A team of researchers led by Dr. Jeffrey Moore, from the Department of Geology and Geophysics at the University of Utah, performed a series of 3D simulations in order to reconstruct the Zion National Park’s topography before a landslide that once occurred.
Around 4,800 years ago, a massive landslide occurred over the Zion Canyon’s Virgin River, which gave its current shape to the park and created a huge lake that is now able to be crossed on foot.
The park receives millions of tourists every year, Memorial Day being the favorite day for visiting. Little do visitors know that the canyon had gone through a catastrophic landslide that would be able to cover New York City’s Central park with 80 meters of debris.
A massive avalanche
Scientists estimate that the volume of the landslide was of 10.1 billion cubic feet, an amount so big that it is four times larger than Utah’s latest major landslide, which occurred in the Bingham Canyon in 2013. The landslide seems to have originated from a formation known as the Sentinel, which stands at 7,157 feet above the ground.
It was initially theorized that Zion Canyon was formed due to glacial debris and sedimentation. The first records about the existence of the canyon surfaced in 1945, which sets the national park as a fairly recent finding. It is worth noting that another smaller landslide occurred recently in 1995 in Zion Canyon. It managed to reach the road that linked the visitor center and the park’s lodge.
Recreating the events
The development of the massive landslide was drafted on computer simulations which showed that, as the rocks fell, they reached a speed of at least 200 miles per hour. All it took was a minute, and the shape of the Zion Canyon was altered forever.
Dr. Jeffrey Moore considered the implications of a similar event occurring again since millions of visitors have enjoyed the bottom of the valley over the 700 years through which the lake has transformed into a flatland. It was estimated that the lake took around 10 years to fill. It covered 2.4 square miles and it reached an elevation of 4-thousand feet. After the lake had filled with sediment, people were able to walk on it. Dr. Moore referred to the landslide as “a minute with up to 10,000 years of consequences.”
Researchers were able to know that a landslide had occurred thanks to the boulders that lie on the upper part of the rock formations. Boulders whose upper surface has been exposed to light for a shorter time than others are a clear indication of a landslide occurring. When rocks are exposed to sunlight, a radioactive isotope known as beryllium-10 is formed.
The rocks with a higher amount of beryllium-10 are known to have been exposed to cosmic radiation for longer. Previous examinations have led experts to believe that the landslide occurred between 3,900 and 7,900 years ago, but thanks to the review of beryllium-10 concentration, 4,800 years ago was chosen as the most probable period.
Landslides such as the one that occurred on Zion Canyon were not common. Dr. Moore commented that there are no clear indications on whether this may or may not occur again in the near future. The reason behind the landslide was not able to be discerned, as there are no records of massive earthquakes that have occurred at the time of the avalanche.
How rock formations reveal the past
Dr. Moore added that the most frequent factor that causes landslides and avalanches are earthquakes., and although landslides are an apparent danger, they allow for people to settle and build villages or farms.
Dr. Jeffrey Dr. Moore has gained recognition for working on the analysis of rock formations and movements. He had previously led a study of America’s rock arches in order to place an increased monitoring on their preservation. The team measured how the stone arches resonated in order to spot potential spots of weakness from within the structure.
Tourists often walk underneath the stone arches, which were formed due to erosion, just like the formations in the Zion Valley. It was Dr. Moore’s objective to make sure that there weren’t any indicators that pointed towards the collapse of these arches in the near future.
Geology takes a lot from engineering, as geologists use similar procedures to those inherent to structural health monitoring, where they assess the state of a mountain or a rock formation in order to predict whether it is likely to fall down or to crack at any moment.
This allows researchers to have a deeper understanding of the history of these marvelous formations that have taken thousands of years to be formed. Some rock formations, like the Landscape Arch in Utah, are now forbidden for the public as it is possible that it might collapse at any moment. In the state of Utah, there are over 2,000 stone arches in its Arches National Park.
Erosion, the process through which rocks degrade, is how rock arches, canyons, and valleys get formed and get destroyed. But it is possible that erosion leads to more severe and binding consequences, as it was the case of Zion Canyon’s grand avalanche.
Source: GSA Today