by SALT LAKE CITY (AP) — A common line of questions has emerged from visitors to Utah’s Arches National Park in the week since an iconic arch at Lake Powell known as the “Toilet Bowl” collapsed.
Are these arches also in danger of falling soon? What are you doing to prevent their fall?
The answers: They could be, and anything, said Karen Garthwait, spokeswoman for Arches and Canyonlands national parks.
“Our mission is not to dilute time and preserve these structures just as they are,” she said. .”
When the geological formation formally known as “Double Arch” collapsed last Thursday at Glen Canyon National Recreation Area, it was a sad reminder to many that arches are not guaranteed to last forever. Each arch has a lifespan, which scientists are trying to shorten – or avoid extending.
Experts say human activity has accelerated erosion over the past century, making the arches susceptible to crumbling at any given time. But it is difficult to predict exactly when they will fall.
The appearance of an arch gives little indication of its stability. The ones that look the most solid can have internal cracks, while others that look like gravity is fighting the elements may have internal cracks.
Southern Utah’s sandstone bedrock is strong enough to support the weight of the great arches — one of the sturdiest shapes found in nature — but soft enough to be sculpted over time by wind, water and gravity, according to Survey Utah Geology. The region’s semi-arid climate also plays an important role in the formation and maintenance of sandstone wonders.
Although the National Park Service is not physically reinforcing arches — it abandoned a plan to coat one with plastic in the 1940s — it has enacted strict policies to limit human impact on the natural structures.
As recently as decades ago, parkers could be seen walking on top of some arches and hanging onto them for photos. A climber even scaled Delicate Arch, the most recognizable of Utah’s more than 6,000 arches, leaving rope grooves in the sandstone that Garthwait said are still visible today. As a result of the park’s rise, park officials reworded the regulations in 2006 to clarify that climbing arches are prohibited.
At Lake Powell, a large reservoir on the border of Utah and Arizona, families often climbed the now-collapsed arch and plunged 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 have been declining due to drought and climate change since 2001, according to the National Park Service.
“Some people have the impression that rock is strong and not affected by people,” said Jeff Moore, a professor of geology and geophysics at the University of Utah. “When a collapse like this happens, it’s a reminder that arches are very fragile. Small changes can make a difference.”
Moore leads research projects that measure the seismic activity under Utah’s arches and use civil engineering principles to assess their structural health. The rock formations are constantly vibrating, he said, and man-made energy sources such as trains, trucks and helicopters are amplifying those vibrations, stressing the arches and accelerating crack growth.
The Federal Aviation Administration imposed air restrictions last year on helicopters flying near Utah’s Rainbow Bridge National Monument — one of the world’s largest known natural bridges — to avoid vibration-induced damage in light of Moore’s research.
Humans have greatly altered the seismic landscape over the past century, he said, and more arches may soon fall as a result.
“This is a very rapid change in the life cycle of an arch,” Moore said. “Geology moves slowly. People came quickly and, in some places, they are making major changes to the environment.”
A US Bureau of Reclamation facility in western Colorado that extracts salt water from the Colorado River system and injects it deep into the ground has also been linked to earthquakes near Utah national parks. The site was temporarily closed after a 4.5 magnitude earthquake was recorded there in 2019 but has 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 collapse in his lifetime adds urgency to visiting them before they disappear.
“It’s like losing an old friend,” Beckman said. “I’m sad to see them go, but I’m more hurt by the fallen arches that I’ve never seen in person. We don’t know how long they will last, so you have to respect them.”
