Original subtitles

As continents shift and clash,

volcanoes erupt, 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.

How The Earth Was Made 01x08 Yellowstone Original Air Date on March 31, 2009

== sync, corrected by elderman ==

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 three

million tourists a year.

To understand where Yellowstone

came from, and why it is so

active today, we need to take a

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 Idaho

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 US. 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.

>> 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.

>> Rainwater saturating the

ground around the geyser slowly

fills its underground reservoir.

Hot rocks below ground 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.

>> 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.

OK, 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.

>> 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 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.

>> 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.

>> 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 we 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.

>> 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 burr 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.

>> 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.

>> 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.

>> 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.

>> Scientists began

investigating Yellowstone even

before it became the world's

first national park 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--I don't see a smoking

volcano, I don't see a big

steep volcanic, uh, uh,

crater," all the things that one

normally thinks of for an active

volcano.

>> So, without obvious signs of

a volcano, scientists hunted for

other clues.

They would find them in the

sweeping forests of Lodge Pole

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.

>> 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 or more

viscous. If we put a bunch of

gas in it, we can have a very

explosive eruption.

>> 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.

>> 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, modern soil has

formed and we can see growing up

there various sorts of

vegetation, trees and grasses

and things of that sort.

>> 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.

>> The geologists have recreated

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, um,

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.

>> 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.

>> I think you would be

disarticulated, burned and--and!

unrecognizable, and it would be

very difficult to find any of

you.

>> 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.

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 US, confirming the huge

size of the eruption.

At least 80 times the size of

the 1883 explosion that

destroyed the island of

Krakatoa.

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.

>> 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.

>> 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.

>> 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 the same physics

to reconstruct the structure

of the geology of the Earth

beneath us.

>> 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 ten 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.

>> 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 hotspohad 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.

>> 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?

Measuring the amount and

geographical spread of ashfall

from Yellowstone's

supereruptions produced some

terrifying figures.

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.

>> 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 to thr--about three or four

feet, so if the ground moves up

and down, the antenna moves up

and down.

>> 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, uh, 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.

>> 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.

>> 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, uh, there is no

reason to think that volcanism

has stopped.

>> 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.

>> 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.

== sync, corrected by elderman ==