- Yellowstone seems to pop up in the news every few years with the same terrifying headline.

It's a super volcano that could end civilization.

- There are pyroclastic flows that come shooting out of the caldera and that'll wipe out everything.

- This ash would travel across the world.

- It might be several degrees of cooling.

- It would really feel like the end of the world.

- But is that just fearmongering?

Is Yellowstone really that bad or could it even be worse than the headlines make it sound?

- If there's something else that can cause 90% of the species to die out, I'd like to know what that is, man, because it could happen again.

- Yellowstone might destroy America, but there's something else out there that almost definitely would.

And not just America, but maybe civilization altogether.

This is what led to the creation of Yellowstone in the first place.

And they've been behind nearly every mass extinction in Earth's history.

And they could tell us a lot about what we might be facing today.

For many people in the us, especially the Northwest, Mount St.

Helen's was the biggest volcanic eruption they've ever known.

It was the largest ever recorded in the continental US and created the largest landslide ever recorded on earth.

But it's far from the biggest eruption our planet can create.

The 1991 eruption of Mount Pinatubo was 10 times bigger than Mount St.

Helens, and by many estimates cooled the earth by up to one degree Fahrenheit.

The Mount Tambora eruption of 1815 was 10 times bigger than Pinatubo and led to the infamous year without a summer and famines then 10 times bigger than that, or a thousand times bigger than St.

Helen's was Yellowstone.

- My name is Michael Poland and I'm the scientist in charge of the Yellowstone Volcano Observatory.

The last three big explosive eruptions in Yellowstone occurred about 2.1 million years ago, about 1.3 million years ago.

The last really, really big event in Yellowstone was about 631,000 years ago, and it formed Yellowstone Caldera, which really occupies the central part of Yellowstone National Park.

- Lava and debris flowed from the fracture zone hardening into layers hundreds of feet, thick and sulfur, aerosol, and ash encircled the globe likely cooling the planet for years.

So what happens if Yellowstone erupts again?

- These large explosive eruptions have a tendency to collapse under their own weight.

The ash plumes are so big and so heavy that they fall apart, and that creates these dense plumes of hot gas and ash that can rush across the landscape, and they really just scour the area clean.

- That initial shockwave in pyroclastic flows would kill everything near the blast.

Then there's the ash fallout.

Alexa modeled what the ash plume from a future eruption could look like, and it's pretty shocking.

- So what we can see in these bullseye color zones are different amounts of ash fall that would would accumulate on the ground.

So the densest portion here represents more than a thousand millimeters.

So the area well beyond Missoula into Canada and down into Colorado and Utah would all see extremely devastating effects of ash fall to the point where it would be dark in the middle of the day.

This ash would travel across the world and encircle the globe multiple times.

- Unlike wildfire ash, volcanic ash is made of rock, which means it doesn't biodegrade.

- It never goes away.

Just the magnitude of ash cleanup would be really tremendous.

- Seeing and breathing would be a challenge.

Communications would be disrupted or shut down.

Ash would cover fields across the bread belt, devastating crops and resulting in famines, and it probably wouldn't just erupt once.

- There's rarely just a single event.

Imagine dealing with the aftermath of this size eruption and then having another one happen a couple weeks later or even years later.

When do you recover?

How do you move on?

- But those cataclysmic impacts aren't even the worst part of it.

We don't know exactly how much global cooling would happen, but possibly several degrees Fahrenheit and quickly.

The global consequences would be huge.

So you might be surprised to hear that you probably shouldn't worry about any of this.

- I guarantee Yellowstone will not erupt tomorrow.

Prior to any eruption of Yellowstone, we would be seeing really dramatic changes.

We would see huge numbers of earthquakes.

The ground would be swelling possibly by many, many feet.

There'd be park wide changes in hot spring and geiser activity changes in the amount of heat that was coming outta the ground.

Changes in the amount and the composition of the gases were coming out.

Right now at Yellowstone, we're not seeing anything that indicates that this magmatic system is particularly active.

- And despite what some headlines would have you believe, it probably wouldn't be the end of humanity.

- These explosive eruptions are probably not long enough in duration, big enough in impact to cause global extinctions.

There are volcanic eruptions though that do have that potential.

- And so while Yellowstone is really big, hundreds of cubic kilometers, there's actually even larger events that we know about in earth history, and those are associated with what are known as large igneous provinces.

- Large what?

It turns out, there is a geologic force bigger than any of the volcanoes we've talked about, and somehow no one's talking about it.

- We're here at Wahclella Falls in the Columbia River Gorge, and at the end of this trail, even though we're 600 miles away from Yellowstone, there are some geologic clues to the origin of the Yellowstone hotspot.

- To understand Yellowstone, you sort of have to take a step back and and understand a little bit about how the solid earth works.

It's conceptually similar in some sense to what happens when you put a pot of water on your stove.

It's heated from the bottom and cooled from above, and the hotter fluid is less dense, so it rises right, and it circulates.

And so that's what's going on in the solid earth under our feet all the time.

And the upwelling limb, the sort of buoyant plumes that are coming up are one of the primary drivers of plate tectonics.

And those mantle plumes are these sort of blobs.

It's rising from deep in the earth, perhaps even at the core mantle boundary.

Once it gets to the surface, it starts to melt.

It starts to push up the earth's crust, and that melting produces a tremendous amount of magma that previously wasn't there.

You have the potential for truly enormous eruptions, possibly up to 10,000 cubic kilometers erupted in a single event.

And so that will happen repeatedly over the course of a large igneous province event.

These lava flows that blanket the earth and they travel for, you know, hundreds of kilometers, single lava flows.

The flow rate is so high that they are not cooling, flooding the landscape, filling in topography, and forming a stack of basaltic rocks that can be kilometers thick.

- The most recent such event happened in the Northwest US starting about 17 million years ago.

It's called the Columbia River Flood Basalts.

- Look at this.

So you can see there's a whole stack of lava flows here.

The columns in the middle, there are where the lava flow cooled, nice and slow, and then you've got a a break, and then there's another set of lava flows.

So there's a whole stack of lava flows sitting right here.

There was a huge outpouring of lava that occurred all along Eastern Washington, Eastern Oregon, western Idaho, and lava flows from those eruptions flow all the way across the states and into the Pacific Ocean.

Right here in the Columbia River Gorge these cliffs all around us are made of lava flows.

- It would not have been a very fun thing to have been alive during that time.

The deepest parts of the Columbia River flood basalts are over four kilometers thick.

That's a lot of lava.

- And surprisingly, Yellowstone is evidence of this massive, large igneous province event.

It's a hotspot, essentially an opening in the earth's crust following the massive eruption that hasn't quite closed up yet.

- The hotspot is more or less stationary, right?

And the crustal plates that make up the surface of the earth move across this stationary plume.

This is expressed really well in Hawaii where you see this chain of volcanoes that get older, the farther away you get from the big island, the same thing's happening in Yellowstone.

The youngest Vulcan is right there in Yellowstone National Park.

And then as you go to the southwest, you see a chain of volcanoes that's getting older and older.

The farther away you get from Yellowstone.

- These large igneous province events happen every 10 to 30 million years and will continue to happen.

The Columbia River flood basalts is the most recent event, but it's far from the biggest.

- If we wanna look at the largest of the largest.

These things are for example, the Deccan Traps, the Siberian traps, the North Atlantic Igneous Province.

These events are associated with the in placement of millions of cubic kilometers of magma in a short amount of time.

- The theory of plate tectonics wasn't widely accepted until the sixties, and the large igneous provinces weren't fully recognized until the nineties.

And their discovery has led to breakthroughs in our understanding of life and death on earth.

- For a long time, geologists ignored mass extinctions because they couldn't explain them, and so they didn't pay any attention to them.

But then in 1980, when the Alvarez Group at Berkeley discovered evidence for that asteroid impact at the time of the dinosaur extinction 66 million years ago, right.

Now, people became more interested in mass extinctions.

And so people began to think, well, okay, now their asteroids impacts could cause a mass extinction.

What about something terrestrial?

What about something from inside the earth?

And a couple of people pointed out that if you look at some of the mass extinctions that we knew about then and looked at the time of large igneous provinces, that the dates, which weren't that well known, but they seemed to match up.

- And for the past three decades, Mike has been piecing this story together, getting more and more accurate dates for mass extinction and large igneous province events.

- And lo and behold, they match up exactly.

There are probably 14, 15 mass extinctions in the last 600 million years, right?

Almost all of them match up with the ages, the dates of these large igneous provinces.

- These events are catastrophic regionally, but how could they cause global extinction?

Well, you guessed it.

Climate, - Initially, we have a huge outpouring of lavas.

These are the largest volcanic eruptions on earth, and they produce a tremendous amount of volatiles, CO2, sulfur, and so forth.

- And what we think is that there's so much carbon dioxide released in these eruptions that they warm the earth significantly, - Almost without exception, after large igneous province events.

there are these local hot house climates where you have intervals of abnormally warm temperatures globally that last a few million years.

The onset of these events is often quite abrupt, and we can think about that initial pulse as providing the really rapid changes that are necessary to cause mass extinctions.

- After that initial pulse of gases and warming, the earth continues to warm for some time, but slowly, and while that quick pulse of warming can cause mass extinction, the slower gradual warming actually can lead to a diversification of life over millions of years.

- Rapid perturbation leads to, you know, widespread death.

The longer term forcing say over the next few million years is slow enough that species can recover.

- Our earth is incredibly good at adapting, just not quickly.

Does that sound familiar?

Some scientists think we're now headed towards a sixth mass extinction, but this one isn't coming from outer space or erupting magma.

It's from us.

Paleoclimatologists have studied the extreme global temperature spike that happened 56 million years ago in order to better understand anthropogenic climate change.

The Paleocene-Eocene thermal maximum was triggered by rapid emission of greenhouse gases, likely caused by a large igneous province event.

Global temperature spiked by four to six degrees Celsius, and the world experienced dramatic changes, but the rate of CO2 released then was still four to 10 times slower than what we're causing today.

These massive volcanic eruptions will happen again, but probably not during our lifetimes.

But what is happening now is an anthropogenic climate change, and there's so much we can do about it.

So I'm curious, do you think we're headed towards another mass extinction or can we slow warming down enough to adapt and even thrive.