canyon National Park. Renowned Lava Falls
Rapid is just downriver and can easily be seen and heard from the
overlook.
Toroweap, a Paiute term meaning "dry or barren valley," refers to many
local features, including the geologic formation and fault, the valley,
and the overlook.
Tuweep came into use to describe the local white
settlement and later the park district. Tuweep in Paiute refers to "the
earth," but this place name may be derived from a longer Paiute word
meaning "long valley."
A visit to this area can be challenging, but rewarding. Since the
National Park Service manages the area for its primitive values,
improvements and services are minimal.
GEOLOGY
The geologic history of the Tuweep area is similar to the rest of Grand
Canyon, but includes a more recent chapter of volcanism. The Toroweap
Fault underlies the valley, crosses the Colorado River, and continues
south up Prospect Canyon. Volcanic activity began along this fault
around seven million years ago. Over time lava issued from more than 60
vents.
Beginning about 1.2 million years ago some flowed into Toroweap
Valley, forming the flat-bottomed valley we see today. Vulcans Throne,
Mount Trumbull and the Uinkaret Mountains are other features that are
the result of volcanic activity.
More than a dozen times, lava spilled over the canyon rim, damming the
Colorado River. Remnants of these flows and dams are easily visible
just west of the overlook.
Sediments clinging to the canyon walls high
above the river indicate the formation of large lakes. The river eroded
the lava dams and continued its downward cutting. It is now 50 feet (15
m) deeper than the base of the dams.
Despite its name, Lava Falls Rapid
was formed from debris washed down Prospect Canyon, not from remains of
the lava flows.
It is less than one mile across the canyon to the Hualapai Indian
Reservation on the South Rim, making this one of the narrowest and
deepest segments of the inner canyon. The colorful redrock of the
Hermit Shale and Supai sandstones to the east contrasts with the black,
basaltic lava flows to the west, making Toroweap Overlook a memorable,
and often-photographed, viewpoint in Grand Canyon.
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