Mysteries Surround Formation of Grand Canyon

Written by on September 17, 2009 in AZ Outdoor Adventures - Comments Off on Mysteries Surround Formation of Grand Canyon

The first time you look out over the Grand Canyon, you will find it almost impossible to believe. It’s so big, so deep, so impressive, it can’t possibly be real. In fact, lots of people say that the vast vistas look more like a photograph than reality. It’s not uncommon for people to feel a little disoriented, awed and speechless, just from the sheer size and beauty. For that same reason, it’s extremely difficult to put into words just what you will see when you visit. But it helps to understand how the canyon might have formed so you’ll know what you are seeing when you get there!

The Grand Canyon is 277 miles long, 14 miles wide at its widest point, and over a mile deep in many places. As huge as it is, you would think it had to have been created by some vast cataclysm, but it wasn’t. The Grand Canyon was carved by the Colorado River over the last 2 to 6 million years — the blink of an eye in geologic terms (geologist still argue over the dating of the canyon).

The birth of the canyon is surrounded in mystery. It seems to have been carved through an uplifted plateau, instead of flowing around it. Rather than following the weak spots or fault lines in the rock, the Colorado River plowed straight through these weak areas, something almost unheard of in geologic terms. How on earth did the canyon got so deep — surely one river couldn’t do that, could it? And why is there evidence that the river once flowed in the other direction?

Geologist have struggled to explain these mysteries and may have come up with a few answers. We know that the Kaibab Plateau in which the canyon now sits, was uplifted before the river began cutting its path. So why didn’t the Colorado River go around this uplift and follow the low-lying ground surrounding the plateau? The answer may be simply that the river actually started on the plateau. Two major rivers probably drained the highlands. One flowed from east to west toward California, while the other flowed west to east toward Colorado. Hence the evidence that the Colorado River once flowed in the other direction. Year after year, the headlands of these rivers carved themselves deeper and farther east or west into the plateau, until eventually, the two headlands met. Once the headlands met and dug themselves deep enough, the two rivers merged and the flow of water reversed itself on the eastern end and began draining vast tracts of  land in Colorado and Utah toward Southern Arizona and California, where the river once drained into the Gulf of California. This may also explain why the river ignored the obvious north-south fault lines that run across the canyon in places, about where the two rivers might have joined.

The final question of how the canyon got so deep is entirely due to the influence of water. On average, a river doesn’t scour that much earth when it is running normally. However, huge floods will pick up boulders the size of buses and tumble them downstream. The rocks act like huge plows or earth movers and scour the river bed, digging deep trenches. The Monsoon Season in Arizona can cause these kinds of enormous floods. It’s not unheard of for a gigantic thunderstorm to drop 6-8 inches of rain in a couple of hours. With very little soil to absorb the moisture, the water gathers and builds into tremendous floods. When the Glen Canyon Dam was erected, many people worried that it would prevent these earth-moving events. While it has calmed the river some, it hasn’t stopped the flooding. In August 2008, a tremendous Monsoon storm dumped huge amounts of water on the South Rim of the Grand Canyon and Coconino Plateau country that gushed into dozens of Grand Canyon tributaries, causing major flooding along the Havasu River through the Havasupai Indian Reservation. Near Supai, Havasu Creek’s flow surged from a normal 65 cubic feet per second to an astonishing 6,000 cubic feet per second! Because the river cuts so deep into the Kaibab plateau, it exposes dozens of layers of rock, including the black Vishnu Schist of the inner gorge which dates back two billion years. In essence the canyon is a calendar dating back billions of years and shows the history of the land, from rock that was once lake and ocean bottom, to deserts
and volcanic periods.

For a more complete explanation of the canyon, stop by the Visitor’s Center on the South Rim. Ranger led hikes are available daily and explain more about the canyon. However, if you’d prefer to learn about the canyon in more detail, consider the Grand Canyon Field Institute. They offer guided educational tours in the park led by expert instructors.

More stories in the Grand Canyon Series include:

Formation of the Grand Canyon
South Rim of the Grand Canyon
North Rim of the Grand Canyon
Inhabitants of the Grand Canyon
River Rafting the Grand Canyon
Grand Canyon Railway
Grand Canyon Skywalk
Condors Make a Comeback in the Grand Canyon
Top 10 Things To Do at the Grand Canyon
Legend of Egyptian Artifacts in the Grand Canyon
The Ghost of Crash Canyon
Phantom Ranch at the Grand Canyon

Grand Canyon National Park
P.O. Box 129
Grand Canyon, AZ 86023
General Visitor Information: 928-638-7888
Backcountry Information Center: 928-638-7875
River Permits Office: 800-959-9164 or 928-638-7843

Grand Canyon Field Institute
www.grandcanyon.org/fieldinstitute/
Grand Canyon Field Institute
PO Box 399
Grand Canyon, AZ 86023
Toll-Free: 866- 471- 4435
Phone: 928- 638-2485

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