All language subtitles for Deadliest Volcanoes PBS NOVA 2011 720p HDTV x264 AAC EN Sub

NARRATOR:
Volcanoes.

One of nature's
most powerful forces,

and one of its
greatest mysteries.

There are more than 1,500 active
volcanoes around the globe.

Half a billion people
live in their shadows

and under constant threat.

From the U.S....

Yellowstone is one
of the world's

largest active volcanoes.

NARRATOR:
...to Europe...

...to Asia...

The potential for a deadly
eruption is very real.

But what's actually happening
deep below the surface?

What causes them to erupt?

Can we predict
when they will explode

or how big an eruption will be?

Each volcano is unique.

There is no single approach

that can unlock
all of their mysteries.

These are the challenges
facing scientists.

But now, new technologies

are opening up the earth
like never before.

BOB SMITH:
So we can reconstruct
a three-dimensional picture

like an MRI scan
or a CAT scan.

NARRATOR:
Scientists use invisible gases
and volcanic springs.

They measure minute movements
of the earth,

and they're using
cosmic rays from space.

All in an effort
to reveal the secrets

of the earth's
"Deadliest Volcanoes."

Up next on NOVA.

Major funding for NOVA
is provided by the following:

Shouldn't what makes
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Supporting NOVA and promoting
public understanding of science.

And the Corporation
for Public Broadcasting,

and by PBS viewers like you.

NARRATOR:
The tiny island nation
of Vanuatu,

located in the Pacific Ocean.

This is Ambryn, one of the
world's most active volcanoes.

Explorer Geoff Mackley

climbs into
the half-mile-wide crater

above a seething lake
of molten rock.

Well, we're hanging
on the side of a cliff

that's about a mile high

and just down below us is
a furiously boiling lava lake,

and it's incredible.

Words cannot describe
how amazing this is.

The noise is unbelievable.

The heat...

There's just waves of heat

that you can feel
even from here.

Amazing.

NARRATOR:
Heat rising from the depths
of the earth

reaches almost
2,000 degrees Fahrenheit,

hot enough to turn solid rock
into liquid magma.

The energy required to boil rock

and throw it through the air
like water...

Mother Nature,
it's the ultimate show.

NARRATOR:
But what exactly triggers
these eruptions?

The answer lies several miles
below the surface,

in the magma chamber,

a vast reservoir
of partially molten rock.

Magma contains gases
at very high pressures.

As it rises up into the chamber,
the pressure builds.

When the pressure
gets too great,

magma pushes through the rock

and explodes
through the surface,

causing an eruption
capable of throwing magma

thousands of feet into the air.

In the past two centuries, there
have been over 200,000 deaths

from violent eruptions
around the globe

and many thousands
of injuries...

...including the 2010 eruption
of Mt. Merapi in Indonesia,

which killed more than
200 people

and forced 100,000 more to flee.

With so much at stake,

can scientists predict
when these eruptions will occur

and how big they will be?

It's not only lives
that are in danger.

National economies
face crippling losses.

Iceland.

April 2010.

A volcano called
Eyjafjallajökull

throws a giant ash cloud
30,000 feet up

and over 2,000 miles away,

covering large parts
of Europe.

Scientists here
see this one coming,

but its size and impact takes
them completely by surprise.

A few months
before the eruption,

scientist Sigrun Hreinsdottir
installs a new generation

of sensors around
Eyjafjallajökull.

It's not the nicest
road in Iceland.

NARRATOR:
She tracks the sensor's position
using satellite GPS.

They're so sensitive they can
measure a change in position

to within an eighth of an inch.

She wants to see how magma
moves underground.

If she can detect it
moving towards the surface,

it could indicate
an eruption is on the way.

But the magma is thousands
of feet down.

She can't see it directly,

so she measures the way
a point on the ground travels.

If magma starts to move,

it causes the ground
above it to move, too.

The idea is that if magma
moves into a volcano,

it will push
the ground outwards,

which the GPS sensors
will be able to pick up.

HREINSDOTTIR:
We installed this station,
and first we didn't see much,

but it started showing
odd behavior.

It started moving up and down
and north and south,

like centimeters a day,

which is very unusual.

And this behavior...

I thought,
"The station must be unstable."

NARRATOR:
By the beginning of March 2010,

all the GPS stations
move away

from the center of the volcano.

Dr. Hreinsdottir realizes

that the movement must be caused
by a large amount of magma

moving up
through the earth's crust,

pushing the ground sideways.

On March 4,

she becomes concerned
an eruption is on the way.

HREINSDOTTIR:
I got nervous.

I have to say, we got nervous.

We had a meeting
with the authorities of Iceland,

and they raised the alert level.

NARRATOR:
Then, on March 20, 2010,
the volcano erupts.

It starts out as a beautiful
but harmless event.

But over the next three weeks,
that changes.

It erupts
more explosive magma,

which mixes with ice
on top of the volcano,

creating huge clouds of ash.

Video captures lightning
discharging

from inside the cloud,

the result of ash particles
creating electric sparks.

The cloud rises 30,000 feet
into the sky.

Ash spews into the air at a rate
of 200 tons per second,

carried by the wind right across
the heart of Europe

at the same altitude
used by commercial airliners.

Volcanic ash can destroy
aircraft engines.

For more than a week,

air traffic across Europe
is brought to a near standstill.

The United States is cut off
from most of Europe.

Thousands of transatlantic
travelers are left stranded.

This isolated spot
in the North Atlantic,

hundreds of miles
from Europe or the U.S.,

causes the worst airline
disruption since 9/11.

The total cost
is over $2 billion.

GPS technology allowed
Dr. Hreinsdottir

to observe the volcano
waking up,

but it couldn't tell her how big
the eruption was going to be.

HREINSDOTTIR:
I really got a shock

when I realized what this
volcano had done.

I thought it would
be a little... pop!

and then we would
enjoy the data,

but there were surprises
at each corner.

NARRATOR:
This is one of the challenges
facing scientists.

Every volcano is unique,

and different techniques are
needed to unlock their secrets.

And there are some places

where understanding
a volcano's behavior

is more urgent than ever.

Yellowstone National Park,
Wyoming.

This magical place
is a major tourist attraction.

Home to strange colored pools

and otherworldly
rock formations.

And geysers like Old Faithful,

which regularly spits
200-degree water

over 100 feet into the air.

But the beauty masks
a powerful force

that could threaten life
across the planet.

Yellowstone is a supervolcano.

HENRY HEASLER:
Yellowstone is one
of the world's

largest active volcanoes.

Most people, when they visit
Yellowstone, don't realize that

because there's not
the steep peak

associated with most volcanoes.

But behind me here,
you have some of the evidence

for the active volcanism
of Yellowstone.

NARRATOR:
One of the greatest mysteries

surrounding the Yellowstone
supervolcano is its location.

The earth's surface is made up
of giant plates of rock

called tectonic plates.

Most of the world's volcanoes

lie on the edges
or between these plates,

where it's easier for magma
to form and reach the surface.

The most active edges

are the ones surrounding
the Pacific Ocean.

This is the Ring of Fire.

It includes some of the most
populated countries on earth,

including Indonesia,
Japan and the U.S.A.

More than half
of the world's active volcanoes

are on the Ring of Fire.

But Yellowstone is different.

It isn't on the edge of a plate.

It's in the middle of one:
the North American plate.

How can there be a volcano here,
so far from a plate boundary?

We know from looking
at the rocks of Yellowstone

that the volcano has been active
for a long time.

Two million years ago,

Yellowstone produces
one of the largest eruptions

ever seen on the face
of the earth.

It blasts away the peaks

we normally associate
with volcanoes

and leaves this strange,
flattened landscape.

Yellowstone hasn't had
a major eruption

on this cataclysmic scale
for over 640,000 years,

but the hot springs
and geysers are signs

that there's a lot
of heat under the surface.

This volcano is very much alive,
and it is intensely monitored.

Here, seismometers are vital.

Bob Smith is the scientist
in charge.

I'm opening the lid--

this is going to fall down--

of a seismic vault,
and inside is a seismometer

which sends a signal
on to a telemetry network,

and that antenna is pointed
to a receiver

about 20 miles down on the lake,

so anything that we're doing
right now

is recording right now on my
computer in Salt Lake City,

as are the entire seismic
and GPS network.

NARRATOR:
The easiest way underground
magma reaches the surface

is through a channel, created
by fracturing the rock above it.

As the rock cracks, it creates
vibrations, small earthquakes

that occur days or weeks
before an eruption.

It's these vibrations
that seismometers detect.

Smith is confident
that the seismometers and GPS

will give some kind of warning
of the next eruption,

but when that might happen,
no one knows.

At the moment, there's no
major increase in activity.

Yellowstone is sleeping.

But scientists also use
these earthquakes and GPS

to reveal what's
deep inside the volcano

and solve the mystery
of why Yellowstone is here

in the middle of North America.

Well, the seismographs
do two things:

they record the earthquakes
that are active

and then they're used
to record or scan the subsurface

that we can't otherwise see.

NARRATOR:
Seismic waves travel faster
through cold solid rock

and slower through hot
and molten rock.

As seismic waves
from distant earthquakes

travel through underground
magma reservoirs,

they slow down.

By measuring these waves
at multiple points,

it's possible to build up
a three-dimensional picture

of where the magma underneath
Yellowstone is located.

We can reconstruct
a three-dimensional picture,

like an MRI scan or a CAT scan,

by recording thousands
of earthquakes

into our array of seismographs.

NARRATOR:
The seismic network
at Yellowstone is extensive,

with over 150 seismometers
spread out

over 100,000 square miles.

Bob Smith is able to look deeper
than ever before,

hundreds of miles down.

And what he's discovered
is striking:

a huge structure of partially
molten rock beneath Yellowstone.

This is a mantle plume,
a rising column of hot rock

stretching at least 400 miles
into the earth.

This is the same concept
as a lava lamp.

You heat up the wax
in the base over a bulb,

and then it slowly rises up
because it's less dense.

And that's the basic concept
of a mantle plume.

NARRATOR:
For scientists, seeing this
for the first time

is a breakthrough.

It solves the mystery of why
the Yellowstone volcano is here.

This plume is powerful enough
to force its way

through the middle
of the North American plate

and create a volcano where there
wouldn't normally be one.

HEASLER:
Are there eruptions
in Yellowstone's future?

Definitely.

Now, will there be another
catastrophic eruption?

That we don't know.

NARRATOR:
A major eruption
would be cataclysmic.

What it would create would be
massive volumes of material.

It probably goes on
for days and weeks and months.

And it's destroying all the
surface rocks, if you wish,

in its path.

NARRATOR:
Most of the western
United States

would be buried
in thick ash deposits

capable of collapsing buildings
and suffocating people.

Hurricane-force flows
of superheated gas and ash

would blast out, covering
a 2,000-square-mile area.

A towering column
of choking ash cloud

would rise 25 miles up
into the atmosphere,

blocking out sunlight
across the planet.

Temperatures would plummet,
crops fail,

and millions of people
would die of starvation.

The awesome power
of such an eruption,

equivalent to the force

of a thousand Hiroshima bombs
every second,

is impossible to defuse.

All we can hope for
is a warning,

a chance to prepare
as best we can.

SMITH:
There's no way to know
when an eruption

is occurring in the future.

It could happen tomorrow,
hundreds, thousands of years.

We simply don't know
where we are in these cycles.

That's why the instruments
are so critical.

NARRATOR:
As scientists keep a watchful
eye on Yellowstone,

on the other side
of the Atlantic,

there's a volcano that could
pose an even greater threat.

Many experts believe

the place where people are most
at risk from volcanoes is here:

Naples, in Italy.

This is one of the most densely
populated cities in Europe.

Three million people live here.

And it lies at the foot of the
most famous volcano on earth,

Vesuvius.

(thunder)

At 4,200 feet high,
Vesuvius towers over the city.

It has erupted over 25 times
in the last 2,000 years,

the most deadly in 79 A.D.,

when it buried the town
of Pompeii, killing thousands.

They had no warning,
no time to run.

If it were to erupt today,

the effects would be
devastating.

Burning clouds of ash and gas
called a pyroclastic flow

would wipe out large parts
of the city.

Over half a million people
are at direct risk.

Scientists keep a very close eye
on Vesuvius.

They watch
for any seismic signals

that magma is escaping
from the magma chamber.

They're confident
that will give them

at least a few days' warning
before Vesuvius erupts.

And now, scientists are using
a brand-new technique

to help them predict
how large an eruption could be.

Inside a volcano is a tube,
the throat of the volcano.

It's the structure through
which magma flows in an eruption

to the surface.

The larger the tube,
the more magma flows through it

and the bigger the eruption
is likely to be.

Until now, there's been no way
to see inside a volcano.

Not even X-rays
can penetrate solid rock.

But surprisingly, a solution
is found in events happening

thousands of light-years away,
in deep space.

Dr. Hiroyuki Tanaka

is harnessing the power
of the universe.

Far out in the cosmos,
violent explosions of stars

send out particles
flying at enormous speed.

They're called cosmic rays.

These fly across space,
and some of them hit the earth.

When these rays hit
the upper atmosphere,

they create a shower
of invisible particles.

Dr. Tanaka is interested
in the ones called muons.

Muons are from everywhere,

from this direction,
from that direction,

or from vertical or horizontal.

The muons' penetration
is very strong,

so that building, that building,
or that building

are almost transparent
for a muon to penetrate.

NARRATOR:
Here is something powerful
enough to pass right through

thousands of feet of solid rock.

They can even pass through
whole mountains.

Dr. Tanaka has a brilliant idea:
perhaps they can be used

to create an image
of the inside of a volcano.

He builds a device that detects
the naturally occurring muons.

At the heart of the device
is a special kind of plastic.

When the cosmic muon
arrives at this device,

this device emits
a very faint blue light.

NARRATOR:
These blue lights are picked up
by a light sensor,

which converts them
into an electric current

that a computer can analyze.

Tanaka places these muon
detectors around a volcano.

As the muons pass through
the volcano, some are absorbed.

But where the rock
is less dense,

more muons pass through.

These muons are picked up
by the detector

and form an image
of what's inside the volcano.

By placing detectors
at different points,

it's possible to build
a 3-D image.

His first target is Mt. Asama.

This is one of Japan's
most active volcanoes,

and it lies just 90 miles
from Tokyo.

He leaves the detectors
in place for months

to collect enough muons.

This has never
been tried before.

It may not work.

But if it does, it could
revolutionize prediction

by revealing the inner structure
of a volcano.

Tanaka sees the first image.

TANAKA:
I was very, very skeptical,

so in order to validate this,
I tried many things,

and finally, I found
that it was true.

Everybody was excited,

so that was a very exciting
moment for me, too.

NARRATOR:
The image is crude,

but it reveals the structure
of the volcano.

The red is the dense rock
of the volcano cone.

In the middle is a hole,
the throat of the volcano,

visible for the first time.

It proves the technique works

and reveals the size
of the throat,

critical for predicting
the size of an eruption.

Tanaka uses these images
to correctly predict

information about Mt. Asama's
recent eruption.

By measuring the size of the
throat and changes in density,

he's able to track
the movement of the magma.

In this case, he calculates

how much magma
will reach the surface,

as well as where it's located.

Tanaka's revolutionary
new technique

is now being tested
on Mt. Vesuvius.

It's the first volcano
outside Japan

to be analyzed with muons.

It could give
the people of Naples

warning of what Vesuvius
has in store.

But here in Naples,

the scientists fight
a battle on two fronts.

Vesuvius is just the tip
of the iceberg.

There's a hidden danger
lurking beneath the ground.

And the clue is in these ruins.

This is the marketplace
of Serapeo.

It was built
almost 2,000 years ago.

But something strange
has happened since then.

Ten feet up the columns
is a dark band

where marine mollusks
burrowed into the rock.

These creatures
live only underwater,

which means this building
was once submerged.

Just standing here,

we have absolutely remarkable
evidence of the fact

that the land must have subsided
into the sea

and come back up out again
at least once

in the last 2,000 years or so.

NARRATOR:
What could be causing the ground
to rise and fall?

It's not just the temple.

The whole region is lifting,
including entire towns.

And the movement
is going on today.

Since the 1970s, the ground has
lifted up by almost ten feet.

In the port, these boat ramps
were once underwater.

They're now high and dry.

And just outside the town

is a place that reveals
the cause of this movement.

Here, superheated steam
and sulphurous gases

burst out of the ground.

The evidence is clear:

This entire area
is one giant volcano

containing farms, villages,
whole towns within it.

CHRISTOPHER KILBURN:
In our view here,

there are probably
at least 100,000 people

in the houses that we can see,

most of whom perhaps
are not completely aware

that they're actually living

in the heart
of an active volcano.

Psychologically,
it's quite difficult

to get that message across,

because there's no physical
evidence of danger.

NARRATOR:
With no obvious cone
like the one at Vesuvius,

the scale of the volcano
is only clear from above.

The entire picturesque bay

is in fact a giant volcanic
crater eight miles across.

It's called Campi Flagrei.

Using the movement of the
ground, scientists calculate

that there's a huge magma
chamber under the bay.

39,000 years ago,
this volcano erupts.

Billowing columns
of hot gas and magma

spew from the magma chamber.

As the chamber empties,
the pressure lowers

and the ground above it
sinks down.

It forms a large
bowl-shaped depression

called a collapsed caldera,

similar to the shape
of Yellowstone.

Eventually, the sea floods in,

forming the bay we see today.

It is the largest eruption
Europe has seen

in the last 100,000 years.

If Campi Flagrei ever erupts

on the same scale
as the prehistoric eruption,

the effect
would be devastating.

Pyroclastic flows
would flood out,

destroying everything
in the vicinity.

If they weren't evacuated,
millions would die instantly.

Ash would spread out
across the whole of Europe,

triggering climate change
that could last for decades.

Now, researchers are about
to embark on a bold project

to find out what's actually
happening underground.

Muon scanning won't work

for a flat volcano
like Campi Flagrei,

so their plan is to drill
right into it.

The scientist in charge
is Guiseppe De Natale.

DE NATALE:
This is an old steel factory,
now abandoned,

and the drilling place
will be just here, around.

NARRATOR:
They intend to drill a hole
over two miles deep.

They're hoping to get
a sample of rock

from right inside Campi Flagrei.

The drill will curve
under the bay

toward the heart of the volcano.

And they hope that rock samples

help answer
a crucial question:

is it magma causing
the ground to lift up,

or just gas and heated water?

One of the objectives

of the deep drilling project
that's about to start

is that we might be able
to resolve this debate

about whether the fluids
that have been accumulating

at three kilometers' depth

are in fact magma, or heated
water or some other fluid.

NARRATOR:
Settling this debate
is critical for predicting

the risk of an eruption.

If Chris Kilburn is right

and it's magma building up
two miles underground

causing the uplift,

there could be
a devastating eruption.

Others think it's more likely
that gas and heated water

inflate the ground
like a balloon.

KILBURN:
Now, if that's the case,
the potential for an eruption

is actually quite low,

because all that's accumulating
is water and hot gases.

The alternative, that it's
actually magma accumulating,

suggests that the possibility
of an eruption is higher.

NARRATOR:
Analyzing rock samples
from the volcano itself

tells the people
of Campi Flagrei

whether the volcano
they're living on

is heading for an eruption.

DE NATALE:
This experiment will allow us

not only to understand much
better this kind of volcano,

but also to understand how
to forecast the next eruption.

NARRATOR:
This project is only
just beginning,

and scientists are years away

from fully understanding
Campi Flagrei.

But nearby, scientists find what
might be the holy grail

of accurate prediction.

150 miles from Campi Flagrei,
in the Mediterranean Sea,

is Stromboli.

This island is one big volcano
rising from the sea.

It's erupting,
as it's done every day

for at least 2,000 years.

But without warning,
the volcano can change.

It can suddenly become
more explosive,

sending blocks of lava five feet
across flying through the air.

For the thousands of tourists
who visit the volcano each year,

these explosions can be deadly.

Volcanologist Alessandro Aiuppa

is responsible for the safety
of the visitors.

He knows the only way
to protect them

is to predict
the violent explosions.

What we have been looking for
is precursory signals

in the hours or in the days
prior to the explosion itself.

NARRATOR:
Aiuppa focuses
on the volcanic gas

that causes these explosions.

Deep underground, the magma
is at such high pressure

that gases actually dissolve
in the molten rock.

But when the magma rises,

the pressure goes down
and the gas is released.

It's like a bottle of soda.

If you have a capped
bottle of soda,

you don't see
any gas bubbles here

because all the gases will be
dissolved into the soda,

and at the same time,

if you think of the magma
deep in the crust,

all the gases will be dissolved
into the magma.

But as soon as you remove
the cap,

all the gases will be going
out of your bottle,

and this is more or less
the same as what is happening

as the magma is being
decompressed,

as it is ascending through
the crust up to the surface.

NARRATOR:
As the magma starts to rise
from deep underground,

it releases gases.

Aiuppa wants to find out
whether the amount of gas

released by the volcano
might give a warning

of a larger violent explosion.

One of the gases released
is the deadly sulfur dioxide.

But sulfur dioxide
is invisible,

so how can you measure it?

Aiuppa's answer is
a new type of camera.

So what they do is that they
take images of the gas plume,

but they are working
in the UV region.

NARRATOR:
In normal light,
there's just a wisp of steam.

But with the UV camera,
the plume of sulfur dioxide

is clearly visible
in red and yellow.

Aiuppa also measures
another gas: carbon dioxide,

CO2, one of the most common
volcanic gases.

CO2 is impossible
to measure remotely

because the atmosphere contains
naturally occurring CO2,

which interferes
with the measurement.

The only way to detect it is
with instruments at the summit.

Scientists have to climb right
up to the rim of the crater,

even when the volcano is in
a state of high alert.

This is the device
that detects CO2

and continually transmits
the reading

down to the control center.

Aiuppa measures the two gases
for over five years,

looking for a change
that happens

before an explosive eruption.

He notices a pattern.

What we have seen is that 12
of the last 14 major explosions

have all been preceded
by CO2 increases.

NARRATOR:
Aiuppa's theory is that

the normal small explosions

are caused
by sulfur dioxide-rich bubbles

that form at low pressure.

But the big, deadly explosions

are caused by magma,
rich in CO2

that bubbles out deeper down
at much higher pressure.

When CO2 starts appearing,

a dangerous event
is on the way.

The theory has recently
been put to the test.

In May 2010, the level
of CO2 increases.

Aiuppa recommends that the
volcano be closed to tourists.

AIUPPA:
The volcano is an attraction,

so it's a big responsibility.

But on the other hand,

you know that if the volcano
is creating a major explosion

and tourists are up there,

that's a dramatic event,
which we really want to avoid.

NARRATOR:
Just a few days later,
the volcano explodes.

If it hadn't been closed,

visitors to the island
might have been killed.

For Aiuppa and his team,
it's a triumph.

Not only have they predicted
when, but just as importantly,

they knew how large this
eruption was going to be.

Could this technology
be the breakthrough

scientists have been
waiting for?

When you close the volcano
and then you have an explosion,

you feel so excited

because you understand
what you are doing

is not theoretical science,

but it has such important
practical implications.

You maybe are saving
human lives.

NARRATOR:
But different volcanoes
give off different signals.

Scientists don't yet know
if all volcanoes

emit an increase in CO2
before a large eruption.

This is why they use
many different techniques

to predict eruptions.

And nowhere is that
more important

than in the shadow
of one volcano

here in the United States.

Washington State.

50 miles south of the city
of Seattle is Mt. Rainier.

It dominates
the landscape around it,

a beautiful and seemingly
peaceful mountain.

But it's a potential killer.

It's part of the same range
as Mt. St. Helens,

which in 1980 exploded with huge
force, killing 57 people

and causing over a billion
dollars' worth of damage.

A similar sized eruption
of Mt. Rainier

would be far more deadly

because of the much larger
population around the mountain.

But the biggest risk comes
not from an eruption itself,

but from what it unleashes.

This is a lahar,

one of the most dangerous
hazards that volcanoes produce.

It's a churning avalanche

of volcanic mud, rocks
and water.

In 1985, the Nevado del Ruiz
volcano in Colombia erupts.

Within hours,
it unleashes a lahar

that swallows a town
of 28,000 people.

Most of them are buried
or swept away.

It's one of the deadliest
eruptions in history.

Mt. Rainier has more snow
and ice on its summit

than any other mountain
in the lower 48.

If this ice comes into contact
with hot lava,

it rapidly turns
into a torrent of mud.

One of the towns
most in danger is Orting.

6,000 people live here
at the base of Mt. Rainier,

and the population is expanding.

It's a risk
which Jody Woodcock,

a public safety official for the
county, is all too aware of.

What we're looking at
in the city of Orting

is potentially
20 to 30 feet of mud.

That flowing concrete
could actually travel

NARRATOR:
And it's not just Orting
that's at risk.

Geologists find evidence for
many lahars from Mt. Rainier,

going back thousands of years.

The volcano produced some of
the largest mudflows ever seen

on the face of the earth.

Some reached as far as the
present-day city of Tacoma

and created floods that entered
the outskirts of Seattle,

60 miles away.

It's been quiet since 1882.

The pressure is on scientists

to forecast the next eruption
of Mt. Rainier.

Like other volcanoes,
it's monitored with GPS

and seismometers
to warn of ground movement

caused by magma flowing
underground.

But Steve Ingebritsen
is searching for another way

to predict eruptions:

using water.

About 18 degrees here.

Bob, are we going to walk
around a little bit...

NARRATOR:
Normally, a mountain stream is
less than 40 degrees Fahrenheit,

but the water here
is 70 degrees.

INGEBRITSEN:
What's interesting
about this stream--

which you wouldn't give a second
glance to if you were hiking,

you might actually
take a drink out of it--

is there is chemical evidence
and thermal evidence

of some deep volcanic fluids
affecting it.

NARRATOR:
These deep volcanic fluids
could be magma or volcanic gas.

Scientists don't know
exactly how it happens,

but somehow the heart of the
volcano, over six miles down,

heats up the water
near the surface.

How did this water
come to be a bit warm

and have these funny
chemicals in it?

That's something we would really
like to know more about.

I think that's one of the great
unknowns in these systems.

NARRATOR:
Scientists hope the water
gives them a clue

that the volcano is waking up.

At Mt. St. Helens,

before the eruption of 1980,
there are reports of the streams

getting warmer
and even changing color.

It seems these streams are
giving us a warning,

but one that's been missed
by scientists in the past.

INGEBRITSEN:
Oh, that looks like
a nice place, too.

NARRATOR:
To make sure
it's not missed again,

Steve Ingebritsen is installing
a new kind of sensor

into the streams here
on Mt. Rainier.

INGEBRITSEN:
This probe will record
water pressure,

electrical conductivity of the
water and temperature of water

for five to seven years
at hourly intervals

with internal storage
and internal power.

We're calling this site
"Paradise," right, Bob?

NARRATOR:
Ingebritsen and his team
install these sensors,

not just on Mt. Rainier,

but on volcanoes all along
the Cascade Range.

Their work is so new,

they don't know
what kind of warning

the sensors will give them.

But it could be
a valuable new weapon

in the battle to predict
eruptions.

We definitely hope that these
sorts of water features

are going to tell us something

about what's going on
deep in the volcano.

NARRATOR:
But even if science
can predict the next eruption,

the people of Orting
are still at risk.

There's enough unstable rock
on the volcano

to form a lahar,
even without an eruption.

A rock slippage at the summit
could be enough to trigger one.

And if that happens,
there could be little warning.

The only hope is to escape
to higher ground

in the minutes before
the lahar hits.

An alarm system is installed
to give them a chance.

WOODCOCK:
The key to our warning system

are the sensors, or what
we call acoustic flow monitors.

There's five on each
upper river valley.

What these do
is detect ground vibration.

NARRATOR:
Lahars make a very distinct
kind of vibration

that tells the system
a mudflow is on its way.

WOODCOCK:
Once the acoustic flow monitors
pick up activity,

the siren that you see behind me

and those throughout
the rest of the valley

will be
activated immediately.

NARRATOR:
This is the first automated
lahar warning system

installed anywhere in the world.

But even with the alarm,
it's a huge challenge

to get everyone out in time.

WOODCOCK:
The city of Orting

has approximately 40 minutes
to evacuate.

So it really doesn't
allow much time,

and we have to be ready
to act swiftly.

NARRATOR:
In the last few years,
scientists have found new ways

of uncovering the secrets
hidden inside volcanoes.

They've made great advances

in accurately predicting
volcanic eruptions.

(thunder)

In some cases, they can tell
not just when, but how big

an eruption will be.

But there are some volcanoes
that are so powerful,

they could devastate
the whole planet.

For now, all we can do

is hope that they stay quiet
for many years to come.

This NOVA program is available
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Captioned by
Media Access Group at WGBH
access.wgbh.org