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Science: "to know"

In Arizona the Colorado River flows through the Grand Canyon.

How was the Canyon formed?

"Observations of erosion and depositional rates today are slow enough to indicate that a vast amount of time is required to deposit and erode, say, the sedimentary rocks of the Grand Canyon in Arizona."

"Over millions of years, the Colorado River has carved out the Grand Canyon from solid rock." Prentice Hall General Science 1992 p.174


"The Colorado River" has cut through layer upon layer of rock over millions of years." Prentice Hall Biology 1998, p. 279

The consensus hypothesis seems to be that the Colorado River carved out the Grand Canyon over millions of years.

What should we find if that hypothesis is correct?  The scientific evidence all should indicate the same thing.

Lets test that against the observable and measurable evidence.  What do we know about the Grand Canyon and the Colorado River?

1. Where the river starts in the Rocky Mountains it is about 9,000 feet above sea level.  It steadily declines until it is about 2800 feet above sea level at the rim of the Grand Canyon.

2. The river is 1,450 miles long.

3. At the rim where the river enters the Grand Canyon it is 8,000 feet above sea level.
4. The average width is 300 feet wide; and the depth averages between 40 feet and 85 feet deep.

5. The top of the Grand Canyon averages between 6,093 above sea level.

6. The canyon averages about 10 miles wide and is 18 miles wide at its widest point; and it is 277 miles long.

Possible Problems:

1. Where the river enters the canyon it is already down to 2800 feet above sea level.  The top of the canyon at that point is 8,000 feet above sea level.

2. The average width of the river is 300 feet; but the canyon averages 10 miles in width.

There is geological evidence that at one time there were two lakes that have been named: Grand Lake, and Hopi Lake that covered parts of what is now Utah, Colorado, New Mexico, and Arizona.  This area contained about 30,000 square miles of lakes.  That is about 3 times the size of Lake Michigan today.


It looks as though those 2 great lakes emptied out in a location approximately where the Grand Canyon is today.

The Colorado River runs through the area where Grand Lake used to be.  The San Juan River runs through the area where the southern branch of Grand Lake used to be. The Little Colorado River runs through the area where Hopi Lake used to be.

What did form the Grand Canyon?  Was it a little water over a long, long time flowing uphill perhaps?  Or could it have been formed by 30,000 square miles of lakes emptying out flowing downhill in a fairly short amount of time?

Evidence of Rapid Canyon Formation

In 1980, Mt. St. Helens in the state of Washington had three volcanic eruptions in less than a two year period. The last eruption carved out a canyon about 1/40 the size of the Grand Canyon in about 6 minutes. Today you can see three separate finely stratified layers that were formed by those three eruptions.

Canyons can form in a short amount of time under certain conditions. Could the Grand Canyon have formed in a fairly short amount of time as well? 

The Canyon formed by the Mt. St. Helen's eruption.

Much of the clip art on this site is courtesy of Phillip Martin.


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