SALT LAKE CITY — Visitors to Utah’s Arches National Park were faced with a number of frequently asked questions this week after an iconic rock arch near Lake Powell, known as the “Toilet Bowl” has collapsed.
Are these arches also at risk of collapsing soon? What are you doing to prevent collapse?
The answer: It could be, but there isn’t anything, said Karen Garthwait, spokeswoman for Arches and Canyonlands national parks.
“Our mission is not to freeze time and preserve these structures as they are,” she said. “Our mission is to preserve the natural processes that create these structures, which of course is the same process that will eventually undo them.”
When the geologic formation formally known as “Double Arch” collapsed last Thursday in Glen Canyon National Recreation Area, it served as a sad reminder to many that arches aren’t guaranteed to last forever. All arches have a lifespan, which scientists are working to avoid shortening — or extending.
Experts say human activity has accelerated erosion over the past 100 years, making the arches susceptible to crumbling at any time. But exactly when they will fall is difficult to predict.
The appearance of an arch gives little indication of its stability. Those that appear the sturdiest may have internal cracks, while others that seem to defy gravity may be better able to withstand the elements.
Southern Utah’s sandstone bedrock is strong enough to support the weight of large arches — among the sturdiest forms found in nature — yet soft enough to be shaped over time by wind, water and gravity, according to the Utah Geological Survey. The region’s semiarid climate also plays a major role in forming and preserving the sandstone wonders.
While the National Park Service is not physically reinforcing arches — it abandoned a plan to coat one in plastic in the 1940s — it has implemented strict policies to limit human impact on natural structures.
Just twenty years ago, park visitors could be seen walking on the arches and hanging from them for photos. One climber even scaled Delicate Archthe most recognizable of Utah’s more than 6,000 arches, leaving rope grooves in the sandstone that Garthwait says can still be seen. The climb prompted park officials to revise the rules in 2006 to make it clear that climbing the arches is prohibited.
At Lake Powell, a large reservoir on the border of Utah and Arizona, families often climbed onto the now-collapsed arch and jumped into a swimming hole below. Park rangers and geologists suspect that a combination of regular foot traffic and fluctuating water levels contributed to the arch’s demise. The reservoir’s water levels are decreasing due to drought and climate change according to the National Park Service since 2001.
“Some people have this idea that rocks are strong and that humans can’t affect them,” said Jeff Moore, a professor of geology and geophysics at the University of Utah. “When these kinds of collapses happen, it’s a reminder that arches are really fragile. Subtle changes can make a difference.”
Moore has led research projects that measure seismic activity beneath Utah’s arches and use civil engineering principles to assess their structural health. The rock formations are constantly shaking, he said, and man-made energy sources such as trains, trucks and helicopters magnify those vibrations, putting stress on the arches and accelerating crack growth.
The Federal Aviation Administration last year imposed flight restrictions on helicopters flying near Utah’s Rainbow Bridge National Monument, one of the largest known natural bridges in the world, to prevent damage from vibrations, in light of Moore’s research.
According to him, humans have drastically changed the vibrational situation over the past century and more arches could collapse soon.
“This is a very rapid change in the life of an arch,” Moore said. “Geology moves slowly. Humans have arrived quickly and are causing dramatic changes in the environment in some places.”
A U.S. Bureau of Reclamation facility in western Colorado that pumps saltwater from the Colorado River system and injects it deep into the ground has also been linked to earthquakes near national parks in Utah. The site was temporarily closed after a 4.5 magnitude earthquake was recorded there in 2019, but has since resumed operations at a reduced pace.
For Richard Beckman, president of the Natural Arch and Bridge Society, knowing that some of the world’s most iconic arches could collapse in his lifetime is a fact that makes him want to visit them before they disappear.
“It’s like losing an old friend,” Beckman said. “I’m sad to see them go, but I’m even more hurt by the arches that collapsed and I never got to see them in person. We don’t know how long they’re going to last, so you have to appreciate them.”