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Picture this: You’re roaming Yellowstone National Park as the ground begins to rumble, pressure builds, and then…KA-BOOM! Goodbye to Montana, Wyoming, and Idaho.

The last Yellowstone explosion happened 661,000 years ago, but could it happen again? On our latest episode of Ask Us Anything, editors Sarah Durn and Annie Colbert explore the chances of Yellowstone’s supervolcano erupting today. Let’s just say you shouldn’t cancel your vacation. But that doesn’t mean nothing else is brewing underneath the national park.

Ask Us Anything answers your most outlandish, mind-burning questions—from the everyday things you’ve always wondered to the bizarre things you never thought to ask. So, yes, there’s a reason why most people are right handed and no, not all cats hate water and that’s okay. If you have a question for us, send us a note. Nothing is too silly or simple.

This episode is based on the Popular Science article “What would happen if Yellowstone’s ‘supervolcano’ erupted today?”

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Full Episode Transcript

Sarah Durn: Picture yourself walking through Yellowstone National Park, about 2.1 million years ago. There are no tourists. No boardwalks. No Old Faithful gift shop. Instead, mastodons and saber-toothed cats roam the landscape. And deep beneath their feet, something enormous is happening.

Magma is accumulating beneath the Earth’s crust. The ground is swelling. Earthquakes are rattling the landscape. Pressure is building underground.

Until—Yellowstone erupts in a SUPER VOLCANO, sending over 660 TRILLION gallons of rock, ash, and magma into the atmosphere – enough to cover the ENTIRE state of Rhode Island under nearly half a mile of debris.

The total output is roughly 6,000 times larger than Mount St. Helens’ famous 1980 eruption—and when it’s over, the ground collapses into an enormous crater, known as a caldera.

Yellowstone would have two more giant, caldera-forming eruptions after that. The most recent happened about 631,000 years ago. Which raises a slightly terrifying question: When might Yellowstone erupt again? And if it does… what exactly would happen?

Welcome to Ask Us Anything from the editors of Popular Science, where we answer YOUR questions about our WEIRD world.

From “What are the most common sunscreen myths?” to “How fast would New York City fall apart without people?” No question is too offbeat or mundane.

I’m Sarah Durn, an editor at Popular Science.

Annie Colbert: And hello, I’m editor-in-chief, Annie Colbert.

SD: Here at PopSci, we’re always pondering quirky questions.

AC: And this week, we’re wondering: what would happen if another Yellowstone supervolcano erupted today?

Okay, Sarah, this is terrifying. So I need to know, how scared do we really have to be of a national park becoming a volcanic powder keg?

SD: Okay, so I have some good news.

AC: Ooh, I do love good news.

SD: Experts say a giant Yellowstone eruption probably will happen again someday.

AC: That does not sound like good news.

SD: The good news is the someday part. A major eruption likely won’t happen for thousands, potentially even millions of years. The magma beneath Yellowstone right now is mostly solid, which means it isn’t really capable of feeding a massive supervolcano eruption.

AC: Okay, so we can cancel the emergency volcano bunker?

SD: For now, but here’s where things get interesting. A giant eruption also isn’t necessarily the next volcanic event Yellowstone will experience.

AC: Oh, no.

SD: Oh, yes. Something like a massive superheated water explosion or even a slow-moving lava flow is much, much more likely. In fact, scientists say calling Yellowstone a supervolcano can be a little misleading because it makes it sound like every eruption has to be catastrophic.

AC: But I’m guessing we’re still gonna talk about the catastrophic version of events.

SD: Oh, absolutely, because while a giant eruption is incredibly unlikely anytime soon, scientists have studied what would happen if Yellowstone had another super eruption.

AC: And I’m gonna guess that the answer is not great.

SD: Not great.

That would be, you know, putting it mildly. And what happens wouldn’t necessarily stay anywhere near Yellowstone.

AC: Okay, now I need to know details. What would an eruption actually look like? How far would the damage spread? Would scientists know it was coming, and perhaps most importantly, would humanity survive?

SD: We will get into all of that.

AC: Ugh, cliffhanger.

SD: I know. I’m sorry. But before we dig into all of those harrowing questions, we wanna hear from you. What questions are erupting in your brain?

AC: If there’s something you’ve always wanted to know, you can submit your questions by clicking the Ask Us link at popsci.com/ask.

SD: Send us your questions.

AC: Yes, send them. All right. Coming up, we’ll dig into what’s actually happening underneath Yellowstone right now.

SD: And what would happen if one of the largest volcanic systems on earth really did blow.

AC: That’s after this quick break.

SD: Welcome back. Okay, Annie, before we get into what’s going on under Yellowstone National Park, I think we need to start with the basics. Can you explain to listeners what a volcano is? 

AC: Yes, absolutely. So very basically, a volcano is an opening in the Earth’s crust where magma, gases, and other material from inside Earth can escape.

And a little fun bonus fact, the word volcano actually comes from Vulcan, who is the ancient Roman god of fire. 

SD: Of course it does. Of course. Very dramatic, very appropriate. 

AC: And volcanoes are actually much more common than you might think. There’s around 1,350 potentially active volcanoes around the world.

SD: Whoa.

AC: And most of the volcanoes are concentrated around the edges of the Pacific Ocean in what’s known as the Ring of Fire.

SD: Another incredibly reassuring name.

AC: Yes, volcanologists really know how to name things. There are around 170 volcanoes in the US and its territories. Most are in places like Alaska and the Cascade Range in the Pacific Northwest, but Yellowstone is a little different.

SD: Very different because when you picture a volcano, you probably picture a mountain with a crater on top. Yellowstone, you know, doesn’t really look like that.

AC: Mm-hm.

SD: In fact, Yellowstone National Park doesn’t just sit on a volcano, much of the park is part of this enormous volcanic system called the Yellowstone Caldera.

AC: So when millions of people are wandering around Yellowstone looking at geyser and bison every year-

SD: They’re essentially walking around inside a volcanic crater.

AC: Very cool.

SD: Incredibly comforting.

AC: Yes.

SD: All of those famous Yellowstone features, Old Faithful, the hot springs, all that steaming water, are only possible because there’s an enormous heat source underground. So let’s do the scary hypothetical.

Let’s say Yellowstone really is about to have another giant super eruption.

AC: I’m almost scared I ask. What’s the first thing though that happens if Yellowstone erupts?

SD: Right. So long before the actual eruption, there’d be a huge amount of magma accumulating underground. Pressure would build, the Earth’s crust would begin to crack, and eventually magma would force its way through those cracks and erupt at the surface.

And then? Things would get very bad very quickly. Hmm. Huge columns of superheated ash and gas would shoot into the sky. Those eruption columns would actually collapse under their own weight, creating what are called pyroclastic flows. Which are basically avalanches of extremely hot ash, gas, and rock racing across the landscape.

AC: Mm.

SD: They would destroy trees, buildings, roads, pretty much everything in their path. The areas immediately surrounding Yellowstone, including parts of Wyoming, Montana, and Idaho, would be swept clean.

AC: So if you’re near Yellowstone, this is very, very bad.

SD: Oh, yeah, extremely, extremely bad. But the effects wouldn’t just stop at Yellowstone.

Ash would fall much, much farther away. Scientists have actually modeled this. Communities stretching from Missoula, Montana, all the way down to Albuquerque, New Mexico, could get coated in ash. 

AC: That is a huge area.

SD: Yeah, and it gets bigger. Michael Poland, the scientist in charge of the Yellowstone Volcano Observatory, told Popular Science that at least a few millimeters of ash could fall over much of the United States and parts of Canada.

AC: I mean, a few millimeters doesn’t sound like that much.

SD: It doesn’t, but volcanic ash is really, really nasty stuff. That amount of spread across such an enormous area could disrupt agriculture, contaminate water supplies, and cause problems for electrical grids. And then there’s what happens in the atmosphere.

AC: Oh, no.

SD: A giant eruption could blast huge amounts of ash and gas high into the atmosphere. Those particles could block some sunlight from reaching the Earth’s surface and cool the planet. We actually have a historical example of this on a much smaller scale. In 1815, Mount Tambora erupted in present-day Indonesia. It was the largest volcanic eruption in recorded human history.

AC: And this is the one that caused the year without summer, right?

SD: Exactly. Temperatures dropped, crops failed, there was widespread famine and disease. A Yellowstone super eruption would be a very different event, but scientists use eruptions like Tambora and climate models to understand what the global effects could look like.

And volcanologists like Poland say the effects from something on the scale of a Yellowstone super eruption could potentially last five to 10 years.

AC: Oh, okay, this all sounds really, really bad.

SD: Yeah.

AC: So are we talking about the end of humanity here?

SD: Surprisingly, no. Oh. It would be catastrophic. A lot of people could die, but Poland told Popular Science that no explosive volcanic eruption has ever been associated with a mass extinction, so humanity would survive.

AC: Hey, yay. It’s a little reassuring.

SD: On a very relative scale.

AC: Yes, extremely relative. So now that you’ve thoroughly terrified me, how likely is any of this to actually happen?

SD: Yeah, and this is the part I really want everyone to remember. Not very likely at all. Poland says the chance of a giant Yellowstone super eruption happening on a human timeline is about as close to zero as you can get.

AC: Okay. Can you explain? Because there is magma underneath Yellowstone.

SD: There is, but scientists say that magma is currently mostly solid. So even though we talk about a magma chamber, don’t picture some, you know, enormous underground lake of glowing liquid rock just waiting to explode.

AC: That is absolutely what I was picturing.

SD: I know, me too. But right now there simply isn’t enough liquid magma in Yellowstone to feed an enormous eruption. Poland gave this great analogy. Imagine the odds of getting struck by lightning are one in a million, but then imagine you’re standing outside and there isn’t a cloud anywhere in the sky. So

AC: Lightning exists, and it could strike me someday-

SD: But the conditions you need for it to happen right now just aren’t there.

That’s basically Yellowstone. Scientists think a major eruption probably will happen again eventually, but we could be talking thousands or potentially millions of years from now.

AC: So what should we actually be worried about at Yellowstone?

SD: Probably something much smaller. A hydrothermal explosion, basically superheated water erupting as steam and violently exploding is considered much more likely.

Those can create impressive craters and be extremely dangerous if you’re nearby, but they’re not gonna devastate all of North America. Yellowstone could also eventually have another lava flow, and those tend to be much slower-moving events. Basically, thick lava erupts from the ground and slowly creeps across the landscape over months or years.

In fact, lava flow eruptions are much more common at Yellowstone than enormous super eruptions. The last lava flow there happened about 70,000 years ago.

AC: Which makes super volcano sound a little misleading.

SD: Definitely. Poland actually isn’t a huge fan of the term for that reason. Calling Yellowstone a super volcano makes it sound like this thing that has two settings, peaceful national park and apocalypse.

AC: Nothing in between.

SD: Exactly. When in reality, Yellowstone is this incredibly complicated and active volcanic system that can do lots of different things, and scientists are watching it constantly. The Yellowstone Volcano Observatory uses things like seismic stations to track earthquakes and instruments that monitor heat coming out of the volcanic system.

AC: So we would know if a giant eruption was coming.

SD: Yeah, most likely. Scientists think they’d probably see warning signs weeks to months in advance. So Yellowstone isn’t a giant bomb that could suddenly explode beneath everyone’s feet without warning.

AC: Okay, I feel considerably better than I did six minutes ago.

SD: That was the goal. Yellowstone could erupt again, a giant eruption could be catastrophic, but right now there’s no evidence that anything like that is on the horizon,

AC: So maybe don’t cancel the Yellowstone vacation.

SD: Definitely not.

AC: And if you wanna learn more about what would happen if Yellowstone did erupt, you can check out the full story on Popular Science. We will link it in the show notes.

SD: Read it. It’s super interesting. Now, we have to take a quick break, but when we come back, we’ll talk about the volcanic activity that has been happening in Yellowstone just in the last few months. Wait, what? I know, I know. It’s gonna be okay. That’s coming up after this quick break.

AC: Welcome back.

SD: So, Annie, after spending this entire episode telling you Yellowstone probably isn’t going to erupt anytime soon, Yellowstone has actually been doing some pretty weird stuff lately.

AC: Sarah.

SD: I know, but I promise this is not a forget-everything-we-just-said situation. Earlier this year, scientists detected a giant bulge forming along the northern edge of the Yellowstone caldera.

AC: How giant is giant?

SD: About 19 miles across.

AC: That sounds concerning.

SD: I know. It does. The ground had risen about an inch from July 2025 to February of this year. But scientists say this kind of swelling or uplift isn’t particularly concerning at Yellowstone. It’s happened before. Researchers think this one could be caused by magma moving around about nine miles underground.

AC: So the giant bulge is not Yellowstone’s supervolcano waking up?

SD: No, no. In fact, 2025 was actually a relatively quiet year for Yellowstone earthquakes, so there we go. But then in June 2026, Yellowstone gave scientists another surprise.

AC: Of course it did.

SD: Remember those hydrothermal explosions we talked about earlier?

AC: Yes, the much more likely alternative to the super eruption.

SD: Exactly. On June 13, a small hydrothermal explosion happened at Biscuit Basin. Super heated underground water suddenly found a path to the surface, flashed into steam, and exploded out of the ground.

AC: Oof. Was anyone hurt? 

SD: Thankfully, no. Biscuit Basin was already closed because there had been a bigger hydrothermal explosion there in 2024.

AC: Mm.

SD: But here’s the really cool part. A couple days later, geologists came back and discovered that the landscape had changed. A brand-new pool of vigorously boiling water about 21 feet by 17 feet had formed in a spot where scientists had literally been walking just two days earlier.

AC: Ah. All right, Yellowstone, we get it. You’re alive.

SD: It’s alive.

AC: It’s alive.

SD: So maybe that’s the real takeaway from this episode. Yellowstone is absolutely active. It’s moving, it’s bubbling. Occasionally, it even explodes.

AC: Just probably not in the civilization-ending way.

SD: Exactly. So enjoy Old Faithful. Respect the boiling water.

AC: And maybe don’t lose sleep over the supervolcano just yet.

SD: Exactly.

AC: And that’s it for this episode. But don’t worry, we’ve got more episodes of Ask Us Anything live in our feed right now. Follow or subscribe to Ask Us Anything by Popular Science wherever you enjoy your podcasts. And if you like our show, leave a rating and a review.

SD: We care what you think. Our producer is Alan Haburchak. This week’s episode was based on stories written for Popular Science by Nidhi Sharma and Andrew Paul.

AC: Thank you, team, and thanks everyone for listening.

SD: And one more time, if you want something you’ve always wondered about explained on a future episode, go to popsci.com/ask and click the Ask Us link. Keep those questions coming.

Keep ’em coming. Until next time, may your magma stay underground.

AC: Your hydrothermal explosions stay far, far away…

SD: And your national parks remain decidedly un-apocalyptic.

 

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