Ancient landslide destroyed area size of Cincinnati


University of Cincinnati geologists reconstructed a massive landslide in Nevada that wiped out an area the size of a small city more than 5 million years ago.

UC College of Arts and Sciences graduate Nick Ferry and UC assistant professor of geology Daniel Sturmer pieced together details of the Blue Diamond landslide, a natural disaster that sent rocks and boulders tumbling more than 6 miles across what is now a desert outside Las Vegas.

The landslide in Red Rock Canyon National Conservation Area had such mass and force that it propelled fragmented rock 2 miles uphill, cresting the enormous Blue Diamond Hill, and flattened an area larger than downtown Cincinnati. Rubble from the landslide stretches over an area of more than 7 square miles.

“You can imagine this being pretty catastrophic in nature,” said Ferry, now a doctoral student at the University of Kansas.

The study was published in the Journal of Sedimentary Research.

The Blue Diamond catastrophe was a rock avalanche, an extremely rapid landslide that propelled fragmented rock and soil downhill at more than 5 meters per second.

Piecing together details of a landslide that occurred millions of years ago is a challenge, but geologists use a combination of field observations and laboratory analysis. By learning more about these natural disasters, researchers hope to find ways to predict future ones.

A landslide more than 5 million years ago originated at the Wilson Cliffs and covered an area of 7 square miles. Credit: Nick Ferry

That’s becoming increasingly important as people build homes, schools and businesses in more precarious places, Sturmer said.

“Landslides are one of the major disasters in the world in areas where you have significant topography, which represents a growing percentage of where people live,” Sturmer said. “It’s critical to be able to predict these hazards and prevent them or at least be smart about construction when you’re expanding cities.

“It’s one of the critical things geoscientists are doing.”

Ferry said the landslide might have been triggered by heavy rain. This part of Nevada was much wetter millions of years ago than it is today.

“We believe one reason the landslide reached so far is because it was flowing over saturated substrate, which reduced the friction resistance,” Ferry said.

Determining the date of a landslide is a little tricky. Researchers can use radiocarbon dating for events that occurred less than 50,000 years ago. For older events, they can turn to cosmic ray exposure dating. Researchers can tell how long a rock has been exposed on the surface of the Earth by studying the isotopes of certain elements in the rocks that were affected by high-energy cosmic rays. It’s a tool also used to study the movement of glaciers.

UC researchers say the Blue Diamond landslide occurred sometime between 5 million and 23 million years ago during the Miocene Period. This was a period of rapid evolutionary diversity. One Miocene bird, Argentavis, found in South America weighed as much as 200 pounds and had a wingspan of 23 feet.

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