Roughly every 100,000 years, our planet undergoes one of the most-violent catastrophes imaginable.
Supervolcanoes are to regular volcanoes what supermassive black holes are to regular black
holes or the Incredible Hulk is to Hulk Hogan.
Bigger, badder, and infinitely more-terrifying.
Capable of ejecting over 1,000 cubic kilometers of material, even the smallest supervolcano
dwarfs any eruption in human history.
Mt St Helens, Krakatoa, Vesuvius… all are mere sparks against such infernos.
But while no supervolcano has erupted since the dawn of civilization, that doesn’t mean
they’re gone.
If you live in America, you may have even visited one.
Yellowstone national park is famous for its beauty.
But just under the surface lies something far uglier: a plume of molten rock that - were
it to cause an eruption - could potentially kill millions.
Where did this supervolcano come from, how likely is it to explode, and what would happen
to the world if it did?
Today, Geographics is uncovering Yellowstone’s explosive past… and taking a glimpse into
its apocalyptic future.
The Exploding Earth
On April 10, 1815, Tambora volcano in Indonesia exploded with a force unprecedented in recorded
history.
Over 3 days, 175 cubic kilometers of debris was ejected into the atmosphere atop a plume
of ash 45km high.
So much material was hurled into the sky that it darkened the sun.
The following year, 1816, would become known as the Year Without a Summer - a year in which
ice froze rivers in August, flooding destroyed crops, and famine and disease ran riot.
Thanks to these climactic effects, it’s thought as many as 82,000 people across the
globe died.
It was by far the biggest eruption since the dawn of human civilization, dwarfing even
the Hekla 3 eruption that may have triggered the Bronze Age Collapse.
But here comes the kicker.
This apocalyptic volcano that affected the entire planet was just a regular ol’ volcano.
By contrast, were a supervolcano to explode today, it would make Tambora look like a Girl
Scout bake sale.
In the history of the Earth, there have been around 50 known supereruptions.
The most-recent occurred at New Zealand’s Lake Taupo about 26,000 years ago.
But while a video about Taupo’s explosive past would be great, that’s not what we’re
here to discuss today.
No, we’re here to talk about the most-famous supervolcano of them all: Yellowstone.
To get an idea of the how the Yellowstone supervolcano formed, you have to go back in
time.
Way, way back into prehistory.
Until roughly 66 million years ago, the entire Yellowstone area was covered by an inland
sea.
But then the Cenozoic era began, and brought with it a burst of volcanic activity.
Now, this was volcanic activity unrelated to the modern supervolcano.
But it did result in the Absaroka mountain Range popping into existence, giving Yellowstone
its northern and eastern borders.
However, it was what happened some 49 million years later that changed the park’s fate.
If you’d been floating above the North American continent and watching the millennia pass
on fast forward, it would’ve looked like a whole bunch of volcanoes suddenly started
springing up around the Nevada, Oregon, and Idaho border.
Those volcanoes would’ve started marching east, popping up one by one on an 800km journey
toward northwest Wyoming.
But this would’ve just been the view from above.
Underground, a very different story would’ve been taking place.
Rather than the volcanoes themselves marching northeast, the reality was that the North
American plate was slowly grinding southwest over a sunken bubble of magma.
Imagine a carpet being dragged across a warped old wooden floor with a bump in it.
As the carpet moves, the bump would stay in the same place, making different parts of
the carpet rise up at different times.
In a very simple way, that was what was happening in prehistoric America over millions of years.
Finally, some 2.1 million years ago, that bump found itself under a thin, threadbare
piece of carpet marked Yellowstone.
It’s at this point that things got interesting.
Not long after the magma bump found itself below Yellowstone, it gave its first supereruption.
Since we don’t have any records of a supervolcano blowing, we don’t know what it would’ve
actually looked like.
But we can guess.
Over thousands of years, magma, water vapor, and gasses would’ve built up inside the
bump, until the pressure made it start to grow.
Stood on the ground, you would’ve seen a dome, getting bigger and bigger.
Finally, it would’ve gotten so big that the edges started to tear, providing a release
for the pressure below.
By the time you noticed that, though, your last chance to run would’ve been long gone.
The first Yellowstone supereruption was almost beyond comprehension.
Over 6,000 times the size of Mt St Helens, it released 2,500 cubic kilometers of debris.
Over 15,000 square kilometers of North America were coated in ash.
Where the magma blew, the Earth collapsed, forming a depression the size of Rhode Island.
In the aftermath, the gasses expelled would’ve dimmed the sun, plunging the entire planet
into a winter that lasted for years.
It was the first example of the supervolcano’s raw power.
It wouldn’t be the last.
The Great Eruptions
In its two million years of existence, the Yellowstone supervolcano has never again erupted
with the force of its first major blast.
But even its two smaller supereruptions were still what we’d call “pretty damn big.”
Take the supereruption of 640,000 BC.
The third of Yellowstone’s three major explosions, it went up with the force of 2,500 Mt St Helens
eruptions.
That meant a plume of ash 30km high, so big it left debris as far away as the Gulf of
Mexico.
It meant gigantic, superheated clouds of rock and ash nearly 1,0000C hot sweeping across
modern Wyoming, burying the land beneath a layer over 100m deep.
Anything within 1,000km of the eruption almost certainly died.
In the aftermath, another gigantic caldera formed, this one capable of swallowing the
whole of Samoa.
Even the smallest of the three supereruptions, the one that blew in between these two monsters,
would’ve been an awe-inspiring sight to behold.
Well, at least until it would’ve until it killed you.
However, it would be wrong to think that the Yellowstone volcano is only capable of planet-cooling
blasts.
Between 640,000 and 70,000 BC, some 80 eruptions transformed the Yellowstone landscape.
Although some created features we’d still recognize today - like the Pitchstone Plateau
- none of them were even close to being Tambora-sized, let alone supereruptions.
It’s here we get to one of the biggest misconceptions about supervolcanoes: that, because of their
size, anytime they blow it must be a supereruption.
The reality is that most supervolcanoes only rarely erupt at their full capacity.
They’re far more likely to just sit there, bubbling away, creating groovy effects on
the surface.
Yellowstone volcano is a prime example of this.
All those steam vents, hot springs, and mud cauldrons you’ve seen in your auntie’s
vacation photos?
They’re all due to that great big magma chamber we talked about earlier.
Because the ground in Yellowstone is cracked, water is constantly worming its way down to
the magma, getting superheated, and shooting right back up to the surface.
The 300 geysers in Yellowstone park - over half the total in the world - only exist because
they’re on the surface of a volcano so big you can’t even see it.
So next time you roll out there in your RV and watch Old Faithful do its thing, just
remember that the supervolcano below isn’t only good for inspiring scary YouTube documentaries.
In fact, without that plume of molten rock under Wyoming - a plume that stretches at
least 960km down, and likely as far as 3,000km - there wouldn’t be a national park for
you to visit at all.
That’s because it was these outside signs of volcanic activity that made people think
the area was worth preserving in the first place.
The Invisible Volcano
On August 29, 1870, the gloriously be-moustached Gustavus Doane scaled Mount Washburn.
A Civil War veteran turned explorer, the 30-year old Doane was in Wyoming as part of - as his
name might suggest - the Washburn-Langford-Doane expedition.
At this point in American history, much of the interior was still a fascinating mystery.
The West had been tamed, but many of those places lying between the coasts were still
the 19th Century equivalent of an olde timey map marked “Here be monsters”.
It was a mere 43 years earlier that the first description of Yellowstone had appeared in
a newspaper; only 34 years earlier that the first rough map had been made.
In the decades since, trappers, explorers, and one priest had visited the area, but the
stories they brought back of the landscape were too fantastical to be believed.
At the moment Gustavus Doane started scrambling up the side of his mountain, the average American’s
opinion of Yellowstone was basically “what’s Yellowstone?”.
It was the Washburn-Langford-Doane expedition’s task to make sure that changed.
At long last, Doane reached the top of Mt Washburn.
All around him stretched the wilds of Wyoming, the great, rugged view that would soon become
known as Yellowstone national park.
To the south, the Rocky Mountains rose and fell, adding texture to the view.
But there was an anomaly.
As Doane squinted, he noticed there was a break in the mountain range, a place where
a flat circle of forest seemed to have been crudely carved out the landscape.
Not long after, the explorer recorded his theory on it.
“The great basin,” he wrote, “has been formerly one vast crater of a now extinct
volcano.”
It was the first time in history anyone had realized the explosive secret Yellowstone
was hiding.
Prior to Doane’s expedition, humans had been coming to the Yellowstone region for
thousands of years.
We know this, because tools dating back to 9,000BC have been unearthed at sites across
the park.
Since they’re from so far back, though, we have no idea who they belonged to.
The name of the people that produced these tools has been lost to time as effectively
as if it had been written on paper then dropped into a raging river.
It wasn’t until the fifteenth century that we got a Yellowstone-based culture that still
survives.
Known as the Shoshone or sometimes the Sheepeaters, the tribe settled the park around 1400 AD.
Quite what they made of all the strange lakes, geysers, and hot rivers wasn’t recorded,
but we can assume it probably blew their minds.
That’s because minds being blown is a pretty consistent feature of Yellowstone’s past.
When the first white people arrived in Yellowstone 400 years after the Shoshone, their accounts
were often laughed off by those living on America’s coasts as the wild ravings of
deluded woodsmen.
The idea of hot rivers and jets of boiling water was simply too far-fetched; like if
someone told you today about a secret place in Idaho with candy floss trees.
It didn’t help that the government’s official expedition to the area failed to reach it,
leaving most people in the dark about the awe-inspiring landscape.
But as the 19th century rolled on, more explorers and trappers started coming back from Yellowstone
with similar tales, until it was decided this mythic place needed to be surveyed properly.
And so it was, in 1870, that both Doane’s three-name expedition and the near-simultaneous
Hayden expedition set off to uncover Yellowstone’s secrets.
In their own ways, both would transform how humankind saw this remote corner of Wyoming.
As Doane clambered back down Washburn Mountain that hot day in 1870, he was heading back
into a different world.
When the Hayden expedition returned, it would be with photographs and paintings of Yellowstone
that would capture the public’s attention.
It would be off the back of these images that Congress acted, passing a bill signed into
law on March 1, 1872, that made Yellowstone one of the very first national parks in the
world - possibly the very first (there’s a contender in Mongolia that may have pipped
it to the post).
But it would be Doane who eventually made the most intriguing contribution.
The idea of a vast, dead volcano underneath Yellowstone lingered in the imagination.
For a long time - almost 8 decades in fact - it was part of the lore of the park.
But then, at some point in the mid-20th century, people decided to check if the volcano really
was as dead as Doane had claimed.
What they eventually found would explode everything America thought it knew about its favorite
park.
The Volcano Made Visible
The fact that we ever discovered the truth about Yellowstone is down almost entirely
to two things: a lump of rock, and a disappointing boat trip.
Let’s start with the rock first.
In the late 1950s, a Harvard grad student named Francis "Joe" Boyd was poking around
the park when he stumbled across something called a welded tuff.
Now, to you or me, a welded tuff would look no different from any other lump of rock.
But Boyd was a geologist, and to him a welded tuff didn’t look like random rock.
It looked like what it was: ash that had once been burning hot before becoming compressed
and solidifying.
It also looked like something that had come from a geologically recent eruption.
But one rock, no matter how weird, does not a theory prove.
Even as two more welded tuffs were discovered in Yellowstone park, the jury remained out.
It would take a weird boat trip to change that.
Jump cut ahead to 1973.
Bob Smith, another geologist, was boating across Yellowstone Lake for some work when
he came to an old dock.
A couple of decades before, Smith had moored his boat at this same dock, but now it was
underwater and useless.
What’s more, the treeline was flooded out too.
Being far brainier than us, Smith didn’t just shrug this off as a weird thing and carry
on with his life.
Instead, he took a survey of the entire Hayden Valley area, then compared it to data from
1923.
What he found was jaw-dropping.
The north end of Yellowstone Lake had risen nearly 75cm, sending extra water flooding
down the southern end and submerging the old dock.
There was only one reason the ground might swell upwards like this.
The volcano beneath Yellowstone must still be alive.
Smith’s findings caused a minor sensation.
It helped that Smith was good at turning a phrase, such as when he described Yellowstone
as a “living, breathing caldera”.
But it also helped that the park kept on doing weird things.
In the mid-1980s, there was a cluster of earthquakes, after which the the ground settled back down
again to the height it had been in 1923.
Whatever was down there was like some great beast, a modern Cthulhu, dreaming in his layer
at R'lyeh.
The only question was, what would happen when it woke up?
Over the next couple of decades, geologists, volcanologists, and lots of other people with
jobs ending in “ologist” studied the heck out of Yellowstone.
It’s during this time that the giant magma plume was discovered.
That the volcanic timeline from this video’s first section was pieced together.
Slowly, as the sheer size and power of the Yellowstone volcano dawned, a term rose to
describe it.
A term that started as strictly unscientific, but soon became so widely-used that science
co-opted it: supervolcano.
Barely had the apocalyptic connotations of that term become clear when, in the mid-2000s,
the ground started rising beneath Yellowstone Lake again.
But if you’re expecting to hear that we’re now in the run up to an eruption… well,
you’re about to be very disappointed.
It’s been estimated that the odds of Yellowstone erupting in any year are about 0.00014 percent.
By way of comparison, it’s actually more likely that another Chicxulub-sized asteroid
will come slamming into Earth than it is that Yellowstone will blow its top in our lifetimes.
Even when it does finally blow again, the odds are even-slimmer that it’ll be a supereruption.
You may have seen claims that Yellowstone erupts on a schedule and that we’re “overdue”
another catastrophic eruption.
But volcanoes - with rare exceptions - simply don’t work like that.
The boring truth is that Yellowstone probably won’t go off for thousands more years and,
when it does, it’ll likely be a lava flow that’s destructive within the park itself,
but barely noticeable for the world at large.
That being said, though, there is still the tiniest, tiniest chance that the big one really
could happen.
And if it did…
Well, let’s just say it’s time for this video to take a turn into the speculative.
It’s time for us to witness America’s Armageddon.
The World on Fire
Because no supervolcano has erupted in recorded history, we don’t really know what it would
look like if Yellowstone suddenly went Old Testament on America’s ass.
But we can make some educated guesses.
For instance, it seems reasonable to assume that the ground around Yellowstone Lake would
start swelling again, doming upwards as magma rose into the chamber.
Quite possibly, this dome would rise on a scale we’ve never witnessed before.
With the ground heaving upwards, we’d start to get earthquakes, as the magma pushed solid
rock out of its way to get to the surface.
The closer we got to lift-off, the shallower these earthquakes would get.
Pretty soon they’d likely be detected across the entire park, along with a sharp and sudden
increase in CO2.
In other words, we’d probably have some pretty distinct warning signs.
But that almost wouldn’t matter.
Because when the magma finally reached the surface, we’d hit midnight on the doomsday
clock.
Assuming an eruption as big as Yellowstone’s last supereruption, the effects would be devastating
beyond belief.
Lava would inundate the park within a radius of roughly 65km.
This would suck for campers, but the real problem wouldn’t be on the ground.
It’d be in the air.
Thousands of cubic kilometers of volcanic ash would be blasted high over Wyoming.
What happened next would depend a lot on the wind, but one likely outcome would be a layer
almost a meter thick settling over most of Wyoming, Colorado, Montana, Idaho, and Utah.
This wouldn’t be like a layer of snow.
Just 30cm of ash can collapse a rooftop.
Every water supply it touched would be poisoned.
But it’s not like anyone would be around to worry about it, apart from a few unfortunate
survivors.
Within 1,000km of the blast, it’s estimated that 90 percent of people would be killed.
A quick, back of an envelope calculation puts that at north of 10 million people dead.
And Yellowstone would just be getting started.
As the ash traveled, it would blanket the Midwest.
Not deep enough to crush buildings, but deep enough to cause large-scale crop failures
and to make travel - and thus escape - an impossibility.
It would also be thick enough to cause major respiratory problems in anyone caught outside.
As the BBC once memorably put it:
“Inhaled ash forms a cement-like mixture in human lungs.”
Yuck.
By the time you reached the East Coast, the ash layer would be a single centimeter thick.
Even at this thinness, though, it would badly disrupt travel, which would in turn mess up
supply chains.
Overall, its estimated that three quarters of the USA would be plunged into a deranged,
post-apocalyptic fantasy.
And that would just be for starters.
Over the coming days, the ash from Yellowstone would drift across the Atlantic, until it
also coated Europe.
Remember the Icelandic eruption in April, 2010, that grounded every single plane on
the continent?
Well that would happen all over again.
While actual damage in Europe would be minimal, the economic cost would be enormous.
Finally, once three weeks had passed, the gasses unleashed into the atmosphere by Yellowstone
would have completely shrouded the planet.
When Tambora erupted in 1815, causing the Year Without a Summer, it cooled the planet
by something like 1.7C.
A Yellowstone eruption, on the other hand, would cool the planet by up to 12 degrees
C. Nor would the effects only last a year.
Were Yellowstone to blow today, the 2020s would become known as the Decade without a
summer.
Ten whole years in which every day was like a wet November in northern England.
Crops would fail.
The Monsoon would be disrupted, causing mass-starvation in Asia.
When the aftereffects finally faded, the sun would shine back down on a planet - on a human
civilization - that had been irrevocably changed.
But it would also shine down on a human race that was still alive.
Yep, it would be a decade of catastrophe, misery, and really awful experiences, but
it wouldn’t be the end of the world.
It’s not even a sure bet that it would be the end of the USA.
Back in the Cold War, government scientists estimated that losing a quarter of America’s
population in a nuclear exchange still wouldn’t be enough to destroy the United States as
a political entity.
In the aftermath of a Yellowstone supereruption, the US would slowly, surely, rebuild from
its Armageddon.
It might take decades.
It might take centuries.
But, in the end, the most-devastating eruption in human history would fade into memory just
as surely as the Black Death or Napoleonic Wars.
But this most probably won’t happen.
As the American continent continues to move southwest, the magma chamber has found itself
no longer under Yellowstone’s thin Basin crust, but under the thicker crust of the
Rockies.
This could be enough to keep the supervolcano bottled up now forever.
So that’s it then, the history of both Yellowstone Park, and the volcano sleeping beneath it.
The volcano that will almost certainly never blow.
But if you do one day find yourself in northwest Wyoming, and hear reports about the ground
rising up wildly… and earthquakes getting shallower and shallower… and CO2 escaping
across the park…
Then don’t run.
Just close your eyes, cross your fingers, and pray.
Because if the big one is coming - and that’s still a pretty big if - there’ll be nothing
else that you can possibly do.