How Old is the Grand Canyon? (broadcast Friday, March 7th, 2008)

Redwall Caverns, a large grotto in the Redwall Limestone in Marble Canyon, eastern Grand Canyon. Image courtesy of Victor Polyak

How old is the Grand Canyon? Writing in the journal Science, a group of scientists describes using features found in caves in the canyon's walls to try to put a date on the natural wonder. The researchers studied structures known as mammillaries or “cave clouds” — carbonate deposits that form at or near the water table level, and dated the features using uranium-lead isotope dating techniques.

The new research suggests that the formation of the Grand Canyon, when the first cuts began to form in the rock, began at least 17 million years ago, making the canyon significantly older than previously thought. The canyon channel is thought to have been completely cut through by 5 or 6 million years ago.

The new study is controversial, with several geologists speaking out vocally about the study's methods and its findings. In this segment, Ira talks with one of the scientists behind the new dating study about the team's work and findings. Teachers, find more information about using Science Friday as a classroom resource in the Kids' Connection.