Original subtitles

[intense music]

NARRATOR: Yellowstone, America's first national park,

and home to one of the world's largest super volcanoes.

Beneath the scenic geysers and waterfalls,

an eruption a thousand times larger than any

in human history awaits.

It's happened before.

Less than a million years ago, it devastated more than half

the continent, and it could happen again.

There will definitely be additional eruptions

in this area.

NARRATOR: And not just one, but a series

of monstrous eruptions--

a million times more powerful than an atomic bomb.

MICHAEL RAMPINO: It's absolutely devastating.

Everything would be killed.

NARRATOR: Destroying thousands of square miles

of land and countless lives across the northwest.

It'll just be over.

It'll be toast.

It'll be finished.

NARRATOR: We go beneath the earth

to probe the volcano, revealed for the first time

the source of its power to discover what will happen when

the sleeping giant of Yellowstone

awakens and becomes a mega disaster.

[theme music]

The dance of geezers is one of nature's greatest spectacles--

it's why millions of visitors each year

come to America's oldest national park, Yellowstone.

Its spectacular beauty inspired President Ulysses S. Grant

to protect these two million acres of northern Wyoming

wilderness back in 1872, and it's

been a haven for outdoor enthusiasts ever since.

Its incredible hot springs, bubbling

pools of mud, unearthly ponds, and the most celebrated

natural feature, the Old Faithful geyser

are some of nature's greatest wonders.

But beneath this primal beauty simmers a hidden threat.

Five miles below the waterfalls and mountain peaks

lies the heart of a super volcano, a constantly moving

cauldron of molten rock the size of Mount Everest.

Over countless millions of years,

it fills with lava to the breaking point.

Like a bomb with a hidden timer, it finally explodes.

We don't know how long it's going to just sit there

before it decides to go off.

NARRATOR: If sometime in the future it were to erupt,

as it has before, the Yellowstone volcano

would overwhelm everything within 100 miles

and disrupt lives across the globe for years.

The first sign of trouble will be increasing seismic activity.

The ground would rise as pressure from the molten rock

begins to grow.

There would be a lot of ground defamation,

and then if it was moving up slowly enough,

we would actually start seeing large changes in the geyser

basins.

NARRATOR: Finally, the lava would shatter the earth's

surface with an explosion 10 times larger

than Mount St. Helens.

A hurricane of hot gases would spread out in all directions

as the ash cloud reaches 80,000 feet into the air.

Already larger than anything man has experienced,

this would be just the beginning of a Yellowstone

super eruption.

Within days, a second enormous eruption

would begin, then another.

Soon, a ring of monstrous explosions 50 miles wide

would be spewing molten rock and burning gases

across the landscape.

Certainly within 100 miles at Yellowstone,

there wouldn't be much that was not destroyed.

NARRATOR: High in the atmosphere, the ash cloud

would surround the planet, sending temperatures plunging.

Global agriculture would fall into chaos.

How do we know it will happen?

Because it's happened before.

The evidence is etched into the geologic record

of past super volcanoes.

There are 1,500 volcanoes around the world,

but there are fewer than 10 super volcanoes, the ones

with the potential to not only destroy the surrounding area,

but to create a global disaster, and Yellowstone is

one of these super volcanoes.

Imagine something 10,000 times the size of Mount St. Helens.

It's almost unimaginable.

NARRATOR: Unlike a conventional volcano with its crater

atop a mountain, Yellowstone's crater is so large,

it can only be seen from the air.

This is the rim of a monstrous crater called a caldera that

collapsed into the magma chamber during the last super eruption.

It's large enough to hold the city of Los Angeles.

People drive 35 miles, 45 miles commuting

to work in that.

Well, that's the distance across this caldera.

NARRATOR: And this is only the last

of three monstrous calderas formed over the past two

million years.

The volcanic history of Yellowstone

is really marked by these three giant cataclysmic eruptions

of the scale that we haven't seen in the history of man,

really.

The first eruption vented somewhere around 600

cubic miles of material.

And if you took all of that and you spread it out

over the state of Texas, you'd have about 12-feet thick

of deposits.

NARRATOR: The second eruption was hundreds of times

larger than Mount St. Helens, and it's

the smallest of the Yellowstone super eruptions.

The most recent one, known as the Lava Creek eruption,

occurred 640,000 years ago.

At the time, early man had yet to arrive on the scene.

Exotic prehistoric animals roamed the North American

continent.

Five miles beneath the earth, however, a magmatic cauldron

three times the size of New York City was coming to a boil.

There would have been hundreds to thousands of earthquakes

becoming fairly large, so there'd

be a lot of shaking as the hot rock was moving up.

NARRATOR: A million tons of molten rock heated to 1,800

degrees Fahrenheit pressed its way to the surface.

Jets of superheated water suddenly burst

through the cracks in the earth's surface,

shooting into the air.

Hundreds of geezers were erupting over 500 square miles.

JACOB LOWENSTERN: We get explosions

out of the hydrothermal system that put holes in the ground

as big as a mile across, they they're big events.

NARRATOR: But this was just the overture before the main event.

After days of increasing earthquake and geyser activity,

under mounting pressure from magma and superheated gases,

Yellowstone's last super eruption began.

ROBERT SMITH: Material may have started to leak out

of one side, perhaps forming part of the edge

of the fracture zone.

As you start to decrease the pressure,

it starts to then explode.

NARRATOR: With the power of a hydrogen bomb,

a monstrous cloud of searing ash and melted rock

shot into the stratosphere at supersonic speeds.

The heavier debris fell back to the ground,

turning into colossal pyroclastic flows.

MICHAEL RAMPINO: It was sort of like a hurricane

made up of 800 degree ash, and pumice, and hot gases.

Just wipes things out completely.

NARRATOR: For miles, these lethal rivers of ash and gas

cooked animals alive and brushed forests aside like twigs.

ROBERT SMITH: They extend, actually,

outside of Yellowstone into Idaho and into the Teton

region.

Some of this material flowed down and actually covered

parts of the floor of Jackson Hole,

so these scenes extend tens of miles

away from the actual eruption location.

NARRATOR: For days, the Yellowstone volcano

continued to heave tons of molten debris into the air

and devastated the nearby terrain.

Then, across the caldera, another colossal explosion,

then another.

Eruption after eruption began shooting more and more lava

and pulverized rock into the air.

JACOB LOWENSTERN: Typically, when these eruptions begin,

they begin at a single event, and the event may then

get larger, moving out along some sort of a fracture system.

NARRATOR: Yellowstone had turned into a super eruption.

Its devastation would reach around the world.

Yellowstone's last super eruption

occurred 640,000 years ago.

It started as a single massive volcano,

but soon turned into a series of eruptions,

exploding with the full force of a super volcano.

Entire sequence of pyroclastic explosions

that formed the Yellowstone caldera may have taken as

little as two weeks to happen.

NARRATOR: Pyroclastic flows slashed across the landscape,

obliterating thousands of square miles.

Separate clouds of ash fused into a massive column of smoke.

Winds drove it across the country,

darkening the sky for hundreds of miles.

During the eruption of all this material,

that's when the caldera would have started forming.

NARRATOR: In a final massive display of nature's fury,

hundreds of square miles of mountain

dropped thousands of feet into the pit of roiling magma.

ROBERT SMITH: The Gallatin range, the Madison range,

and the Mount Washburn range to the north continued somewhere

into the Yellowstone region.

These mountain ranges were destroyed.

Now, when I say destroyed, I don't

mean they were blown to smithereens

into the atmosphere.

Much of it just then just fell back into the magmatic system,

just fell back into the cauldron, if you wish,

of the caldera itself.

JACOB LOWENSTERN: We're talking about mountains that might be

12,000 feet high that are now at the ground

surfaces on the order of 8,000 to 9,000 feet high, so 3,000

foot mountain that is no longer there.

NARRATOR: Finally, after perhaps weeks of constant activity,

the Yellowstone volcano subsided, but the devastation

was far from over.

A global disaster was about to begin.

2 and 1/2 trillion tons of sterile volcanic ash

drifted with the winds and buried 2,000 square miles

of the North American plains, destroying much

of the continent's plant life.

HANK HEASLER: The volcanic ash that's

ejected high up into the atmosphere,

and then falls many, many miles away,

that goes as far as Louisiana and some

of the states along the Mississippi River, so quite

an ash cloud.

NARRATOR: The lighter particles remained

in the air for more than a year, forcing temperatures to plunge

across the hemisphere.

It acts as a veil and cuts out the sunlight,

and so it cools the climate below.

I think there were certainly of been climatic changes

due to Yellowstone.

We estimated 3 to 5 degrees Celsius drop

in temperature, which is quite severe on a global basis.

NARRATOR: 5 degrees was enough to kill off

much of the tropical plant life across the globe.

Over the next year, animals died from lack of food

as the ash continued to block out the sun.

It took years for the planet to recover,

for sunlight to reach the earth's surface,

for plants to push through the layers of ash,

for animals to repopulate the continent.

This Yellowstone eruption 640,000 years ago

changed the face of North America,

but that wasn't the only super eruption

to ever strike the area.

Besides the three calderas found near Yellowstone park,

geologists have discovered a series

of eruptions and super eruptions that extend back

16 million years.

JACOB LOWENSTERN: There have been

a series of volcanic eruptions similar to those that occur

at Yellowstone, and there are all sorts of calderas that

are preserved in the Snake River Plain in Idaho

and extending back into Nevada.

NARRATOR: To date, 15 calderas of more than 140

large eruptions have been mapped.

They create a trail running Northeast to Southwest and

are an indication of what geologists call a hot spot.

A hot spot is a portion of the earth's mantle

that contains a massive pool of partly molten rock.

JACOB LOWENSTERN: There is an area within the earth's mantle,

deep underneath where we live, that is molten,

and it's causing a lot of heat to rise towards the surface.

And that heat causes melting in the crust,

and so we get a large magma chambers.

NARRATOR: From time to time, as the pressures build,

the magma works its way to the surface--

and explodes.

ROBERT SMITH: There are 20 or 30 hot spots

around the earth's globe, such places as Hawaii and Iceland.

These are long lived zones of active volcanism.

NARRATOR: The Hawaiian islands, for example,

were created one by one over the millennia

by an underwater volcano.

Though it appears as if the volcano had moved

along the earth's surface, in reality,

the area of molten rock has remained relatively stationary.

It is the earth's crust which has moved.

The same is true for the Yellowstone hotspot.

Above its magma chamber, the North American plate

is slowly sliding to the southwest, about an inch

a year.

With each new eruption, a caldera

is formed, and appears to be further to the north.

We find caldera as all the way back into northern Nevada,

and it's possible that there have been

as many as 50 eruptions just as big as some of the ones that

have come out of Yellowstone.

NARRATOR: With a history of multiple cataclysmic eruptions,

Yellowstone is becoming the most studied super volcano

in the world, and its hundreds of yearly earthquakes,

thousands of geysers, and massive magma chamber

make it one of the most geologically active regions.

This thing is a breathing system,

and it's a dynamic system.

So I called it a living, breathing, shaking caldera.

NARRATOR: At the heart of these super eruptions

is thought to be a mantle plume, an upwelling of molten

rock rising from deep within the earth.

But no one could be sure.

Recently, however, scientists have

been using extremely sensitive monitoring systems

to capture data from earthquakes centered around the world.

The data has helped create the first 3D image of the source

of Yellowstone's power.

Once we put out an array of seismographs

with sufficient resolutions, like getting a high resolution

CAT scan, we saw that this thing was going off laterally

about 150 kilometers to the northwest.

And it is basically coming up from the depth

of about 600 kilometers.

NARRATOR: Yellowstone's magma source begins 450 miles

below the surface, and, surprisingly, not directly

under the park, but 150 miles away

beneath the Montana-Idaho border.

It was totally unexpected and would not

fit into anyone's textbooks or classic ideas.

NARRATOR: As the research continues,

scientists are realizing how little they really know

about the Yellowstone volcano.

JACOB LOWENSTERN: Since humans haven't seen an eruption

of this magnitude, we're somewhat

challenged to know exactly how the systems work.

NARRATOR: One thing is known for sure,

if Yellowstone erupts again, pyroclastic flows will destroy

everything near the volcano, and its ash cloud would overwhelm

humanity across the globe, and predicting its eruption

could be a matter of life and death.

The ash from the last three Yellowstone

eruptions would fill the Grand Canyon.

Yellowstone, its dreamlike natural beauty

may sometime in the future turn into a nightmare.

With little warning, the gigantic volcano

could awaken and explode, putting the entire planet

at risk.

Unlike most disasters, such as tornadoes or hurricanes, which

are short lived and localized, a volcanic super eruption

in Yellowstone would have global effects for years.

Its impact would be on the scale of an asteroid, large enough

to change the way we view our history.

For a long time, the earth history

was gradual changes, slow changes over long periods

of time, and now we realize that every once in a while, boom,

out of the sky comes something catastrophic.

NARRATOR: Most scientists believe an asteroid caused

the disappearance of the dinosaurs 65 million years ago,

but new discoveries suggest volcanoes can cause planet

wide devastation as well.

One of the early volcanoes fueled by the Yellowstone

hotspot left a gruesome graveyard

a thousand miles downwind.

MIKE VOORHIES: 12 million years ago, the wildlife in Nebraska

was similar to what we have in Africa today.

We have elephants, rhinoceroses, camels,

horses related to zebras, all kinds of critters

that aren't here anymore.

NARRATOR: Their bones, discovered

in northern Nebraska, tell a distressing story

of Yellowstone's impact.

They were found buried under several feet of ash, volcanic

debris linked to a super eruption.

We first thought that maybe all these critters

had been buried alive in ash, like the people at Pompeii.

But the more closely we looked at the fossils,

it turns out that that wasn't true.

NARRATOR: Most of the fossil bones

exhibited evidence of a strange illness, a clue

to why so many animals died.

It has the extra growth of bone on the leg bones

and on the jaws.

NARRATOR: The unusual bone growth is a signature symptom

of Marie's Disease, a rare lung condition resulting

from breathing large amounts of dust or ash.

This is a jawbone of a camel from the ash bed.

This shiny bone here is healthy.

It's normal, fossilized bone.

And you can see where the healthy bone stops

and this new growth begins.

You can see the color changes and the texture changes.

It looks like a sponge, and this is the diagnostic feature

of HPOD, or Marie's Disease.

NARRATOR: Voorhies believes that ash from the Yellowstone

hotspot caused Marie's Disease in these animals.

MIKE VOORHIES: Ash is nothing but very small

pieces of glass--

that's how you can tell volcanic ash from other types of fine,

powdery rocks is that volcanic ash sparkles because it's

made out of little teeny pieces of glass.

NARRATOR: During a super eruption,

the tremendous pressures caused the molten rock to explode.

It turns the rock into tiny pieces of glass

which drift with the wind and land hundreds of miles away.

MIKE VOORHIES: Just as soon as the volcanic ash fell,

the whole landscape, for thousands of square miles,

was covered with this very fine powder.

And every step that those animals took,

they would raise a cloud of ash.

And they just kept breathing it day, after day, after day,

so what we think happened to the animals

is that they breathed this material night and day

until their lungs just gradually gave out.

NARRATOR: Most of the animals on the Nebraska plane

suffocated on the ash within a week of the eruption, this

from a super volcano a thousand miles away.

Volcanoes can kill at a distance.

I really wouldn't have bet 20 years ago that a volcano

a thousand miles away could actually cause mass death,

but ash fall has made a believer of me.

NARRATOR: More recently, the 1815 eruption

of the Indonesian island of Tambora

proved ash could kill indirectly through dramatic climate

change.

50 times larger than Mount St. Helens,

the impact of the Tambora volcano was overwhelming.

The eruption reduced the mountain by 4,000 feet

as nearly 150 million tons of ash and debris

were ejected into the air.

The ash cloud could be seen for hundreds of miles.

MICHAEL RAMPINO: The cloud went over India, darkened the sky,

and caused the temperature to go down.

The temperatures went below freezing.

NARRATOR: It took almost a year for the ash

to spread across the rest of the globe, but when it did,

the results were staggering.

A New England newspaper from 1816 published this account.

MAN: Snow and hail began to fall about 10:00 AM,

and the storm continued till evening, accompanied

by a brisk wind.

NARRATOR: This was June 15.

There was, in some places, essentially no summer.

In the eastern United States, there was snow and ice

in June, July, August.

They replanted the crops.

The crops died.

They replanted them again.

NARRATOR: The unusually frigid weather

reached Europe, some 9,000 miles from Tambora,

throwing life there into chaos.

1816 was the last time there was widespread starvation

in Europe.

That's never happened since, and it's almost certainly involved

with the eruption of Tambora.

NARRATOR: And the Tambora eruption

doesn't begin to match the fury of a Yellowstone

super eruption.

The Tambora eruption is on the order of 50 to 100 times

smaller than these large sort of super volcano

eruptions out at Yellowstone.

NARRATOR: Even smaller than Tambora was the 1991 eruption

of Mount Pinatubo in the Philippines,

which devoured villages out to 200 miles.

Yet despite its modest size, Pinatubo

altered the global climate for years,

and has been linked to the destructive hurricanes Andrew

and Iniki.

After the eruption of Pinatubo,

there was a definitely measurable change

in the global temperature as a result of that eruption.

It was on the order of 2 degrees for the year following

the eruption.

NARRATOR: It may sound trivial, but a 2 degree change

in global temperature over a long time

could create unusually severe storms and kill off all but

the hardiest plant life.

Pinatubo was a hundred times smaller

than the last Yellowstone super eruption

and had cataclysmic effects across the globe.

Imagine what Yellowstone would do.

In recent geological history, only the colossal eruption

of Toba on the island of Sumatra can match the size

of Yellowstone, and that eruption, some 70,000 years

ago, may have nearly destroyed the human race.

Well, Toba is the largest super volcano

that we know about.

There is now a large lake called Lake Toba which is the hole out

of which the eruption came.

NARRATOR: It likely erupted for two weeks,

dropping ash 6 inches deep on the subcontinent of India.

But Toba's greatest impact was felt halfway

across the planet in Africa.

Around the time of the Toba eruption,

it's thought the population of early man

was catastrophically reduced.

It appears a bottleneck, or a contraction,

of the human population occurred, reducing our numbers

from possibly hundreds of thousands

to just a few thousand.

We know from the genetic data that something happened

in the human history, in the history of our species,

that reduced the amount of genetic variation a lot.

And the argument is all about what

was the nature of that event.

One possibility is that there's some catastrophe that happened

70,000 years ago, like the Toba super volcano, that just wipes

out plants, and animals, and humans all over the earth

until there's hardly any of them left.

NARRATOR: The massive eruption of Toba,

more than 25 times larger than Tambora,

likely created a catastrophic change in climate.

Ice core samples suggest that the average temperature may

have dipped as much as 20 degrees for years

after the eruption, likely killing off

plant life across the globe.

Hardest hit would have been tropical areas like Africa.

Africa is where we were at the time,

and so would affect us directly.

And secondly, it's the tropical vegetation that never

experiences cold temperatures, so it has no adaptations

for cold temperatures whatsoever.

NARRATOR: The frigid temperatures killed off

much of the African plant life, and the resulting famine

may have decimated much of the human race.

It may be that the 6.5 billion people who inhabit the earth

today are the direct descendants of the few

who survived the Toba eruption.

If a single eruption like Toba is powerful enough

to almost destroy the human race,

what would a similar super volcano do today?

When a large, giant eruption were to occur,

I think there's little that man can do about it.

The biggest thing we have to do first is understand them.

NARRATOR: That's why scientists are studying every aspect

of the Yellowstone volcano.

What they discover may be the key to our survival.

For most of us, Yellowstone National Park

is one of our greatest natural treasures,

but what lies just below the surface could destroy it all.

The sense of scale of the catastrophic eruptions

for Yellowstone is very hard to grasp.

NARRATOR: 640,000 years ago, a super volcano in Yellowstone

devastated the region.

Today, scientists monitor the ground movement in Yellowstone

to determine if, and when, another super eruption might

occur.

We don't know exactly what happens before a super eruption

takes place and how much time one has before the eruption

actually goes off.

NARRATOR: The rise and fall of the ground, for example,

could indicate the movement of magma below, a possible danger

sign.

These movements cover very short distances over long periods

of time, so scientists have placed throughout the park 12

global positioning satellite monitoring stations that

can detect ground movements within a quarter of an inch.

Geologists have also gained a bird's eye view

of the situation.

We use satellites, in this case,

to take pictures of the ground as it's moving over time,

and so we can compare two different passes

of the satellite that are perhaps a year apart

and make a map of how much different spots on the ground

have moved.

NARRATOR: With these tools, geologists

have been able to document changes

in the caldera, its constant rising and falling over time.

According to recent satellite data, much of the caldera

is being lifted up.

What we've seen has been uplifting, now at rates

of 6 to 8 centimeters per year.

Those are very high rates.

NARRATOR: The most dramatic uplift

is just north at Yellowstone lake in the area geologists

call a resurgent dome.

ROBERT SMITH: And we have, within this caldera,

these orange areas here.

These are resurgent domes.

These are areas that are uplifted while the caldera was

collapsing and subsiding.

NARRATOR: Geologists believe that these two areas were

lifted up by the magma chamber as the caldera was formed.

It's thought that some magma is still inside these domes,

holding up these areas.

But they couldn't be sure until now.

We've seen this model of the Yellowstone magma plume,

the tube through which molten rock from the Earth's core

reaches the magma chamber sitting on top of the plume.

Using similar data, geologists have created this 3D

illustration of the magma chamber

as it sits below the Yellowstone caldera.

This is a three dimensional image,

like a CAT scan or an X-ray of the earth,

is giving us an image of what we think is the magma system that

drives Yellowstone.

NARRATOR: This u-shaped chamber is thought

to contain more than 300 cubic miles of partially molten rock,

a hundred times larger than Pinatubo's magma chamber,

and is just five miles below the surface.

More importantly, the area of the most dramatic uplift

spotted by the satellites is directly

above a peak of the chamber.

This suggests the magma chamber is expanding, pushing up

against the earth's surface at this peak.

The other area of striking ground deformation

is near the Norris Geyser basin, the hottest and most unstable

thermal basin in the park.

JACOB LOWENSTERN: Norris Geyser basin

is one of the most dynamic of the hyperthermal areas

at Yellowstone.

It's always changing.

We're always noticing new things that are happening.

NARRATOR: Just a few years ago, satellite images

showed Yellowstone's greatest rise in this area.

Recently, however, it's reversed its direction

and is now subsiding.

JACOB LOWENSTERN: It's not actually within the Yellowstone

caldera, yet it's one of the highest temperature

thermal areas in the park.

And it is possible that there is some magma extending

to the north beneath that region.

NARRATOR: The source of the basin's volatility

could be magma or another key component

to volcanic activity, earthquakes.

ROBERT SMITH: The earthquakes are essentially

the heartbeat of the system.

They are an integral part of the active, if you wish,

mountain building and volcanism of Yellowstone.

NARRATOR: Like smoke and fire, volcanoes and earthquakes

go hand in hand.

The pressure from the magma which

can explode into a volcano also forces the ground to shift,

causing earthquakes.

They can be the telltale signs of an impending eruption.

The two main precursors to a volcanic eruption, seismicity

and ground deformation, are very carefully

monitored in Yellowstone.

NARRATOR: In this computer model,

each red represents an earthquake.

Typically, hundreds of earthquakes

are detected across the park each year.

In recent years, the greatest earthquake activity

has been centered under two areas of the park.

You can see we have earthquakes that

are concentrated on the north side of Yellowstone

coming down through the park, and then

extending on the east side of the Teton fault right here.

NARRATOR: What concerns geologists

is when a center of earthquake activity

overlaps an area of shifting terrain.

At the Norris Geyser basin, that seems to be what's happening.

There are dozens of fault lines at this spot.

That's very critical because if magma is starting

to move up, we would expect to see a bulging

in an area and associated earthquakes

as the ground starts to crack.

NARRATOR: The fear is faults that make up the earthquake

zone could crack under pressure from the magma below,

releasing an eruption.

Geologists are also watching the park's geysers, hot springs,

and mud pots, looking for drastic changes in temperatures

and chemical content, anything that might indicate

a major movement of magma.

At the moment, geologists do not believe

an eruption is imminent.

But if the water temperatures were to rise,

the ground begin to swell, or there were an increase

in earthquake activity, another Yellowstone eruption

could be building.

I think that we are smart enough as geoscientists now

that we would probably have weeks

to perhaps months of indicators before anything

like that would occur.

NARRATOR: However, predicting the precise timing

of an eruption is far from simple.

Scientists have been fooled in the past.

MICHAEL RAMPINO: We've seen it in Yellowstone.

There is a bulging.

There's vibrations.

There's increased seismicity.

There's all the things one would expect and go,

oh, uh oh, we're in trouble.

And then-- nothing.

NARRATOR: Therein lies the problem.

All we can do is monitor the volcano,

but it may not be enough to predict a possible eruption.

Mount St. Helens was the most scrutinized volcano in history,

and it exploded before the area could be cleared,

killing 56 people.

At Yellowstone, despite its remote location,

a giant eruption could put thousands of lives at risk.

Remember, we have maybe 100,000 people per night

staying in the Yellowstone-Teton system in the summer.

This is equivalent to a community of a modern US

city that are compacted into this zone

of potential eruption, so the exposure is rather high.

NARRATOR: At Yellowstone, we may be on the edge of a precipice,

and the question is not if it will erupt, but how and when.

There's nothing you can do about a volcano.

If it's going to go off, it's going to go off,

and the effects on civilization are going to be drastic.

NARRATOR: We may not be able to prevent an eruption,

but when the molten rock begins to move up toward the surface,

will all the scientific data warn us in time?

Now, using historical records, scientific models,

and the latest in computer technology,

you will witness the devastation that

follows when the giant volcano at Yellowstone erupts.

The force of the earth's gravity is weaker at Yellowstone

due to the hot water and molten rock below the surface.

For 70,000 years, the Yellowstone volcano

has remained quiet.

But sooner or later, its magma chamber

will slowly fill with millions of tons of molten rock.

Gas pressures will push up toward the surface,

bringing the volcano to the breaking point.

This is one of the rules of geology--

if it happened in the past, it'll

happen again in the future.

We know there's going to be super eruptions, and probably

one at Yellowstone, and it's going

to have catastrophic effects.

NARRATOR: Now, using computer models and the latest

scientific information, you will experience

what would happen if the largest volcano in North America

were to erupt.

When that eruption occurs, there

is no doubt whatsoever that parts of the northwest

of the United States will be completely and comprehensively

devastated.

It'll just be over.

It'll be toast.

It'll be finished.

NARRATOR: The first indications of a Yellowstone eruption

will be rumblings heard underfoot as dozens of smaller

earthquakes begin.

The ground begins to rise from the pressure of the expanding

hot waters, gases, and surging magma.

The templors grow in strength, spreading across the entire rim

of the caldera.

All the tourists have to be cleared from the park.

Officials send out warnings to towns

within a 100 mile radius, the danger zone of a Yellowstone

super eruption.

The cities of Bozeman, Montana and Cody,

Wyoming prepare for the worst.

Throughout the park, new cracks in the ground

release huge geysers, spouting superheated water hundreds

of feet into the air.

The earthquake shaking itself will

create fractures and cracks, allowing more material

to come out.

NARRATOR: The last of the tourists and park personnel

must rush to leave the park, trying to reach a safe distance

some 100 miles away before the caldera lets go.

They may not have enough time.

Lava first appears, oozing out of cracks in the surface.

Then, steam and ash explode hundreds of feet into the air.

But instead of this relieving the pressure,

it pushes the volcano over the edge.

JACOB LOWENSTERN: The magma contains a lot of gas,

and if you were able to depressurize the system

rapidly, then the magma will lose its gas explosively,

and you can have a very, very large eruption.

NARRATOR: From five miles below the surface,

molten rock heated to 1,200 degrees bursts into the air.

It begins to erupt, and you see these flows coming out

sideways.

And there's nowhere to go.

NARRATOR: Like a hurricane of ash,

pyroclastic flows rip along the ground at 100 miles per hour.

For those who left the park within the past half hour,

their luck has run out.

50 miles away, the 30,000 residents of Bozeman, Montana

watch in horror as the plume of ash and rock reaches

into the sky.

If they know anything about Yellowstone's past,

they'll know they have little time

before their city is devastated.

MICHAEL RAMPINO: The pyroclastic flows

may go out as far as 50 to 100 miles away from the volcano.

And so you'd see the pyroclastic flows coming across ridge,

after ridge, after ridge, and then,

finally, hitting where you are.

So locally, regionally, it's absolutely devastating.

Everything would be killed.

NARRATOR: The sky begins to darken as the ash cloud

obscures the afternoon sun.

The material is going to explode violently

to the surface, and the material's are coming out

at supersonic velocities.

And the finer materials go 50,000, 60,000, 80,000 feet

into the atmosphere.

NARRATOR: Then, a second eruption

begins on the other side of the caldera, then another.

It is no longer a simple volcanic eruption.

Like it did hundreds of thousands of years ago,

Yellowstone builds into the largest eruption known to man.

The giant cauldron of magma spews a million tons

of melted rock thousands of feet into the air

as several volcanoes continue to erupt.

Wave after wave of burning ash and debris

destroy everything in their paths.

With so little warning, nearly 400,000 people are at risk,

and it gets worse.

ROBERT SMITH: Material falls back

onto the surface of the earth, and so you

get ashes that are maybe 10, 20, 30 feet deep

around Yellowstone.

NARRATOR: A brilliant summer afternoon

begins to look like a blustery, snowy night.

The weight of the falling ash collapses roofs

across the states of Wyoming, Idaho, and Utah,

killing thousands, while a cloud of lighter ash a thousand times

larger than the one produced by Mount St. Helens

drifts eastward with the wind.

JACOB LOWENSTERN: There's so much ash

put into the atmosphere, and it gets distributed so globally

that it would cause disruption to air traffic

not just near the scene of the eruption, but,

really, globally for a period of time.

The ash goes in the jet engine and becomes ceramic and coats

the jet engine, and there have been horrifying descriptions

of airplanes just losing their power and diving

while the pilots try to figure out what to do to start

the engines again.

NARRATOR: Air travel grinds to a halt

as the ash cloud reaches the upper atmosphere,

and then the deadliest part of the Yellowstone eruption

begins.

MICHAEL RAMPINO: There's lots of ways

you can die in a pyroclastic eruption,

and one way is to inhale the stuff

and inhale these sharp pieces of glass.

They attack the lungs.

They attack the bones.

They kill you from the inside.

NARRATOR: Across the country, masks

are supplied to protect people against the ash,

but farm animals have no protection.

Within weeks, vast numbers of the country's livestock

die, like the animals that roamed the Nebraska plains

12 million years before.

And volcanic ash covers much of the Midwest farmland.

MICHAEL RAMPINO: They can't grow anything in that ash.

Fresh volcanic ash is sterile, like Mount St. Helens

just after the eruption.

And so it wipes out the breadbasket

of the world, breadbasket of Canada,

breadbasket of the United States.

NARRATOR: And the effects could last for years.

Recovery is going to be a long process.

So where does food come from in the meantime?

I don't know.

NARRATOR: Millions of people could die from starvation

related directly to the ashfall in America's Midwest.

Countless more would suffer as the ash cloud drifts

across the globe, dramatically changing our climate.

JACOB LOWENSTERN: It's quite likely

that the climatic effects would be much worse than humans had

experienced in the last couple years.

NARRATOR: The Toba eruption suggests that ash particles

would remain in the atmosphere for six years,

radically cooling the planet.

It could mean snow in June, frost in August,

and the killing off of crops for years to come.

Imagine six years without a growing season.

What does that mean?

I foresee a very difficult period of time

when civilization would really be strained at the roots.

This would be the most severe condition that human beings

have ever met.

NARRATOR: It may not happen for thousands of years,

but one day, history will repeat itself.

The slumber of the Yellowstone caldera will end,

and the planet will face potential catastrophe.

Hopefully, by then we'll be prepared, but if not,

it could be one of nature's greatest mega disasters.

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