All language subtitles for How the Earth Was Made HC 720p HDTV S01E08 Yellowstone

Male narrator:; Earth,

a 4.5 billion-year-old planet,
still evolving.

As continents shift and clash,

volcanoes erupt,

and glaciers grow and recede,

the Earth's crust is carved
in countless fascinating ways,

leaving a trail
of geological mysteries behind.

And one of the greatest
is right here

at Yellowstone National Park
in Wyoming.

This is one of the world's
most geologically active places,

shaken by up to 5,000
earthquakes every year,

and with more geysers
and hot springs

than in the rest of the world
combined.

Why is Yellowstone so active?

How did it form?

And why here in the heart
of the Rockies?

Scientists studying Yellowstone
are uncovering a violent past

carved by water,
crushed by ancient glaciers,

and blasted by the
biggest volcanic eruptions

ever known on the planet.

And even today,

Yellowstone is one of the most
dangerous places on Earth.

Yellowstone National Park is
one of the most amazing places

on Earth, and it's unique.

It contains some of America's
most stunning scenery

and wildlife that attracts
3 million tourists a year.

To understand where Yellowstone
came from

and why it is so active today,

we need to take a journey back
into the distant past

of the North American continent

and deep
into the Earth's interior.

Yellowstone sits 8,000 feet up
on a remote mountain plateau,

primarily within Wyoming

but stretching into parts
of lldaho and Montana.

The park covers
3,468 square miles,

63 miles north to south
and 54 miles east to west.

And it's on top of one
of the world's most unusual

and deadliest
geological structures.

- What's unusual about the park?

Are the wildlife unusual?

No.

Is the wide open space unusual?

No. You've got it all over
the western U.S.

What's unusual?

It's a very unusual geology
that created the park.

Yellowstone was founded
as the world's first

national park
because of the geology.

Narrator: It's this
strange geology

that attracts teams
of scientists to the park.

Their task?

To piece together the story
of the incredible processes

that built this unique,
extraordinary landscape

by digging deep
into Yellowstone's past.

- The geologic history
of Yellowstone

goes back to the formation
of the North American continent.

Some of the rocks
in Yellowstone

are 2.8
to 3.2 billion-year-old rocks,

some of the oldest
in North America.

- Only by traveling back
into the past

can we figure out why
in this particular location

there are 2,400 miles of rivers,

more than 300 waterfalls

and the world's greatest
concentration

of 10,000 hot water springs,

bubbling mud-holes,
gas vents and geysers.

What do these features reveal
about this landscape

and how it was formed?

The investigation begins at
Yellowstone's star attraction,

Old Faithful.

It's a key clue

to what's going on
underneath the surface.

Located in the southwest
of Yellowstone Park,

the geyser puts on an explosive
display every 90 minutes or so,

blasting out thousands of
gallons of scalding hot water.

Yellowstone is like no other
place on Earth.

There is so much heat
coming out here.

It's really
a singular phenomenon.

Well, after about a 90-minute
nap,

Old Faithful
has roared back to life.

It wasn't actually napping,
it was recharging,

and the temperature of the water
was increasing.

The system was pressurizing.

Beneath Old Faithful

is a rather complex
plumbing system

filled with caverns and conduits
and constrictions.

Narrator. Rainwater saturating
the ground around the geyser

slowly fills
its underground reservoir.

Hot rocks belowground
heat the water under pressure

for around 90 minutes.

Suddenly, some water spurts

through a tiny, five-inch-wide
crack in the rocks.

This causes a drop
in the pressure

within the water chamber.

In an instant,
thousands of gallons of water

are turned to steam
and blasted up into the air.

- When the pressure
builds up enough,

steam bubbles start rising
to the surface,

the system depressurizes,
and a full eruption can occur.

Narrator: Old Faithful shows
that rocks below the surface

are very hot.

Scientists find clues
to a violent past

34 miles southeast
of the hot springs

on the shores of a circular lake
called Indian Ponds.

- As a field geologist,

my job is to basically be
a rock detective.

And so I try to determine
what their origin is

and what the history is
of that particular rock.

There we go.

Okay, now, in this particular
case-let's look at this.

This rock, when it started,
it was just a loose sand.

You could just put your fingers
through it.

Narrator: The solid boulder
is formed

from millions of individual
grains of sand.

Microscopic analysis reveals
the grains

have been cemented together
by chemicals and pressure

deep under the ground.

But how did the rock
get to the surface?

Morgan has chemically dated
the rocks

and discovered
that 3,000 years ago,

the boulder was blasted out
of the ground

by the hot water explosion
of a gigantic geyser.

- You would see boiling water,

rock fragments
and fine muddy material

being ejected up into the air
as high as 3,000 to 5,000 feet.

And then, at some point,

material would start raining
down from this explosion column.

Now, you wouldn't want to be
standing next to one of those.

Narrator:
Indian Ponds is the crater

that the geyser left behind.

But it is dwarfed by the crater
Morgan has found

at Mary Bay
in Yellowstone Lake.

Morgan has dated this geyser
explosion to 13,000 years ago.

- So here we are in the middle
of Yellowstone Lake,

and it's, as you can see,
a beautiful day

and it's nice and placid,

but on the floor
of Yellowstone Lake,

it's anything but quiet.

Narrator. Morgan's research
proves that geysers

were exploding around the lake,
and even under the water,

between 13,000 and 3,000
years ago.

And their size suggests

that whatever was powering them
was huge.

But is it still active today?

A clue
comes from underwater vents

at the bottom
of the geyser crater.

They pump out vast quantities
of hot water and gases.

To find out what's creating
the gases,

Jake Lowenstern
and his assistant

collect samples
from the hot springs

in the center of the park.

The funnel they use is designed
to collect up gas bubbles

before they reach the surface

so that they're not contaminated
by ordinary air.

- So you let it sit
for five minutes

and let the oxygen get out?

- Yeah.

It is a very complex mix
of gases and-

but we have a-a lot of tools
that we can use

to try to unravel this rather,
uh, complicated information.

So we'll look at all of
the gases that are coming out.

We can learn about the different
kinds of rocks

beneath Yellowstone
and try to understand

how things might be changing
from-from week to week

or year to year or-
or decade to decade.

Narrator:
Analysis of the gases reveals

that they are a mix of carbon
dioxide, sulphur dioxide

and hydrogen sulphide.

It is the same mix that is found
coming out of volcanoes.

But the final clue to what's
actually going on underground

is found on the edge
of the same hot springs.

- So these are quartz crystals
that we collected

on the side of the pool there.

This stuff is what remains.

It gets tossed up
and forms a little berm

around the side of the cr-pool

and it's all beautiful
little quartz crystals.

Some of them have a little bit
of iron staining

and other things, um,
but most-

most of them are-are nice, uh,
shades of yellow and-and clear.

Narrator: Quartz crystals
like these

can only have formed as a hot,
molten rock lava flow

slowly cooled after being
erupted onto the surface

from deep underground.

So the crystals
are clear evidence

that under the springs
is a volcano.

Yellowstone's hot water features
all point to one conclusion.

Yellowstone must be powered by
the heat of a volcano.

Geysers only erupt if the rocks
are hot enough

to turn water into steam.

Gases from underwater
have the same composition

as those from volcanoes.

Quartz in the hot springs

must have come
from volcanic lava.

- There is an immense amount of
energy coming out of the ground

that's expressed by the geysers,

the mud pots, the hot springs

and the steam vents.

Where's all that heat
coming from?

It's coming from the molten rock

associated
with the Yellowstone volcano.

Narrator: But that leaves
a big question unanswered.

In this gentle
rolling landscape,

where's the volcano?

Yellowstone's unique
volcanic geology

is potentially deadly dangerous.

It makes it crucial
to monitor what's happening

under the ground.

- The Yellowstone volcano

is a very, very active
volcanic system,

and so it really
requires observation.

Everything that we do here
has a research component,

but it also has
a volcano monitoring component

and, uh, you know, if-if-
if activity picks up here,

we're going to want to know
something

about the plumbing system
beneath us here.

Narrator: To try and predict

when Yellowstone's
hidden volcano

will erupt in the future,

scientists study
its geological past.

- Part of our task is to look
at the landscape

and read the geologic story,

and there are so many clues
and so much evidence here

to look at that it's
a fascinating place to work.

Narrator: Scientists began
investigating Yellowstone

even before it became

the world's first national park
in 1872.

But observations
of this astonishing land

began long before that.

Dating ancient arrowheads

shows that Native Americans
first lived here

11,000 years ago.

Their legends of Yellowstone's
angry spirits

who made the ground tremble

were passed on
to early explorers

such as Lewis and Clark.

Later reports from trappers,
explorers and mountain men

like John Colter and Jim Bridger

told of geysers that fired
70 feet into the air

and springs so hot that meat
was readily cooked in them.

But these were thought to be
tall tales until the 1860s,

when geologists investigated
and found that the lava flows

and hot vents were signs
of volcanic activity.

But something
clearly wasn't right.

Nobody could actually find
the Yellowstone volcano.

- We say that Yellowstone

is one of the world's most
active volcanoes.

People come out here-
visitors, other scientists-

and they say, "What do you mean?

I don't see a smoking volcano.

I don't see a big steep
volcanic, uh, crater,"

all the things that one
normally thinks of

for an active volcano.

Narrator: So without obvious
signs of a volcano,

scientists hunted
for other clues.

They would find them
in the sweeping forests

of lodgepole pines.

These are the only plants
that thrive on the poor soil

that comes from a particular
type of lava called rhyolite.

And Yellowstone's
constant plagues of mosquitoes

also reveal the presence
of that same rhyolite lava.

- The rhyolites are-
are not very permeable,

and so in-it creates
these little ponds of water

that never go away,

and those are wonderful breeding
grounds for mosquitoes.

There are a lot of mosquitoes,

if you can't see them
flying around my head.

Narrator. So the pine trees
and the insects

both indicate
that there's a lot of rhyolite

in Yellowstone.

And that's important,

because rhyolite lava creates
incredibly violent

volcanic eruptions.

- It's much more
like a bread dough.

It's about a thousand
to a million times thicker

Oor more viscous.

If we put a bunch of gas in it,

we can have a very explosive
eruption.

Narrator: But if rhyolite lava
is that explosive,

how big a bang
did it produce?

To find that out,
scientists looked

not inside Yellowstone Park

but in a faraway river valley
at Meadow Creek, Wyoming.

Cutting down through the land
over millions of years,

the river has exposed
an unusual thin layer

of black rock in the cliff face.

A nearby road
cutting lets investigators

examine the mysterious
dark rock.

- If you look at this sample,
um, in detail up close,

you can see that here's
a pumice fragment.

These-these red fragments
here are-

are little rock fragments.

And, uh, if we were to make
a thin section of this rock

and look at it under
the microscope,

you would, in fact, see
compressed, uh, glass shards.

Narrator: The black layer
that geologists call obsidian

is actually a type of glass.

It's crucial evidence
that the rocks and soil here

came out of a volcano...

because obsidian is forged

when boiling hot ash and gas
rapidly cool

under great pressure.

And that's just what happens
when hot volcanic clouds

roll out across the landscape.

The obsidian forms
in the very bottom layers,

cooled from below

and crushed by the weight
of hot debris on top.

The ash layer that crushed
the obsidian at Meadow Creek

is still visible today.

- Its base is characterized

by this very thick, dense,
obsidian as-

as the flow came to rest
and was compacted

and then above this dense
glass layer

as it grades upwards
into a tan sort of region

and continues up for about
an additional 30 feet.

And then up on top of that,
as it's exposed today,

a modern soil has formed
and we can see

growing up there various sorts
of vegetation:

trees and grasses
and things of that sort.

Narrator. Studying the mineral
composition of the ash

proved that it came
from an ancient volcanic blast

in Yellowstone Park.

And there's only one way
that so much ash

could have been blasted
so very far away

from its source.

The eruption must have been
larger, far larger,

than anything ever seen by man,

so big that scientists now label
it as a supereruption.

- We're looking at this deposit
from a supereruption,

and yet we're over 50 miles
from the source of the-

of the eruption.

Narrator. The geologists
have re-created

what must have happened here

on the day
that Yellowstone exploded.

Incandescent avalanches of ash

raced out of the park
in all directions.

- So this is traveling
at very high velocity,

easily over 100 miles per hour,
across the land surface

and obliterating everything
in its path.

- It was extremely hot when
it arrived here,

and-perhaps as hot as-
as 1,500 degrees Fahrenheit,

two-twice a pizza oven.

I mean, it's just very hot.

Narrator: So what would it
have been like

to be standing on this spot

hundreds of thousands
of years ago

on the day
when the Yellowstone ash cloud

roared over the horizon?

- The-the impact
of this would-

would be, uh, absolutely
unimaginable.

It would be-
- Yeah.

- 1 think you would be
disarticulated, burned

and-and unrecognizable,

and it would be very difficult
to find any of you.

Narrator: All of the evidence
about the size

of the supereruption
helped solve the mystery

of the missing volcano.

Scientists realized
that the supereruption

was so enormous that it must
have blown the volcano

to pieces.

[roaring and explosions]

Swarms of mosquitoes show
that explosive rhyolite lava

underlies parts of the park.

Obsidian glass 60 miles away
reveals that ash flows

spread for miles
around Yellowstone.

And thick layers
of debris confirm

how gigantic an explosion
this must have been.

The problem now
is the explosive legacy

that the supervolcano
left behind,

because a deadly danger
still lurks here

hidden deep under the ground.

For nearly a century
after Yellowstone National Park

was established, nobody realized
one astonishing fact...

that the park is located

inside one of the biggest
volcano craters on Earth.

It wasn't until the late 1960s

that American geophysicist
Robert Christiansen

realized that rock formations
he had been studying

for several years all around
the edges of the park

in fact formed a giant
circular ridge.

He compared his findings
on the ground

with a series of NASA pictures
taken between 1966 and 1970,

confirming that the ring
was the rim of a giant crater

45 miles across.

Parts of the crater rim
are still clearly visible today,

but the other edge
is almost out of sight.

Finding the crater

coincided with another
scientific discovery

in a totally different part
of the country.

In California,

scientists identified a strange,
thin layer of ash

buried underneath
the modern-day soil.

The ash matched material
from the Yellowstone crater.

Dating the soil layers

proved that the ash
arrived 640,000 years ago.

Scientists at last had a date

for the Yellowstone
supereruption.

Ash was later found all over
the western U.S.,

confirming the huge size
of the eruption...

at least 80 times the size
of the 1883 explosion

that destroyed the island
of Krakatoa...

[rumbling]

And 2,500 times bigger

than the 1980 eruption
of Mount St. Helens.

The almost unimaginable size
of the Yellowstone blast

means that scientists
now call it a supervolcano.

But that creates
another mystery.

In this peaceful landscape,

where is the steaming hot crater

that the volcano
must have left behind?

- Today, when you're looking out
across the landscape,

you see rolling hills
and-and trees,

so, obviously, there's not
a big hole

left in the ground, um,
from the eruption of the-

of the Yellowstone volcano.

So something else has happened.

One of the first processes
was infilling

with all sorts of volcanic
lava flows,

and if you look just down
from the landscape

toward those trees,

you'll see one of the oldest
lava flows that happened

after the 640,000 year eruption.

Narrator: Over hundreds
of thousands of years,

this flow has weathered
into soil

and been covered with trees.

But elsewhere in the park

are a different type
of lava deposit,

still bare of vegetation

because this lava
was still erupting

up until about 100,000
years ago.

The later lava was far less
explosive and more runny

and cooled slowly.

It smoothed the harsh
volcanic landscape

into Yellowstone's
softer countryside.

That made Yellowstone, at first,
more tranquil.

But there's evidence here

that the land was soon buried
once again,

this time by freezing snow
and ice.

The ice that polished the rocks
has a story to tell.

It offers crucial evidence
about volcanic forces

still shaping the park
to this day.

Its tale unfolds
through the tiniest of clues.

Scratches on the rocks reveal
which way the ice was moving.

They show that glaciers
always slid the same way,

outwards and downwards
from an icecap

at the heart of the park.

The only conclusion

is that something pushed up
Yellowstone Park

so much higher
than the surrounding hills

that glaciers formed on the top.

But what force could possibly
be powerful enough

to have raised
Yellowstone's peaks

up into the air?

The first clue to help
answer that question

comes from Yellowstone's
numerous earthquakes.

- When the ground deforms,

it creaks and groans
like a Stradivarius violin.

And the creaks and groans
are essentially earthquakes.

Narrator:
The quakes are recorded

by seismometers
all over the park.

- The earthquake monitoring

is a critical part
of the picture

because it's basically-

it's the stethoscope
that we have

to really see and sense the-
the heartbeat of the system.

Narrator. Smith is investigating
a puzzling geological mystery.

Yellowstone has up to 5,000
earthquakes a year,

even though
it's in the stable heart

of the North American continent.

Scientists needed to know
what was happening underground

to shake the park so much.

To find out, they plotted
the precise locations and depths

of earthquakes under the ground.

So why are there so many quakes?

The answer had to wait
until the mid-1980s,

when ever-more powerful
computers

first let scientists see
into the Earth.

Seismic waves spreading out
from earthquakes

travel rapidly
through cold rock

but slow down
when the rocks are hot.

The varying wave speeds can be
translated by computers

into color 3D images,

revealing exactly where hot rock
lies under the ground.

- Seismic waves propagate
through the Earth

just like X-rays
go through a body,

and so we use the same physics

to reconstruct the structure
of the geol-

of the Earth beneath us.

Narrator: The seismic waves
have outlined

the park's underground
structures,

revealing a graphic history

of what's happened
under Yellowstone.

They reveal this gigantic
reservoir of molten rock

which created
Yellowstone's crater

when lava erupted out

and the ground above collapsed
into the space left behind.

And the seismic waves still slow
down under Yellowstone today,

showing that the magma chamber
still lurks under the park.

It's more than 30 miles long,
25 miles wide

and 10 miles in depth.

But its size alters
from year to year

as it fills or empties
with semi-liquid rock

at an incredible 1,500 degrees
Fahrenheit.

This is the hidden beating
heart of Yellowstone Park.

The way it moves
deforms the ground above,

explaining the fault lines
and the earthquakes

they produce.

And its heat ultimately powers

all of Yellowstone's
hot water pools and geysers.

Subterranean Yellowstone
is giving up its secrets.

Seismographs record thousands
of earthquakes in the park,

and the evidence
of earthquake waves

reveals a massive magma chamber

miles under
Yellowstone's surface.

But the Yellowstone
investigation

is far from finished
because there's evidence

of another, even more monstrous
sized structure

under the park.

By the beginning
of the 21st century,

scientists investigating
how Yellowstone was made

had images of what lay
under the park.

But there was a problem.

Technology only allowed a view
of a few miles

below the surface.

Then, as more and more data

was fed into more and more
powerful computers,

there was a breakthrough.

In April 2006,

geologists published
new diagrams

of hot structures,
far deeper under the park,

and computers painted
more detailed pictures.

The results were startling.

Investigators saw for the first
time the sleeping monster

that lies below
Yellowstone Park.

Snaking down hundreds of miles
into the Earth,

far deeper than the relatively
shallow magma chamber

is a colossal volcanic pipe.

Nobody's certain how deep
it goes,

but they can picture it
down to 400 miles or more,

twice the distance between
Washington and New York.

Smith makes an educated guess

about what the underground plume
is like.

- Our best estimates now
as we start doing the physics

and the dynamics
of these things,

it's like a conduit
of melted rock,

like a chimney.

Narrator. That chimney,
called a hotspot,

pumped up enough heat
to melt the rocks of the crust

and fill the overlying magma
chamber,

which then erupted to blast out
Yellowstone's vast crater.

Understanding
how the crater formed

was an important moment
for the investigation,

because there was evidence
that similar eruptions

had happened before,
many times before.

Throughout the 1960s,

various teams of geologists
studied the Snake River Plain

to the southwest
of Yellowstone Park

and found traces
of ancient volcanic craters.

The crater rims
had long been eroded,

but their outlines were
confirmed by aerial pictures

over the following decade.

They ran in a straight line
along the plain,

heading for the heart
of Yellowstone Park.

On average, each crater was
a couple of million years older

than its neighbor.

Investigators realized
that these are the remnants

of earlier supervolcano
explosions,

an unbroken chain stretching far
back into geological history.

It seemed clear that,
time after time,

the hotspot had blasted out
a supereruption

and then moved on.

The hotspot appeared to have
traveled hundreds of miles.

But that posed
yet another riddle.

How could a hotspot anchored
to the core of the planet

be moving?

An important clue
had been found in 1985

by American volcanologist
William Scott.

He realized that plotting
the location

of 30,000 earthquakes
around Yellowstone

produced an amazing pattern.

The quakes traced out
a giant V shape

on the surface of the Earth.

The V shape wrapped around
the hotspot's location.

It seemed at first to confirm

that the hotspot
was still moving,

rippling up the land around it
with fault lines

and tens of thousands
of earthquakes.

But the real answer lay with
the theory of plate tectonics.

It showed that
it's the American continent,

not the hotspot,
that's moving.

And the chain of craters
on Snake River Plain

is there because for millions
of years,

the moving American continent
has continually pushed new land

over the stationary hotspot.

- But as the North American
Plate moved

across this source of heat,

it pops through the lid
and creates the hotspot track.

That's the Snake River Plain.

Yellowstone is just
the active component today.

Narrator. The repeated hotspot
explosions on land

have made Yellowstone unique.

Other hotspots have been
identified around the world,

like the one that has created
the island chain of Hawaii,

but Yellowstone
is the only place

where a hotspot has erupted
in the middle of a continent.

Each of the earlier explosions

blew the original mountains
to pieces.

Then the land smoothed over
with later flows

of more runny lava
that was released

from deep
under the Earth's crust.

Multiple strands of evidence

combine to reveal Yellowstone's
slumbering monster,

the gigantic hotspot plume
lying under the park.

Earthquake maps
show the hotspot's location.

Seismic waves reveal the depth
of the plume.

And earlier craters
prove regular supereruptions

over millions of years,

All of which leads to the most
frightening question of all.

When will Yellowstone
erupt again?

[rumbling and explosions]

Measuring the amount
and geographical spread

of ashfall from Yellowstone's
supereruptions

produced some
terrifying figures.

[explosions]

640,000 years ago,

the eruption poured out around
240 cubic miles of material

enough to bury the whole
of New York State

tens of feet deep in ash.

If it happens again,
thousands will die

and vast areas
of the United States

will be buried in volcanic
debris.

But when will Yellowstone
erupt again?

One clue to when that next
eruption will happen

comes from investigating
the eruptions of the past.

The hotspot punches out
a supereruption, on average,

every 600,000 years.

And the last one was
640,000 years ago.

But geologists expect that
there will be warning signs

before Yellowstone
explodes again.

Volcanic eruptions
are usually preceded

by an increasing number
of earthquakes.

The quakes are a sign that
underground volcanic chambers

are filling with molten rock
and expanding

to stretch and deform
the land up above.

Yellowstone Park
usually experiences

an average of 12 tiny earthquake
tremors every day.

Most are too weak to be felt
by tourists

and register only on the
most sensitive seismometers.

But in early 2009,

more than four times
as many quakes

started striking every day.

Over one ten-day period,
there were more than 500 quakes,

some of them
up to magnitude 3.9,

powerful enough to frighten
the visitors

and put the scientists on alert.

There's a second indicator
of increasing volcanic activity.

If more molten rock does inflate
the underground chamber,

the ground above will rise.

And that, too, seems to be
happening right now.

Unusual evidence to prove it
comes from an unlikely source:

the waters of Yellowstone Lake.

Around 100 years ago,

small steamships
carried tourists

on sightseeing trips
across the lake,

but one of the ships caught fire
and sank forever

below the surface of the lake.

But now, Yellowstone's
astonishing geological forces

have resurrected the ship's
remains from their watery grave.

- Here we have a boat
which burnt down to water level,

and so this tells us
something about

the deformation of Yellowstone,

and basically, what's happened
is that the floor of the lake

has risen, bringing the boat
out of water.

Narrator:
The reappearance of the wreck

shows that land under and around
the lake is rising

because of the expansion
of the magma chamber.

Even more alarmingly,

the rate at which it's rising
seems to be increasing.

In geological terms,
a huge area of Yellowstone Park

is positively soaring up
into the air

faster than it's ever done
before.

The biggest uplift of all
has been recorded

just a few miles from the shore
of the lake.

There's a GPS system here,

a much more sophisticated
version of the one in your car.

It measures not only
its surface position

but also its exact altitude
to within fractions of an inch.

- There's a small radio antenna
about the size of your thumb

that sits on top
of this steel rod,

and it is anchored in two-
about three or four feet,

so if the ground moves
up and down,

the antenna moves up and down.

Narrator: The GPS and the land
on which it's anchored

are moving upwards.

- We're above the magma chamber,
and, beginning in late 2006,

this whole area of ground
started to rise

at the order of two to three
inches per year.

And as of today,
this whole system right here

has risen about that much,
and it's still moving today,

and so we're measuring
and keeping close track

of the deformation,
the-of the uplift

that we're seeing
at this station.

Narrator:
But does the uplift mean

that Yellowstone's supervolcano
is threatening to erupt

once again?

- The question of what lies in
Yellowstone's geologic future

is fascinating, and I and all
of my colleagues

would love to know the answer
to that question.

Narrator. The scientists keep
a careful watch

on the volcano's activity.

- The idea of science
is to understand the process,

and so we have a responsibility

to see how this system
is deforming

and how it's working,

hence we have to be aware
there is still a possibility

of-of volcanic eruptions
or earthquakes.

After all, that's what made
this system,

and there is no reason to think
that volcanism has stopped.

Narrator:
The Yellowstone investigation

has shown that the park's
sleeping supervolcano

is still alive and dangerous.

Old Faithful's underground
plumbing reveals volcanic heat.

Obsidian glass
tells of a massive eruption.

Seismographs record
thousands of earthquakes,

while the earthquake waves

reveal terrifying underground
chambers.

And the reappearance
of a sunken boat

shows that the land is rising.

And yet, the ultimate
Yellowstone geological question

remains to be answered.

When will the supervolcano erupt
once again?

- We know there's enough
magma left.

We know there's enough heat.

We know that there will be
future eruptions in Yellowstone.

But we don't know
if there will ever be

another catastrophic eruption.

Narrator. So the investigation

is left with a deadly serious
warning.

On the timescale that geologists
work to,

a coming supereruption
in Yellowstone

may well be right
around the corner.

That corner could be 10,000
or 100,000 years

in the future.

Or it could be tomorrow...

a new and devastating chapter

in the ever-changing story
of how the Earth was made.