Hi decresentmoon,
Thank you for your interesting question.
The Grand Canyon was created by the Colorado River cutting a channel
over millions of years.
For millions of years, the Colorado River has cut through rock on the
high plateau of northern Arizona to create one of the largest canyons
in the world. This process is called erosion. The colors of the canyon
rock range from black and red to lavender and cream.
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WordIQ.com - Grand Canyon
http://www.wordiq.com/definition/Grand_Canyon
The Grand Canyon is a colorful, steep-sided gorge, carved by the
Colorado River, in northern Arizona. The canyon is one of the seven
natural wonders of the world and is largely contained in the Grand
Canyon National Park.
The canyon, created by the Colorado River cutting a channel over
millions of years, is about 277 mile (446 km) long, ranges in width
from 4 to 18 miles (6 to 29 kilometers) and attains a depth of more
than a mile (1,600 m). Nearly 2000 million years of the Earth's
history has been exposed as the Colorado River and its tributaries cut
through layer after layer of sediment as the Colorado Plateaus have
uplifted.
The Grand Canyon is a deep - in places a mile deep - 277 mile (446 km)
long cut in the Colorado Plateaus that exposes uplifted Proteozoic and
Paleozoic strata. The exposed strata are gradually revealed by the
gentle incline beginning at Lees Ferry and continuing to Phantom
Ranch. At the point where the river crosses the Grand Wash Fault (near
Lake Mead) the Canyon ends.
Uplift associated with plate tectonics-caused mountain building events
later moved these sediments thousands of feet upward and created the
Colorado Plateaus. The higher elevation has also resulted in greater
precipitation in the Colorado River drainage area, but not enough to
change the Grand Canyon area from being semi-arid. Landslides and
other mass wasting events then caused headward erosion and stream
capture - all of which tend to increase the depth and width of canyons
in arid environments.
The uplift of the Colorado Plateaus is uneven, resulting in the North
Rim of the Grand Canyon being over a thousand feet (about 300 meters)
higher than the South Rim. The fact that the Colorado River flows
closer to the South Rim is also explained by this asymmetrical uplift.
Almost all runoff from the plateau behind the North Rim (which also
gets more rain and snow) flows toward the Grand Canyon, while much of
the runoff on the plateau behind the South Rim flows away from the
canyon (following the general tilt). The result is much greater
erosion and thus faster widening of the canyon and its tributary
canyons north of the Colorado River.
Temperatures on the North Rim are generally lower that the South Rim
because of the greater elevation (8000 feet/2438 m above sea level).
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A wonderful site that has a complete explanation along with pictures
and diagrams can be found at The Geology of the Grand Canyon:
http://www.kaibab.org/geology/gc_geol.htm
Subjects include -
How was it formed?
Where did all the rock come from?
Why does it look like it does?
When did all this happen?
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Grand Canyon National Park Arizona - Geology Fieldnotes
http://www2.nature.nps.gov/geology/parks/grca/
There are really two separate geologic stories at Grand Canyon:
The older story is the one revealed in the thick sequence of rocks
exposed in the walls of the Canyon. These rocks provide a remarkable
(but incomplete) record of the Paleozoic Era (550-250 million years
ago), as well as scattered remnants of Precambrian rocks as old as
2000 million years. The story these rocks tell is far older than the
canyon itself. Mesozoic and Cenozoic rocks (250 million years old to
the present) are largely missing at Grand Canyon (they've either been
worn away or were never deposited).
(see diagram: The rock record at Grand Canyon is summarized in the
geologic cross section below.)
The second geologic story at Grand Canyon concerns the origin of the
canyon itself:
When and how did it come to be?
* On one level the answer is simple: Grand Canyon is an erosional
feature that owes its existence to the Colorado River (which is
largely responsible for the depth of the canyon).
* Of equal importance are the forces of erosion that have shaped it
and continue to shape it today - mainly running water from rain,
snowmelt, and tributary streams which enter the canyon throughout its
length.
* The climate at Grand Canyon is classified as semi-arid (the South
Rim receives 15 inches (38 cm) of precipitation each year; only 8
inches (20 cm) each year reach the canyon bottom). But what rain
received comes suddenly in violent storms, particularly in the late
summer of each year, and the power of erosion is therefore more
evident here than in places which receive more rain.
How old is the canyon itself?
The early history and evolution of the Colorado River (of which Grand
Canyon is only a part) is the most complex aspect of Grand Canyon
geology and far beyond our scope here. We do know, however, that the
erosion which has shaped the canyon has occurred only in the past five
to six million years - only yesterday, considering the age of the
rocks through which the Canyon is carved.
Grand Canyon continues to grow and change. As long as rain and snow
continue to fall in northern Arizona, the forces of erosion will
continue to shape the Grand Canyon of the Colorado River.
Why does it look the way it does ?
Grand Canyon owes its distinctive shape to the fact that the different
rock layers in the canyon walls each respond to erosion in different
ways:
* some form slopes,
* some form cliffs,
* some erode more quickly than others.
The vivid colors of many of these layers are due mainly to small
amounts of various minerals, most containing iron, which impart subtle
shades of red, yellow, or green to the canyon walls. Climate plays an
important role, too. If the climate at Grand Canyon were wetter, the
planes and trees that grow there would be very different, and the
canyon walls might be covered with lush vegetation.
[edit]
How old is the Canyon?
That's a tricky question. Although rocks exposed in the walls of the
canyon are geologically old, the Canyon itself is a fairly young
feature. The oldest rocks at the canyon bottom are close to 2 billion
years old. The Canyon itself - an erosional feature - has formed only
in the past five or six million years (6,000,000). Geologically
speaking, Grand Canyon is very young.
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Grand Canyon
http://www.fact-index.com/g/gr/grand_canyon.html
The canyon, created by the Colorado River cutting a channel over
millions of years, is about 350 kilometers long, ranges in width from
6 to 29 kilometers and attains a depth of more than 1,600 m. The
details of its development are still somewhat controversial. The most
likely scenario is that a large lake overflowed the Kaibab Plateau
about 5 million years ago, following the route taken by the Little
Colorado River up to 70 million years ago. That accounts for the
narrow lower (western) canyon and the much wider upper (eastern)
canyon, as well as several other lines of evidence.
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Here are 3 websites that have a webcam at the Grand Canyon. Of course
nothing is visible at night! :)
http://www.anasaziinn.com/grand_canyon_webcam.html
http://www.grandcanyonchamber.org/grand_canyon_cam/default.htm
http://www.grandcircle.org/webcams/grand_canyon_webcam.htm
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Best regards,
tlspiegel |
