Scientists Uncover Surprising Ash from Two Mysterious Volcanic Eruptions – What It Means for Our Planet

Scientists in Wyoming have stumbled upon evidence of two ancient volcanic eruptions, predating the last major eruption at Yellowstone. They discovered these ash deposits buried beneath the Lava Creek Tuff, which formed after a significant eruption about 631,000 years ago. The findings are intriguing, and researchers expect more details by fall 2025 when tests on the samples are complete.

Madison Myers, an associate professor at Montana State University, was part of the team that made this discovery. Initially, she thought the area’s geography was confusing. However, as they explored, they found layers of ash that hinted at more volcanic activity than previously documented. "It was impressive," she shared with Live Science.

The Lava Creek Tuff consists of two ash layers, known as member A and member B, which suggests changes in the type of volcanic material ejected during Yellowstone’s last supereruption. The field team was looking for evidence of these layers, but the older, hidden ash deposits caught them off guard.

Due to their buried nature, these ash deposits must have formed before the Lava Creek Tuff. Yellowstone has had two previous supereruptions—1.3 million years ago and 2.1 million years ago—and these may be linked to the newly found ash. However, early tests indicate that the younger deposit likely originated from the Bishop Tuff eruption that occurred in California about 767,000 years ago.

The older ash deposit, however, remains a mystery. It’s not uncommon for geologists to find ash layers that don’t align with known eruptions, which suggests there may have been undocumented volcanic activity. "We’ve seen similar findings in Yellowstone, where we are still mapping an unknown eruption," Myers pointed out.

Once the ash layers are dated, the results should clarify their origins. The dating process uses a method called argon geochronology, which can determine the age of volcanic rocks by measuring the ratio of argon isotopes. This summer, scientists expect to uncover more about these ancient deposits.

Interestingly, Myers shared that the preserved state of the ash could be due to its placement in areas that received less weather exposure.

Aside from this surprise discovery, the research team achieved their original goal of examining the two members in the Lava Creek Tuff. However, the findings reveal a more complex eruption history, indicating multiple magma sources throughout the eruption.

This research underscores that the understanding of Yellowstone’s volcanic history is still evolving. As more data comes in, we may gain deeper insights into the area’s geological past, potentially reshaping our knowledge about other volcanic processes. For more about Yellowstone volcanoes, check out the USGS Yellowstone Observatory.

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