All language subtitles for How the Earth was made 2009 HC 1080p BluRay EN sub_Subtitles01.UND

male narrator:
Planet Earth is unique,

an immense ball of rock
25,000 miles around.

lt is a refuge,

1/3 land, 2/3 water,

and with an atmosphere
rich in oxygen,

it is the only known home
in the universe

for living creatures.

But this blue-green oasis

has not always been
so welcoming.

The planet bears the scars
of a traumatic past,

a past
of extreme environments

and extreme catastrophes.

Over the course
of nearly 5 billion years,

it has been a changing world,

a world of fire,

a world of ice,

one of raging seas

and poisonous skies.

The life-forms
that now cling to its surface

are the lucky survivors

of a succession
of deadly mass extinctions.

Forjust over 200 years,

determined scientists
have explored the planet

and unearthed its secrets.

Their remarkable discoveries
have led them to tell

an incredible story,

the story
of "How The Earth Was Made."

For thousands of years,
humans had no knowledge

of the true age and origin
of the world.

Butjust over 200 years ago,
all this would change.

Scotland,
the Edinburgh coast:

it was here,
one day in 1 788,

that the discovery
of a small rocky outcrop

would completely rewrite
the history of the Earth.

Geologist Geoffrey Boulton

is on his way
to the desolate Siccar Point,

where this discovery was made

by a maverick Scottish farmer,
James Hutton.

Hutton was to become the father
of modern geology.

- Hutton was a man
who was enthusiastic

in the pursuit of truth,
a very inquiring mind.

When he took over
his father's farm,

he saw, underneath the soils,
rocks

and wondered what these were.

narrator: Hutton spent years
obsessed with understanding

how the rocks of the Earth
were made.

His intrepid field expeditions
took him all over Scotland,

and they led him to realize
that extremely slow processes

could create the rocks he saw
from layers of sediment.

- He rode miles and miles
on his horse

to go places where he thought
he could find

exciting geological experiences

even though he suffered terribly
from saddle sores.

narrator: Hutton concluded
that rocks could take

hundreds of thousands of years
to form.

But his claims were speculative,

and his radical ideas
flew in the face

of the accepted version
of Earth history,

provided by the church.

For generations,
the Christian church

had been the sole authority
on all creation,

based on the book of Genesis.

And using
the biblical genealogies,

church leaders
were now confidently claiming

they knew the exact age
of the Earth itself.

- Archbishop Ussher
in the 1 7th century

had calculated that the Earth
was 6,000 years old,

and indeed, he calculated
that it was made

on October the 14th
in the afternoon.

narrator: Hutton was convinced

that the Earth
had to be much older.

And when his explorations
led him to Siccar Point in 1 788,

he would finally find the proof
he was looking for

in the unusual formation
he discovered.

- These rocks
are notjust any old rocks.

They're very special rocks,
and the reason they're special

is because of the story Hutton
was able to tell from them.

narrator: Here,
two layered rock formations

stand at right angles
to each other.

- He knew these rocks

had once been laid down
horizontally on the seafloor.

They must then have been buried
under great depth

to recrystallize.

They must then have been tilted
on end by great Earth forces.

Then they were eroded away
and truncated.

Then these rocks
were deposited on top.

And he realized that that would
not take hundreds of years

nor thousands of years
but many millions of years.

narrator: Hutton's discovery
was a turning point.

From that day forward,
it was rock, not scripture,

that would become the trusted
guide to the distant past.

And over the next two centuries,

the study of rocks
around the globe

would lead
to the awesome revelation

that this blue-green planet

has been on
the most astounding journey...

Ajourney that began
in a world of fire.

lt is now believed
that the Earth

was formed from collisions
among the countless meteors

that made up
the early solar system.

Back then, the surface
was an ocean of molten rock

miles deep.

Temperatures exceeded
8,000 degrees Fahrenheit,

similar to the surface
of the sun.

And huge meteorites rained down
in a relentless bombardment.

The man who first proposed this
hellish origin for the planet

was the Victorian scientist
Lord Kelvin.

A British expert
in thermodynamics,

Kelvin believed that the Earth
was slowly cooling down.

The fires
of the planet's interior,

visible in volcanic eruptions,

suggested to him that the planet
had once been completely molten.

Kelvin used thermodynamics

to calculate a new age
for the Earth.

He reasoned
that the molten planet

would need
nearly 20 million years

to cool
to its present temperatures.

Kelvin was correct
about the Earth being molten

but not about its age.

His figure
was a colossal underestimate.

Like all
1 9th-century scientists,

Kelvin was unaware
of a key source of heat

inside the early Earth

that prevented the planet
from cooling as he predicted:

radioactivity.

ln the early Earth,
radioactive particles

of uranium, thorium,
and potassium

were in huge abundance.

The heat produced from the decay
of these particles

would keep the Earth
extremely hot

for an extremely long time.

But although these particles

confounded
Kelvin's calculations,

they would eventually
prove the keys

to unlocking the true age
of the Earth.

ln the 20th century,

rare particles
of surviving radioactive uranium

were collected together

to create the first
atomic weapons.

But scientists had earlier found
a different application,

using the radioactive particles
to accurately date the planet.

ln 1 91 1 , a gifted 21-year-old
geology student, Arthur Holmes,

used radiation
to revolutionize

our understanding
of Earth history.

After Holmes,

geologists would talk
in billions,

not millions,
of years.

Radiometric dating
was simple in principle.

lt was based on the discovery

that traces of the radioactive
element uranium,

found throughout
the rocks of the Earth,

decayed into another element,
lead.

Like sand trickling
through an hourglass

over hundreds
of millions of years

and at a steady rate,

a sample of radioactive uranium
will decay to lead.

By measuring the proportion
of uranium to lead

in crystals trapped
in ancient rocks,

Holmes could accurately
calculate their ages.

Collecting data from samples
from all over the world

would be a lifetime's work.

But as Holmes grew older,
so did the Earth.

lts calculated age
extended first to 1 billion,

then 3 billion,

then finally
to 4.5 billion years.

Today 4.5 billion years

is still the accepted age
for the Earth.

Time on this incredible scale

is known to those
in the business

as deep time.

- lt's difficult to imagine
how vast deep time is.

But think of it this way.

That's a grain of sand.

lf it represented a year,
then the length of my finger

would be equivalent
to the whole of my lifetime.

From the tip of my finger
to my elbow

would take us back
to the pilgrim fathers.

From here to the rocky island
you see on the horizon

would take us back
to the age of the dinosaurs.

And if we were to turn round
and go to the equator,

then it would be equivalent
to going back

to the beginning of the Earth
4 1/2 billion years ago.

narrator: The search for the age
of the Earth was over,

and the results had opened
a window on the past.

For the first time,

scientists could put rocks
in the correct order,

look deep into the Earth's past,
and tell its story.

They would discover evidence
of an epic journey

with many twists and turns.

But the most significant step
may well have been taken

within just a few hundred
million years of its birth,

when the planet
became a water world.

4.5 billion years ago,
the Earth was formed

from the collisions
of millions of meteors

in the young solar system.

Temperatures were so high

that the planet's surface
was a molten ocean.

But even at that time,
Earth was beginning to cool.

The radioactivity
that provided much of the heat

was slowly declining,
paving the way

for the planet's
first radical change,

its transformation
into a water world.

The Barberton Hills,
South Africa:

this remote region is home

to some of the oldest rocks
on Earth.

South African geologist
Gary Stevens

is on the lookout for some

of these incredibly rare
survivors

from the first billion years
of Earth history

whose unique shape
tells a story.

- This area
of South African geology,

here on the eastern side
of Mpumalanga, is critical

for our understanding
of early Earth processes.

narrator: Gradual erosion
along the trickling creek

can occasionally expose
these primordial rocks.

- Here we have
an interesting rock.

The rounded shape
of this rock over here

is very different
than the rounded shape

of the rest of the rocks
in this river.

This is one of these

3.5-billion-year-old
pillow lavas.

The rounded pillow shape
in the rock

is a result of the lava

that formed underwater
in an ocean

approximately
3 1/2 billion years ago.

narrator: Pillow lavas
are created today

off the coast of Hawaii,

where volcanic vents
erupt into the Pacific Ocean.

This unique pillow shape
is only formed

when lava solidifies
under deep water.

All rocks found from the period
3.5 billion years ago

have been pillow lavas.

By 1 billion years
into the planet's existence,

water had taken over.

But geologists believe
that it had already been around

a long, long time.

4.4 billion years ago,

the Earth was around
1 00 million years old.

Meteors still crashed
into the planet,

but gradual cooling of the core
had allowed most of the surface

to solidify into a crust
of dark volcanic rock.

And even then,
at this early stage,

water was forming
on the surface.

No rocks now survive
from this most early period,

but tiny crystals
of zircon do.

Uranium-carrying zircon
is one of the crystals

that helped date the Earth.

But these crystals
can also retain

the chemical fingerprints
of water molecules,

and these fingerprints

are all over
the most ancient zircons.

But the origin of the majority
of the planet's water

remains a mystery.

As the planet cooled,
the surface rocks

began spewing out
tons of carbon dioxide.

Some water vapor

would have been vented
during this process,

but some believe
it would not have been enough

to cover the surface.

- The rocks,
the material that accreted

to form the Earth itself,

would have been too dry,
too close to the really hot sun.

We have this problem
of trying to understand

where our water world
got all of its water.

narrator: lmpact expert
Dan Durda supports the theory

that the source
of most of the Earth's water

was extraterrestrial.

- The idea today
is that the Earth's oceans

arrived from above.

They were brought in

in the water-rich asteroids
and comets

which peppered the Earth
during the tail-off

in its accretionary process.

What l have here is a piece
of an actual meteorite.

This is the material

from which
the Earth itself formed.

This primitive
little meteorite

contains about 5% of water.

lt's that water,
in objects like this,

that was delivered to the Earth
to form the Earth's oceans.

narrator: Scientists
are divided on this,

but wherever the water
came from,

when it did arrive,

it changed the planet
dramatically.

As it evaporated
off the surface,

huge amounts of water vapor
rose to join the carbon dioxide

in the young atmosphere,
forming thick blanketing clouds.

This condensing water
would trigger

the greatest downpour
the Earth would ever see.

[thunder booming]

As thunderstorms
rocked the skies,

the rain began to fall
on the rocky surface below,

and it kept on falling.

[thunder booming]

lt would rain
for millions and millions

and millions of years.

The result would be
a water world.

4 billion years ago,

the Earth was now
1/2 billion years old.

Over 90% of its surface
had become a vast ocean.

Small volcanic islands
poked out from the waves.

The monstrous seas
were iron-rich,

making them
an olive green color.

Carbon dioxide
filled the skies so thickly

that they appeared red.

The dense atmosphere
produced enough pressure

to crush a human body flat.

And it was hot.

Temperatures exceeded
200 degrees Fahrenheit.

This toxic, hostile water world
would remain

for another 1/2 billion years.

But dramatic transformations
were on their way.

Renewed volcanic activity

would trigger the construction
of the continents

by creating
a totally new kind of rock.

Earth was about to become
a granite planet.

3.4 billion years ago,

the Earth was just over
a billion years old.

Huge green oceans dominated.

None of the crumbling
volcanic islands

dotting the surface

survived the punishing seas
for long.

But everything
was about to change.

An upsurge
in undersea volcanic activity

was about to create
a tougher type of rock

and give birth
to the continents.

ln remote areas of the globe,

the primeval cores
of these first continents

have been exposed.

South Africa:

geologist Gary Stevens
is climbing

on some of the oldest
continental rock on Earth.

These rocks are special.

- We're standing here
on an ancient granite.

This granite
forms the nucleus

of one of the world's
oldest continents.

And we can see it here

in the Barberton area
in South Africa.

narrator: These eroded
outcrops of rock

are the visible peaks

of what is known
as the Kaapvaal craton,

a titanic mass
of ancient granite

underlying southern Africa,

a remnant of the early Earth.

3.5 billion years ago,

granite was appearing
everywhere.

An upsurge of volcanism
had fractured

the crust of the Earth
underneath the vast oceans,

allowing water
to plunge into the cracks

alongside the molten lavas.

The mixture of superheated water
and basaltic lava

produced the new rock,
granite.

lt rose from the depths

to form the first
true continental crust.

- This is why granite
is special and important.

lt's light.

This rock, granitic rock,
has a much lower density

than this rock,
a basaltic rock.

The difference in density
between these two rocks

is greater
than the difference in density

between water and air.

This rock would be typical
for oceanic crustal material.

This is typical
of the continents.

Continents are light
and buoyant,

oceanic crust
denser and heavier.

lt literally floats
on the mantle.

narrator: Granite crust
was not only light.

lt was tough,

tough enough to withstand
the erosive power of the oceans.

For the next
couple of billion years,

slowly but surely,

the granitoid
proto-continents grew larger.

On different parts of the globe,
granite crust appeared

that would one day form
the hearts

of the major land masses.

The dominance of the oceans
was over.

The continents had arrived.

The slow expansion
of the granite proto-continents

was to change more than just
the appearance of the planet.

The shallow coastlines

would bring life
to the sunlit surface

and help trigger
the production of oxygen.

Almost since the arrival
of the first oceans,

it is believed that primitive
single-celled life-forms

had appeared
deep beneath the waves,

living off the heat produced
by the subsea volcanic fissures.

But now they were evolving
and spreading upwards.

On the continental coasts,
an organism was appearing

that was to transform
the planet:

the stromatolite.

The stromatolite
would live off sunlight,

and it would fill the atmosphere
with oxygen.

This primeval organism
can still be found today.

Western Australia:

Martin van Kranendonk
is over 1 00 miles

from the nearest town,

heading across the outback
to a remote beach.

- We're going down this track

to one of the most unique places
in the world,

where you've got
living stromatolites

on the shoreline
here at Shark Bay.

narrator: On the narrow,
sandy coast of Shark Bay,

a multitude of stromatolites
fill the tidal shallows.

Each of these unusual
rocky mounds

are up to one foot across
and two feet high.

lt was only in the 1 950s

that the importance of Shark Bay
was realized.

Following trips
to this remote site,

Australian geologist
Phillip Playford

was the first to discover
how stromatolites formed.

Playford identified
a rare bacterial algae

found in a slimy film
coating their surface

as the creator
of the mounds themselves.

- Stromatolites
are made up

of very thin layers
of microorganisms

that build up slowly,
layer by layer,

year by year,

as they use light energy
to gain their food,

and as a waste product,
they precipitate rock.

narrator: Other geologists
recognized the significance

of Playford's findings.

Patterns they had seen
in rocks billions of years old

were in fact
fossilized stromatolites.

Playford's discovery

had sparked off
a fossil revolution.

- Once people knew
that these kind of structures

were made by living organisms,

they went back
into the rock record

and found that they found
the same kinds of structures

and therefore could deduce
that life occupied planet Earth

3 1/2 billion years ago.

These are really the ancestors
of everything on Earth.

We're actually looking at our
great-great-great-great-great-

great-great-great-great-
grandmothers and grandfathers.

narrator: The rock record shows
that by 2.5 billion years ago,

stromatolites
were blossoming globally.

All beaches on Earth
would've resembled Shark Bay.

And as stromatolites
filled the shallows,

they began to fill
the atmosphere with oxygen.

- Planet Earth
in the solar system

is the only planet
that has an atmosphere

composed of a large amount
of oxygen.

Geoscientists think
that that oxygen

came only from the reaction
of stromatolites.

narrator: The algae
turned sunlight into oxygen,

a process known
as photosynthesis.

Over a period
of 2 billion years,

countless generations
of stromatolites

pumped out over 20 million
billion tons of oxygen.

At first, the gas dissolved
into the oceans,

where it rusted out
billions of tons of iron.

But eventually, it would also
fill the atmosphere

and transform the planet.

The planet's very appearance
was dramatically altered.

As the iron left the oceans,
they changed from green to blue.

When the oxygen moved on
to the atmosphere,

it diluted the remaining
thick carbon dioxide

and cleared the air.

After nearly 2 billion years
of oxygenation,

the blue planet was born.

The Earth now had
its blue oceans

and its blue sky.

Relics of this great
transformative period

survive today in immense layers
of iron-rich sediment

originally deposited

on the floors
of the ancient oceans.

Scattered
all throughout the globe,

the banded iron formations,
as they are known,

are vital
for today's economies.

They are the major source
of all the iron mined today.

Following its oxygenation,
the Earth was more recognizable.

But before it would become
the planet we know,

a new cycle of cataclysmic
events would take place.

Over the next billion years,

deep movements
would wrench apart the crust,

and life, which had just begun
to make its mark,

would face
its toughest test yet.

1 .5 billion years ago,

planet Earth was almost
3 billion years old.

For the first time
in its history,

it was beginning to resemble
the planet we know.

Newly arrived oxygen
had turned the oceans blue,

and the continents had grown

to cover nearly 1/4
of the surface.

But their expansion
was not over,

and beneath the oceans,
deep forces were at work,

rearranging their positions.

lmperceptibly,
the continents were on the move.

Mark McMenamin is an expert
in plate tectonics,

the study
of continental movement.

Until the 1 960s,
this was radical science.

- ln the 1 9th
and early 20th century,

the consensus view was that
the continents were fixed.

All geology was local,

and the continents
stay in one place.

narrator: But problems
for this view had been mounting.

One of the greatest mysteries

was the geographic position
of certain fossils.

- Trilobites like the one
on my left here

belong to the genus
Paradoxides.

narrator: The Paradoxides
really was a paradox.

lt was a freshwater creature
with a curious distribution.

- This trilobite is found

in the eastern part
of North America...

- And also in Britain,

on the other side
of the Atlantic Ocean.

narrator: The freshwater
Paradoxides

could not have swum
the vast salty ocean.

And they were not
the only fossils

showing bizarre
intercontinental distribution.

Geologists struggled
for an explanation.

ln 1 912, a radical new theory
would emerge from Greenland

that would lay the foundations
for plate tectonics

and shake Earth science
to its foundations.

The new theory was put forward

by a German weather scientist,
Alfred Wegener,

a man who had spent
much of his career

conducting atmospheric research
in Greenland's frozen wastes.

But Wegener
had always been fascinated

by the geologist's
fossil paradox,

and he boldly claimed
that the answer

was staring them in the face.

- Ever since accurate world maps
were available,

schoolchildren and others
have pointed out the fit

between the east coast
of South America

and the west coast of Africa.

And this was always dismissed
in reputable scientific circles

as just a coincidence
of no meaning.

And so many
disappointed children

were turned away and told
that their idea was wrong.

narrator: Wegener proposed
that the continents

had indeed
once been joined together

and had subsequently
drifted apart.

His observations in Greenland
convinced him

this continental drift
was possible.

- l think that his inspiration
was meteorological.

Perhaps he saw
breakup of ice floes

and made what we would call
an extrapolation

to the hard rock part
of the planet.

narrator: But few geologists
could accept

the radical theories
of a mere meteorologist.

- There was complete rejection
of what Wegener was saying.

This is a tall order,
to take a gigantic continent

and shove it
through the ocean floor

to get it
halfway across the globe.

narrator: Throughout his life,

Wegener fought to gain evidence
for his theory.

But his brave attempts
eventually led to his demise.

ln 1 930, his last expedition
to Greenland ended in tragedy

when he lost his way
in a snowstorm.

- ln an icy situation
on a glacier,

it's difficult to find your way.

Separated
from both his base camp

and the other members
of his expedition,

he basically got lost
and died of exposure.

narrator: Wegener was dead,

but his theory
of continental drift lived on.

The breakthrough came
after the U.S. Navy

produced a global map
of the ocean floor,

originally commissioned
for submarine warfare

during World War ll.

[sonar pinging]

This detailed map revealed one
of the Earth's greatest secrets:

the fractured network
of submarine mountains,

volcanic rifts, and trenches

that split the oceans
into enormous plates of crust.

These plates would be
the building blocks

for the new science
of plate tectonics.

The rifts and trenches
would provide a solution

to how continents drift

by proving that the ocean floors
are continuously being recycled.

- Plate tectonics
is completely driven

by the destruction of the old
and the creation of the new

narrator: Deep below
the surface,

mobile mantle rock is in
continuous circular motion,

following convection currents
of heat

generated
deep within the planet.

Where these currents rise,
the rifts form,

and the plates are pushed apart,

with new ocean crust
created in the gap.

Where the mantle currents
sink back down into the Earth,

they drag old oceanic plate
down with them

towards the interior.

As the ocean plate moves,
so do the continents.

- That oceanic plate drags
the continent along with it.

The process is like
an escalator or a conveyor belt.

narrator: The process
of ocean creation

is visible today
on a rocky island

in the middle of the Atlantic:

lceland.

lceland lies
on the Mid-Atlantic Ridge,

a 1 0,000-mile-long range
of subsea volcanic mountains

that mark one of the deep rifts
in the Earth's crust.

- lceland is really like a peak
of this mountain chain.

lt's like huge volcano
sitting on top of it.

narrator: Seismologist
Páll Einarsson

studies the volcanism
of this remote island,

volcanism that is helping
to expand the Atlantic Ocean.

Occasionally, an unusual type
of volcanic eruption on lceland

confirms
the plate-tectonic process:

a fissure eruption.

A fissure eruption
is a wall of fire.

They can be 25 miles long

and spew lava
hundreds of feet into the air.

- People fear eruptions.

They respect the volcanoes.

narrator: The fissures
mark the path

of the deep plate boundary
that is creating the Atlantic.

All across the island,

running from northeast
to southwest,

are the remains
of these fissure eruptions,

scarring the rocky landscape
with shallow canyons.

These canyons are very slowly
widening lceland.

At their base,
new crust is being created,

pushing Europe
and America apart.

- So here we are
located in the fissure

between the two
continental plates,

the two crustal plates.

Here on my left,
we have the North America plate,

and on the other side,
we have Europe.

This fissure here
is in a lava flow

that's only
about 8,000 years old.

So in 8,000 years,

that's how much
the two plates have moved.

- The rate
of continental drift

averages about 2.5 centimeters
per year,

the rate at which fingernails
typically grow.

narrator: 2.5 centimeters,
one inch per year,

means that in one
human lifetime,

America and Europe will move
just six feet further apart.

But over millions of years,
this speed of movement

was enough
to shift the continents

thousands of miles.

Using plate tectonics
as their guide,

geologists
such as Mark McMenamin

have reconstructed
the epic story

of continental movement
from the beginning.

From samples taken from
present-day continental margins,

they've compared fossils
and microfossils

and matched up distinctive types
of ancient rocks

to reconstruct
where the continents used to be.

- lt's a tricky task.

lt's kind of like Humpty Dumpty.

You've got all of these pieces.

You need to use
whatever clues you can,

whatever fingerprints you can,

to put one continental margin
against the other.

narrator: They are now confident

that they can trace
the movement of the continents

back over a billion years

to a time of a mass
continental collision.

As the oceans between them
were swallowed up,

the large land masses
drew together

in what was to become
a supercontinent, Rodinia.

lt is believed that Canada
and the U.S.A.

formed
the supercontinent's heart,

with other continents
bunched around them.

But Rodinia was unlike
any continent seen today.

lt was a desolate,
lifeless place.

- lt would've been very much
like being in the desert.

lt would've been similar
to parts of the Sahara,

Death Valley.

There would have been
no plants, no forests,

no grasslands.

Rodinia would have been
a barren continent.

narrator: Rodinia
may have been lifeless,

but it was to have
a profound effect

on life in the oceans.

ln the oxygenated waters,

primitive life-forms
were blooming

alongside the stromatolites.

But the huge supercontinent
was about to give them

a tremendous shock.

Rodinia was to trigger
what is now known

as "snowball Earth,"

the biggest freeze
the world has ever seen.

By around 700 million years ago,
Rodinia's position

was blocking the currents
that brought warm water

from the equator to the poles.

Without this heat,
the polar regions froze.

The resulting ice
reflected more of the sun's rays

away from the Earth,

and in a catastrophic
snowballing effect,

temperatures dropped
still further,

and the ice advanced
to cover the Earth.

Surface temperatures
fell below minus 40 degrees.

The oceans were covered
in an ice sheet

almost a mile deep.

The only life on Earth,
marine bacterias and algae,

were trapped beneath
in the darkness.

The result was disaster.

All but a tiny fraction
of organisms

were driven to extinction.

The whole planet was dying.

650 million years ago,
climate changes triggered

by the formation
of the supercontinent Rodinia

had left the surface
of the Earth

covered with a sheet of ice
one mile thick.

Temperatures hovered below
minus 40 degrees Fahrenheit.

Marine organisms,
the only life on the planet,

had almost been wiped out.

The future of life on Earth
hung in the balance.

But beneath the ice,

the supercontinent
was in turmoil.

Vast volcanic eruptions
were splitting Rodinia apart.

- lt's thought
that the accumulation of heat

at the base
of the supercontinent

is what eventually leads
to its undoing.

lt's like putting a blanket
over the Earth.

The heat that's generated
in the Earth's interior

will accumulate
underneath that blanket.

narrator: The heat would spell
the end of the snowball.

As Rodinia ruptured,

carbon dioxide
released by the eruptions

created a temporary
greenhouse effect.

The ice sheets drew back.

Rodinia had broken
into giant fragments.

And the icy grip on life
was broken.

As shallow seas opened up
in Rodinia's wake

and oxygen levels increased,

the primitive organisms
were free

to take their next
great step forward.

They would become complex
and a lot more dangerous.

The Canadian Rockies:

these remote mountains
are home to a rare record

of this key event
in the evolution of life,

the so-called
Cambrian explosion.

- For the first time
in the history of life on Earth,

we have some
of the highest oxygen levels

that we've had since the Earth
was actually formed.

Life bloomed.

We see animals
unlike we've ever seen before.

narrator: Paleontologist
Paul McNeil

is hiking up
to a remote mountain quarry

known as the Burgess Shale.

The astonishing fossils
in this quarry

are a window on the world
as it existed

over 500 million years ago.

- lf you surveyed
all the people

who study the history of life,

you get
almost unanimous agreement

that this is one
of the most important

fossil sites in the world.

narrator: The man who discovered
the Burgess Shale

was an American,
Charles Doolittle Walcott,

the president
of the Smithsonian lnstitute.

This fanatical fossil hunter,
who was born into poverty,

had lived the American dream.

Armed only
with a high school diploma,

he had fought his way
to the top

of the American
scientific establishment.

But it was his tenacious
fossil-hunting expeditions

in the most remote mountains
of North America

that would lead to his
most stunning achievement.

- This is the actual location

where Walcott first made
his amazing discovery.

As the legend goes,
it was August 31 , 1 909,

riding along this very trail
with his wife in a snowstorm.

And as they were riding along,
a large slab of rock came down,

blocked the trail,
and they couldn't get by.

Now, being a gentleman,
as all paleontologists are,

he immediately
leapt off his horse,

flipped over the slab of rock,

and found an incredibly
well-preserved fossil.

lt was down on the trail.

Where did it come from?

Nowhere but up there.

narrator: The source
of the rockfall

was a section of the cliff
no more than 1 00 feet across,

a small area that became

the celebrated
Burgess Shale quarry.

Walcott, often aided
by his own family,

eventually extracted
over 60,000 fossils.

And since Walcott,

a further 1 00,000
have been excavated

from this uniquely rich
cliff face.

- Quarrying the rocks
out of the mountain

requires a tremendous amount
of work,

a lot of backbreaking labor.

But it's also
extremely exciting,

because every time
you split open a rock,

you never know
what you're gonna find.

Most of the time,
you find nothing,

but every once in a while,
you find a new animal,

one that's never
been seen before,

one that's been revealed
for the first time

in 1/2 billion years.

narrator: The thousands
of fossils

found in the Burgess Shale

reveal that starting
500 million years ago,

life exploded with staggering
diversity and complexity.

- The preservation
of these fossils

is actually incredible

in that they're actually
preserved in three dimensions.

You can excavate
through the fossils themselves,

see the internal organs,

remove the organs,
see the digestive tract.

This is fantastic preservation.

Oh, look,
it's starting to crack,

and there goes a piece.

What we have here
is an actual anomalocaris.

These guys
were up to a meter in length.

That actually made them
the T. rex of the Cambrian.

narrator: ln the Cambrian seas,
the oxygen-rich shallow waters

were teeming
with complex organisms.

And creatures were feeding
not just on plants

but on each other.

- The Cambrian is actually
one of the most special times

in the history of life.

We see more different types
of animals

than we see in the rest
of the entire history

of life on Earth.

narrator: From this time
onwards,

with a biological arms race
driving their evolution,

creatures would become
increasingly complex,

with the development
of hard shells, skeletons,

eyes, and teeth.

Modern animals
had arrived on Earth.

The high level of oxygen
that had triggered

this explosion of life
in the seas

was also making
a final modification

to the atmosphere.

Over the next 1 00 million years,

oxygen reached
today's high levels,

a level dense enough
to allow an ozone layer

to form
in the upper atmosphere.

This layer was to free
life-forms from the oceans.

Previously,
powerful ultraviolet light

would destroy any organism
not protected by the water.

Now the ozone layer
would act as a UV shield.

400 million years ago,

the Earth is more
than 4 billion years old.

Over the next 1 00 million years,

the continents
would once again converge.

And this time,
thanks to the ozone shield,

life was free
to leave the oceans

and conquer the land.

Planet Earth had become a world
of tropical swamps.

South Georgia, U.S.A.,
the Okefenokee Swamp.

- The Okefenokee
is believed to be

what we would call an analogue,

a modern analogue,
or an environment

that's very similar
to the wetlands

that existed on Earth
in the past.

narrator: Fred Rich is an expert
on prehistoric swampland.

Geologists like him believe
that this freshwater swamp

closely mimics
the surface of the continents

300 million years ago

in a period known
as the Carboniferous.

- The Carboniferous
was an unusual time

because it was the first period
in Earth history

when large plants
occupied Earth's surface,

40, 50, 70 feet high,
that grew in dense groves

and produced
a vast forest canopy

and a steamy tropical jungle
atmosphere

that was something entirely new
on the face of the Earth.

narrator: This dense
tropical swampland

would dominate the Earth
for the next 60 million years.

The evidence is present

on all of today's continents
in the form of coal.

The coal we use for fuel
was formed

from millions of years' worth
of accumulated plant matter,

most of which existed
less than 300 million years ago.

And it formed
because of the unique way

freshwater swamps decompose.

- Okefenokee is derived
from a Native American word

that means
"land of the trembling earth."

lt's not very easy
to walk through the swamp,

because the subsurface
is soggy plant remains.

narrator: The freshwater

prevents the vegetation
from decaying,

allowing huge amounts
to build up over time.

- Beneath me is not
the regular sort of soil

that you would have
in your backyard.

The soil that you see here
is the plant material

that accumulated last year
or perhaps five years ago.

lt's leaves, stems, twigs.

There's still a good bit
of water in this.

But if we put this under
a tremendous amount of pressure

and add some heat,

by covering over
with layers of rock

and leaving it in the ground
for millions of years,

eventually it will change
to this.

This is a piece
of bituminous coal,

and it's around the order
of 200 million years old.

narrator: As the dead plants

were transformed to coal
on land,

the shallow waters
surrounding the continents

were preserving
millions of generations

of dead marine organisms

that would become
our other major fossil fuels,

oil and gas.

Every year, mankind mines
almost 5,000 megatons of coal,

30 billion barrels of oil,

and 3,000 billion cubic meters
of gas.

This fertile period
of Earth history

has given us much of the energy
we use today.

Without it,
the lndustrial Revolution

may never have happened.

Plants were not alone
in making a new life on the land

300 million years ago.

As time went on,
first enormous insects...

Then ambitious amphibians

and finally early reptilians
left the seas

to take their first steps
on the muddy shorelines.

The U.S. east coast back then
would have teemed with monsters:

three-foot millipedes on land,

two-foot dragonflies
in the air,

and proto-alligators
patrolling the nearby waters.

The world was over
4 1/4 billion years old,

and for the first time,

the surface was host
to a complete modern biosphere.

But the all-conquering
life-forms

were about to experience
a hell on Earth.

Forces deep within

were about to give
life on the surface

its sternest test ever.

Enormous volcanic eruptions

would herald the biggest
mass extinction

in the planet's entire history.

250 million years ago:

for hundreds of millions
of years,

life on the surface

had faced numerous challenges
to its survival

but nothing on the scale
of what was about to happen.

ln what would one day
become Siberia,

the Earth's crust
became a volcanic morass.

The cause was a rare
mantle plume eruption.

No one knows for sure
why they occur,

but occasionally,
huge masses of hot mantle

from deep within the Earth
surge upwards,

melting and smashing
the crust above.

The eruptions continued
for over 1 million years.

They spewed out over 1 million
cubic miles of molten rock,

enough to bury the modern U.S.A.
in a layer over 1 ,000 feet deep.

Clouds of poisonous gases
spread out

and shrouded
the entire globe.

lt was too much
for most species of life.

Over 95%
were driven to extinction.

lt was the most
cataclysmic event

the planet
has ever witnessed.

The planet that emerged
from the chaos was much changed.

A new supercontinent,
the great Pangaea,

now dominated.

And the climate
was altering dramatically.

Over the next 200 million years,

oxygen and carbon dioxide
would rise to new peaks.

And under these conditions,

the animals
that had survived the extinction

were to evolve
into the most infamous creatures

ever to walk the Earth...

[screeching roar]

The dinosaurs.

Utah, U.S.A.

Paleontologist Reese Barrick
is on the hunt for dinosaurs.

ln this dusty corner
of the western U.S.A.,

the rocks are packed
with their bones.

- Almost 1/3 of the history
of life on this planet

was dominated by dinosaurs.

lt really, truly is
a dinosaur planet.

We have, from the bottom
of this slope,

sediments that are
1 50 million years.

And as you go up the slope,
you actually end up

in the Cretaceous
at 125 million years.

How we doin', Barb?

- Doin' great.
- Find anything fun?

- A small rib
and some interesting fragments.

- Well, that's a start
for the day.

narrator: Compared
to modern creatures,

dinosaurs were enormous.

The average mammal today
is smaller than a dog.

The average dinosaur
was larger than a grizzly bear.

[dinosaur roaring]

- Marvin, excellent.
Look at that.

That is a spectacular
therizinosaur claw.

This animal's gonna have to be
300 kilograms,

so it's about the size

of a National Football League
lineman.

[chuckles]

These are absolutely fantastic

because they're
very well-preserved bone.

A perfect claw.

Absolutely brilliant, Marvin.
Nice job.

narrator: The first recorded
dinosaur fossil find

was a bone discovered
by young Mary Ann Mantell

in England in 1 822.

Her husband, Dr. Gideon Mantell,
was intrigued

and set about determining

what type of creature
it belonged to.

The fossil was unlike anything
he'd ever seen.

After much research,

he decided
it was in fact a tooth

from an enormous lizard.

He named the beast lguanodon,

after the iguana lizard
he thought it resembled.

Over the next few decades,
across Europe and the U.S.A.,

more and more huge bones
were unearthed,

and given their similarity
to modern lizards,

the name dinosaur,
meaning "terrible lizard,"

was coined.

[dinosaur roaring]

But many paleontologists today

believe one of the reasons
dinosaurs grew so large

was that they weren't
cold-blooded

like today's lizards.

They were lukewarm-blooded.

This gave them the advantages

of both cold-blooded lizards
and warm-blooded mammals.

- Dinosaurs
were able to be active

and collect food
all year long,

and yet they could put
a greater amount

of the food that they ate
towards growing

as opposed
to just heat generation.

narrator: But another reason
for their size

may have been the sweltering
oxygen-rich environment

that came to dominate
the dinosaur era,

an environment triggered
by volcanism.

Starting around
1 80 million years ago,

a new upsurge
in volcanic activity

split apart
the supercontinent.

The continental fragments
began their long journeys

into the positions
they occupy today.

North America, South America,
Africa, and Europe

all went
their separate ways.

The Pangaean supercontinent
was no more.

Each of the new continents
still carried dinosaurs,

and the steamy volcanic climate
seemed to suit them.

lt was global warming
gone wild.

CO2 levels increased over 500%,
and temperatures soared.

ln the greenhouse conditions
this created,

huge tropical forests spread
across many of the continents.

- The increasing amount
of tropics

meant that there was a lot more
lush vegetation,

which means there's a lot more
food for dinosaurs,

which allowed them
not only to specialize

and evolve to specialize

on different types
of plant materials

but allowed them
to get extremely large.

narrator: Many scientists
believe

that evolving
for millions of years

in this warm oxygen-rich world

allowed
the lukewarm-blooded dinosaurs

to reach their enormous sizes.

Huge dinosaurs may have been
a biological response

to a volcanically
overactive planet.

But size would not save
the dinosaurs

from what was to come.

Their time on Earth would end

in sudden,
unstoppable devastation.

1 00 million years ago,

planet Earth
was ruled by dinosaurs.

[dinosaur screeching]

Huge beasts filled the land,
the sea, and the air.

They lived in a sweltering world
defined by overactive volcanism,

and before it was finished,

this volcanism
would bring to the surface

some of the planet's
most wondrous riches:

diamonds.

Kimberley, South Africa:

Jock Robey is chief geologist
at De Beers,

the largest diamond company
in the world.

- Diamond is simply
the high-pressure form

of the element carbon.

This is a typical eight-sided
crystal called an octahedron.

Uncut, it is worth $2,000
a carat.

As a cut stone, it would
probably sell for $80,000.

narrator: For thousands
of years,

diamonds
had been found worldwide

washed up in sandy riverbanks,

but their source
had remained a total mystery.

lt was not until 1 869

when huge unique
diamond discoveries

were made in South Africa

that their remarkable origin
was revealed.

- What is special
about the diamonds

found in the Kimberley area

was, here,
for the first time ever,

they found the source rock
of diamonds.

This is a piece of rock
mined from the kimberlite,

and as we turn it,
it contains a diamond.

narrator: The diamond-bearing
rock was extracted

from strange
vertical formations.

- As the miners were digging,
they found that the diamonds

were contained in a body of rock

that had a shape
of an ice cream cone:

slightly broader at the surface,
yellow in color,

tapering down
to a narrower point.

narrator: Henry Carvill Lewis,

a visiting American
mineralogist,

put together the pieces.

He realized these diamond mines

were actually the mouths
of ancient volcanoes.

The miners were digging down
into their roots,

through the diamond-bearing
magma that remained.

But these were clearly not
normal volcanoes.

They were
over three times deeper,

extending nearly 1 00 miles

beneath the surface
of the continent.

Uniquely intense pressures
and temperatures at this depth

make it the only place
that diamonds can form,

and the diamonds
could only be brought up

by uniquely intense eruptions.

The diamond-bearing magma
exploded out of the Earth

at over 300 miles an hour.

- lmagine the force
and the power of this volcano

to cut those sheer
vertical walls

and blow this up
another thousand meters.

This is the power
of these volcanoes.

narrator: When the Pangaean
supercontinent split apart

over 1 00 million years ago,

scientists believe
the enormous upheaval

triggered these supereruptions.

Because supercontinental
breakups are rare,

so are the diamonds
they bring to the surface.

The diamonds that erupted
into the dinosaur world

would survive unblemished
until the present day.

But the dinosaurs
would not be so lucky.

65 million years ago,

the planet was lush.

Vegetation was thick
on the surface.

Living things were prospering
like never before.

But the dominant dinosaurs

were about to be wiped
from the face of the planet.

[dinosaur roaring]

- Dinosaur bones
are found continuously

throughout
the sedimentary record

from 230 million years ago

right up
to 65 million years ago,

and then, instantaneously,
they vanish.

narrator: Not only dinosaurs

but over 70% of species
on Earth disappeared.

From plant life upward,
something terrible had happened

to the entire ecosystem
of the planet.

This mass extinction
remained a mystery

for generations
of paleontologists.

But it is a mystery no longer.

Colorado, U.S.A.:

Dan Durda is taking samples

from an exposed layer of rock
exactly 65 million years old.

Scientists now believe
that it holds the answer.

For Dan Durda,
this powdery rock

is an indication
that the dinosaurs perished

in a sudden
astronomical catastrophe.

- Dinosaurs and 75% of all
the other plants and animals

that lived with them,
this layer is their tombstone.

This thin layer of clay
is the important evidence

of a violent event
in the history

of life on the planet.

narrator: The evidence
held in the tombstone layer

is a huge amount

of an exceptionally rare
element, iridium.

The remarkable concentration
of iridium

was discovered accidentally
in 1 980

by a father-and-son team
of scientists,

Luis and Walter Alvarez.

On the planet's surface,

iridium is usually found
in very small concentrations.

Most of this rare element
originates from space rock

deposited from the multitude
of small meteors

vaporizing in the upper
atmosphere every day.

The Alvarezes
were looking for variations

in the strength
of these tiny meteor showers,

but when they realized
this huge concentration

was held in the infamous
tombstone layer,

they proposed a radical
new theory for the extinction:

death from above.

The dinosaur planet had been hit
by an enormous meteor.

Their theory remained
controversial for over ten years

until the final piece
of the puzzle

was discovered in Mexico:

a hidden crater
over 1 00 miles across.

- ln 1 990, the Chicxulub
impact crater was discovered,

and its age,
when finally dated,

turned out to be precisely
65 million years old.

lt turned out to be,

it was the smoking gun
for the Alvarez theory.

narrator: Worldwide,
the tombstone layer

contains an estimated
200,000 tons of iridium.

This translates to a meteor
over six miles in diameter.

lts impact on the planet
would have been devastating.

- You've got to imagine
Mount Everest

flying at you across the sky
at 20 kilometers per second.

Several thousand
cubic kilometers

and launched
around the entire planet,

slowly raining back down
through the atmosphere

to settle across
the surface of the Earth

as a thin layer
of dust and debris.

narrator: But the meteor
was not alone

in wreaking destruction.

Today in lndia,
ancient lava flows exist

that are so thick,

whole temples have been carved
into their layers.

The lavas were the result
of a massive eruption

that was occurring
simultaneously

with the meteor strike.

Although not as extensive

as the earlier
Siberian eruptions,

these lava flows
in western lndia

could have buried the U.S.A.
to a depth of over 600 feet.

The huge clouds of toxic dust
they produced

would have rivaled
those of the meteor.

65 million years ago,

the meteor impact
and the eruptions

would have been
a deadly double blow.

Whichever had
the stronger effect,

the combination
of these events

sounded the death knell
for the dinosaurs.

[dinosaur roaring]

A dust cloud lingering high
in the upper atmosphere

and blocking the sun
devastated the life below.

The huge dinosaurs,

along with most other
major species,

were extinct.

The new world
that was to follow

would be the world
of the mammals

and the world of man.

50 million years ago,

life was slowly recovering
after the cataclysmic extinction

that obliterated
the dinosaurs.

The Earth had been around
for over 4.4 billion years,

but only now
were the first mammals,

our ancestors,
beginning to flourish.

Long before humans arrived,

the continents continued to move
and crash into one another.

Slowly but surely, the surface
started to look familiar

as plate tectonics and erosion

created the dramatic landscapes
we see today.

The Swiss Alps:

some mountain chains
can be explained

by volcanic eruption of rock
from the depths of the Earth.

But the greatest,
including the Alps,

contain no volcanoes.

They appear to have risen
as if by magic

up from the plains beneath.

This famous range
runs through the heart of Europe

and reaches over three miles
above sea level.

How was such a huge mass of rock
pushed up so high?

Adrian Pfiffner is an expert

on the structure
of the Alpine chain,

and he knows the answer.

- The scene we see
in front of us

is the result of a collision
between two continents,

the African continent
and the European continent.

narrator: A close study
of the Alpine rocks

can provide clear evidence

of how the mountains
were formed.

The secret is revealed
in quartz crystals

that are extremely small.

- These slices are about
25 thousandths of a millimeter.

At that thickness,

you see through
one single grain.

narrator: The tiny crystals
in the rock

reveal massive deformation.

- The quartz grains
have been really stretched,

elongated and flattened.

You need large stresses
in order to deform these rocks.

One process that is doing this

is actually the collision
of two continental plates.

narrator: For the last
45 million years,

as the continents
have continued to move,

the African plate and subplates
have been grinding into Europe.

The continental crust
along the collision point

experiences extreme pressure,

and the solid rock itself
is warped and buckled.

- lf you assume that my hands
are two plates

which are squeezing
the rocks in between,

you can see that some
of the material escapes upwards

and leads to the building
of a mountain chain.

narrator: The twisted folds
of the rock strata are exposed

as the mountains are slowly
squeezed higher and higher.

One famous Alpine mountain

demonstrates clearly
this collision

of the African and European
continental plates:

the Matterhorn.

The Matterhorn is the child
of two continents.

- What's amazing
about the Matterhorn is,

the top pyramid
of the Matterhorn

is a piece of Africa,
and it lies on Europe.

narrator: ln the formation
of this classic mountain,

the two continental plates
have actually overlapped.

- You can think of a car crash.

lf two cars crash
with each other,

maybe one car
slides over the other one.

The two continents
moved together,

and Africa
moved on top of Europe.

narrator: Plate tectonics
are responsible

for all the Earth's
mountain ranges,

and over millions of years
of growth,

the only thing
that has stopped them

grinding inexorably skywards
is erosion...

Erosion by snow, wind, and rain.

- This is the action of water
that is eroding the mountains.

Now, this might seem to be
something very small,

but actually, if you look
at the entire Swiss Alps,

50 million tons
is eroded every year,

and this corresponds
to a small mountain

roughly 1 ,000 meters high,
one every year.

narrator: The height
of mountains around the world

are determined
by these two opposing forces---

uplift and erosion---

changing them by fractions
of an inch,

up or down, each year.

But plate movement
and water erosion

can also create
the opposite of a mountain.

Under the right conditions,

the surface itself
can be cut away,

sometimes spectacularly.

The Grand Canyon:

over 1 mile deep,

1 0 miles wide,

277 miles long,

and still growing.

- One of the great stories
of exploration

is when the first Europeans

saw the Grand Canyon
in the year 1 541 ,

and a couple of those men
came over to the rim,

they saw the river down below,

and they thought
it was six feet wide.

The explorer sent
a couple of his men down,

and they came back later
and said,

"The canyon is deeper
than it looks."

narrator: Wayne Ranney
is an expert

on this geological phenomenon,

its unique scale the consequence
of titanic forces of nature.

Over the course
of the last 6 million years,

this spectacular canyon
has been carved

by the slow, winding
Colorado River

in combination
with dramatic uplifting

of the Colorado Plateau.

Plate tectonic processes

have pushed the whole plateau
upwards.

lt now lies over 8,000 feet
above sea level.

- This uplift probably occurred

with the Pacific plate coming
into the North American plate

and wrinkling the crust,

much like if you took
a throw rug on a hardwood floor

and pushed it
along the hardwood floor.

When the edge of that rug
reaches the wall,

you'll see this big bow-up
in the rug,

and that's exactly
what's happened

to the western edge
of North America.

narrator: The river
looks too small

to cut a canyon so deep,

but its height above sea level

means that the force of gravity
gives it great power.

- All you have to do
is look at big rivers

like the Amazon
or the Mississippi.

They have much more
volume of water

than the Colorado River does,

and yet they don't cut
large canyons,

because their landscape
is not elevated.

So uplift brings the rocks
into an elevation

where the river
can then saw down

through all of those layers

and create the canyon landscape
we see today.

narrator: Plate tectonics
combined with erosion

have sculpted
many of the features

on the surface of our planet,

and as a general rule,
the mostjagged, tallest peaks

and the deepest canyons

are the youngest
of these grand structures,

all formed within
the last 50 million years.

But the final touches
have been added

by yet another
major force of nature.

2 million years ago
in east Africa,

ancestors of modern humans

were taking their first steps
on Earth.

At the same time,
down from the North Pole,

enormous icy glaciers
began to descend.

The Earth was about to enter
the ice ages.

2 million years ago,
ancestors of modern humans

had begun to spread
out of Africa.

But the Earth around them
was cooling down.

Before long, much of the planet

would be coated
in huge glaciers.

The ice ages had arrived.

The grand freezings
were triggered

when overflowing volcanoes
in Panama

created the land bridge
joining North to South America

and radically altered
global ocean currents.

The polar seas
cooled significantly.

The result was that pronounced
dips in global temperature

could now tip the planet
into ice ages

lasting tens of thousands
of years.

lceland:

the Langjökull glacier.

ln the highest,
coldest parts of the planet,

glaciers still reign supreme.

Few venture out
in these hostile terrains,

but glacier climatologist
Finnur Pálsson and his team

regularly battle
the freezing elements.

- When you're doing
glacier fieldwork,

conditions can be very bad.

narrator: Outside, it is below
minus 20 degrees Fahrenheit.

- l like to work
in harsh conditions.

Difficulty is something
you need to tackle.

narrator: Finnur is keeping tabs
on the growth of the glacier.

At present,
it is over 350 square miles,

the size of New York City.

And although it may look static,

in fact,
it is in constant motion.

Glaciers are formed initially
by snowfall on high areas.

The compacted ice
is then dragged down

by the force of gravity.

The glaciers move
like slow-motion rivers.

- You can think of ice

as soft material
like toothpaste.

lt flows.

lf you make a big blob
of toothpaste on a plate,

it will slowly sink down
and flow away to the edges.

narrator: Finnur and his team
in lceland regularly check

on the incremental movement
of the ice.

- This is a satellite
positioning system.

We can calculate
the position of this point

with an accuracy
of about two centimeters

to calculate how fast
the glacier moves.

narrator: Finnur's measurements
tell him

that this glacier is moving
at over 1 50 feet per year.

ln today's mild temperatures,

glacial advance is kept in check
by glacial melting,

but if global temperatures
were to drop

byjust a few degrees
for a long period,

then the glaciers
would grind slowly forward,

and the Earth would enter
another ice age.

The existence of ice ages
was first discovered

by 1 9th-century Swiss geologist
Louis Agassiz.

As he explored
the Swiss Alps in the 1 830s,

Agassiz couldn't help but notice

the immense boulders
scattered over farmland

and the bizarre towers of gravel
capped by stones

that stood guard over some
of the mountain valleys.

To explain how the rocks
arrived at these positions,

he speculated that they had been
carried and deposited

by ancient glaciers that had
once filled the Alpine valleys

and covered
the Northern Hemisphere.

lnitially ridiculed
by his peers,

Agassiz's ice age theory
became accepted

as telltale signs
that these huge glaciers

had indeed covered
the continents

were found
all over the globe.

The evidence is everywhere.

New York's Central Park:

this oasis of green
in the middle of Manhattan

exposes part
of the island's ancient bedrock.

Many large outcrops
are visible,

and they contain the footprints
of the glaciers.

Climate expert Joerg Schaefer

is looking for subtle traces
of this frozen world.

- lt's actually
something l bet

that most New Yorkers
do not know.

You see the ice age
is everywhere

if you open your eyes.

narrator: Look closely,
and the superhard bedrock

is marked with scores
of tiny parallel lines

fractions of an inch deep.

- So this point here is actually
one of the most amazing spots

of evidence for an ice age
in the middle of New York City.

narrator: The grooves
were caused by small rocks

caught under the massive weight
of a moving glacier.

- These little rocks
basically cut like a knife

into this very hard bedrock.

This is clear proof that, once,

an enormous ice sheet
was moving in this direction

in the middle of New York City.

narrator: The glaciers
that hit New York were massive.

They rolled down from the Arctic

and buried Manhattan
under a huge depth of ice.

- To give you an idea
about the thickness

of the Laurentide ice sheet
in the Manhattan area,

it was at least twice as thick

as the Empire State Building
is high today.

narrator: Over the last
2 million years,

as the climate fluctuated,

the huge ice sheets
waxed and waned.

With every pass,
they gouged and crushed

and reshaped
the land beneath them.

As the last glaciers retreated
1 0,000 years ago,

they left behind
a bruised and battered landscape

and created features
we still see today.

ln the U.S.A.,
Cape Cod and Long lsland

are built on immense piles
of boulders

dropped from the retreating edge
of the North American ice sheet.

And the great weight of the ice
formed huge depressions

that now make up
the Great Lakes.

ln the warmer climate

that followed
the last glacial retreat,

early humans had free reign
over the surface.

ln this brief period,
a fraction of a fraction of 1%

of the history of the Earth,

the entire history of human
civilization has taken place.

Human ingenuity
has reshaped our planet.

From our perspective,

our achievements
are breathtaking.

But will we continue
to survive and prosper?

- Humans have, with technology,

dominated the planet
more completely, perhaps,

than any other animal
in the history of life,

but we've done it
for such a short period of time

that we've got
a long ways to go.

narrator: Over the past
4.5 billion years,

the Earth has been
on the most incredible journey.

Over the eons of its existence,
the planetary environment

has undergone
immense transformations.

And since the arrival of life,

these transformations
have in many ways

determined which organisms
will survive

and which will be swept aside.

lf this turbulent past
is any guide to the future,

life and humans in particular

will face further battles
for survival

as the planet continues
along its path of change.

- Life is highly dependent
on the Earth.

What the Earth gives us
is what we have to deal with.

- lt's hard to separate
completely

the processes of geology
and the processes of life.

Life in some ways
drives geology,

and geology creates
the environments

in which life thrives.

narrator: Our first major
challenge will be the climate.

At the start
of the 21st century,

we may worry
about global warming,

but most scientists recognize

that we are in a gap
between ice ages.

Our whole civilization
has occurred

in a brief warm period,
1 0,000 years so far.

This warmth has proved crucial.

- lt's definitely not
a coincidence

that civilizations developed
over this period of time,

because the climate
is so favorable to our species

to develop and flourish.

The period we live in the moment
climate-wise

over the last, let's say,
1 0,000 years

is exceptionally stable.

lt's almost unbelievably stable

if you look
into the geological record.

lt certainly will not
stay forever like that.

narrator: Even
if our industrial economies

effect a global warming

over the next
couple of centuries,

they can do no more
than delay the inevitable.

The continents'
current positions

keeping the polar oceans cool

mean that in just 1 5,000 years,
a new ice age may occur.

- The New York area is going
to be completely changed

by the next cycle of glaciation,

and at some point,
glaciers are going to move down

and grind New York
into the North Atlantic Ocean.

narrator: But even if we survive
the big freezes,

there will be
greater challenges to come.

As plate tectonics
move the continents

and end the ice ages,

coastal regions
will be engulfed,

and whole countries
will disappear.

200 million years from now,

a new supercontinent,
Pangaea Ultima,

is due to take shape

as first the Mediterranean
and then the Atlantic Ocean

are swallowed up.

- There will be continents
eventually colliding

with the east coast
of North America,

so New York, in the long run,
will be destroyed

in a continent-to-continent
collision

and will be completely crushed

and thrust upward
as a new mountain range.

narrator: The Earth
will once again

be thrown into deadly turmoil.

Oxygen levels
and surface temperatures

could fluctuate wildly

and lead to new
mass extinctions.

But even the trauma
of supercontinental disruption

is nothing compared
to what will follow.

Everything will grind to a halt

when the plate-tectonic engine
finally stops.

- The maintenance
of habitability on this planet

is involved
with the plate-tectonic cycle.

lt's not an infinite cycle.

There is an end in sight.

lt's billions of years from now,

but we know, eventually,
the system will wear out.

narrator: The fires
in the depths

that have dominated activity
on the surface

will one day use up their fuel,

and the story of planet Earth
will be over.

Without its burning heart,
the Earth will share

what many believe
was the fate of Mars.

The atmosphere and oceans
will be stripped away,

and the surface will become
a bone-dry barren desert.

The planet will be dead.

But this is a picture
of an incredibly distant future.

For at least
the next billion years,

as the Earth continues
its epicjourney,

some form of life
should continue.

But the human species,
which has walked the Earth

for over 2 million years

and mastered it
only in the last 1 0,000,

may be in danger.

As the environment transforms,

Earth could well become unfit
for humans.

lf that happens
in the distant future,

rather than be forced
to face extinction

like our predecessors,

technology may allow us
to leave Earth

in search of new homes,

other blue-green planets
on which to make a new start,