Bad vibes: U of U scientist analyzes potential effects of human-caused vibrations on arch formations

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(MARK RALSTON/AFP via Getty Images)

(ABC4) – If a rock formation in Arches National Canyon collapses and no one is around to hear it, does it make a noise?

While the sound of the Rainbow Arch’s crash to earth in the winter of 2018 wasn’t captured by a human ear, the potential cause of the collapse was heard, in the form of vibrations were recorded by University of Utah geoscientist Jeff Moore’s seismometers.

The falling of the small arch – not the iconic Rainbow Bridge, which is much larger – left an important question among its rubble that Moore has been trying to answer with the data his devices have been picking up; did human activity play a factor in the collapse?

The answer: maybe. It’s certainly not outside of the realm of possibilities.

“Did its proximity to the highway, somehow hasten its collapse?” Moore asks theoretically, referring to nearby Highway 91. “There’s a train line through there that’s moving this radioactive waste from the shores of the Colorado River up to Crescent Junction. Those trains pass several times a week, and they make their own rumbles, did this additional vibrational energy hasten the collapse of his arch?”

It may sound odd when speaking about what are essentially giant inanimate objects, but Moore states that the rock formations that make the National Parks in Southern Utah so visually striking, can feel what’s happening around them. In the lifespan of a naturally crafted arch, the formation can feel the sensations of rainstorms, earthquakes, and other weather activity in the form of vibrations. Humans visiting the formation can also create vibrations, but typically when on foot, those shakes are microscopic.

However, introducing foreign elements such as a highway frequented by large semi-trucks, a train passing by on the rails, or worse, a helicopter swooping in to give aerial tourists a closer look at the arches, can create larger vibrations than the formations would ever otherwise experience.

Moore’s goal in using carefully placed seismometers, which have been scattered throughout Bryce Canyon, Canyonlands, and Arches National Parks since 2015, is to find out exactly what that impact might be.

While it would be easy to assume that the increase in attendance at the national parks during the pandemic could have resulted in increased vibrations, Moore states that that wasn’t witnessed by his data. Picking up exactly how much impact humans can make on the arches is an extremely subtle science. Whereas one national publication reported that the recording shaking captured by the seismometers was around the same loudness of a rock and roll concert, Moore says that isn’t the case.

“The actual vibration amplitudes are micrometers and less, they’re so tiny, you can’t feel them,” Moore explains. “You can’t feel them, you can’t hear them. They are beyond the range of human senses.”

The infrasound, however, the subsonic frequencies that are below the range of human hearing, created primarily by the helicopters circling the hoodoos and arches of the parks, are comparable to a rock concert. The arches themselves, however, remain virtually silent as their cracks form faster and larger, perhaps due to the increase in vibrations.

The study Moore is undergoing relates to a larger issue at hand, the balance of conservation and visitation. He credits the National Parks Services for its work on drafting air tour management plans, which could greatly reduce any damage being caused by the swirling of the propellers.

Other measures already in place will also help to extend the lifespan of Utah’s dazzling arches. Not too long ago, it used to be commonplace for visitors to climb on top of the arches for a photo op. This practice has now been banned, something Moore sees as a good idea.

“People used to in some cases, get 10 people out on an arch for a family photo,” he remembers. “And that’s a practice which only can be detrimental to the arch, it can never do any good.”

Besides refraining from posing for a cool but harmful picture and perhaps reconsidering a ride on a helicopter, Moore feels there aren’t too many drastic steps visitors should take to preserve the arches.
The key is to simply be aware, he says.

“I think people should just proceed with respect,” Moore states. “I think if they just have an image of the future to the vibrating response to your steps, as you step closer that just might change your approach a little bit, that might make you visit with an extra bit of care, an extra bit of respect. And that’s really what we hope to inspire.”

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