March 7, 2008

Grand Canyon Three Times Older Than Believed

Scientists from the University of Mexico reported Thursday that the Grand Canyon began being formed 17 million years ago, nearly three times longer than previous scientific consensus dating the canyon's formation to only 6 million years ago.

The researchers based their conclusions on new findings obtained through a dating technique called uranium-lead isotope, which they used to date mineral deposits in the canyon's walls over a 9-state area.  The deposits came from cave formations in the canyon, which provided a record of dropping water tables as the canyon became deeper.

The team discovered a type of dual history in the canyon, with the eastern portion forming approximately 6 million years ago in keeping with previous estimates for the canyon as a whole.   However, they determined the western portion of the canyon starting forming around 17 million years ago when water from a predecessor to the Colorado River began to slowly erode the rock.

"Essentially, it formed in two parts," said Carol Hill, a University of New Mexico geologist, in a Reuters report.  "The older Grand Canyon formed and then hooked up once the Colorado River became through-flowing (all the way to the Gulf of California), then it hooked up with the eastern Grand Canyon."

"Not only were we able to figure out the time scale information but also the way that the canyon may have formed. It was one of those beautiful complete stories," University of New Mexico scientist Yemane Asmerom told Reuters.

The Grand Canyon is 277 miles long, and reaches a depth of 1.1 miles at its deepest point.  At its widest, it is 18 miles across. The Colorado River that runs through the canyon begins in the Rocky Mountains of Colorado and flows southwest about 1,400 miles to the Gulf of California. 

The study was published in the journal Science.  A summary of the report can be viewed here.


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