Grand Canyon may not be as old as once thought

ALBUQUERQUE, Jan. 27 (UPI) -- Certain sections of the Grand Canyon may be only five to six million years old, while other sections date back 70 million years.

A new study suggests that certain segments of the canyon are indeed 70 million years old, but the canyon was completely formed only a few million years ago. Earlier research had suggested the canyon was carved out in its entirety 70 million years ago at the same location and depth as it currently stands.

"We are also refuting the 'young canyon model', which claims the canyon was cut entirely in the last six million years. Instead, we show that the Colorado River used some old segments as it found its path from the Rockies to the Gulf of California in the past six million years," said Professor Karl Karlstrom from the University of New Mexico, Albuquerque.

Researchers found that two of the three central segments of the canyon, called the "Hurricane" segment and the "Eastern Grand Canyon," were carved out 50 to 70 million years ago and 15 to 25 million years ago respectively.

But the two end segments, known as the "Marble Canyon" and the "Westernmost Grand Canyon," were created five to six million years ago, when the Colorado River found a path from the Rockies to the Gulf of California.

The study, published in the journal Nature Geoscience, relied on a technique called thermochronology, which measures the changes in the structure of minerals as they cool. Rocks below the surface are warmer and as they make their way to the surface over time, they cool and create a signature on the outer surface of the rock.

Karlstrom believes this study should lay to rest speculation regarding the age of the 280-mile-long Grand Canyon.

"If you were to add up the 280-mile length and ask, 'how much is young? More than half of it is young; a quarter of it is middle-aged -- 15-25 million years old; and the rest of it is 70 million years old," Karlstrom told the BBC.

[Nature Geoscience] [BBC]