Scientists believe that parts of Utah's landscape may represent an ancient landslide, which spans a piece of land 39 times larger than Manhattan. This would make it one of the largest known landslides ever to occur on Earth.
Over 21 million years ago, the land in modern-day Utah shook, forming this giant landslide. Geologists say the fall likely happened in minutes.
The research detailing this find was published in the journal Geology this month.
This landslide was too large for geologists to easily notice. Geologists had noticed that there were large pieces of rock that were out of place in the area, and they put that together with the knowledge that the area in this part of Utah would have been volcanically active about 21 to 31 million years ago to surmise that the rocks were most likely placed there as debris from multiple landslides. This new research shows that all of these rocks came from the same landslide, however, a massive one that covers an area that is 90 km long and 40 km wide (roughly 55 miles by 25 miles). That area is called the Markagunt gravity slide.
It is currently a mystery as to what caused the landslide. One theory is that magma from a volcano pushed the land upward, triggering the landslide. It may also have been triggered by some kind of wedge ejected from the volcano. Whatever the cause, the geologists believe that the landslide happened very quickly, because the surface of the slide was only tilted by a few degrees originally, so the momentum would have need to build up very quickly.
This landslide is now one of the two largest known landslides on Earth. The Heart Mountain gravity slide in Wyoming currently ties for first place. Once more is known about the Markagunt slide, it may prove to be even larger than the Heart Mountain slide.
Though events like these are extremely rare, this Markagunt slide shows how destructive volcanoes have the potential to be.
"We study events from the geologic past to better understand what could happen in the future," said David Hacker, one of the authors of this paper.
