Grand Canyon Facts
The Grand Canyon of the Colorado is a
canyon composed of many canyons.
It is a composite of thousands, of tens of
thousands, of gorges...
In the grand Canyon there are thousands
of gorges like that below Niagara Falls,
and there are a thousand Yosemites. Yet
all these canyons combine to form one
grand canyon, the most sublime spectacle
on the earth.
John Wesley Powell, 1895
Grand Canyon measures 277 miles
(466km) from Lees Ferry on the east
to the Grand Wash Cliffs on the west.
The canyon is bounded by two great
dams and the lakes they contain:
Glen Canyon Dam and Lake Powell
upriver, and Hoover Dam and Lake
Depth: An average of 35 feet (11m).
Width: Varies from 76 feet (23m) to
to 300 feet (90m).
Volume: Usually between 1,000 to
30,000 cubic feet per second
(28 to 850 cubic meters
Upstream, Glen Canyon Dam controls
river volume as water is released
from Lake Powell. The demand for
electricity as far away as Los Angeles
can determine the amount of water
that is released.
Climate differs dramatically between
rim and river. Temperatures on the
rime are usually about 30oF (17oC)
cooler than at the river.
Each year about 15 inches (38 cm) of
moistures fall on the South Rim, and
25 inches (64cm) fall on the North
Rim, but only 8 inches(20cm) reach
the canyon bottom. The rim supports
a cool forest; the canyon depths
contain hot, dry desert.
To form Grand Canyon, the Colorado
River cut through one mile (1.6km)
of rock layers. The canyon's upper
rocks formed from sediment deposited
in ancient seas, swamps and deserts.
The lowest (and oldest) rocks formed
from deep within the earth's interior.
In some areas relatively recent
volcanos have played a part too.
Although rocks exposed in the canyon
are hundreds of millions of years old,
geologists believe the canyon itself is
less than 7 million years old.