Original subtitles

[beep]

[music playing]

NARRATOR: On planet Earth, there are 500 active volcanoes,

every one a potential killer.

BRYAN WALSH: When a volcano erupts,

it's like nothing else on this planet.

It's just a truly awesome reminder

of the power of the earth.

NARRATOR: Once they erupt, nothing can stop them.

CHRISTOPHER JACKSON: Their activity can affect

millions to billions of people.

NARRATOR: And one of the deadliest of all,

a super volcano, lies in America beneath Yellowstone National

Park.

You can imagine what the scale of this, the amount of material

that you'd be injecting up into the atmosphere

would cover or blanket most of the United States.

[explosion sound]

NARRATOR: A super eruption here will

be like nothing seen before.

JOHN GRATTAN: Hurricanes of superheated volcanic ash

traveling across the landscape at several miles an hour

with burning everything in its path.

CHRISTOPHER JACKSON: It would look like hell on Earth.

NARRATOR: This disaster could soon

overwhelm the United States and have a global impact

that lasts for years.

[lightning strike]

BRYAN WALSH: There's no system.

There's no emergency plan in place to deal

with anything on this scale.

NARRATOR: The human cost, unthinkable--

Entire cities wiped off the map.

BRYAN WALSH: Potentially, a super volcanic eruption

on the scale of Yellowstone could

be a species-ending event.

NARRATOR: Yellowstone is a ticking time bomb.

But amazing new technologies are revealing

the inner workings of this dangerous beast like never

before.

MATTHEW WATSON: We're actually flying

smack dab into the middle of the ash cloud,

as the volcano erupting.

NARRATOR: Can we survive and how likely is

it to happen in our lifetime?

[explosion sound]

NARRATOR: Yellowstone-- Its breathtaking beauty

has attracted both settlers and tourists

for thousands of years.

BRYAN WALSH: Yellowstone is really

an amazing natural wonder.

There's a reason why it was one of the first national parks

the US ever created.

NARRATOR: The park is home to an extraordinary range

of wildlife.

It's been called America's Serengeti--

From elk and bison, to super predators like grizzly bears.

BRYAN WALSH: You get a glimpse of what the US West used

to be like before it was settled,

before it was clear, before it was turned a bunch of it

into farmland.

NARRATOR: Yellowstone is more than a haven for wildlife.

The forces that shape the land makes

for a park like none other.

BRYAN WALSH: Yellowstone has a sense of magic around it.

It's really being able to see the workings of geology

in real time.

NARRATOR: Across the park, there are more than 10,000

spewing colorful and wildly energetic geothermal features--

From the mighty Old Faithful geyser spouting up

to 8,400 gallons of water every time it gushes,

to Mammoth Hot Springs--

A fantastical landscape of limestone terraces.

But what is it that fuels the rolling mud

and breathtaking geysers?

BRYAN WALSH: You know you're seeing a landscape

that's being shaped by the volcanic and geologic

forces beneath it.

NARRATOR: With forces this powerful below ground,

the outcome is inevitable.

[explosion sound]

BRYAN WALSH: There's going to be one day with Yellowstone

where enough pressure, enough heat, enough energy will build

on that system that they will actually burst to the surface

all at once.

NARRATOR: Yellowstone is a disaster

waiting to happen with the power to change

the face of the Earth.

To better understand the impact of a modern day super-blast,

scientists look to the deadliest eruption

recorded so far in US history.

Mount St. Helens sits 50 miles Northeast

of Portland, Oregon, part of the Cascade Mountain range.

It's young in geological terms.

Its highest peaks only formed within the last 100,000 years.

The Pacific Northwest of-- Of the USA is famous for its--

Its volcanoes.

There's-- there's a long line of them going

up from California, up through Oregon,

and into Washington State.

NARRATOR: People knew it was a volcano.

But since there had been no major eruption here

within living memory, few visitors or locals

fear the mountain.

Like Yellowstone, it seemed peaceful and dormant.

There were people living on the margins of Spirit Lake

here.

And there were lodges.

There were summer camps.

This was a very active recreational area.

And this was all a dense, old growth forest.

NARRATOR: But then, in early 1980,

this serene getaway started to show its true colors.

An earthquake swarm.

An alarming series of seismic events

indicated trouble was brewing.

[machine clicking sounds]

CLIVE OPPENHEIMER: The signs of an impending eruption

really became obvious as a flank of the volcano

was bulging out tens and eventually about 100 meters.

This is a phenomenal scale of what

we call ground deformation.

ALEXA VAN EATON: That bulge was new magma coming

into the volcano, and it was growing

at a rate of 5 feet per day.

So that alerted scientists.

It alerted locals that there was something seriously

going on at Mount St. Helens.

NARRATOR: Geologist Keith couldn't resist

getting a closer look at this development

happening in real time.

KEITH RUNHOLM: I got there in the afternoon with a six

pack of beer and a science fiction novel

and sat there and watched.

And the mountain was very similar to what you see today--

Just quiet, a mountain off in the distance.

NARRATOR: Keith set up camp at an observation point,

10 miles from the mountain.

If you think you're 10 miles from the center of a city,

and a bomb goes off, or something,

you're pretty safe because in our normal day-to-day life,

nothing gets us from 10 miles.

NARRATOR: But then, at 8:32 AM, May 18, Keith witnessed

something he couldn't believe.

I glanced out at the mountain, and

the entire north face of Mount St. Helens was sliding down.

NARRATOR: The deadly eruption had begun.

Immediately, a magnitude 5.1 quake triggered a landslide.

And not just any landslide, this was the largest

in all of recorded history, barreling down the mountain

at up to 155 miles per hour.

KEITH RUNHOLM: This cloud kept coming-- coming

towards me and towards me.

And so I just said, I have to get out of here.

NARRATOR: Keith bolted to his vehicle

and raced down the mountain.

KEITH RUNHOLM: I was frantically driving down the road,

trying to escape a onrushing ash cloud.

There were golf-ball-sized rocks coming through the trees

and cascading down around me.

NARRATOR: Narrowly escaping death,

Keith survived mother nature's wrath by following

another vehicle to safety.

Mount St. Helens was an extreme and violent volcanic event,

a startling reminder of the devastating power

of the volcanoes in America.

Scientists needed to understand what had just shaken

the ground beneath their feet.

And luckily for them, Mount St. Helens

left behind an amazing trail of evidence.

ALEXA VAN EATON: We're about four miles north

of the volcano, and we can see these incredible layers

with a really sharp contact between deposits

from that lateral blast and pyroclastic flow deposits

from the afternoon on May 18.

[explosion sounds]

NARRATOR: While many eruptions leave a similar record behind,

this one is clearer than most.

Now, what's extraordinary about Mount St. Helens

is that we can pin these layers down to the minute

because we have the visible evidence and the stories

to reconstruct what happened during this eruption.

NARRATOR: To the trained eye, it's

possible to read each layer and forensically reconstruct

the events that produced them.

In this lower section from the deposits of the lateral blast,

you can see there are big clasts in here.

These are rocks from the bulge that blew out.

It was uncorked like a champagne bottle and blew out laterally.

NARRATOR: This was the first stage

of the eruption, the explosive moment that punched

out the side of the volcano.

And then, on top of this, we can see that there's

a very, very slender layer from that fine ash

that had been lofted up.

And then, it rained right back down.

[crackling sounds]

NARRATOR: The geology bears witness

to a deadly torrent of superheated gas and ash,

known as pyroclastic flows.

ALEXA VAN EATON: After the eruption column rose vertically

into the atmosphere 17 to 18 kilometers,

there were boil-over pyroclastic flows-- meaning,

the eruption column filled up the crater

and kind of spilled over.

And those pyroclastic flows of ash and gas

traveled all the way up here to the ridge

and deposited these thin layers of fine ash.

NARRATOR: The nine-hour eruption killed 57 people,

destroyed 200 homes, 47 bridges, and 185 miles of highway.

But as large as it seems, Mount St. Helens

is far from the biggest volcanic event on record.

Volcanic eruptions are measured on the VEI scale.

The volcanic explosivity index takes into account cloud

height, amount of material thrown out,

and how long the eruption lasts on a scale from 0 to 8.

It's not that 5 is just a little bit bigger than 4,

or 6 is a little bit bigger than 5.

Instead, there's a 10-time factor between each of these.

So a 5 is 10 times bigger than a 4.

A 6 is 10 times bigger than a 5.

An 8 is 1,000 times bigger than a 5.

So these are epically big eruptions when we're talking

about VEI 8 scale explosions.

[explosion sound]

NARRATOR: The 2018 Krakatoa eruption

came in at a VEI 3, categorized as a catastrophic event.

Pompeii, regarded as one of the deadliest eruptions in

European history, hit a VEI 5.

But an event on the scale of a super volcano

is almost off the charts.

With a mega-colossal event from Yellowstone,

projected to unleash a VEI eight,

an event last seen over 630,000 years ago.

CLIVE OPPENHEIMER: When we get up to magnitude 8,

if you've stuck it all within the entire USA,

you know, you were still knee-deep in ash.

NARRATOR: So what would the immediate aftermath

of an eruption at the massive Yellowstone volcano look like?

The initial impact would be devastating.

A full eruption would launch 2 million tons of sulfuric acid

into the atmosphere, demolishing Wyoming, Utah, and Idaho

in its kill zone, submerging the states under 13

feet of ash and magma coverage.

The air would be toxic.

But there is only one way to appreciate

the sheer awesome size of Yellowstone,

and that's from the air.

[helicopter whirring]

[music playing]

NARRATOR: Volcanologist Madison Myers

has been studying Yellowstone's geology for many years.

She understands the terrifying secrets hidden below the park's

picturesque landscape.

Today, she'll be flying overhead to get a bird's-eye view

of this vast expanse.

MADISON MYERS: We're flying over a really

large hydrothermal field.

And so this is shown by all of this kind of white material

that we see.

We see hydrothermal holes everywhere.

So this is the-- the signal of Yellowstone saying,

I'm still here.

I'm a magma body.

Pay attention to me.

NARRATOR: It's this intense heat, driven

by underground magma, that's given

rise to many of Yellowstone's most iconic sites.

Grand Prismatic is the largest hotspring

in the US and third largest in the entire world.

MADISON MYERS: Grand Prismatic is

supplying the heat that is necessary to fuel

this geothermal activity.

NARRATOR: Yet, the Yellowstone ecosystem contains one

geological feature, so large it simply cannot be

grasped from the ground level.

Its epic scale can only be appreciated from way above.

MADISON MYERS: We are approaching

Yellowstone caldera.

We're approaching the edge here, and you

can see that there's kind of a cliff feel

to what we're about to see.

NARRATOR: A caldera is what forms

after a magma chamber empties out

in a super volcanic eruption.

With nothing left to support the ground above an empty chamber,

it collapses, leaving a cauldron-shaped depression.

It's only from this vantage point

that the full scale of the Yellowstone caldera is visible.

MADISON MYERS: And to give you perspective,

it's taking us about 20 minutes to fly

from one side of the caldera to the other side of the caldera.

So it seems like everything that Yellowstone does,

it supersizes.

NARRATOR: Geologists think this gigantic caldera formed

in Yellowstone's last super eruption 640,000 years ago

and measures 35 miles by 45 miles.

It would have been right at the top of the volcanic explosivity

index.

The ashfall alone from this event

would have had a continent-wide impact.

You can imagine, with the scale of this, the amount

of material that you'll be injecting up

into the atmosphere, how it would cover or blanket

most of the United States.

And this would be something that would not be a quick event.

This would likely occur over days or weeks.

NARRATOR: Within the first 24 hours of a new eruption,

scientists predict a 10-foot layer of molten ash

would spread up to 1,000 miles from the park.

Depending on wind direction, the rest of Colorado, South Dakota,

Nebraska, and Kansas are engulfed

in the primary ash zone as the plumes of toxic clouds

choke the skies.

Any living creature in America would

be in great danger, potentially smothered by ashfall.

Before we understood that Yellowstone was a volcano,

there was a smoking gun for the destruction

these catastrophic eruptions can cause

but in an unlikely place, about 1,000 miles away in Nebraska.

In 1971, paleontologist Mike Voorhies

was out in the field in Nebraska,

mapping rock exposures at a farm, when a protruding

bone caught his eye.

MIKE VOORHIES: There happened to be a skull of a baby rhinoceros

sticking out of this ash bed.

And once we started checking it out,

it turned out that there was not just one,

but hundreds, and hundreds, and hundreds of skeletons

buried in this ash bed.

NARRATOR: Mike had stumbled across

a giant prehistoric graveyard.

And now, he works in a unique and active

museum, uncovering the mysteries hidden beneath his feet.

This is the one place in the world where you can stand

and see whole three-dimensional skeletons of large animals

preserved in volcanic ash.

So it is something unusual to turn up at the edge

of a cornfield in Nebraska.

When you dig down to the bottom of the volcanic ash,

you would be looking at what the bottom of the waterhole

looked like on the day before the ash fell.

This was something that happened almost 12 million years ago.

Herds of prehistoric rhinoceroses,

camels, and horses met their death in a waterhole.

NARRATOR: All these animals were buried

in ash that remained relatively soft,

so they're incredibly well-preserved.

One rhino still bears her unborn fetus.

And in others, we can actually see the contents

of their last meal.

The question was, what had killed all these animals?

It turns out, there was a clue in the bones.

Dr. Winsome Eu is a veterinary pathologist.

When cadavers arrive at the lab, it's

her job to perform a necropsy or animal autopsy to determine

the cause of death.

WINSOME EU: A normal, healthy skeleton,

the bones will be smooth.

They'll be thin.

They won't have these bumps and fluffy protrusions.

NARRATOR: This bone growth is an affliction

known as Marie's disease.

WINSOME EU: So this is excess bone growth

that would be similar to what you

would see in Marie's disease or hypertrophic osteopathy.

This is the rear foot of a cat that

has these bony proliferations around the toes, and then

the paw, and around the nasal cavity--

And then, finally a little bit here around the mandible.

Generally, in veterinary species,

this happens due to lung disease.

So it could be tuberculosis, or some sort of pneumonia,

or most commonly, it would be seen in cancer.

NARRATOR: The presence of Marie's disease on the Nebraska

fossils was a sure sign the animals

died from severe respiratory problems.

When scientists compared ash samples from Nebraska

and Yellowstone, their similar compositions

confirmed a shared source.

Despite the volcano eruption over 1,000 miles away,

the ash was falling thickly enough here in Nebraska to kill

these large, powerful animals.

It was the first evidence of how wide

the impact of a Yellowstone eruption can be.

Scientists now think Yellowstone sits

atop a volcanic hotspot, a source of intense heat

from deep within the Earth.

CLIVE OPPENHEIMER: The heat that is escaping from the Earth

as solid rock in the mantle, and some of it

melts, generating volcanoes.

And it's a bit like having some soup in a pan on a stove, where

it's being heated from below, and it's

been cooled from above.

And this sets some currents of-- of hot liquid that then,

as they cool, they sink back down again.

NARRATOR: The Yellowstone hotspot

has produced not one, but three super eruptions over

the past two million years.

Could an eruption on that scale happen again on a continent

that's now heavily populated?

BRYAN WALSH: The Earth beneath Yellowstone

is literally moving up and down every day.

It almost breathes because that's

the power of the molten rock.

NARRATOR: It's an ominous sign that this is

still a highly active system.

JOHN GRATTAN: There are no indications at the moment

that the-- that the magma chamber below Yellowstone

is cooling down and settling down.

So certainly, there is the potential

for a super volcanic eruption from that site.

NARRATOR: One of the deadliest effects of a Yellowstone

super eruption would be the massive volume

of volcanic ash ejected.

Seattle, San Francisco, and Los Angeles in the West to New York

and Washington D.C. in the East would be covered

in between 6 to 10 feet of ash.

Yellowstone could once again blanket all of the US.

But to learn more about the risks,

it's vital scientists explore volcanoes' inner workings.

And to do that, it's necessary to venture deep underground.

There's a sleeping volcanic monster beneath Yellowstone

National Park, a deadly hotspot that's produced

world-shattering eruptions.

CLIVE OPPENHEIMER: Yellowstone volcano has been responsible

for three super eruptions, one 2 million years ago,

one 1.3 million years ago, the most recent 640,000 years ago.

NARRATOR: Each of these eruptions

had a devastating impact on what is now the United States.

CLIVE OPPENHEIMER: These are all colossal events

that dispersed ash over a very wide

part of the American continent.

We can-- we can locate still the ash deposits in--

In many places.

NARRATOR: Today, a super eruption would cause power

grids to fail across the US.

Inhaling the toxic ash would cause millions of deaths,

with people buried below it like a modern day Pompeii.

But to understand the subterranean causes

of Yellowstone's previous eruptions,

you need to travel thousands of miles across the Atlantic

to Iceland.

[music playing]

NARRATOR: Most of the time as the name suggests,

this small island is frozen and windswept.

But Iceland is also a place of raging fire.

CLIVE OPPENHEIMER: Iceland is a geologist's paradise.

It's a vulcanologist's paradise because it's essentially

one great big volcano.

The whole thing is volcanic.

NARRATOR: Volcanologist Freysteinn

Sigmundson studies Iceland's extraordinary geology.

Today, he's heading into the field

to explore a hidden giant.

Discovered in 1974, its exact origin is

still something of a mystery.

NARRATOR: Rocky landscapes like this form

when flowing lava cools, solidifying

into bizarre rock formations.

Today, little more than moss and grass

grow on the area's exposed rocks.

NARRATOR: Freysteinn is following

the trail back to its source.

It leads him to the craggy summit

of the Thrihnukagigur volcano.

Currently inactive, its last major eruption

was around 4,000 years ago.

Freysteinn is about to do something

that would mean certain death anywhere else in the world.

He's going to explore inside a magma chamber.

NARRATOR: 4,000 years ago, this chamber

was seething with molten rock at over 2000 degrees Fahrenheit.

Just prior to its eruption, the pressure

would have mounted, eventually reaching

the point of no return.

Understanding this behavior could serve

as a warning for Yellowstone.

Today, the chamber is fully drained, leaving

only a huge empty cavern.

It extends almost 700 feet into the depths.

NARRATOR: This vast cavern was once bursting with molten rock.

NARRATOR: Thousands of years ago,

red hot magma forced its way toward the surface

through these very cracks.

But the chamber provides another vital piece of evidence

to the mind-bending scale of an eruption.

NARRATOR: Freysteinn measures each side of the chamber

to estimate its total volume, and the results

are staggering--

Around a quarter of a million cubic meters,

equivalent to nearly 400 Olympic swimming pools.

When it erupted, it was a massive volcanic event.

But it would be dwarfed by a super volcano eruption.

NARRATOR: A full-sized super eruption

would be a geological event on a totally different scale,

potentially big enough to reshape a continent.

So just how large is the present day magma chamber

sitting beneath Yellowstone?

Spanning from Wyoming into Montana and Idaho,

Yellowstone supervolcano will one day erupt again.

It will be a global catastrophe with

the dangerous volcanic clouds reaching as far as Europe

within the first 72 hours.

Ash and gases causing toxic rainfall

would contaminate water, kill crops, wildlife,

and bring most of the world to a standstill.

If there were to be a large explosive eruption,

then the ash entering the atmosphere

would get high enough that it would go global.

It would affect all parts of the Earth.

The kinds of things we would expect

to see before an eruption would be unmistakable.

There would be tens of thousands of earthquakes uplift

as the ground surface rose due to magma

coming up from some depth.

That would cause the ground to inflate like a balloon

by maybe meters over a short period of time.

We would see changes in gas emissions and thermal activity.

The temperature of the ground would be changing.

These would be unmistakable changes.

NARRATOR: Today, hundreds of volcanoes

worldwide are within striking distance of a town or a city.

Yet even with modern technology, there's

little that can be done to halt the advance of lava and ash.

You do not want to be trapped in

a fast, hot pyroclastic flow.

You will burn, and you will choke because of the gases

it contains.

[explosion sound]

NARRATOR: A supervolcano like Yellowstone

wouldn't just threaten the survival

of one city, but hundreds.

Its initial blast could flatten seven

states like a nuclear bomb.

So even as a geologist, I am amazed

by the scale of the magma chambers present

beneath Yellowstone.

We're talking about 3,000 to 11,000 cubic miles of material

under there.

That is jaw-droppingly huge.

NARRATOR: The dangers recently became

apparent at another deadly volcanic hotspot on US soil--

Hawaii.

And on May 3, 2018, Kilauea volcano erupted--

Its largest eruption in over 200 years.

New fissures formed in the Earth,

causing a caldera collapse.

And lava began flowing in large volumes.

As much as 3,500 cubic feet per second, fountains of lava

reached over 260 feet high.

Flows swallowed roads, water lines, and public parks.

And by June 25, a total of 657 houses had been consumed.

In total, the eruption caused over $550 million of damage.

Hawaii shows that even today, volcanoes

continue to threaten the world cities,

perhaps more than ever before.

[explosion sounds]

NARRATOR: For those caught up in these events,

it can be a terrifying experience.

New Zealand's White Island had long been a popular tourist

attraction, a place to witness the steam and sulfur

of a slumbering volcano.

On the afternoon of December 9, 2019,

there were 47 visitors on the island

when it suddenly awoke in an eruption

lasting just a few minutes.

SPEAKER 1: Go inside.

Go inside.

Go inside.

[interposing voices]

NARRATOR: It produced a massive ash plume

reaching 12,000 feet high.

Those trapped on the island soon found themselves

in the middle of a nightmare.

Clouds of superheated toxic ash and gas engulfing the land.

SPEAKER 2: No, no, no, no.

NARRATOR: Tragically, 22 people lost their lives, while others

suffered severe burns.

The White Island tragedy is a reminder of how deadly

even the smallest volcanic eruptions can be.

But a future Yellowstone super eruption

would make White Island look like a pinprick in comparison.

[sirens wailing]

NARRATOR: Fatalities could number in the millions.

But is the world ready for this super event?

Will we have time to save ourselves?

Clues may lie with a very different

geological phenomenon, one that can be every bit as deadly--

Earthquakes.

[glass shattering]

Quakes have their origin deep within the Earth's crust--

Often, where tectonic plates collide.

CHRISTOPHER JACKSON: Earthquakes form

due to the rocks which are being stressed,

so they're being pushed.

And then, suddenly, there's a catastrophic release

of that energy.

And that energy is an earthquake.

NARRATOR: The results frequently create carnage.

[objects collapsing sound]

CHRISTOPHER JACKSON: 2009, there was the L'Aquila

earthquake in central Italy.

And that caused intense ground shaking.

And that ground shaking caused many buildings and villages

to-- to fall to the ground.

NARRATOR: And it can be far worse.

In the 2010 Haiti quake, between 100 and 300,000 people

lost their lives.

Entire towns were flattened.

Despite the destruction earthquakes cause,

there are things we can learn from them.

One day, this knowledge may help prevent

loss of life in a super volcanic eruption, such as Yellowstone.

[machine clicking]

It's thanks to a technique known as seismic imaging

that lets scientists peer into the inner workings

of the planet.

CHRISTOPHER JACKSON: So we're trying

to use the ways in which seismic waves-- so acoustic sound waves

travel through the Earth to try and image areas of velocity

change within the Earth.

NARRATOR: With this tool, they can hunt down

and measure the size of pockets of molten magma

below the ground.

CHRISTOPHER JACKSON: So we'd expect a seismic wave

to take-- you know-- a certain amount of time

to travel through a rock which isn't molten.

But if there is some melt in there,

that seismic wave will travel more slowly.

And so it's that an anomaly which might tell us

about the composition of the Earth or those compositional

anomalies.

NARRATOR: Using this approach, scientists

have built up a complex 3D model of volcanic hotspots

around the world.

And when they look at the ground below Yellowstone,

the results are alarming.

CHRISTOPHER JACKSON: It reveals an incredibly complex

and quite unusual picture.

We probably have in our head that most volcanic centers are

underlain by one magma chamber.

But Yellowstone actually seems to have two underneath it

at different levels.

And they are made of different types of magma.

NARRATOR: Not only are there two chambers instead of one,

but the scale of each is simply terrifying.

CHRISTOPHER JACKSON: So these magma

reservoirs underneath the Yellowstone

are absolutely enormous.

The shallow one is about 3,000 cubic miles,

and the deeper one is four times the size of that-- almost

12,000 cubic miles.

I can't in my head visualize how much melt that is.

NARRATOR: These chambers could contain enough magma to fill

the Grand Canyon 14 times over.

It's clear evidence that Yellowstone could

still pack a massive punch.

CHRISTOPHER JACKSON: Geological history would tell us

that Yellowstone in the future will

have a big, big catastrophic eruption again.

Whether we're here to see it is a--

Is a different thing entirely.

But it's likely to happen again.

NARRATOR: The wait could be as long as a million years,

or it could be next month.

[explosion sound]

The Yellowstone supervolcano is big enough

to threaten towns and cities hundreds of miles away.

And in the past, even small eruptions

have shown just how disastrous they can

be for anyone in their path.

[sirens wailing]

Southern Italy, the glittering Bay of Naples--

Beaches, fertile farmland, vineyards.

Also scattered across this area, the telltale signs

of volcanic activity.

SOPHIE HAY: In the West of the Bay of Naples,

there's the Solfatara, which is constantly

sort of smoking and cracking.

And the smell of sulfur is-- is overwhelming

in-- in places as well.

So you do feel like that whole area

is sort of a-- a ticking bomb.

NARRATOR: Most threatening of all is Mount Vesuvius.

SOPHIE HAY: It just sit there as a-- as a black sort of pyramid

in front of you.

And you-- you do feel its sort-- sort of ominous presence.

The volcano is active, and it's completely

surrounded by heavily populated areas,

like the major city of Naples.

The proximity of population in general to that volcano

is incredible.

Many of them have lived there for generations.

NARRATOR: It's thought, up to three million people

could be impacted by a future eruption,

700,000 of them living right in the danger zone.

But despite the obvious threat, even 2000 years ago, the area

was drawing vacationers.

SOPHIE HAY: It attracted a lot of wealthy Romans

to it to come and have their sort of summer residences.

It's a stunning, stunning area.

NARRATOR: At the time, the biggest town

was Pompeii, with a population around 13,000.

In 79 AD, it was struck by one of history's

most infamous eruptions.

A famous Roman writer, named Pliny the Younger,

kept a record of the tragic events.

It's actually Pliny's mother who's

first spots on the horizon this strange cloud in the sky.

Pliny the Younger describes it as "a pine tree."

It's like a huge trunk with branches

splaying out at the top.

NARRATOR: Even today, eruptions with this type

of distinctive plume are still known as Plinian.

Within hours of Vesuvius awakening,

ash and pumice started to fall on Pompeii.

SOPHIE HAY: The sun, it became very, very dark.

And I think, a lot of people start

thinking that the open spaces are actually

safer because as this pumice is accumulating,

it's weighing down on the rooves.

Things are beginning to collapse.

NARRATOR: Many people tried to flee the town.

SOPHIE HAY: There's a sense of panic.

I'm sure that they were absolutely

terrified in all of this.

NARRATOR: Then, at around 6 AM came the fatal blow.

Pyroclastic flows, liquefied ash and gases

headed straight for Pompeii.

SOPHIE HAY: They flow down the side of Vesuvius

at speeds of up to 150 kilometers an hour.

And they're hot.

They-- they reached temperatures of up to 400 degrees Celsius.

They come shooting down the mountain.

And at that point, you know, there is no escape.

That seals the fate of the individuals.

[people screaming]

NARRATOR: The 18-hour eruption completely

buried the town in ash.

Nobody knows for sure how many died.

But the remains of over 1,000 victims have been discovered.

Their decomposing bodies left voids, from which archeologists

have made plaster molds.

SOPHIE HAY: We see this sort of horror in-- in the casts.

It's incredibly poignant.

We suddenly become sort of face to face

with-- with this horrendous end to their lives.

NARRATOR: This human tragedy is a lesson

about the threats posed by volcanoes

close to populated areas.

SOPHIE HAY: The end of an entire settlement really

does bring home the-- The power of the volcano.

As humans, we-- we don't always stand

a chance against these things.

And we are mortal.

And in the face of natural disasters, we're-- you know--

We're on the losing side.

NARRATOR: A Yellowstone eruption has the potential

to change the face of our planet, the initial blast

killing millions.

Its fallout would be felt across the US, South America,

and Canada, with toxic ash clouds reaching

Europe within 72 hours.

Weeks later, parts of the Earth would

be covered in sulfuric acid aerosols,

as we attempt to survive a nuclear winter.

During a super eruption at Yellowstone,

as much as 5 million tons of material

could spew into the atmosphere every second,

equivalent to the weight of 50,000 blue whales.

And it could go on for days, weeks, or months.

But however huge the blast, what goes up

must eventually come down.

Alexa Van Eaton has modeled the projected ashfall for such

a world-shattering event.

I've printed off the maps that show the results

of numerical simulations, where we've tried to examine what

would happen in the extremely unlikely

event of a super eruption from the Yellowstone volcano.

NARRATOR: The results of her simulation are terrifying.

ALEXA VAN EATON: What we can see here

is that the ashfall dispersal reaches from coast to coast

here in North America-- so from San Francisco all the way

to New York.

NARRATOR: There's no way to know how long a Yellowstone

super eruption would last.

So Alexa modeled three different scenarios.

If we change those timescales and look at an eruption that

lasts only a week, or only three days,

we can see that the model distribution of volcanic ash

dramatically changes.

But no matter how we cut it, even if New York only

receives about an inch, that would

have dramatic consequences.

NARRATOR: Alexa's simulation includes comparative data

from other recent eruptions.

ALEXA VAN EATON: Downwind of Mount St. Helens in Yakima,

Washington, the catastrophic effects of only about

10 centimeters or so of volcanic ash are really well documented.

NARRATOR: Within an hour of the eruption,

day turned into night in Yakima, 90 miles

downwind of the volcano, as ash blanketed the city.

The area was crippled by major power and water outages.

Rooves collapsed from the sheer weight of the ash fall.

The fine particles persisted for weeks, destroying $1.1 billion

of agriculture.

Ash from a Yellowstone super eruption

could have an alarming impact on the health

of millions of people.

To assess the dangers of inhaling this material,

it's essential to understand its chemical properties.

ALEXA VAN EATON: What we can see about these particles

is that they really are solid.

They don't dissolve in water.

They don't melt away like snow, and they don't biologically

degrade like wildfire ash.

NARRATOR: It turns out that volcanic particles

aren't really like ash from combustion at all.

ALEXA VAN EATON: Wildfire ash is chunks of combusted plant

matter, but volcanic ash is made up of tiny particles of rock--

Tiny little crystals and older oxidized or rusty

looking pieces of rock excavated by the eruption

and fresh pieces of frothy magmatic glass.

NARRATOR: These tiny pieces of rock

wreak havoc inside the body.

ALEXA VAN EATON: If the particles are very small,

smaller than the width of a human hair,

we can breathe them right into our lungs.

And that can cause lung damage and have

impacts on the whole cardiovascular system.

NARRATOR: One terrible disaster showed just how serious

and long-lasting the effects of ash inhalation

can be for human beings--

The 9/11 terrorist attacks.

Michael O'Connell was a newly qualified

firefighter at the time, based at ladder 129 in Queens.

MICHAEL O'CONNELL: I got a phone call from a friend saying

that the towers were struck.

I threw the news on real quick, realized that there was a plane

into the World Trade Center, the first one had-- had--

Had flown in.

And I knew right away I was going to have to get to work.

NARRATOR: While Michael was in transit

to the Twin Towers site, the first tower came down.

29 minutes later, the second--

Between them, they contained 10 million tons of cement,

steel, and window glass--

All of which was instantaneously pulverized.

MICHAEL O'CONNELL: What you're seeing is--

Is 220 stories of office building.

And as you're on top of the pile, and you're digging,

the only thing you could think of

is like, I have to get these guys home.

I have to-- I have to find, you know, some of my brothers

that are under this pile.

NARRATOR: The building materials,

along with thousands of computers,

miles of electrical cable, and heating and cooling ducts, jet

fuel and asbestos became a deadly cocktail of dust,

suffocating survivors and rescue workers.

MICHAEL O'CONNELL: They were covered in just white film dust

and debris all over them-- Caked into their hair,

caked onto their face.

NARRATOR: None of Michael's crew had respirators

or masks of any kind.

There was no option but to work and breathe in the dust.

MICHAEL O'CONNELL: I guess in the magnitude of everything

that was going on, you weren't really thinking of yourself

or the environment you were in.

You had stuff up your nose and your mouth the whole time

you were there.

I remember going back to the firehouse,

and I was, you know, blowing stuff out of my nose--

You know-- for a full day, you know, spitting stuff up.

NARRATOR: Over time, many firefighters started to develop

health complications.

They had something called the methyl choline test

and all these lung function tests

that they were starting to do.

So I remember just thinking to myself-- at the time,

I was 25 years old.

I-- I just had it in my head that this

is going to be a long haul.

NARRATOR: Countless survivors and first responders

experienced symptoms.

It became known as the 9/11 cough.

For Michael, the effects appeared years later.

MICHAEL O'CONNELL: I started really

having inflammation all over my ankles,

my knees, my elbows, my--

My wrists.

And I looked at my wife.

I said, something's wrong-- Like, I don't feel right.

NARRATOR: He was eventually diagnosed with a rare disease

called sarcoidosis.

MICHAEL O'CONNELL: I don't think there's ever

been a case of sarcoidosis in the history of the New

York City Fire department.

And now post 9/11, we have hundreds upon hundreds

of firemen, and-- And police officers,

and volunteers that are being diagnosed with sarcoidosis.

NARRATOR: The exact cause of sarcoidosis isn't known.

But many firefighters believe their exposure to the 9/11 dust

may have been a factor.

Volcanic dust could potentially cause

similar long-lasting damage to organs, especially the lungs.

Today, Yellowstone may be a serene place

where visitors come for fresh air and the great outdoors.

A pristine wilderness, free of the smog that

pollutes the world's cities--

But at any moment, this beauty spot

could be transformed into a choking fume-filled hell

on Earth.

And Yellowstone's ash wouldn't stop at national borders.

To help estimate just how far it might reach,

scientists traveled to the most remote place

on Earth, the icy expanse of Antarctica.

It could happen within the decade or several thousand

years from now.

But Yellowstone supervolcano will

erupt again on a massive scale.

And when it does, it will have an impact

on the entire planet with the power

to plunge the world into a nuclear winter.

Clues about what we can expect lie hidden all over the globe.

In the remote, frozen wasteland of Antarctica,

scientists search for priceless and unique data.

These scientists aren't drilling for oil or gas.

They're actually drilling for ice.

The deeper they drill, the older the ice.

ROBERT MULVANEY: The reason why we go to Antarctica

is that ice, when it falls, it collects

material from the atmosphere.

And it has some memory of what was in the atmosphere.

And as it settles on the surface,

it doesn't really melt from one year to the next.

So the layers build up year, after year, after year.

NARRATOR: Like rings in a tree, the air bubbles trapped

in ice layers provide a record of atmospheric changes

over the centuries.

The oldest, deepest ice dates back millennia.

It's a vital resource for scientists

studying climate change.

ROBERT MULVANEY: We can look at what-- what the greenhouse

gases were, for example, in the atmosphere

going back over 800,000 years.

So we're able to reconstruct the climate from the snow itself

and the atmosphere from the air trapped in the-- in the snow.

NARRATOR: And crucially, for volcanologists, the ice bubbles

also contain tiny particles of glass

and ash from ancient eruptions.

ROBERT MULVANEY: So there's very,

very tiny particles that are not really visible to the eye.

So to see them, you've really got

to-- to be able to melt the ice, filter it, and then

look for these glass shards.

NARRATOR: These clues help scientists

figure out the scale of volcanic events in the distant past.

The bigger the volcano, the more material that's

injected into the stratosphere, the more sulfuric acid

into the stratosphere, the more we'll

see deposited in an ice core.

NARRATOR: Atmospheric sulfuric acid levels

surge when large eruptions pump out large volumes

of sulfur dioxide gas.

ROBERT MULVANEY: The sulfur dioxide

will tend to react with water to form sulfuric acid.

And it will tend to sit into the stratosphere for months,

or even a year, or two on end.

And then, it can circulate through the whole globe.

And we'll see that sulfuric acid being

deposited in the polar regions.

NARRATOR: This fact helps solve a long-standing

climate mystery--

An unexplained mini ice age.

ROBERT MULVANEY: There was a period around about 1,500 years

ago, where they believe there was a climate event that

lasted maybe 10 or 15 years.

And people really didn't know what that climate

event resulted from.

By looking very carefully in the ice cores,

we can actually see now that there was several volcanoes

over a period of 15 years-- two or three

volcanoes that probably could have been the source.

NARRATOR: Atmospheric sulfuric acid from big eruptions

reduces the sunlight penetrating Earth's atmosphere.

And a super eruption like Yellowstone

could significantly cool the planet for years on end.

A mysterious discovery in East London

reveals more about the toll of volcano-driven climate change

can have on humans.

The Spitalfields Market Archeological

Project was one of the biggest digs

ever completed in Britain--

A 30-year project undertaken ahead

of the major redevelopment of this whole area.

Dr. Amy Gray Jones was part of a team

focusing on the remains of a 13th century

priory and cemetery.

AMY GRAY JONES: In the pits, the burials

were still laid out carefully on their backs,

in their orientation.

But they were stacked on top of each other,

and stacked next to each other, and kind of quite tightly

packed.

NARRATOR: This method of stacking and crowding

was unusual.

There were a total of 10,500 burials--

2 and 1/2 times more bodies than expected.

For the team, this presented a real historical anomaly.

AMY GRAY JONES: It's always a bit of a mystery

to try and work out why you've got

this kind of different burial practice

and larger numbers of people in a cemetery

than you-- than you might expect.

NARRATOR: At first, the team considered the Black Death,

but the dates didn't match the major outbreaks,

nor was there any evidence of any major injuries

caused by battles on the skeletal remains.

In the lab, the team used every available technique

to analyze the remains.

And it wasn't long before a pattern emerged.

So some of the signs of poor diet that we can see

are interruptions to the growth of the long bones

and interruptions to the development

and growth of the teeth.

And that's usually visible as little lines interruptions

in the-- in the crown of the tooth.

NARRATOR: There were also visible signs

of iron deficiency.

AMY GRAY JONES: On the skeleton, the signs of anemia

are generally porosity, which means lots

of pinprick holes in the bone.

And we see that in the upper border

of the orbits of the eye.

NARRATOR: It looked like these people starved to death,

but could historical records help explain why?

AMY GRAY JONES: And they really documented a series

of poor harvests and cold--

Extra cold summers and wet winters, which

led to food shortages, and essentially

famine in the large cities.

The team then identified a large eruption thousands of miles

away in Indonesia the Samalas volcano.

It erupted around the time of the burials.

The theory might seem far fetched,

but there's further evidence that volcanoes

can affect our ability to grow food even thousands of miles

away.

And it gives us a glimpse into how a mega eruption

at Yellowstone would impact millions

of people across the planet.

[explosion sound]

NARRATOR: Nordstrom is a natural threat with unimaginable power.

A year after a modern day eruption,

we could expect major effects on our global food supply.

Unprecedented changes in worldwide temperatures

could cool the Earth, lasting up to a decade,

sparking a modern ice age.

But with its last eruption hundreds of thousands of years

ago, scientists turned to more recent eruptions

to predict behavior.

Over the centuries, Iceland has seen

hundreds of major eruptions.

Thorvaldur Thordarson is one of the country's top geologists.

Usually, he's on the edge of a volcano doing field work.

But today, he's exploring the country's

historic archives in Reykjavik.

The National Library of Iceland contains manuscripts

dating back over 900 years.

Within this vast collection are clues to the country's

geological history.

Thor's searching through records from the late 1700s

when the infamous Laki eruption took place.

NARRATOR: In an era before volcanoes were

properly understood, Erickson could have

had no idea what lay ahead.

But another diary entry from a few days

later reveals further warning signs.

NARRATOR: Over the next few hours,

things went from bad to a whole lot worse.

NARRATOR: This acid rain is evidence

the volcano was pumping out huge quantities of sulfur.

NARRATOR: The Laki eruption measured 4 on

the volcanic explosives index.

But its effects would be unusually far-reaching.

For the first time, weather stations all around the world

captured data on the eruption.

NARRATOR: The records prove that the Laki volcano changed

global weather patterns.

NARRATOR: The eruption disrupted rainfall patterns as far away

as India with dire consequences.

NARRATOR: And it didn't stop there.

Even Japan, 5 and 1/2 thousand miles away felt the effects.

NARRATOR: These events took place several

hundred years ago at a time when life

was less globally connected.

[explosion sound]

A super eruption like Yellowstone

could be thousands of times bigger than Laki,

and its impact on climate could even

threaten humanity's survival.

Yet, it would affect more than just our global food supply.

It could bring our modern day transportation

to a grinding halt.

Volcanoes a fraction the size of Yellowstone

can pump hundreds of thousands of tons of ash

into the atmosphere.

And this material can have an impact far from the eruption

zone, even when invisible to the naked eye, particularly

for air travel--

A mode of transportation we take for granted.

While even a moderate ash ejection can cause problems

to air traffic patterns, a major volcano like Yellowstone

could cause disruption on an unimaginable scale.

One pilot experienced this firsthand,

and the event impacted air travel protocols ever since.

On June 24, 1982, BA flight 9 was

en route to Perth, Australia.

ERIC WOODY: When we took off into the darkness, yeah, we--

We used to sit back and flew up, flew

straight up to 37,000 feet.

We'd put the autopilots in.

It was a normal flight.

NARRATOR: But a couple of hours later,

the first officer noticed something

outside the everyday routine.

It looked as though in each of the cores of the engine,

there was a bright white light, like a searchlight shining

forward from each of the engines.

We were watching this odd display when the engineer said,

number 4 engine has failed.

NARRATOR: Losing one engine in flight isn't unheard of.

But that wasn't the end of it.

ERIC WOODY: Then, my flight engineer-- yeah,

he wasn't finished.

He said, number 2 is gone.

Number 3 is gone.

NARRATOR: Soon, the plane had lost all four engines.

The pilots had no idea what caused the failures.

They had to stay focused on keeping

the plane and passengers safe.

They knew an unpowered 747 will glide 15 miles for every 1 mile

it descends.

In theory, they could make it to the nearest airport, Jakarta--

Except there was an obstacle in their way.

ERIC WOODY: We didn't have enough height to glide over

the 10,000 or 11,000 feet high mountains along the-- the West

Coast of Java.

NARRATOR: The flight was now facing disaster.

ERIC WOODY: At the moment, it looks like you're

going to land in the sea, which is a no-no as

far as I'm concerned.

Open sea is very difficult and almost impossible.

NARRATOR: To this day, no 747 has ever successfully

ditched in the ocean.

The crew frantically tried to restart

the engines as their plane dropped 13,000 feet.

ERIC WOODY: There was every opportunity for this

to be 247 people plus 16 crew going to their death

in the southeastern Indian Ocean and probably nobody really

ever finding out.

It's the deepest trench in the world we were over.

NARRATOR: Incredibly, as the plane

approached 8,000 feet, three of its four engines

sprang back to life.

The remainder of the flight wasn't

easy with the pilots barely able to see out of their windows.

But Captain Moody and his crew battled

their way to Jakarta airport and landed

without further incident.

Investigations revealed the plane had flown

through a thin cloud of ash.

It had come from a minor eruption of the nearby volcano

at Mount Galunggung.

At that time, ash levels were not widely monitored

nor reported to air traffic control.

And at high altitudes, volcanic particles are so fine,

they can be invisible to the naked eye.

MATTHEW WATSON: It's actually quite easy

to fly into an ash cloud because concentrations

can be quite low.

And you need a tiny amount to actually start impacting

on-- on-- on a jet engine.

NARRATOR: Over time, the microscopic particles

can cause serious damage.

MATTHEW WATSON: The problem with ash is, once it gets hot,

it just sticks to everything.

Air is designed to flow in very, very specific places

to keep bits of it at different temperatures.

And if you start blocking up little holes or little veins,

it-- it just-- it just doesn't work as well at all.

NARRATOR: At the very least, ash can

lead to engines consuming more fuel, potentially more

than the plane is carrying.

But it can also have a much more immediate effect.

What happens over time is your engine gets less efficient,

which makes it more expensive to run.

But you are also running a slight risk of the engine just

gives up the ghost in flight.

And that's, you know, potentially disastrous.

NARRATOR: But thousands of long haul flights

still regularly pass close to an active volcano.

MATTHEW WATSON: If you're flying from somewhere in the Pacific

Northwest like Seattle to Tokyo, you'd

fly up the Cascades, along the Aleutians,

down the [inaudible], , into Japan.

You're probably flying over a couple of hundred volcanoes

that have the potential to be active or have been active

in the last 10,000 years.

NARRATOR: Fortunately, for air travelers today,

there's a huge global network of scientists

monitoring the skies.

MATTHEW WATSON: Every time you get on an aircraft,

there is somebody somewhere looking at a computer screen,

giving the pilot enough information

to make good decisions ahead of the flight,

so that that aircraft doesn't hit an ash cloud.

NARRATOR: In 2010, when the Eyjafjallajokull volcano

in Iceland erupted, nobody took any chances.

Over 100,000 trans-atlantic and European flights were grounded

at a cost of around $3 billion.

That was considered an average-sized eruption

as a VEI 3.

But the effects of a super eruption like Yellowstone

could be global in their impact.

The volume of a large super volcanic eruption

could basically flood the entire atmosphere.

NARRATOR: If Yellowstone does its worst,

it could mean no planes in the skies

for months, or even years.

The world's economy would be brought

to a complete standstill.

The potential consequences are so great that scientists must

do all they can to better understand

how volcanoes behave, even if that means putting

their lives on the line.

[explosion sounds]

NARRATOR: The inevitable eruption

of the Yellowstone super volcano will be unlike anything

seen in modern times.

Yet, scientists are constantly working to better understand

the risk posed by volcanic eruptions,

in hopes of better predicting their behavior,

and ultimately saving lives in our globally connected world.

CLIVE OPPENHEIMER: It's a tremendous thrill

to be out in the field in--

In a remote area in the face both of the weather

and of what the volcano is doing.

NARRATOR: Often, there's simply no alternative

to getting up close and personal with a magma-spewing monster.

CLIVE OPPENHEIMER: We couldn't make the kinds of measurements

we want without actually going up close to the mouth

of the volcano to measure gas emissions in great detail,

to install a seismic sensor, to collect rock samples.

NARRATOR: It's something that no team will ever

undertake lightly without a full assessment

of potential dangers.

Lava temperatures in a flow feel can

reach 1,000 degrees centigrade, enough to blister exposed skin.

Most of us, you know, in our line of work have colleagues--

Know of colleagues who have been killed in-- in the line

of duty, doing field work.

NARRATOR: Conventional monitoring

relies on measuring devices put in place

at active volcanic sites.

It's vital these systems are well maintained.

CLIVE OPPENHEIMER: There are people in volcano observatories

who have an operational 24/7 duty and responsibility

to monitor volcanoes, to-- you know--

Repair equipment that stopped working because it's been

hit by a lava bomb--

You know-- and put themselves in harm's way.

NARRATOR: In recent years, an incredible new technology

has changed the rules.

Instead of risking life and limb,

now, volcanologists only have to risk their drone.

MATTHEW WATSON: It's annoying when you lose a drone.

But if you're flying it sensibly,

and you're not putting anybody at risk,

it is in the final analysis just a bit of a plastic

and not really expensive bit of plastic.

But it is a bit of plastic.

NARRATOR: Drones allow scientists to get

completely new kinds of data.

MATTHEW WATSON: The combination of drones

and these small sensors that weigh a few hundred grams are

completely revolutionizing what we know about volcanic plumes

because rather than making observations at a safe distance

at the stuff that's falling out, we're actually flying

smack dab into the middle of the ash cloud

as the volcano is erupting.

NARRATOR: These remote-controlled gadgets

are able to venture right into the heart of an eruption plume.

MATTHEW WATSON: And what we've been doing

is mounting little ash collection devices onto drones

and flying them into the ash cloud,

grabbing, sucking up some of this ash,

bringing it back down, then analyzing it in the lab

afterwards.

NARRATOR: Matt and his team have focused on one particular South

American volcano.

The most interesting place that I work

is a volcano called Fuego in Guatemala.

And the reason we go there is because it does

constitute some risk to the local population.

But it also produces ash extremely regularly.

This thing goes off for 5 to 10 minutes.

NARRATOR: Fuego's last major eruption was in 2018.

Deadly pyroclastic flows swamped nearby villages.

Around 25 miles away, the country's

main international airport was shut down by ashfall.

At least 69 people lost their lives.

Many more remain unaccounted for.

So it's imperative that scientists

are better able to predict future eruptions here.

Matt and his team work relentlessly to collect

the data to make this possible.

You can get up every morning at 5 o'clock,

put the drone on the catapult, fire it up into the sky.

It goes up.

It collects ash.

It comes back down.

It lands safely.

You collect the sample, and you do

that five or six times until the clouds

come in every day for two weeks.

NARRATOR: By measuring the ash particles collected

from inside an ash cloud, the team gets more extensive data

than ever before.

In the event of a Yellowstone super eruption,

it could help predict exactly where ash will fall

and in what quantities.

This, in turn, could improve disaster responses

and ultimately save lives.

[sirens wailing]

But drones aren't the only new technology

helping predict future volcanic super eruptions.

Another is found in space.

New technology is transforming the study of volcanoes.

A super eruption at Yellowstone would profoundly

impact North America, so the more ways

we can monitor, predict, and prepare

for a record-breaking event, the better chance we have

of surviving.

One new potentially life-saving development

relies on observations made from space--

Satellite remote sensing.

JULIET J BIGGS: Satellites can detect

many different types of volcanic activity,

including pre-eruptive activity.

But there are also techniques that

allow us to measure thermal emissions from lava fields

when the volcano is actually erupting.

NARRATOR: Right now, satellites are observing many

of the world's volcanic sites, and new satellites

come online all the time, sending back

ever-increasing amounts of data.

SentinelOne, which is the European satellite that

we're using most often, is-- we think it's going

to be producing about a million images of volcanoes every year.

So it's really revolutionized the number of volcanoes

we're able to study.

NARRATOR: Using AI, scientists are looking for tiny changes

in ground level that could be an indication of underlying

volcanic activity.

JULIET J BIGGS: We're looking for very tiny changes

in that distance between the satellite

and the ground surface.

NARRATOR: As magma moves upwards,

it raises the ground above, sometimes

by only a tiny amount.

JULIET J BIGGS: Satellite techniques

can now measure rates as small as a millimeter per year.

You can also measure it over very large areas,

which means that it wouldn't necessarily

be visible to the naked eye.

There's no way you're going to be able to see that visually.

But we can detect that with-- with the satellites.

NARRATOR: Juliet keeps a particularly

close eye on a little known volcanic system in East Africa.

JULIET J BIGGS: It's right next to the rapidly

growing town of Hawassa.

We think there's about 1 and 1/2 million people living within

100 kilometers of this volcano.

And we also know that it's been uplifting

at a rate of about 6 centimeters every year

for the past 10 years.

NARRATOR: Currently, there's no cause for concern,

but things can change quickly with any potentially

eruptive volcano.

JULIET J BIGGS: If we're monitoring things,

and we start to see unprecedented levels

of activity, unprecedented numbers of earthquakes,

unprecedented amounts of deformation,

that might tell us that something unprecedented

is about to happen.

NARRATOR: For vulcanologists, the ultimate goal

is to be able to predict when and where a major eruption

could take place.

For a super volcano like Yellowstone,

that knowledge could save tens of thousands of lives

and mobilize rescue operations more rapidly.

JULIET J BIGGS: The final frontier

really is forecasting what--

What that means for--

For future eruptions and for the people

living around the volcanes.

NARRATOR: For now, eruption remains an inexact science.

Nobody knows for sure whether a super eruption

is 10 years away or 10,000.

But scientists on the ground at Yellowstone

are reacting to whatever mother nature throws their way.

They must keep a watchful eye on this ticking time bomb.

Mike Poland is the park's chief scientist

responsible for monitoring activity.

MIKE POLAND: We have many different tools

we can use to monitor activity at Yellowstone.

There are dozens of seismometers scattered

all throughout the park that measure subtle vibrations

of the ground.

We've got many tens of GPS stations

that measure how the ground moves up and down all

over the Yellowstone region.

We sample gases.

We sample waters.

We even measure the chemistry of the rivers.

NARRATOR: Today, Mike's using an ingenious new piece

of technology--

A gravity monitor.

MIKE POLAND: Depending on how much material is beneath,

gravity might pull a little harder or a little less hard,

and we can measure that.

And by looking for changes in gravity over time,

we might be able to see whether there's

more magma beneath our feet.

NARRATOR: It's a new approach for Yellowstone

but one with proven results.

MIKE POLAND: Gravity is showing a lot of promise

worldwide for helping forecast volcanic activity.

For example, at Kilauea, as magma

accumulates beneath the surface, we've

seen increases in gravity.

We're hoping that we might be able to apply the technique

here in Yellowstone as well.

NARRATOR: These different monitoring techniques

help Mike and his team develop a clear understanding of

the region's unique character.

Volcanoes are like fingerprints.

The kind of background activity we see at Yellowstone

might be alarming at another volcano.

But it's normal here at Yellowstone.

And by understanding that background level,

we can learn to recognize when things truly get anomalous.

NARRATOR: Only by measuring Yellowstone's baseline activity

can they identify changes that might

indicate an imminent eruption.

MIKE POLAND: We can kind of characterize

the way Yellowstone should be acting when it's quiet.

And when Yellowstone is quiet, it

turns out it's really noisy-- there's

all kinds of earthquakes, the ground moving up and down,

geysers stopping and starting.

That's how Yellowstone behaves.

NARRATOR: And it's not just ground-based monitoring.

Mike also relies on even more high-tech methods.

Thanks to radar satellite imaging,

Mike discovered a previously unknown feature.

We've actually managed to detect

new thermal areas using satellites that we

didn't even know existed--

Way in the back country, places where people just don't visit,

as we've seen one get hotter, trees

died around it and started seeing even small amounts

of sulfur gas being emitted.

NARRATOR: But changes like this might not indicate

an eruption any time soon.

Scientists are only beginning to understand just

how energetic Yellowstone really is.

MIKE POLAND: It's incredibly dynamic.

It's always changing.

And the fact that we can see these changes

both on the ground and from space is incredibly exciting.

NARRATOR: Yellowstone is one of the most closely watched

volcanic sites in the world.

But no amount of monitoring can actually stop an eruption.

It may not happen until far into the future,

but when a super eruption is unleashed,

it will be truly spectacular.

JOHN GRATTAN: It would appear that Yellowstone is broadly

due for an eruption, but that might not be for, you know,

plus or minus 10,000 years.

And it's inevitable it will happen.

NARRATOR: So how might such a disaster unfold?

MIKE POLAND: If there were an eruption that

were about to happen, magma rising towards the surface,

we would see incredible uplift, the ground

inflating like a balloon.

NARRATOR: Once a full eruption began,

things would very quickly start to feel apocalyptic.

BRYAN WALSH: A super volcanic eruption

would have the explosive equivalent of thousands,

upon thousands, upon thousands of

Hiroshima-scale nuclear bombs.

NARRATOR: With a state-wide area,

the outlook would be bleak.

BRYAN WALSH: The area around the park for hundreds of miles

would be utterly devastated.

We would have no Yellowstone after this.

NARRATOR: Some of the volcanic effects

would reach far beyond the park.

JOHN GRATTAN: One could then conceive of pyroclastic flows,

which are hurricanes of superheated volcanic ash

traveling across the landscape at several hundred miles

an hour, traveling for-- potentially

for-- for 1,000 miles or more.

So something that's 400 degrees centigrade burning

everything in its path--

If you're in its way, you're going to die.

NARRATOR: Before long, immense quantities of ash

will be pumping into the atmosphere.

75% of the US landmass could be buried in volcanic ash.

BRYAN WALSH: There's no system.

There's no scenario.

There's no emergency plan in place to deal

with anything on the scale.

The closest we can kind of imagine really

is quite honestly a nuclear war.

NARRATOR: And this would only be the beginning.

The millions of tons of sulfur dioxide in the atmosphere

could potentially change the global climate.

BRYAN WALSH: You end up with what's known as potentially

a volcanic winter, where temperatures drop by 10, 15

degrees or more-- which is enough to really utterly change

human life as we know it.

NARRATOR: But this wouldn't be the first time human beings

have faced such a test.

JOHN GRATTAN: We as a species are common ancestors.

We're walking on the planet during massive super volcanic

eruptions that devastated the environment,

and we have survived.

And we went on to thrive.

NARRATOR: The human species may survive,

but will America survive this volcanic doomsday?