The collapse of an iconic arch in Utah has some wondering if other famous arches are also at risk

SALT LAKE CITY — A number of common questions have arisen among visitors to Utah’s Arches National Park in the week since an iconic rock arch known as the “Toilet Bowl” collapsed into Lake Powell.

Are these arches also in danger of collapsing soon? What are you doing to prevent them from collapsing?

The answers: They could be, but it wouldn’t be anything, said Karen Garthwait, a spokeswoman for Arches and Canyonlands national parks.

“Our mission is not to freeze time and preserve these structures exactly as they are,” he said. “Our mission is to preserve the natural processes that create these structures, which, of course, are the same processes that will eventually destroy them as well.”

When the geological formation formally called “Double Arch” crumbled last Thursday in Glen Canyon National Recreation Area, it served as a grim reminder to many that arches are not guaranteed to last forever. All arches have a lifespan, which scientists are trying to prevent from being shortened or lengthened.

Experts say human activity has accelerated erosion over the past 100 years, making the arches susceptible to collapse at any time. But it is difficult to predict exactly when they might collapse.

The exterior appearance of an arch does not give much indication of its stability. Those that appear sturdier may have internal cracks, while others that seem to defy gravity may better withstand the elements.

According to the Utah Geological Survey, southern Utah’s sandstone bedrock is strong enough to support the weight of large arches (one of the sturdiest forms found in nature), yet soft enough to be sculpted over time by wind, water and gravity. The region’s semi-arid climate also plays a major role in forming and maintaining the wonders of sandstone.

While the National Park Service is not physically fortifying the arches (it abandoned a plan to cover one with plastic in the 1940s), it has enacted strict policies to limit human impact on the natural structures.

Just two decades ago, park visitors could be seen walking on some arches and hanging from them for photos. One climber even scaled Delicate Arch, the best-known of Utah’s more than 6,000 arches, leaving rope grooves in the sandstone that Garthwait said can still be seen today. The climb prompted park officials to rewrite rules in 2006 to make clear that climbing the arches is prohibited.

At Lake Powell, a large reservoir on the Utah-Arizona border, families used to climb the now-collapsed arch and dive into a swimming hole below. Rangers and geologists suspect a combination of regular foot traffic and changing water levels contributed to the arch’s demise. Water levels at the reservoir have been declining due to drought and climate change since 2001, according to the National Park Service.

“Some people have a sense that rock is strong and that humans don’t affect it,” said Jeff Moore, a professor of geology and geophysics at the University of Utah. “When these kinds of collapses happen, they remind us that arches are really fragile. Subtle changes can make all the difference.”

Moore has led research projects that measure seismic activity beneath Utah’s arches and use civil engineering principles to assess their structural health. Rock formations are constantly vibrating, he said, and man-made energy sources such as trains, trucks and helicopters are magnifying those vibrations, putting stress on the arches and accelerating crack growth.

Last year, the Federal Aviation Administration imposed air restrictions on helicopters flying near Utah’s Rainbow Bridge National Monument (one of the largest known natural bridges in the world) to prevent vibration-induced damage in light of Moore’s research.

Humans have dramatically changed the vibration landscape over the past century, he said, and more arcs could soon fall as a result.

“This is a really rapid change in the lifespan of an arch,” Moore said. “Geology moves slowly. Humans have come in quickly and, in some places, are causing dramatic changes to the environment.”

A U.S. Bureau of Reclamation facility in western Colorado that draws saltwater from the Colorado River system and injects it deep into the ground has also been linked to earthquakes near Utah’s national parks. The site was temporarily shut down after a magnitude 4.5 earthquake struck there in 2019, but has since resumed operations at a reduced rate.

For Richard Beckman, president of the Natural Arch and Bridge Society, knowing that some of the world’s most iconic arches could fall in his lifetime adds a sense of urgency 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 more saddened by the collapse of the arches that I never saw in person. We don’t know how long they’re going to last, so you have to go and appreciate them.”