Dinosaurs (Probably) Never Saw the Grand Canyon

The idea of a Tyrannosaurus rex or Brontosaurus taking in the view at the rim of the Grand Canyon sounds like the stuff of a classic Land Before Time film (or perhaps part of the plot of the next installation in the Jurassic Park series). While it might make for compelling fiction, it turns out there isn't a lot of evidence to suggest that dinosaurs walked the floor of the canyon or glimpsed its walls.

The last dinosaurs went extinct around 65 million years ago, so whether or not they saw the canyon hinges on one key question: Did it exist when they were alive? In an area subject to erosion, determining an exact age for rock formations can prove difficult. Thus, the age of the canyon remains a matter of significant debate.

For many years, researchers estimated that the Colorado River began carving out most of the canyon around five to six million years ago. Another analysis pegged erosion to 17 million years ago. Still, a 2012 study shockingly pointed to an earlier formation around 70 million years ago. The last estimate puts dinosaurs roaming the canyon rim on the edge of plausibility. However, each of these studies employed different dating techniques.

Based on a paper published in Nature Geoscience last year, it's clear that parts of the formation are young, while others are significantly older, as Smart News's Colin Schultz reported. That's likely because what is now the Grand Canyon was once a series of smaller canyons that joined through slow, massive process of erosion. While parts of the canyon began eroding 70 million years ago, most of the key integration happened much, much later.

Now a new study published this week in the journal Geosphere weighs in on the debate and backs up the argument for a younger Grand Canyon. Using a specially designed computer algorithm, researchers at Arizona State University analyzed the topography of the western part of the Grand Canyon and compared it to other geological features that had been thoroughly dated. Their results suggest that erosion on the walls of the western Grand Canyon occurred extremely quickly, compared to those other areas. “We are confident the western canyon is younger than 6 million years and is certainly younger than 18 million years,” Andrew Darling, a co-author on the study and a geology grad student at ASU, said in a statement to the press.

If their estimates are correct, the integration of the canyon is significantly younger than the dinosaurs. "There's no way dinosaurs overlapped with what we call the Grand Canyon," Darling noted. Perhaps that's why no dinosaur fossils have been discovered in the canyon walls.

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Helen Thompson writes about science and culture for Smithsonian. She's previously written for NPR, National Geographic News, Nature and others.