The collapse of a famous arch in Utah raises the question of whether other famous arches are also at risk.

SALT LAKE CITY (AP) — In the week since the collapse of a famous rock arch at Lake Powell, known as the “Toilet Bowl,” visitors to Utah’s Arches National Park have frequently asked the following questions.

Are these arches also in danger of collapsing soon? What are you doing to prevent such a collapse?

The answers: “Maybe” and “nothing,” said Karen Garthwait, spokeswoman for Arches and Canyonlands National Parks.

“Our mission is not to stop time and preserve these structures exactly as they are,” she said. “Our mission is to preserve the natural processes that create these structures, and that is, of course, the same process that will ultimately destroy them.”

When the geological formation officially named “Double Arch” collapsed last Thursday in Glen Canyon National Recreation Area, it was a sad reminder to many that arches don't last forever. All arches have a lifespan that scientists don't want to shorten – or extend.

Experts say human activity has accelerated erosion over the past hundred years, meaning the arches could collapse at any time. But it's difficult to predict exactly when they might collapse.

A bow's external appearance provides little indication of its strength. The sturdiest bows may have internal cracks, while others that appear to defy gravity stand up better to the elements.

According to the Utah Geological Survey, the sandstone rock in southern Utah is strong enough to support the weight of large arches – one of the most stable forms found in nature – but soft enough to be shaped over time by wind, water and gravity. The region's semi-arid climate also plays a major role in the formation and preservation of the sandstone wonders.

While the National Park Service does not physically reinforce the arches—it abandoned plans to cover one of them with plastic in the 1940s—it has enacted strict guidelines to limit human impact on these natural structures.

Just two decades ago, park visitors could be seen walking on some of the arches and holding on to them for photos. One climber even scaled Delicate Arch, the most famous 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 revise regulations in 2006 to clarify that arch climbing is prohibited.

At Lake Powell, a large reservoir on the Utah-Arizona border, families would often climb the now-collapsed arch and jump into a swimming hole below. Park rangers and geologists suspect a combination of regular foot traffic and fluctuating water levels contributed to the arch's collapse. According to the National Park Service, the reservoir's water level has been falling since 2001 due to drought and climate change.

“Some people believe that rock is strong and unaffected by humans,” says Jeff Moore, a professor of geology and geophysics at the University of Utah. “When collapses like this happen, it reminds us how fragile rock arches are. Small changes can make a difference.”

Moore has led research projects that measure seismic activity beneath Utah's mountain arches and apply civil engineering principles to assess their structural health. The rock formations vibrate constantly, he said, and man-made energy sources such as trains, trucks and helicopters amplify those vibrations, stressing the mountain arches and accelerating crack growth.

Based on Moore's research, the Federal Aviation Administration (FAA) last year imposed a ban on helicopters flying near Rainbow Bridge National Monument in Utah – one of the largest known natural bridges in the world – to prevent vibration-related damage.

Humans have dramatically changed the vibrational landscape over the last century, he said, and as a result, more arches could soon collapse.

“That's a really rapid change in the lifespan of an arch,” Moore said. “Geology moves slowly. Humans have arrived quickly and are dramatically changing the environment in some places.”

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

For Richard Beckman, president of the Natural Arch and Bridge Society, it is an urgent concern to see the world's most famous arches before they are destroyed because he knows they could collapse in his lifetime.

“It's like losing an old friend,” Beckman said. “I'm sad to see them go, but I'm even more sad to see the arches collapse, which I never saw in person. We don't know how long they'll last, so you have to cherish them.”