Friday, October 14, 2022

Record-low water levels expose volcanic ash in Lake Mead


The growing "bathtub ring" around Lake Mead, is seen near Hoover Dam, where water levels have declined dramatically in Boulder City, Ariz., on May 22. 
File Photo by Jim Ruymen/UPI | License Photo

Oct. 12 (UPI) -- Record-low water levels in Lake Mead in Nevada and Arizona have exposed volcanic ash from eruptions 12 million years ago as far away as Idaho, Wyoming and Colorado.

The discovery may help investigators better understand future ashfall risks, researchers at the University of Nevada-Las Vegas said in a recent study.

"Ash from even moderately explosive eruptions can travel hundreds of miles from the source, blanketing entire areas with anywhere from a centimeter to several meters of the heavy material," Eugene Smith, a UNLV emeritus professor of geology, said in a news release.

"Although the Las Vegas Valley is currently very far away from any active volcanoes, we can and will have ash from these volcanoes fall over Southern Nevada in the future."

Even small amounts of ash can become heavy enough when wet to take down power lines and block roadways, he said, and inhaling tiny, sharp ash can cause significant lung damage.

Using geographic mapping, researcher at UNLV's Cryptotephra Laboratory for Archeological and Geological Research located ash layers in Lake Mead and collected samples.

Scientists determined that the ash layers were mostly between 6 million and 12 million years old with some dating to only 32,000 years ago.

They found distinctive ash from four possible sources: the Snake River Plain-Yellowstone hotspot track, which is a chain of volcanic centers in the Yellowstone National Park area; the Southwest Nevada volcanic field northwest of Las Vegas; the volcanoes of Walker Lane in western Nevada and southeaster California; and the Ancestral Cascades, which extend from northern California into British Columbia.

"Studying the past can help you plan for the future," CLAGR lab manager Rachael Johnsen said in the new release.

"The ash layers we study come from volcanoes long extinct. However, studying them has helped us determine just how often the Law Vegas area was inundated with ash over time and may help us prepare for future events from active volcanoes far from us."

The volcanic ash is just one relic uncovered as the water levels have receded.

Severe drought has exposed everything from previously sunken boats to human remains in Lake Mead, which has fallen to about 27% of full capacity as of September, according to CNN.

"We knew that these ash units existed, but we were surprised to find so many as the Lake Mead water level lowered," Smith said.


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