40 Years After Mount St. Helens, Scientists Make Tiny Eruptions to Study Volcanoes

Mount St. Helens in 2018. (USGS)

Meet a SI-entist: The Smithsonian is so much more than its world-renowned exhibits and artifacts. It is a hub of scientific exploration for hundreds of researchers from around the world. Once a month, we’ll introduce you to a Smithsonian Institution scientist (or SI-entist) and the fascinating work they do behind the scenes at the National Museum of Natural History.
Forty years ago, Mount St. Helens erupted in an explosion of ash and rock. It was the most destructive volcanic eruption in the continental United States and produced the largest landslide in Earth’s recorded history. The eruption killed 57 people, destroyed tens of thousands of acres of forest, leveled 200 homes and damaged 185 miles of highway. It remains one of the most studied eruptions ever.
It was Mount St. Helens that inspired Ben Andrews, the director of the Smithsonian’s Global Volcanism Program to become a volcano scientist. In the following interview, Andrews talks more about how he makes volcanic eruptions in a lab, Mount St. Helens and his favorite collections items at the National Museum of Natural History.
A person standing in the mouth of a volcano.
What do you do at the Smithsonian?
I’m a geologist — specifically a volcanologist. Most of my work looks at explosive eruptions. Those eruptions can send a plume of ash and gas into the stratosphere — 6 to 30 miles above the ground — which can be dangerous for communities hundreds or even thousands of miles away and pose threats to aircraft.
Explosive eruptions can also generate pyroclastic flows, which are the clouds of ash and gas that go down the side of the volcano and across the landscape, destroying everything in their path. I study both plumes and pyroclastic flows in laboratory experiments.
A cloud of ash and rock spews out of an erupting volcano.
How do you study volcanoes in a lab?
We simulate a volcanic eruption by making very small pyroclastic flows and plumes inside our lab at the Museum Support Center in Maryland. Natural pyroclastic flows are extremely dangerous and hard to study, but the ones we make in the lab are 100 to 1,000 thousand times smaller than in nature. We create them using baby powder, lasers, temperature sensors and cameras. The lasers allow us to see inside our experiment, so we can see how the powder moves and mixes in air. These miniature pyroclastic flows and plumes can tell us where and how quickly the real ones move.
Another part of my work is going into the field and looking at rocks left behind from volcanic eruptions. The sizes, numbers and shapes of the crystals in these rocks show us how fast these magmas came up.
In a different lab, we release pressure on batches of magma at different speeds to grow crystals that match what we see in the natural rock we found in the field. This gives us an idea of how quickly or slowly the volcano erupted, which is very useful for eruption forecasting or hazard mitigation strategies.How has your work changed since COVID?
We’re not in the lab anymore. Instead, I have data from previous experiments on hard drives, and I’m trying to work with it here at home. I’m analyzing it and writing it up.
What excites you about working at the Smithsonian?
I get to work with the finest collections in the world. And I've stepped into the directorship of the Global Volcanism Program, which is the world's best database of volcanoes and their eruptions. We also have world class laboratory facilities, which let me conduct great research. There’s a lot of freedom to do the science that I want.
Do you have a favorite collections item?
One of them is a beautiful piece of obsidian from Yellowstone Volcano. Normally, you think of obsidian as being black. But in this case, the piece also has chunks of red and orange-colored obsidian in it. It records the history of this magma breaking apart, oxidizing — so basically rusting — and then re-squishing together as it flowed across the surface in a lava flow. So, there’s a cool story there.
The other is a rock that was a piece of granite until the Sedan nuclear test happened on July 6, 1962. After the United States detonated a nuclear bomb, what used to be granite turned into a piece of pumice. If you pick it up, it feels way too light because it’s full of bubbles. So on the one hand, it’s a terrible rock, because it represents a nuclear bomb test. But it’s also a really cool rock because we know down to the second when this rock developed that texture. So we can see how exposing a rock to tremendous forces changes it.It’s been 40 years since the Mount St. Helens eruption. What made it so destructive?
Mount St. Helens’ magma was stored about 3 to 5 miles below the surface. From March until May, some shallow magma was pushed up into the mountain, but instead of it coming out and sitting on the surface, it made a great big bulge just beneath the north side of the mountain. Then, on the morning of May 18, an earthquake destabilized that whole side of the mountain, which collapsed. All of that magma that had been sitting there suddenly exploded. It’s like taking a champagne bottle and cutting off the top with a sword. It decompresses very rapidly.
It made a very destructive and very large pyroclastic flow. That's what knocked all the trees down. The other part, of course, was that the landslide was one of the largest recorded landslides ever.
But I think what makes it stick in our minds is that it happened in Washington State, in the continental United States. And it had a really big initial blast that was a huge event for volcano scientists. This eruption remains one of the most studied eruptions ever. It had a lot of scientists observing it. Unfortunately, 57 people died, which is 57 too many, but it also could have been much, much worse if there had been no scientists and civil authorities monitoring the volcano 

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