Research news: It Took Eons to Make Grand Canyon Grand

The News:
It Took Eons to Make Grand Canyon Grand
How old is the Grand Canyon? Study says it took longer than once thought to become grand
By LAURAN NEERGAARD Associated Press Writer AP
Mar 6, 2008
Gazing into the majestic Grand Canyon, awe-struck visitors inevitably ask: "How old is it?" Far older than generally thought, says new evidence that scientists culled from caves lining the canyon's red limestone cliffs.
The Grand Canyon often is referred to as about 6 million years old _ but its western half actually began to open at least 17 million years ago, a University of New Mexico team reports Friday in the journal Science.
Wait: The western side of the canyon is the downstream end of the Colorado River, so how could it be older than the arguably more spectacular eastern side?
Remember, geologists caution, that the Grand Canyon was carved from drainage systems that didn't turn into the single river we now know as the Colorado until roughly 6 million years ago. The new research suggests two canyons formed that eventually joined. And it makes sense that the older side would even look different, less jagged, thanks to more years of gravity and wind erosion to soften its edges.
"This is really exciting for those of us who work in the stories and theories of how the Grand Canyon has evolved," Arizona geologist Wayne Ranney, author of "Carving the Grand Canyon," said of the new work. "This paper helps us to more clearly understand that different parts of the canyon formed at different times. That's how big the Grand Canyon is." more...

The Research:
Read the research behind this story in the journal Science.