Climbers climbing Yosemite in the US noticed a new crack forming near the Royal Arches cliff last week. A subsequent investigation concluded that the cracking was actively occurring, so steps were taken to close parts of the park as a safety precaution, park officials reported.
The new crack was partially splitting a large rock pillar near the climbing route known as the Super Slide. While the National Park Service’s investigations continue, roads are being closed to reduce the risk of rockfall. The closures began August 30 and will continue until further notice.
“The next week, a climbing ranger and a geologist observed it firsthand and could hear it cracking like a frozen lake before it solidified,” Yosemite National Park Supervisory Park Ranger Jesse McGahey said in a conversation with Climbing. “And there were pieces of rock rattling around the crack without touching it.” . The park geologist said they had never seen anything like this before. “He had never observed anything like this in his 15 years in Yosemite.”
A post shared by Yosemite Climber Stewards (@climber_stewards)
The crack reportedly moved about an inch (about 2.5 centimeters) over a seven-day period, but it’s not entirely clear what this will cause in the future. The massive rock pillar may be about to fall, as park officials worry, or it may take years, but parts of the park will remain closed to visitors until the potential threat is more clearly identified.
Rockfalls are not uncommon in Yosemite Valley, whose steep cliffs were carved by a glacier. While this means the terrain here is constantly changing, adding to the beauty of the national park, you’d probably prefer to avoid watching rockfalls up close.
“Trigger mechanisms such as water, ice, earthquakes, and vegetation growth are among the final forces that cause unstable rocks to fall,” the National Park Service writes. If water enters through cracks in the bedrock, it can create pressure behind unstable rocks. Water can also seep into cracks in the rock and freeze, causing these cracks to grow. “This process is called ‘ice wedge’ or ‘freeze-thaw’ and can gradually remove loose rocks from cliff faces.”
54481
