CNN
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Falling water level in Lake Mead She revealed several shocking things in recent months – Previously sunken boatsAnd ancient warships And human remains. Now, scientists are reporting a new discovery on the dry bottom of Lake Mead: boulders covered in volcanic ash that rained over southern Nevada in volcanic eruptions about 12 million years ago.
Rising water levels are revealing sedimentary rocks not seen since the 1930s when the Hoover Dam was built and Lake Mead filled up. Among these rocks, researchers from the University of Nevada in Las Vegas have discovered ash deposits from volcanoes in Idaho, Wyoming and California.
“We knew these cinder units were there, but we were surprised to find so many as the water level in Lake Mead fell,” said Eugene Smith, professor emeritus of geology at UNLV and co-author of the study.
Western drought caused by climate change and overuse of water from the Colorado River Pushed the levels of Lake Mead to unprecedented levels. In September, the lake’s water level was just 1,045 feet above sea level, or about 27 percent of its full capacity.
Scientists are taking advantage of the lower levels to study sediments that have not been exposed for nearly a century.
Smith’s research team found white to gray volcanic ash seeping through the submerged rock. They took samples to their lab to determine the source of the ash, but it wasn’t a single eruption.
They found evidence of several volcanic eruptions millions of years ago in places such as the Snake River Plain – Yellowstone – a stretch of inactive volcanoes that stretches across Idaho along the Snake River and in what is now Yellowstone National Park – and eastern California. They also found ash from volcanic eruptions just 32,000 years ago — not far on a geologic time scale.
Jake Lowenstern, a research geologist with the USGS, who was not involved in the study, told CNN that studying past volcanic eruptions can help paint a picture of future risks.
Lowenstern said the latest discovery at Lake Mead may be one of the “best” volcanic ash collections from this time period, and will be important in allowing us to reconstruct the geological history of the area and understand the frequency. Major volcanic eruptions and their impact on the southwest.
Ash from moderately explosive volcanic eruptions can travel hundreds of miles, covering remote areas of up to several meters with heavy material. Recent eruptions have revealed a few millimeters of wet ash disrupts the transmission of electricity. When inhaled, small, pointed ash particles form a significant health risks.
“This ash can disrupt logistics networks, close airports, and potentially pose a health hazard,” Smith said. “It is important that local governments make plans to deal with this type of event, as they have done with earthquakes and floods.”
Smith said their latest analysis could help society prepare for future volcanic events, even if they come from distant volcanoes — as well as “present and future climate change.”
“Studying the past is the key to understanding the future,” Smith said. “By understanding past volcanic events, we can better understand how a future event could affect a large urban area. We can also make plans to deal with a volcanic eruption when it occurs in the future.