For decades, scientists have posited that the Grand Canyon is about 6 million years old. But according to a paper published today by University of New Mexico researchers in the journal Science, the canyon’s western half actually began to open at least 17 million years ago. This though the upstream end of the canyon ought to be older than the downstream end. The Associated Press reports:

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.”

Here’s a standard explanation for the canyon that appears on a website listing the Wonders of the World:

Compared with the nearly two-billion-year process of deposition, erosion has set a brisk pace. The Grand Canyon itself is less than six million years old, created only since the Colorado River changed course and began flowing through the ancestral Colorado plateau. In just two million years, the river sliced to within 500 feet above its current depth.

Will such exposition now have to be rewritten? And what will the young-earth creationists say?