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During a trip to Lava Creek’s tuff near Shell, Wyoming, scientists have found evidence of two major volcanic eruptions. | Credit: USGS/photo from Madison Mayers.
Wyoming scientists have found evidence of two mysterious volcanic eruptions that are older than Last caldera-forming supermers in Yellowstone.
The deposits of ash were buried under the Lava Creek tuft, a large, white mass of compacted volcanic ash formed by the last giant eruption of Yellowstone 631,000 years ago. The origin of the newly discovered ash deposits is a mystery, but researchers hope to have answers until the fall of 2025 when they expect to receive test results from samples.
“At first, I just thought topography was complicated.” Madison MayersAssistant Professor of Magmatical Processes at the Montana State University, who was on an excursion to Wyoming, Live Science told an email. “But to walk around, we can clearly say that there are other units between the white layers of ashes [of the Lava Creek Tuff]S It was amazing. “
Lava Creek’s tuff is made up of two different bodies of sealed ash, Article A and Article B, suggesting that it had a Change in nature or composition From the volcanic material discarded during the last super -Stock of Yellowstone. The purpose of the excursion was to revalist evidence for the two members, Myers said, and the team was “shocked” to find traces of unknown, older eruptions.
Related: We finally know where the Yellowstone volcano erupts
As the deposits of ashes were buried under the Lava Creek tuft, the eruptions that caused them must have occurred earlier than 631,000 years, according to an article written by Mayers and her colleagues in Yellowstone Caldera ChroniclesS
It is known that the Jelloustone volcano produced two superpets before the eruption of Lava Creek’s tuff – the eruption of the Mesa Falls tufa 1.3 million years ago and the eruption of the Huckleber tufa 2 million years ago – and it is possible for these explosions to create newly disguised assets.
However, early testing suggests that the younger of the two ashes deposits has no connection with Yellowstone. “One of the deposits we found contained biotite, a mineral that was not found in most Yellowstone eruptions,” Myers said. “So we had to think of a certain eruption of a large volume that contained biotite.”
The most likely suspect is the eruption of Bishop of Garganthuan, who formed Long Valley’s caldera in California 767,000 years ago, Myers said.
Meanwhile, the origin of the older ash deposits remains a complete mystery. The ashes may come from an untouched eruption, as it is relatively common that geologists find deposits with dates that do not coincide with some eruptions, according to Myers. “We recently had such an event that happened at Yellowstone and we are still trying to map and find out where this newly undocumented eruption comes from,” she said.
A map of the volcanic ash arising from two supersensions of Yellowstone (~ 2 million years ago and ~ 630,000 years ago), the formation of the Caldoria Long Valley in California 760,000 years ago, and the eruption of the St. Helen Mountain in 1980 | Credit: USGS
The newly opened deposits are not yet dated and the picture will become much more clear after these results come out, Myers said.
The best way to determine the origin of ash deposits is so far the mineral sanidine using a technique called Argon geochronologyS This technique measures the ratio of two different forms or isotopes of the argon element in the samples. Argon 40, a stable isotope of the argon, accumulates in volcanic rocks with a predictable speed after eruption, so that scientists can determine the age of these rocks based on their argon 40 content.
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Argon dating results will be available this summer, Mayers said, revealing age and therefore the likely origin of both deposits. But there will be another mystery, she wrote and her colleagues, because it is not clear how very ancient volcanic ash has remained preserved in Wyoming.
“Probably these ashs were stored in spaces that reduce the exposure to wind and rainy atmospheric influences,” Myers said.
In addition to finding the two unexpected ash deposits, researchers also achieved their original goal to find evidence for two members at Tuff Lava Creek Tuff. But it also turned out to be full of surprises.
“The Deposit of Tuff Lava Creek does not prove to us that there are two members of the Tuff Lava Creek eruption, and more many magma, extinguished and erupted during the eruption,” Myers said. “Now we write this for publication.”