Is a super eruption at Yellowstone imminent? A geophysicist explains.
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POCATELLO — After the “most-recorded” hydrothermal explosion happened in Yellowstone National Park last month, many wonder if a super volcano eruption is imminent.
In short, the answer is no, according to experts. To find out why, as well as what the true warning signs would be, EastIdahoNews.com spoke with Michael Poland, a research geophysicist with the Cascades Volcano Observatory and the current Scientist-in-Charge of the Yellowstone Volcano Observatory.
“(The Biscuit Basin explosion) might be of a size that perhaps occurs every decade or so on average. Hydrothermal explosions that are smaller occur several times a year in some part of Yellowstone,” Poland said.
On July 23, a hydrothermal explosion erupted at Biscuit Basin, a popular and well-traveled portion of Yellowstone National Park. The explosion sent steam and debris hundreds of feet into the air, and threw grapefruit-sized rocks tens to hundreds of feet from the eruption.
Despite park visitors being present at the explosion, no injuries were reported. The boardwalk near the explosion was destroyed.
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The majority of the time, hydrothermal explosions happen in the backcountry and get noticed afterwards by a hiker or geologist. The Biscuit Basin explosion happened near a heavily visited geyser basin in the middle of the day.
“This was absolutely the best-recorded one that we know of,” Poland said.
What causes hydrothermal explosions
Hydrothermal explosions are caused by liquid water boiling, causing steam to accumulate under the sub-surface and crack the rock. Poland explained that these are not a reflection of what’s going on deeper in the ground.
“There was no contact between magma and water that triggered this explosion,” Poland explained. “I think a lot of people would have jumped to that immediate thought that there was magma rising up. If that were happening, we would have seen far different signals.”
It’s important to note that if Yellowstone erupted, it wouldn’t necessarily be a supereruption. The most common style of eruption, which last occured 70,000 ago, is a lava flow.
Poland explained this wouldn’t look like an eruption on television.
“(Lava flows are) really, really thick, pasty things, and they’re humongous,” Poland said. He described them looking, “almost like piles of rubble that move across the landscape.”
Rather than drive people away from visiting Yellowstone, Poland could see a lava flow attracting visitors. Because they wouldn’t move with “tremendous speed” they could be observed by tourists from a safe distance.
“They’re not safe to be real close to. There is always the potential for an unexpected explosion from magmatic gases,” Poland said.
What would happen with a super eruption?
For a super eruption to occur, the volcano’s magma chamber, which is mostly solid, would have to push the magma up to the surface. This would be associated with a “huge amount” of seismic activity.
“There is going to be earthquakes galore, a lot of felt earthquakes,” Poland said.
There would also be “dramatic ground deformation.”
“The uplift due to magma rising up to the surface would be dramatic, and you wouldn’t need instruments to measure it. You’d be able to see places that were rising up,” Poland said.
People would also be able to see gas emissions, and changes would occur throughout the park’s geyser system.
Poland guarantees that Yellowstone won’t erupt tomorrow because they haven’t seen any of these warning signs . If the warning signs did begin, they could possibly last for years before an eruption.
“Geologists worldwide would sort of be going nuts, as would all the people that live and work in and around Yellowstone. There would be pretty obvious changes,” Poland said.
Geologists would also have to figure out how to measure the data and answer a major question.
“Will it culminate in an eruption?” Poland said. “That’s an important question. With a lot of volcanic crises, a lot of volcanoes are restless, and then they go back to sleep.”
The vicinity of the volcano’s pyroclastic flow would be within 100 miles of the eruption. Those under the worst of the potential ash fall, which could blanket nearly all of eastern Idaho in over three feet of ash, would have to decide if they should stay or move to a new location.
Super eruptions not the end
Poland explained it is misleading to say that Yellowstone is overdue for an eruption and this claim is based on the last three explosive eruptions at the park, which average out to 725,000 years between each event.
“Somewhere along the line, someone decided that it was 600,000 years between events, and because the last one was 631,000 years ago, we’re overdue,” Poland said
Poland said three eruptions isn’t enough data to determine a true average in between events. Even if it was, volcanoes only erupt if the right conditions exist.
“Volcanoes erupt when there’s a supply of molten material beneath the subsurface to feed an eruption, and pressure to get that stuff up to the surface, and neither condition exists in Yellowstone right now,” Poland said.
Poland also spoke to what a theoretical supereruption would mean for the rest of the world. The area around Yellowstone would be swept away, and while the ash would be more impactful closer to the volcano, it would still have impacts farther away.
“Even small amounts of ash can be very impactful to agriculture, water, electrical grids and its weight on roofs can cause a lot of collapses,” Poland said.
Ash that enters the stratosphere would also block out sunlight in some places, and cause some level of a global cooling.
While Poland said that this would be a “globally impactful event,” it wouldn’t result in extinction or cause the end of civilization. The global cooling would end in “a few years” when the ash clears out of the stratosphere. Poland pointed out that no super eruption they know of has ever resulted in an extinction.
“These big eruptions, it’s not going to end civilization. It’s not going to result in extinction,” Poland said.