New research suggests that Arizona’s iconic Grand Canyon may be only 5-6 million years old and not 70 million years as was previously believed. A paper published in Nature Geoscience by Karl Karlstrom, geologist at the University of New Mexico in Albuquerque, and associates claims that the canyon was formed when a number of older, smaller canyons merged.

“The ‘old canyon model’ has argued that the Grand Canyon was carved 70 million years ago in the same place and to nearly the same depth as the modern canyon. We are refuting that. 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. What’s different here I think is that we finally have a description of the Grand Canyon that honors all the hard-won data,” Karlstrom told BBC News.

Scientists date canyons based on rock temperature. The deeper a rock is buried the warmer it tends to be. As erosion exposes the rock and moves it closer to the surface it cools. In testing the Grand Canyon, Karlstrom and his colleagues found that the age varied depending on where they tested. Parts of the eastern Grand Canyon tested at 15-25 million years old, other stretches at 50-70 million years, but Marble Canyon and the westernmost Grand Canyon were much more recent.

“Different segments of the canyon have different histories and different ages, but they didn’t get linked together to form the Grand Canyon with the Colorado River running through it until 5 to 6 million years ago,” Karlstrom told Nature.

The study though is not without its critics. Other researchers, including geologists Rebecca Flowers of the University of Colorado Boulder and Kenneth Farley of the California Institute of Technology in Pasadena, have done similar testing and reached very different conclusions. Part of the difference may lie in the fact that Karlstrom and his team used a range of temperatures in their measurements, while other studies have used a constant temperature of 25 degrees Celsius in their measurements.

“It will take a bit more time to understand fully why their interpretations are so different from ours,” Flowers, who published a similar study on the canyon in 2012, told The Washington Post.

Source: Nature