EDMONTON—There’s evidence that the origin of the Rocky Mountains might have looked more like a car crash than science suggests. And now some researchers are trying to recreate the scene.

A recent study including the work of University of Alberta scientists suggests the Rockies erupted from a collision between North America and a smaller, ribbon-shaped continent somewhere between 70 million and 100 million years ago.

Jeffrey Gu, a geophysics professor at the university and co-author of the study, said he was originally trying to get high-resolution images of the area from seismic stations across Alberta and British Columbia.

Using a process called seismic tomography, which he compared to the medical use of X-rays for projecting images of internal organs, they tracked the speed of seismic waves from earthquakes travelling through the Earth.

What they found surprised them.

Most scientists endorse what is known as the accretion model, which holds that the Rockies formed over a longer time through the buildup of “crustal flakes” caused by smaller collisions on the North American continent.

Read more: Warming temperatures signal dramatic change for alpine ecosystems: report

But if that was the case, Gu said, they wouldn’t have found the waves travelling at dramatically different speeds on opposite sites of a boundary in the mantle.

“Based on the accretion model, there should not be a mantle boundary,” he said. “And I think, in this study, we clearly show that this boundary does exist. It’s very sharp, and it likely represents the boundary between two colliding continents rather than just the North American continent with additional crustal flakes.”

Stephen Johnston, chair of the university’s department of earth and atmospheric science who also contributed to the study, painted a picture of how the crash might have played out.

“In our model, there would have been an ocean between North America and this ribbon continent, and the margin of that ocean would have been roughly near the Alberta-B.C. border,” he said. “So that ocean had to disappear, and how you get rid of oceans is by subduction.”

Subduction, he explained, occurs when the oceanic lithosphere, the rigid part of the earth consisting of the upper crust and mantle, sinks because it’s cold, wet and more dense than the earth beneath it. Here it would have happened beneath the eastern edge of the smaller continent.

“In essence, this ribbon continent gets sucked towards the North American continent as this slab of oceanic crust starts sinking down,” he added. “It just follows the subducting slab as it disappears, until, eventually, the ocean is closed, and the two continents come together.”

But that alone wouldn’t have caused the Rockies. Inertia from the two continents coming together would have caused them to grind together, up until about 50 million years ago, deforming the landscape to create the majestic mountain range we know today, Johnston added

“It’s just like getting rear-ended in a car collision,” he said. “So the Rockies themselves are mostly North American rocks that were mangled and deformed during the collision.”

And if this was the way they were made, they weren’t the only ones, said Gu, pointing to the Himalayas in South Asia, which show clear evidence of the Eurasian Plate colliding with the Indo-Australian Plate.

Loading... Loading... Loading... Loading... Loading... Loading...

“This is the start of a new chapter in the modelling and understanding of the Rockies,” he said, cautious not to make a mountain out of what’s still a scientific mole hill. “There’s certainly a lot more work that needs to be done to validate this model, and this ‘transition area.’”

Their research findings were published Tuesday in the scientific journal Nature Communications.

Read more about: