The American Southwest has been marred by a persisting megadrought for over 20 years. Because of this, bodies of water, like Lake Mead and Lake Powell, have dropped to record lows, raising concerns about access to drinking water for the surrounding areas.
Lake Mead, the largest human-made lake in the U.S., made a slight recovery in 2023 and 2024 after a dangerously dry 2022; however, the megadrought continues, and 2025 doesn’t look like it will bring any signs of relief.
At full capacity, Lake Mead sits at about 1,229 feet. However, it hasn’t been near that level since the summers of 1983 and 1999. With the changing water levels also comes a change in the shoreline. As the waters receded, sediment that had been seen since the 1930s was once again at the surface, and researchers scrambled to see how much of it they could.
Volcanic Ash of the Past
Lake Mead is formed by the Hoover Dam on the Colorado River. It’s a reservoir that provides water for parts of California, Nevada, and Arizona. Upon completion in 1936, water from the Colorado River filled the area that would become the lake.
Once sunken ghost towns and abandoned vessels weren’t the only things the megadrought has exposed in Lake Mead. As the water levels dropped, sediment along the shoreline once again came to the surface. Researchers from the University of Nevada, Las Vegas (UNLV) Cryptotephra Laboratory for Archaeological and Geological Research (CLAGR) team took this opportunity to review and analyze the exposed sediment on the lake’s banks and found something surprising.
Volcanic ash from volcanoes in Wyoming, Idaho, and California was deposited in the rocks along the shore. The ash samples ranged from 6 million to 12 million years old.
“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,” said Eugene Smith, a UNLV emeritus professor of geology who specializes in volcanology, geochemistry, and geologic mapping and has worked on projects in Africa, Asia, North America, Europe, and Antarctica, in a press 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,” Smith added in the release.
Read More: Lake Mead Water Levels Drop Again as Snow Drought Takes Over Western U.S.
Volcanic Eruption Nearby?
Through their findings at Lake Mead, the research team published a study suggesting that, although the closest active volcanoes are a considerable distance from the Lake Mead area, eruptions could potentially reach the area in the future. For example, when Mount St. Helens erupted in 1980, volcanic ash fell on different states, not just Washington.
A potential eruption from a nearby active volcano could spread ash to the Lake Mead area again in the future.
Volcanic ash, even just a few inches thick, can cause disastrous effects on power lines, communication systems, and roadways. Above all, the ash is extremely hazardous to inhale. The ash contains tiny fragments that can damage lung tissue and cause respiratory illnesses, like silicosis.
“Studying the past can help you plan for the future,” said CLAGR lab manager and longtime Southern Nevada geologist Racheal Johnsen in the press release. “The ash layers we study come from volcanoes long extinct. However, studying them has helped us determine just how often the Las Vegas area was inundated with ash over time and may help us prepare for future events from active volcanoes far from us."
Read More: Drought At Lake Powell Reveals Preserved World That Was Once Lost
This article is a republished version of this previously published article here.
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Drought.gov. Research Spotlight: Climate-Driven Megadrought
Earth Observatory. Lake Mead Keeps Dropping
The Geological Society of America. Discovery of Ash in Sediments Around the Las Vegas Valley: Implications for Future Ashfall Hazards From Distal Volcanoes
A graduate of UW-Whitewater, Monica Cull wrote for several organizations, including one that focused on bees and the natural world, before coming to Discover Magazine. Her current work also appears on her travel blog and Common State Magazine. Her love of science came from watching PBS shows as a kid with her mom and spending too much time binging Doctor Who.
