Scientist Busts Myths On Yellowstone Volcano

May 20, 2019

Yellowstone National Park is famous for its explosive geysers, bubbling mud pots and psychedelic hot springs. Some visitors don’t realize it’s all part of a very large, active volcanic system. Others worry it’s going to erupt at any moment. Michael Poland, the Scientist-in-Charge of the Yellowstone Volcano Observatory, busts some myths and shares what’s really happening below the surface.

A quick Google search for "Yellowstone Volcano" brings up some apocalyptic results with titles like Eruption 'can kill 5 BILLION' in fiery fallout from The Daily Express, a tabloid newspaper in the UK, and Yellowstone supervolcano: A countdown on the clock from Fox News.

The last eruption was more than 600,000 years ago. It was 2,500 times bigger than the 1980 eruption of Mt. Saint Helens in Washington and left behind a massive crater or ‘caldera’ that spans most of Yellowstone National Park.

But scientist Michael Poland says it’s not something people should be worried about.

“The most common misconception might be that the volcano is overdue for some kind of eruption or that it only explodes in these catastrophic, massive explosions,” says Poland. He gave a presentation about the Yellowstone Volcano last week at the Gardiner Community Center.

“You have to have enough magma to erupt, and then you have to have pressure to get that magma to the surface. So those are things we can actually monitor for and tell whether or not that situation is likely,” Poland says.

Scientists at the Yellowstone Volcano Observatory use a vast array of instruments to constantly record and monitor data remotely. Poland is based at the Cascades Volcano Observatory in Vancouver.

He says lava flows in Yellowstone are much more frequent than eruptions, but that’s on the geological time scale.

“The last one was 70,000 years ago so it’s not at all a common sort of thing. But when it happens, the flows are pretty big,” says Poland.

And those flows, he says, have covered up a lot of the caldera, which leads to another common misconception.

“A lot of people hear Yellowstone ‘volcano’, and they’re looking for a pointy mountain," he says. "They think maybe Mt. Washburn is the volcano and not realizing it’s this gigantic system.”

During the presentation in the community center, Poland describes the system as a big blow torch underneath a slow-moving tectonic plate. As the plate moves over the hotspot, the mantle begins to melt and heat the earth’s crust. The crust expands and eventually breaks or slips along fault lines, which creates earthquakes.

“Everyone talks about the earthquakes and rightly so," says Poland. "There are anywhere from 1500 to 2500 earthquakes that are located every year in the Yellowstone region. It’s one of the more seismically active places in the country.”

Poland says most of the earthquakes are very small and cannot be felt, but there tend to be one to three big ones every century. He shows a map full of dots representing the more than 2,000 earthquake locations from last year. The biggest cluster is east of Hebgen Lake or northwest of the Norris area.

“And this is a real hot bed of seismicity. It flares and then goes away, and flares and goes away. So seeing a swarm up here was not particularly surprising, especially given that in 2017 in that area there were 2500 located earthquakes just in that area alone in three months,” says Poland.

The 1959 Hebgen Lake Earthquake was a magnitude 7.3. It killed 28 people west of the park and caused measurable changes to Old Faithful Geyser and other hydrothermal features.

He says big hydrothermal explosions happen more frequently than earthquakes but are less hazardous. When underground water rapidly turns into steam, it can push through the earth’s crust. Poland says hydrothermal explosions occur about once a year and usually take place in the backcountry.

Yellowstone National Park hosts more than 10,000 hydrothermal features, and because they are part of a large, complex system of heat, water, rock and gas, they change over time.

“If that was a single word I could describe the place is dynamic. The only thing you can count on is that they’re going to change, which is also maybe one of the coolest things about them because you can go every year, and it’s going to look different every year,” Poland says.

Poland will host another talk Wednesday, 6:30 to 7:30 PM at the Holiday Inn in West Yellowstone. The event is free and open to the public.