Two previously unknown super-eruptions occurred in Yellowstone

Two previously unknown super-eruptions occurred in Yellowstone. In a new study from the Geological Society of America, experts are describing two previously unknown super-eruptions associated with the Yellowstone volcanic hotspot. The researchers found evidence that one of these eruptions was the most catastrophic event in the supervolcano’s history. 

Yellowstone National Park sits on top of a massive hotspot that fuels the activity of geysers and hot springs. The most recent super-eruption, the Lava Creek eruption, occurred 640,000 years ago. 

Volcanic super-eruptions are much more explosive than the eruptions seen in more recent years. For example, if the Yellowstone supervolcano erupted again, it would have between 1,000 and 2,000 times the force of the 1980 eruption of Mount St. Helens.

Despite the enormously destructive nature of super-eruptions, as well as their potential to impact the entire planet, relatively few of these events have been documented in the geologic record.

For the current study, the researchers used a combination of techniques including bulk chemistry and magnetic data to connect volcanic deposits scattered across tens of thousands of square kilometers. 

“We discovered that deposits previously believed to belong to multiple, smaller eruptions were in fact colossal sheets of volcanic material from two previously unknown super-eruptions at about 9.0 and 8.7 million years ago,” said study lead author Thomas Knott, a volcanologist at the University of Leicester.

“The younger of the two, the Grey’s Landing super-eruption, is now the largest recorded event of the entire Snake River-Yellowstone volcanic province.” 

Based on the current knowledge of super-eruptions, the Grey’s Landing event is one of the top five eruptions in the history of the Earth. The Grey’s Landing explosion was 30 percent larger than the previous record-holder in Yellowstone, the Huckleberry Ridge Tuff, according to the study authors. 

“The Grey’s Landing eruption enamelled an area the size of New Jersey in searing-hot volcanic glass that instantly sterilized the land surface,” said Knott. Anything within this region, he added, would have been buried and most likely vaporized during the eruption. 

“Particulates would have choked the stratosphere, raining fine ash over the entire United States and gradually encompassing the globe.”

The newly identified super-eruptions both occurred during the Miocene, which refers to the timespan between 23 and 5.3 million years ago. 

“These two new eruptions bring the total number of recorded Miocene super-eruptions at the Yellowstone-Snake River volcanic province to six,” said Knott.

The experts now estimate that Yellowstone experienced hotspot super-eruptions during the Miocene about once every 500,000 years. In the past three million years, the hotspot seems to be slowing down, with only two super-eruptions so far. 

“It therefore seems that the Yellowstone hotspot has experienced a three-fold decrease in its capacity to produce super-eruption events. This is a very significant decline.”

Knott said the findings have little bearing on assessing the risk of another super-eruption occurring today in Yellowstone. 

“We have demonstrated that the recurrence rate of Yellowstone super-eruptions appears to be once every 1.5 million years. The last super-eruption there was 630,000 years ago, suggesting we may have up to 900,000 years before another eruption of this scale occurs.”

Knott emphasized that this prediction is far from exact and noted that the continuous monitoring in the region, conducted by the U.S. Geological Survey, is extremely important. 

The study is published in the journal Geology.

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By Chrissy Sexton, Earth.com Staff Writer