NARRATOR: For over 4 1/2 billion years,
the Earth has been blasted, burned, ripped, and scoured.
These phenomenal events have sculpted our planet
through a series of devastating cataclysms.
Our ancestors thought volcanoes were the doorways to hell.
We think we know better.
But we still live in a world driven by natural forces
which we cannot control
and which are indifferent to our needs.
We live on a restless planet.
We are only just beginning to understand the awesome power
that can raise mountains, form the continents,
open and close the seas.
The fragile truce between man and the Earth
is being broken all the time.
We are learning more about the forces that drive our Earth
and how to live with them.
But it may be too late.
79 A.D. Pompeii, ltaly.
A peaceful Roman city was overwhelmed
by pyroclastic fires from Mount Vesuvius,
a volcano that had slept through recorded history
until it suddenly exploded.
20,000 people lived in Pompeii.
Very few escaped the volcanic shroud.
2,000 years later,
the people of Montserrat, a small Caribbean island,
faced the same threat.
ln June 1995,
the volcano of Soufriére burst into malignant life.
lt had been dormant for 400 years.
19 people have died, and half the island is uninhabitable.
Where once there was a green forest
is total devastation -- an ash desert.
Scientists from all over the world
are trying to forestall an even greater disaster.
What we're looking at here is the Soufriére Hills Volcano.
And basically what it is is this big scooped valley.
And part of this valley is what we call English's Crater.
And that's that big amphitheater.
Sitting within the amphitheater is the present active dome.
The magma is pushed up from below, and it comes out.
lt's exceptionally viscous.
And it just builds up and up and up,
forming this big dome structure.
lt's exceptionally hot. Very unstable.
And these blocks that are overhanging
is what usually falls off,
generates the rock avalanches and then the pyroclastic flows.
NARRATOR: Mark Davies can't just watch
from the safety of the helicopter.
He must get as close as he can to the flow.
lt's incredibly dangerous.
At any moment, and without warning,
the volcano might erupt again,
and he'd have no chance of escaping.
DAVlES: We're quite close to the dome here.
You can feel the heat coming off it.
So it's not really a place we want to hang around.
The cracks have opened up six centimeters in three days.
So we'll have to keep an eye on them.
A pyroclastic flow
is essentially like a snow avalanche,
the only difference being
that it's around about 800 degrees C.
lt contains big, huge blocks within it,
sometimes the size of houses.
lt contains lots of poisonous gases.
And all of that will travel at around about the speed
of 80 meters per second in some cases,
sometimes a heck of a lot faster.
So you can't outrun it. You can't outdrive it.
And in some cases, the only thing
that can get you out fast enough is a helicopter.
Essentially, if you get caught in a pyroclastic flow,
you really don't know whether you'll get crushed,
whether you'll suffocate,
whether you'll burn to death first.
And, frankly, l wouldn't want to know, myself.
NARRATOR: This is how Montserrat used to be
before the catastrophe --
an eight-mile paradise with green hills and tiny farms
that had crept close to the mountain.
The towns were full of memories of the colonial past.
Now all that is gone.
Sometimes ash falls like hail for a day at a time.
The heat can be felt a mile away.
The smell of burning sulfur fills the air.
The sun is obliterated,
and the midday sky becomes as dark as night.
There is nothing to be done but take cover.
Plymouth, the capital, was like Pompeii --
a thriving port, center of island life.
lt, too, lay in the path of the pyroclastic flow.
Because they had warning, the people were able to escape.
But slowly their town is disappearing
under the pitiless flows and remorseless ash.
A volcano can sit quietly for centuries
until the pressure from below becomes too great
and it explodes.
What everyone on Montserrat wants to know is,
will it explode again and will it ever stop?
The scientists' best hope is to monitor the earthquakes
they know will shake the mountain before an eruption.
24 hours a day, they listen and watch.
DAVlES: This is the operations center
for the volcano observatory.
lt's monitoring the whole of the volcano.
lt's an early-warning system, if you like.
We have points all around the volcano.
So if the ground is moving,
then the information that those machines gather
out on the volcano is sent back here.
And it's recorded on these pens.
So it's a visual way of determining
how much motion is occurring.
When the drum and the needle on the drum and the pen
is going back and forth --
The bigger the earthquake,
the more violent that pen will move.
NARRATOR: And the greater the chance of a violent eruption.
But the technique is only a best guess.
lt's not foolproof.
Distrusting science to save them from the force of nature,
the population dwindles daily as more and more people escape
to the safety of neighboring islands.
Those who can't leave
eke out a precarious existence in makeshift camps.
Families are split.
The young see no futures.
The old can only remember the past.
One in 10 of us live near an active volcano.
Many choose to because volcanic soil
is so fertile and productive.
But will the people of Montserrat ever be able
to return to their fields and old ways of life?
Or has that gone, as lost as Pompeii?
People and politicians would like clear-cut answers.
But scientists know that's impossible.
DAVlES: lf the eruption stops tomorrow,
the dome is still up on top of the volcano.
lt's still unstable, and it will still retain its heat.
And it might stay like that for five years
after the eruption finishes.
Or it might cool down exceptionally quickly
and, within one year, people could move back.
We don't really know.
NARRATOR: Montserrat's disaster is caused by something
that happened over four billion years ago,
when the Earth's crust broke into gigantic sections,
forming the tectonic plates.
Understanding Earth's tumultuous history
is like reading an intricate detective story,
for the Earth is unlike any other planet.
lts restless surface is changing constantly,
destroying the evidence of the past.
But if you know where to look for them,
the clues are still there.
About 18,000 meteorites hit the Earth every year,
hurtling down at 70,000 miles an hour.
Most are small and do little damage,
but each brings clues
to the catastrophic formation of our planet.
Geologist Roger Buick is working in northwestern Australia.
Even though it's just arrived,
this is the oldest thing on Earth.
lt's a chondrite -- a type of stony meteorite --
and it's been wandering around the solar system
for about 4 1/2 thousand million years.
lt's stuff like this that the Earth is made of --
space junk glued together.
NARRATOR: 4.6 billion years ago, the molten Earth grew
as a continual rain of mega-meteorites
pummeled it on its orbit around the sun.
Each strike brought with it raw rock,
the material from which Earth could grow.
lt also brought explosive energy,
raising the surface temperature of the primitive planet
to over 1 ,800 degrees.
A vast ocean of molten rock 100 miles deep
covered the globe.
lnternal radioactivity raised the temperature even further.
Earth became a melting pot.
The meteoric iron began to sink to the center,
dragged by the relentless tug of gravity.
A kilometer sphere of molten iron would make the journey
from the surface to the center of the Earth
in less than a million years -- a blink of geological time.
The constituents of the Earth were forming.
lt had an iron core surrounded by molten rock.
On the surface, a thin crust was developing.
lt behaved like these lava ponds.
And the turbulent forces beneath began to fracture the crust.
These are the tectonic plates --
vast sheets of the Earth's crust,
tearing and crashing over the planet's surface.
They drift endlessly around the globe like giant bumper cars,
joining and separating,
carrying with them all the continents and oceans.
There are nine huge ones, many thousands of miles wide.
And it's at their boundaries that catastrophes occur.
When they clash, new landscapes are created.
Oceans shift.
And mountains soar into the sky.
Montserrat sits on the boundary
of the Caribbean and North American plates,
where volcanoes erupt and earthquakes shudder.
The actual fabric of the land itself is made here.
Where the tectonic plates that form the ocean floor
are torn apart,
new lava continually emerges, and new volcanoes are born.
ln 1963, this act of creation could be seen by all.
Some 10 billion square feet of lava
erupted off the coast of lceland
to form the new island of Surtsey.
lt emerged in a matter of days,
just like volcanic islands on the primitive Earth.
All over the planet, these islands appeared.
And in time, they were to form the first continents.
Clues as to how this happened
are found in the Canadian Rocky Mountains.
The outer shell of Earth -- the lithosphere --
carries the continents.
lt's made up of great stratas of different rocks
extending 60 miles down into the earth.
Most of its structure is unknown.
The deepest man has ever drilled is nine miles.
Exploring deeper needs a different approach.
To discover just how their land was formed,
a team of 700 scientists --
the modern equivalents of early mapmakers --
are charting this invisible territory.
They use shock-wave detectors -- geophones --
which the teams are placing all over the landscape.
This is the world's biggest
subsurface exploration experiment -- the Lithoprobe.
ln the Yukon province, the chief scientist is Charlie Roots.
ROOTS: Geologists who work in sedimentary rocks
are used to continuity,
both in oldest rocks to youngest rocks,
as well as being able to take the same rock formation
for a long distance.
You can't do it in these mountains.
The rocks on the surface
indicate a large platform of limestone,
and the surrounding areas are rocks
that have no relation to that.
They are bits that are not part of the continent,
that appear to have come from somewhere else.
These canyons show the folds and the twists
that the rocks have undergone
as they've been pushed up against the ancient continent.
The problem is that you only get to see the rocks
that are at the surface.
And in an area where rocks are steeply dipping,
there is far more of the story buried beneath our feet.
NARRATOR: To send shock waves deep into the crust,
200 pounds of explosive are buried in the ground.
WOMAN: We're digging three holes
for the geophones that we're going to be putting in here
so that we can have a three-component
orientation system
to measure the seismic wave that comes in.
We have a vertical geophone
which will measure the vertical component of the arriving wave.
There is a north-south geophone
that will measure the north-south component
of the incoming wave.
And we have an east-west geophone
to measure the east-west component
of the incoming seismic wave.
[ Alarm blares ]
MAN: 10, 9,
8, 7,
6, 5,
4, 3,
2, 1 .
NARRATOR: As the shock wave races down through the ground,
they hit something hard --
much harder than the surrounding rock.
The shock waves are reflected and speed back to the surface,
taking their precious information to the geophones.
Analysis of the result shows that under the Rockies
are the buried remains of ancient volcanic islands.
Over the last 200 million years,
hundreds of these islands were grafted
onto the North American continent.
They form much of the land west of the Rockies,
stretching from Mexico to Alaska.
This is a clue as to how the first landmasses were created.
But until very recently,
science was at a loss to say just when it happened.
Then, one day,
prospecting for minerals in northwestern Australia,
Roger Buick made a startling discovery.
This rock is part of the oldest land surface on Earth.
lt has miraculously survived the never-ending cycle
of formation and destruction of the crust.
The vertical stripes have endured
for over 3.6 billion years.
At the same time, the Earth began to cool.
condensing in pockets,
but not enough to create oceans or rivers.
There was no oxygen in the air.
lt was inhospitable, with no trace of life.
A new theory suggests that, in time, water --
maybe enough to fill the world's oceans --
arrived from deep space, brought on ice comets.
Cosmic rain continues today with small, 20-to-40-ton ice comets
striking the Earth's atmosphere once ever three seconds.
They add one inch of water
over the entire surface of the globe every 20,000 years.
When the atmosphere was saturated, the rain began.
An endless ocean grew.
And when the skies finally cleared,
the Earth had been transformed into a watery globe.
This is the time when life is thought to have begun.
Echoes of those beginnings can still be heard today.
Our most ancient ancestors,
the most resilient creatures ever evolved,
have survived unchanged for billions of years
living in solid rock.
Drilling to great depths into the rocks at ldaho Falls,
Princeton microbiologist Tullis Onstott
is hoping to take a closer look at their descendants.
Hey, thanks.
What l find truly remarkable is that within this core barrel
is a massive piece of rock from 200 feet below the surface,
and yet it contains as many bacteria in it
as there are people on this planet.
Now, these are living bacteria.
And they live at temperatures
approaching the boiling point of water.
They live at pressures that are 100 times of atmosphere.
They live in a salty, briny solution that's alkaline.
lt contains gases that are toxic to us.
And yet they still manage to survive.
NARRATOR: They are known as extremophiles
because of their extreme living conditions.
To get a closer look,
the scientists first extract them from their rocky home.
ONSTOTT: The really exciting thing about heat-loving bacteria
is that they're the most primitive organisms
on the Earth.
And the fossil evidence in the most ancient rocks on Earth
indicate that these types of organisms
must have existed 3.7 billion years ago.
NARRATOR: With skill and care,
the team work inside glove boxes.
Here they can manipulate the sample under sterile conditions.
They go to great lengths to ensure
that the only bacteria inside the tent
are those that have made the journey up from the earth.
MAN: We need to pare away the outside of the core
so that we can remove any contamination
that may have occurred during the process of coring.
NARRATOR: The core is then placed in a press
and crushed to a fine powder.
Then a sample is taken from the powder
and a culture developed of the bacteria.
These are the earliest common ancestors of all life --
a colony of extremophiles.
Observing how microbes survive
thousands of feet below the surface,
some scientists have speculated about life elsewhere.
Could there be tiny extraterrestrials
buried in the same way on other planets
that appear outwardly sterile?
ln the sedimentary rocks of Australia's Karijini
are all the clues that solve
another chapter of Earth's history.
This was the first place
where life and the land began to interact,
and the traces are clear to this day.
BUlCK: The impressive thing about the place
is how red it is.
ln fact, red rocks stretch for hundreds of miles
in every direction.
The reason they're red
is because of this red mineral, hematite -- iron oxide, or rust.
And the way they formed
was when dissolved iron in the ocean combined with oxygen
and precipitated out as iron oxide,
settled down to the seafloor,
and accumulated on the bottom of the sea.
lnitially, the atmosphere of the Earth had no oxygen.
The same applied to the oceans.
These rocks record an intermediate period
when there was still no oxygen in the atmosphere
but the upper layers of the ocean contained oxygen.
There's a huge amount of iron oxide here.
The sheer volume suggests that the oxygen could only have had
one plausible source -- biology.
Living organisms excreting oxygen
as a by-product of photosynthesis.
NARRATOR: After two billion years,
the oxygen had finally combined with all the iron.
For the first time,
free oxygen was able to escape into the atmosphere,
and the air became breathable.
Deep into the Australian outback
is more evidence of primitive oxygen-producing organisms.
ln a secret location Buick discovered
are some of the world's oldest and rarest fossils.
BUlCK: What l've done is step back
more than three-quarters of the way back
to the beginning of Earth history.
And here are wrinkly layered sediments
that occasionally dome upwards.
These are stromatolites --
sedimentary structures created by filamentous microorganisms
trapping sand and mud between their little filaments.
Those microorganisms were probably photosynthetic.
The layers thicken over the tops of these domes,
competing with each other to get nearer the sunlight.
Now, these stromatolites are remarkable for their great age.
3,450 million years old.
Not only are they remarkable for that,
but we can also infer something
about the environment in which they lived.
Just back here...
...are gypsum daisies.
Little star-shaped clusters of gypsum crystals --
calcium sulfate.
These form when seawater evaporates
in a shallow pond near the edge of the sea.
Living stromatolites only grow
when they're almost permanently submerged in water,
so you only see them exposed at very low tide.
These grew here about 5,000 years ago,
when the sea level was about a meter or so higher.
The living carpet of bacteria that formed them died off
as the sea level gradually dropped,
and the sediment that the bacteria trapped
was turned into limestone.
NARRATOR: These tiny bacteria
were the first organisms to live together in colonies.
By producing oxygen,
stromatolites changed the planet forever.
Life flourished and became a force to shape the world.
But geological upheavals can spell disaster.
200 million years ago, the supercontinent Pangaea,
which stretched unbroken from pole to pole,
began to split in two.
lt took 65 million years.
Two continents we know today were shaped by another upheaval
that hit the remains of the supercontinent in the south.
ln the jungles of South America
are found one of the most remarkable features
on the face of the planet.
This whole landscape owes its existence
to this violent chapter of Earth's history.
RAMPlNO: lguazu Falls, Argentina --
for me, the most spectacular waterfalls in the world,
not only because of the spectacular scenery here --
250-foot-high waterfall a mile wide --
but because of the spectacular geology.
What's more, the rocks of the falls
contain evidence pertaining to a geological event
that took place here 135 million years ago.
The geological evidence is here in these rocks.
This is basalt,
a hard, volcanic rock stained red by iron oxide --
oxidation of the iron within the rock.
ln fact, we're standing here at the base of a basaltic lava flow
more than 100 feet thick,
just one of many lava flows in this area
which form a pile of lava more than a mile thick.
ln fact, in the waterfalls,
one can see steps of the waterfalls
which shows the individual lava flows in this pile.
lmagine volcanic eruptions so enormous
as to produce lava flows
erupting from giant cracks and fissures in the Earth's crust,
flowing out over an area
twice the size of the state of Texas --
more than 250,000 square miles.
An enormous volcanic event.
Massive amounts of sulfur-rich gases
spewing into the atmosphere.
Droplets of sulfuric acid forming a veil
that cuts out the sunlight and cools the climate.
Sulfuric acid rain killing the vegetation.
The makings of an environmental disaster
of enormous proportions.
This is 135 million years ago
at the end of the Jurassic period of geological time,
a time when there were mass extinctions
of many forms of life.
There's evidence here in these rocks
for an even more dramatic event in the history of the Earth.
And here is just the piece of evidence that l need.
NARRATOR: On the other side of the world,
across the Atlantic Ocean,
is the world's most ancient desert.
lt dominates most of
the southern African country of Namibia.
RAMPlNO: l've traveled more than 4,000 miles,
and the rocks are exactly the same.
They're basalts, and the age is 135 million years.
Clearly, when these rocks were erupted
as floods of lava traveling hundreds of miles,
South America and Africa were together as one supercontinent.
NARRATOR: The Atlantic Ocean,
which now divides Africa and South America,
owes its very existence to this geological cataclysm
that tore Pangaea apart.
RAMPlNO: The supercontinent looked like this,
made up of the present-day continents
of Africa, South America, lndia,
Antarctica, and Australia.
The cracking started here and split the continent
into the present-day continents of South America and Africa.
NARRATOR: ln geological terms, it happened incredibly fast.
The crack opened northward at a speed of two inches per year,
the split unzipping the land as it went along.
Fountains of volcanic fire leapt through the crack.
The entire process took only five million years to complete.
Evidence of the unzipping is clear.
The shorelines of South America and Africa match perfectly.
And under the ocean, the mid-Atlantic ridge
divides the two continents almost exactly down the middle,
where it still pushes them apart.
Until recently, scientists had never visited the place
where this spreading occurred.
But now even the depths are giving up their secrets.
Alvin, the world's first deep-sea submersible,
led the way to this unexplored terrain.
MAN: Atlantis, Alvin.
The valve is open. The light is on.
The hatch is shut. Oxygen's on.
NARRATOR: One of the first regions visited
was the East Pacific Rise,
part of the spreading area called the mid-ocean ridge.
They expected to find evidence of the Earth at work.
What they actually discovered lay beyond imagination.
From this pioneering work,
scientists worldwide are able to study
the extraordinary geological systems
four miles beneath our feet.
Lindsay Parson heads a team
at the Southampton Oceanographic Centre.
These are really some of the most amazing images
that l think we have of the ocean floor.
They're taken from about 3,000 meters down.
They're in some of the deepest parts of the ocean floor.
And we're here looking at hydrothermal systems,
where bottom water of the sea
is being sucked into the ocean floor.
lt's being heated from there,
the heat engine inside the Earth.
And it's being delivered out into the ocean floor again
once it's dissolved
and leeched out minerals and chemical compounds
from the rock itself,
which is why the smokers, as we call them,
are black and densely colored here.
NARRATOR: The pressure
is an immense two tons per square inch.
Water is superheated to over 700 degrees.
lt's highly acidic,
full of hydrogen sulfide and heavy metals.
The equivalent volume of the world's oceans
is siphoned through the vent systems
every 30 million years.
Samples prove that the seafloor along the ridges
is the youngest on Earth, endlessly reborn.
But an even greater surprise lay in store.
Even in this harshest of terrain, life takes hold.
The black smokers are warm-water oases
around which familiar species --
shrimps, foot-long clams, and mussels --
thrive alongside more bizarre forms --
six-foot-long tube worms and strange fish.
PARSON: The majority of the life-forms here
depend not on light to maintain their existence.
They absorb and fix chemicals
from the hydrothermal vents to keep them alive.
They are chemosynthetic communities
rather than photosynthetic communities.
NARRATOR: Far from the sun and the air,
these creatures have evolved in a self-contained environment
separated from the rest of the biosphere.
They have managed to survive
the endless geological upheavals that wrack the world above them.
Maybe one day, long after we are gone,
they will inherit the earth.
of the seabed actually creating itself.
The hydrothermal systems lie along the mid-ocean ridge.
The mid-ocean ridge is the line
along which the tectonic plates move apart from one another,
allowing hot, molten rock from the interior of the Earth
to well up and to form new ocean floor --
the youngest part of the world as we know it.
NARRATOR: The mid-ocean ridge is the Earth's crust factory.
New molten magma endlessly emerges
to force the cold, older lava away from the ridges.
Enough lava is created each year
to bury New York over 100 feet deep.
And this unrelenting pressure
is like a wedge between the plate boundaries,
driving them and their continents
on their unstoppable journey.
Accurate mapping of the seafloor is now possible
and crucial to understanding the system on a grand scale.
By careful monitoring, scientists can calculate
just how fast the seafloor is spreading and the plates moving.
A sonar sledge is towed across the ocean bed.
lndividual snapshots are processed by computer
and a photomontage created.
That information is turned into three-dimensional maps.
What emerges is that the seafloor
is full of great valleys and deep trenches,
and that here is the largest and tallest range
of volcanic mountains on Earth,
40,000 miles long, sometimes 5 miles high,
stretching around the globe like a seam on a baseball.
Oceanographic research is difficult.
But there is a country that might have been designed
as a geological laboratory --
the one place where the mid-Atlantic ridge
becomes exposed on land.
lceland.
The land here is being torn apart.
The rift shows exactly
where the plates carrying America and Europe
are being forced away from each other,
at about an inch per year.
And lceland is in the middle.
The land is continually reshaped through eruption and rifting.
The lava from the flows
forms vertical dikes and horizontal beds,
just as it does on the ocean floor.
Geysers and mud pools are evidence
of the heat and pressure just beneath the surface
continually seeking a way to escape.
lce and fire is a deadly mixture.
ln 1996, part of the mid-ocean ridge erupted under the ice cap.
lt rapidly melted its way through 300 feet of ice,
forming a deep gorge.
The meltwater raced away to fill a subglacial lake
until it could no longer be contained.
ln the catastrophic flood that followed,
10 square miles of land was drowned.
This time the damage was only to roads and bridges.
But in lceland, the earth is always menacing.
ln 1975, the Krafla volcanic eruptions began,
lasting nine years.
1 4 square miles of basalt spewed out,
in some places widening the land itself by 28 feet.
ln 1973, the town of Heimaey was almost overwhelmed
when the nearby volcano woke from a 5,000-year sleep.
Five months later, the lava and ash had destroyed 300 houses,
reshaped the harbor,
and added nearly a square mile of new land.
Living in a laboratory can be hard.
But if new land is continually being made
at the crust factory along the ridges,
why isn't the world itself constantly expanding?
The reason is subduction, the giant recycling process
that has been going on since the world began
and which causes most volcanoes and earthquakes.
Subduction zones are the graveyards
of the old, dense oceanic floor.
Where it collides with the lighter continental crust,
it's forced down.
lt pulls the rest of the plate with it,
to be melted in the ferocious furnace of the inner earth.
The plates don't die peacefully. They go with a bang.
The old ocean floor carries water into the mantle,
which mixes with the magma.
When the pressure can no longer be contained,
it explodes in that most awesome of natural events,
a volcanic eruption.
Most of the world's volcanoes are in subduction zones,
but there are exceptions.
Kilauea is on the Big lsland of Hawaii,
part of a chain of islands in the middle of the Pacific Ocean,
thousands of miles away from any subduction zone.
But the whole chain is formed entirely from volcanoes
whose rivers of fire heave and bubble
at temperatures of 2,000 degrees.
What provides the furnace for all this outpouring
if it's not the crashing of the tectonic plates?
The volcanologists have an explanation.
The lava that's flowing and spattering behind me
is the surface manifestation of a thermal anomaly,
or a hot spot,
that's deep within the earth beneath my feet.
Where we are now --
on Kilauea Volcano on the Big lsland of Hawaii --
is at the southeast end of a 6,000-kilometer-long chain
of seamounts and volcanic islands that have formed
as the Pacific plate has moved north and westward
over the last 80 million years or so
at a rate of around 9 or 10 centimeters per year.
So as the plate moves over this hot spot,
you burn through the lithosphere,
forming a volcanic island.
And then the plate moves on,
and a new island forms further to the southeast.
NARRATOR: The hot spot has made Kilauea
the tallest mountain in the world --
30,000 feet from its base on the seafloor.
Taller even than Everest.
lt's also one of the most studied.
But scientists can't always wait for the lava to come to them.
They must catch it as it bursts through the crust.
Carl Thornber often goes fishing with a cable in a red-hot pond.
And sometimes he has to get even closer.
lt's extremely dangerous.
At any moment, the lava may spurt out unexpectedly,
leaving Thornber with nowhere to run.
Behind me is a perched lava pond
that's being fed from a vent off to my left.
You can see that there's lava spattering
and overflowing on its edges.
l'm gonna attempt to scoop a sample of molten lava --
hopefully with a hammer
so l won't have to use a long cable to throw it in.
And it'll be extremely hot. We have to worry about gases.
And we have to worry about breakouts
near the edge of the pond.
So we'll see how it goes.
NARRATOR: Thornber is risking his life.
But unless scientists can learn how to forecast eruptions,
volcanoes will continue to be an uncontrollable threat.
THORNBER: Okay, we'll take this sample
back to the USGS observatory,
and we'll prepare it for chemical analysis.
The chemistry of Hawaiian basalts is unique
compared to volcanic deposits near subduction zones
or near mid-ocean ridges.
And that will be reflected in the chemistry that we see.
More importantly,
we're looking at very subtle variations in chemistry
that can be correlated
with the eruptive history of this volcano.
So it will allow us to predict what may happen next.
NARRATOR: High on Maui, the next island in the chain,
NASA scientists at the satellite laser ranging station
are preparing for a long night's work.
They're setting up to fire a laser beam
at a satellite target orbiting the Earth.
The information they gain will tell them, to the inch,
how fast the island, and the Pacific plate on which it rests,
are moving across the ocean.
They have to time the firing exactly
to be sure that no planes are passing.
The laser beam would blind any pilot
who might look at it directly.
MAN ON RADlO: Okay, we're at 227 Azimuth.
18 degrees ''L.''
This is starlit. Culmination's at 7 4 degrees.
We're rotating clockwise.
Okay, you'll be clear to fire.
We're at 21 . Going down.
NARRATOR: The laser beam flashes out and bounces back,
pinpointing their location.
22 years of calculations confirm that Maui and the Pacific plate
are moving northwest at the rate of 2 1/2 inches a year --
amazingly fast.
This is the absolute proof
that the surface of our planet is in constant motion.
Tectonic theory says that the volcanoes of the Hawaiian chain
should get progressively older and become more eroded
the further they travel from the hot spot.
And they do.
One day, the raging fires of Kilauea
will be as silent and cold as these dead cones.
But the heir to them all is already emerging.
As one island dies, a new one is formed.
THORNBER: The hot spot is currently moving,
or manifesting itself, at Lo'ihi,
which is a submarine seamount
to the south of the Big lsland of Hawaii
and still more than 3,000 feet
beneath the surface of the ocean.
lt may be another 100,000 years before we see Lo'ihi surface.
NARRATOR: At the same time,
the hot spot is causing destruction elsewhere,
the pressure of the continual input of magma from below
is bulldozing open this great crack
which stretches across the length of the island.
lt is more than 80 feet deep,
and it's splitting away at three inches a year.
Eventually, the whole side of the mountain will fail
and collapse into the sea.
lt will send a giant wave racing away to the Pacific Rim,
to reach the west coast of the Americas in a few hours,
causing massive destruction.
We can't predict or prevent these catastrophes.
The geological truce
between ourselves and our restless planet
may be coming to an end.
Cataclysms may have caused extinctions and disasters,
but they have also shaped the Earth
and produced an environment
in which human life could flourish --
the air breathable, the seas are warm,
climate mild, the ice rooted firmly at the poles.
ln fact, a geological truce.
But that truce may be coming to an end.
The forces that drive the Earth are impervious to our needs.
With man so widely spread across the planet,
cataclysms of nature will turn into human catastrophes.
Every movement of the plates
brings the danger of disaster nearer.
50 million years ago,
the Asian and lndian plates were about to clash.
Separated by a dying ocean,
they collided with fantastic force.
Neither would give way,
and the land had only one way to go -- up.
This is the world's highest mountain range, the Himalayas.
This entire area was uplifted from sea level
to over five miles high in less than 30 million years.
How do the scientists know? From the evidence of the rocks.
There's dramatic evidence for this uplift
right in the face of Everest, in Lhotse.
The famous yellow band that you can see cutting across
is actually a marine limestone.
lt was formed in the bottom of the ocean.
NARRATOR: So 50 million years ago,
the tops of these mountains were at the bottom of the sea.
lt's hard to believe.
We have similar evidence from Tibet,
Where we find things like this --
ammonite fossils of marine creatures
that now are more than 4,000 meters above sea level.
Certainly these tell us
that plate tectonics supplies enough force
to lift things from the bottom of the ocean
all the way to here, the top of the world.
NARRATOR: This is the only place
where two continental plates are colliding on such a scale.
And the mountains are still growing
as a result of the tectonic squeeze.
Even Everest is still stretching skywards.
BENDlCK: l can't quite feel it
just standing here on a piece of Himalayan rock --
The earth that l'm standing on
is actually moving up at about 10 millimeters a year
and is moving to the north at an even faster rate than that,
maybe 15 millimeters a year.
The reason why we can measure this
is because of these fantastic receivers.
They use four satellites up in the sky above me
to solve a simple triangulation problem.
But they're so accurate that they can give me something like
one millimeter of accuracy in the horizontal
and more like five millimeters in the vertical.
That way, l can come back year after year,
we can see that this point, drilled into this rock --
that's attached somehow to the root of these mountains
and the continental plate that they're stuck to -- is moving.
NARRATOR: There is another way
that Rebecca Bendick and her colleagues
can discover exactly how the Himalayas are growing.
They have found an area in the foothills,
10 miles south of the highest peaks,
that is rising even faster than the mountains.
The clues to the uplift are found in the fast-flowing rivers
that tumble through these valleys.
BENDlCK: You can think of this river in two different ways.
One is that this land is still and the river is cutting down.
The other way -- and, l think, a better way to think about it --
is that the river is staying at sort of a constant position
with respect to the sea, way off in the Bay of Bengal,
and the earth around it is rising up.
So in order for the river to stay in one place,
it needs to cut down, like a knife through butter.
NARRATOR: But in some places,
the river cannot cut quickly enough
to maintain its natural equilibrium.
Here, the land rises faster than the river erodes it down,
and a giant step is formed, creating white water and rapids.
BENDlCK: We're looking for places where the river is
a lot steeper than its average gradient
anywhere along a stretch.
Those steeper places are corresponding
to places where the uplift is quick --
so quick that the river can't keep up.
This will give us clues about places to come back
and do more intensive GPS research
to try to pin down the uplift rate.
NARRATOR: lt seems this area is continuing to rise
faster than the high peaks.
One day this riverbed will be taller than Everest.
BENDlCK: Taking data in this way is dangerous.
But with a little bit of care,
it's definitely worth the good information
that we get about the Earth.
NARRATOR: That information is vital
for the 100 million people
living in the danger zone around the Himalayas.
Earthquakes are common.
30,000 people have been killed in the last century alone.
This area has been quiet for 700 years,
and a major quake is long overdue.
Rebecca Bendick's monitoring shows that the convergence
of lndia and China at two inches a year
is setting up immense stresses
which must eventually be released.
A solar-powered GPS station
will send back information 24 hours a day,
hopefully giving an early warning.
BENDlCK: The crux of the matter is
that we need to know how that total convergence
is partitioned over the faults.
lf all 60 millimeters of convergence
has to be accommodated in one place on one fault --
on this one narrow line --
then the earthquakes we have there are gonna be big,
and they're gonna happen often.
But if instead all of that strain
is accommodated on several different faults,
something like an accordion,
then each fault can only be expected to fail
less frequently and less violently.
NARRATOR: Earthquakes are appallingly destructive
to human life.
But for scientists, they have their uses.
The seismic waves are like sonar.
By listening as they pass through the earth,
a picture can be built up of a place no one will ever see.
First, the waves race through the crust --
the skin on the planet's surface.
ln some places, only four miles separate us
from the intolerable heat of the mantle
and interior of the Earth.
3,000 miles down, in the core itself,
the temperature reaches an unimaginable 7,000 degrees.
lt is the ultimate nuclear reactor,
the engine driving the planet.
Cooling comes by gigantic convection currents
in the mantle.
And it's that heat rising with the hot magma
that forces the tectonic plates to shift.
Earthquakes are a ferocious manifestation
of the power of the Earth's plates.
More than 1 1/2 million people have been killed by them
in this century alone.
Most quakes occur along fault lines,
where the plates grind together.
Scientists can't tell us
when this terrifying destruction is likely to occur.
They can only tell us why.
BlLHAM: You can't have an earthquake without a fault.
And l'm standing right now on what is perhaps
the most famous fault in the world, the San Andreas fault,
that extends from Mexico down south
way up to Oregon in the north.
This is one of the few places in the world
where you can stand with one foot on one tectonic plate
and one on another.
ln other words, this ground here
is attached to New York and lceland.
The ground here is attached to Hawaii and Japan.
NARRATOR: At this part of the fault, the plates are stuck.
They should be moving at two inches a year.
The last earthquake was 100 years ago,
and the fault is storing up the unreleased energy.
The longer the plates are stuck together,
the larger the ensuing tremor will be.
Further north, the plates are sliding
smoothly past each other.
The evidence is clear from the way this fence has buckled.
We're on the San Andreas fault, south of San Francisco.
And this is an interesting part of the fault zone
because the 1906 earthquake
ruptured through this field here,
across the road, and stopped about here.
But this fence was built after the earthquake.
ln other words, the fault has been sliding ever since then.
So, what's going on in here exactly?
And you can see here there are cracks in the road.
These have grown since l was last here.
All over the road here.
And l have a machine in the field,
and l am absolutely dying to see what it says.
Let's go have a look.
What we have in the field here is a creep meter.
A creep meter measures creep on the fault --
the creep that's caused the offset of this fence.
lt consists of a rod
that is attached firmly to that side of the fault,
passes through the fault into the box here.
lnside the box is a computer that's been measuring things.
Now, l have to be rather careful
because sometimes there are snakes here.
No, not this time.
Good.
What's left are black widows and ants.
All right.
So here is a computer that's been measuring for a year.
lt records the movement of the fault every minute,
to about a thousandth of an inch.
So let's download the data and have a look.
Ah. There we are.
Well, it looks as though we have had
about seven millimeters of creep,
like this site usually has.
But the interesting thing is,
it's all limited to a very short period of time.
lf you look here,
you can see the fault has been locked for most of the year.
But suddenly, in the middle of September, it takes off.
And it slips about five millimeters
in the space of a couple of hours.
And it continues to slip in the next few days.
ln other words, a whole year's budget of slip
occurs within the space of a few days.
That might not seem much -- five millimeters --
but it's affecting a long section of the fault,
maybe five miles long, involving millions of tons of rock.
Now, it really doesn't matter here.
This is a nice little field. There aren't any people.
But further north, this creep process
and the things that are happening beneath the earth
are far more sinister.
NARRATOR: San Francisco is home to 2 1/2 million people
and lies right on the Hayward fault.
ln its 200 years' history,
it's been hit by three killer quakes.
Scientists know the slippage on the fault
has begun to slow down -- a warning sign.
But when will it strike?
ln 1989, 67 people died in an earthquake
at Loma Prieta, part of San Francisco.
No one had foreseen it coming.
[ lndistinct shouting ]
BlLHAM: Earthquakes are an inevitable consequence
of the movement of plates.
We cannot stop plate motions.
And therefore we cannot stop earthquakes.
But we can begin to live with them.
And the first thing we must learn to do
is to build our cities better.
NARRATOR: As the world population grows,
so does the danger.
There are now more than 100 cities around the world
with population of over two million,
and more than half of those are on plate boundaries
or places where earthquakes have already struck.
Los Angeles is the most vulnerable
of all the places on the West Coast fault line.
This stretch of road shows why.
Not only is it on the San Andreas,
but here the fault has been forced around a bend.
Where this happens,
the rocks get compressed with enormous force.
They cannot go sideways, so they go up.
The movement curls the rocks, bends, folds, and crunches them,
faulting and distorting the land.
Many faults never surface,
although scientists know they're there.
Known as blind faults,
they're probably the most dangerous of all.
You come down the hills here until you hit the plains --
the flat area where 1 1 million people live --
and across there, far behind,
the tall buildings of downtown L.A. --
We think there's a fault right there,
right underneath the center of L.A.
[ Rumbling ]
NARRATOR: At 4:24 in the morning on the 1 7th of January 1994,
the suburb of Northridge was shaken to its foundations.
A blind fault had fractured 1 1 miles down,
causing some of the most intense ground-shaking ever recorded.
Ground acceleration exceeded gravity,
throwing buildings, furniture, and people into the air.
61 died. 9,000 were injured.
Buildings, roads, and bridges were destroyed.
Damages ran to $20 billion.
And the aftershocks went on for days.
BlLHAM: When it goes, like Northridge did,
seismic waves are spread all over the basin
as big ripples shaking all the buildings.
lt's exaggerated where the sediments
are concentrated in the basin here
because the basin's completely flat,
and it's flat because it's washed in there
from the mountains by water.
So we have saturated sediments.
NARRATOR: When the sand-and-water combination
is shaken together,
it turns liquid for five minutes after the shocks,
causing tall buildings to destabilize and fall.
lt's called liquefaction
and presents an enormous and unpredictable danger.
And there is another geological trap waiting to spring.
The San Gabriel Mountains
stretch from the San Andreas fault
down to the Los Angeles basin.
As the earthquakes crack and shudder along the faults,
they are being inched towards the city.
Here the fault is pink and the mountains in yellow.
This is how they have swung so far.
ln some distant geological future,
they will cover the city completely.
What does the geological future look like?
What clues are hidden
in the mountains, deserts, and seas?
lt's difficult to grasp
that the march of the Earth is unstoppable.
We've been very lucky because modern society
has actually developed at a time
when very little has been happening geologically.
So we've been in a period of geological quiescence.
Now, this isn't going to last.
We know that there are going to be major global catastrophes
occur in the future --
a gigantic tsunami, big volcanic eruptions, more impact events.
And on that basis, we know that we're all living on this planet
simply by geological consent.
NARRATOR: lce is crucial in helping
to keep the Earth's climate mild enough for life to survive.
But worldwide, the temperature is rising
and the ice is melting.
lf this keeps happening, sea levels will rise.
A rise of only 15 inches would spell catastrophe
for low-lying countries and low-lying cities.
McGUlRE: Major sea-level rise in itself
may be catastrophic for the planet,
but actually there are unexpected effects as well,
and that is that rising sea levels
may trigger volcanic eruptions.
We know this because we've been looking at the relationship
between changing sea levels and volcanic eruptions
in the lce Age,
when we had changes of 100 or 200 meters in sea level
over a few tens of thousands of years.
NARRATOR: McGuire's new work on Etna seems to show
that the more rapidly sea level rises or falls,
the more violently the volcano tends to explode.
McGUlRE: When sea levels rise
around coastal volcanoes such as Etna,
they have a rather interesting effect.
lf you imagine the volcano sitting on a plate,
with Etna here,
if you then load the other half of the plate
by a sea-level change of 100 meters or so,
it has the effect of bending it.
And what that does is set up tensional stresses
within the volcano.
And any magma sitting there
will burst its way out in the form of an explosive eruption.
NARRATOR: ln modern times, we haven't really experienced
the full terror of a volcanic catastrophe.
lf Bill McGuire's theory is right,
such an event could hurry in the new lce Age
because nature can wield a two-edged sword.
Rising sea levels could cause volcanoes to erupt,
spewing debris and sulfur into the atmosphere.
That will cut out the heat from the sun
so the Earth will cool.
That will make the ice form again,
freezing the oceans so sea levels drop once more.
And that sudden fall may trigger more volcanic activity,
pumping more material into the atmosphere,
making the Earth even colder,
ushering in the dark and the ice and the long winter.
There is evidence for many ice ages during Earth's history.
But the last full and most severe one
began 45 million years ago,
just as the Himalayas were being formed.
One theory attributes the dramatic cooling
to this tectonic turmoil.
The mountains are littered with limestone rocks and rubble.
This debris would combine with rain
and carbon dioxide in the air in a chemical reaction
which removed millions of tons of the gas from the atmosphere.
With less greenhouse gas to keep it warm,
the entire planet would cool, triggering the ice age.
At the edge of the vast ice sheets,
immense glaciers advanced relentlessly.
Nothing could resist
as they raced forward at speeds of up to 10 feet per day.
The ice covered more land,
so more of the sun's heat was reflected back into space,
chilling the planet further.
At its coldest,
Earth was covered by three times the volume of ice
on the planet today.
This ice locked the water away, trapping it on the land.
With less available water,
the world's sea level dropped by 425 feet.
Today the Caribbean island of Grand Bahama
holds the clearest clues
to the dramatic change in past sea levels.
Microbiologist Steffi Schwabe
has been piecing the story together.
Hidden deep in a mosquito-ridden mangrove swamp
is an unlikely entrance to a mysterious ancient world.
SCHWABE: These caves have a story to tell
concerning past sea-level fluctuation
and past interglacial and glacial periods.
What makes these caves particularly exciting
is that they are one of the last unexplored frontiers,
and they turned out to be
one of the world's largest and longest known cave systems.
We move from the entrance into a very large cathedral room,
where we can see the ceiling comes up
to what we commonly call these cave systems,
which is a blue hole.
You always find,
when you go into these large cathedral rooms,
a very large rock pile in the center.
And usually the collapse happens
when the water is no longer in the cave supporting the ceiling.
l'm now swimming through what is called a mixing zone.
This is where the freshwater mixes with the seawater
and causes what we call a shimmer.
This mixing zone
is responsible for aggressively attacking the wall rock.
lt's like soft cheese.
Normally, limestone could not be removed with your finger.
You would need a rock hammer and a chisel.
This is how we know that the caves have formed
hundreds of thousands of years ago.
But we also know by evidence that we have found
that the caves have been dry in the past.
20 meters down further into the cave system
are these bat droppings that have been fossilized.
And we know the only way that this can happen
is when the caves are dry, because bats do not swim.
And when bats roost in the ceiling,
the droppings collect on the rock,
and they become very hard.
Deeper into the cave system, we find another bit of evidence,
and that is this red Saharan dust,
which gets blown into the stratosphere
during frequent storms which occur in the Sahara Desert
and will actually find its way into these caves.
Most likely it's happened during periods when the cave was dry.
The final bit of evidence
which supports the fact that the caves have been dry
are these beautiful stalactite and stalagmite gardens
that we find at 28 meters-plus.
Stalactites and stalagmites form during the ice ages
and have formed over a period of hundreds and thousands of years.
What happens is
the water is frozen in the ice caps on the poles,
sea level drops, and the caves become dry.
And usually during ice ages it rains a great deal more
in the tropical regions of the world.
This rainwater percolates
through the bedrock, or the ceiling rock,
and dissolves the rock that's there,
and it comes out in the drip water and crystallizes,
just like an icicle.
And basically these are rock icicles.
NARRATOR: The ice ages affected and shaped the landscapes.
But sometimes the clues are so gigantic,
it's hard to recognize them.
ln Washington state in the Grand Coulee Canyon
are the channeled scablands.
For years, a succession of scientists tried to work out
what could have caused erosion on this scale.
USGS scientist Richard Waitt is the latest investigator.
WAlTT: This rock, the size of a three-story house,
looks like it's part of the bedrock,
part of this basalt that forms this vast landscape.
But the structure in the basalt is horizontal, as you can see,
whereas the structure in this rock is vertical.
ln other words, this big rock has been moved.
But the biggest clue in the landscape
is the landscape itself.
This gorge is carved in basalt,
one of the hardest of rocks.
lt ends in a sheer cliff 400 feet high,
and it's in the shape of an enormous horseshoe.
lt's like the gorge below Niagara Falls.
But this, Dry Falls,
is fully two Niagaras high and three wide.
NARRATOR: Waitt is continuing the work
begun by geologist J. Harlen Bretz in 1923.
Bretz was the first to say that this entire landscape
was a gigantic riverbed formed by 3,000 square miles
of the Columbia Plateau being swept away.
No one believed him because the scale was so huge.
But he was certain that the only explanation
for this scale of damage was an enormous flood.
The whole are was obliterated and changed forever
as the torrent flooded through.
Even on the top of the cliffs,
the water was over 100 feet deep.
The basalt cliffs
are amongst the hardest structures found in nature.
Resistant to weathering and erosion,
these walls could only have been cut
by an enormous body of water.
One by one, these columns of frozen lava
were quarried from the rock face
and carried away by the raging torrent,
causing the wall to retreat and the cataract to widen.
So it was accepted
that this is how the channeled scablands were shaped.
But an important part of the mystery remained --
just where could all that
colossal, earth-shattering volume of water have come from?
WAlTT: 100 miles to the east,
geologist Joseph T. Pardee had described
an enormous lce Age lake -- Glacial Lake Missoula.
This lake held in some 600 cubic miles of water.
600 cubic miles is all of present-day Lake Erie
plus all Lake Ontario.
The lake was held in by an ice dam
that had crossed the Clark Fork River and dammed it.
The lake rose 2,000 feet deep against the side of the ice dam.
But there was no evidence to link the lake
with the channeled scabland.
ln 1939, Pardee discovered a series of giant ripples.
These are like sand ripples on the beach,
but they are of enormous size.
Hundreds of feet apart. 10 feet high and more.
And they're composed of gravel.
Such a feature could only indicate a swift outflow
from Glacial Lake Missoula.
NARRATOR: The gigantic ice dam held back the water
until it reached a critical level.
When it was 1 ,800 feet deep,
the pressure of the water was so immense
that it forced its way through the base of the ice dam.
Having found a weakness, the icy waters raced on,
widening the split
and weakening the dam catastrophically.
The waters of the entire lake
were released in a devastating discharge.
WAlTT: This discharge was 10 times the flow
of all the world's rivers.
That's almost beyond belief.
NARRATOR: ln 1926, a freak flood created a 100-foot-deep canyon
200 miles away in the Walla Walla Valley.
lt revealed many layers of silt.
Waitt realized that this area
must have been in the path of the great floodwaters
that formed the channeled scablands.
WAlTT: This white layer here
is an ash that we know is from Mount St. Helens.
We've analyzed it chemically, mineralogically,
and it clearly came from Mount St. Helens.
And we know its date.
By radiocarbon dating,
we know that this is 15,000 years old approximately.
Therefore, we have a beautiful time line
running through this section of 15,000 years.
NARRATOR: The ash could only have fallen
after the flood had passed and the sediment settled,
yet it's covered by many layers of sediments -- 39 in all.
This was the final piece of evidence
that explained the creation of the scablands --
The catastrophic outburst flood
must have happened time and again.
Once each flood had left its mark,
the vast glacial dam would advance
and the waters of Lake Missoula would start to rise again,
continuing the cycle of flood followed by calm.
Only when the time of the ice was over did the floods stop.
The change from ice age to warmer times
is governed by how close the Earth is to the sun.
Every 100,000 years,
the shape of the Earth's orbit around the sun changes.
This has led some scientists to wonder if the recurring cycle
of catastrophe and extinctions on our planet
is governed by extraterrestrial forces.
Mass extinctions and the catastrophes that cause them
seem to follow a periodicity of about 30 million years.
lt's that cycle that suggests that the cause of a catastrophe
lies outside the Earth.
On a clear night here in Africa
or in other places where you can see the night sky,
we can see astronomical evidence
for the cause of these geological catastrophes
every 30 million years.
Our solar system is on a voyage
through the disc-shaped Milky Way Galaxy.
Every 30 million years,
we pass through the densest part of the galactic disc.
During that time, the comets of our solar system
can become disturbed and fall inward toward the inner planets.
During this period, the Earth is more likely to be impacted.
This cycle may explain
the catastrophic history of the Earth.
The last major mass extinction was 35 million years ago.
We're in the densest part of the galactic disc now,
and the next mass extinction may include us.
NARRATOR: Asteroids are a very real threat.
They even formed our own moon.
Soon after its violent beginning,
our planet suffered a ferocious assault.
A rogue asteroid bigger than Mars
smashed into it with enough power
to blast much of the Earth's surface into space.
The debris was drawn together by gravitational forces
and formed a proto-lunar disc.
From that, the new moon grew rapidly,
sweeping up the debris in orbit around the Earth.
Computer models suggest it only took a year
for the fragments in orbit to coalesce and form a single moon.
This is the Clark telescope at the Lowell Observatory
in Flagstaff, Arizona.
lt's the telescope that was used to take pictures of the moon
in preparation for the Apollo moon landings.
To see the moon tonight,
we need the telescope up in this position.
We can make some fine adjustments.
The density of the craters on the moon's surface was measured
using the photographs taken by the Clark telescope.
What's more, the astronauts visited some of these regions
in their six Apollo missions.
YOUNG: Man, does this thing have steep walls.
DUKE: They said 60 degrees.
YOUNG: Now, l tell you, l can't see to the bottom of it,
and l'm as close to the edge as l'm gonna get.
DUKE: [ Laughs ]
YOUNG: That's the truth.
lRWlN: l can't believe we came over those mountains.
RAMPlNO: The largest impact feature on the moon,
the lmbrium basin, is more than 1 ,000 kilometers across
and was produced by the impact of a comet or asteroid
more than 100 kilometers across.
SCOTT: Yeah, those are pretty big mountains
to fly over, aren't they?
RAMPlNO: The basin is surrounded by mountains
more than five miles high.
This is where the Apollo 15 astronauts
landed and took samples.
They show that these mountains
are not like the mountains on the Earth,
but they're piles of rubble, fragmented rock,
thrown out by this giant impact.
SCOTT: Look at that. Guess what we just found.
l think we found what we came for.
lRWlN: Crystalline rock, huh?
SCOTT: Yes, sir. You better believe it.
RAMPlNO: The pristine moon rocks
that were brought back by the Apollo astronauts
have been radiometrically dated and studied,
and they show that impact has been an important process
in the formation and evolution of the Earthlike planets.
What's more, the radiometric dating of the rocks
has shown that the moon underwent a hellish bombardment
between 4.5 and 4 billion years ago.
After that time, the bombardment died down.
By that time,
most of the asteroids moving around in the inner solar system
had collided with the planets,
and the process of the formation of the planets was over.
NARRATOR: 200 space rocks
large enough to cause global devastation
are known to be on Earth-crossing orbits,
and there may be many more.
RAMPlNO: Here in Namibia,
meteorites have always been considered special objects
worthy of veneration.
These meteorites have been put on display
as the centerpiece of the city.
The impact of small iron meteorites like this
would have little effect on the Earth as a whole.
But the impact of a much larger object --
a six-mile-diameter asteroid or comet --
would cause a mass extinction,
as we know from the geological record.
The impact of a quarter-mile diameter object,
like the one that just missed the Earth in 1996,
would cause widespread destruction.
A hit in the ocean would cause tsunami
that would devastate coastal cities.
And a hit on land would produce a dust veil
that would produce nuclear-winterlike conditions
that would threaten civilization as a whole.
NARRATOR: The geological record
shows impacts brought catastrophe and devastation
which wiped out many species.
There have been five key mass extinctions in Earth's history.
Best known are the dinosaurs.
Why did they simply disappear from the face of the Earth?
lndia may provide the answer.
65 million years ago,
it was still an island drifting towards Asia.
This was when the layered landscapes
of the Deccan Traps were created.
A great volcanic rift
spewed out half a million square miles of lava.
Layer after layer of lava lies on the land,
in places up to 8,000 feet thick.
Some scientists believe that the scale of this volcanic activity
was so great it killed off the dinosaurs.
Professor Michael Rampino thinks the traps were triggered
by an extraterrestrial visitor.
This is the Hoba iron meteorite in Namibia.
lt's the largest meteorite known on Earth.
And like most meteorites,
it contains the rare element iridium.
And iridium has proven to be the clue, the connection,
between the impact event and the extinction of the dinosaurs.
NARRATOR: lridium is found near impact craters
but is extremely rare elsewhere in the Earth's crust.
At these craters, the levels of iridium
are 10,000 times higher than normal.
Such high concentrations have been found
in the sedimentary record all over the world
at a consistent date of 65 million years ago.
Recently, a crater more than 1 10 miles wide
was detected off the coast of Mexico's Yucatán Peninsula.
lt, too, was created 65 million years ago.
lt was formed by a 10-mile-wide cosmic killer
which closed on Earth at more than 60,000 miles an hour.
lt struck with the violence
of the world's entire nuclear arsenal
exploding 1 ,000 times over.
lt sent out a ferocious fireball,
engulfing the land for thousands of miles around.
Enormous fires raged for months,
destroying everything in their path.
The impact may have had other catastrophic effects as well.
The force was so great
that shock waves went out from the point of impact in Mexico
around the world and focused and concentrated
at the exact opposite point of the Earth
in the lndian Ocean.
NARRATOR: The exact opposite point in those days
was the island of lndia.
And Rampino believes the violent volcanic eruptions
which created the Deccan Traps was triggered by the meteorite.
The effects of the impact explosion and the volcanic flood
poured millions of tons of dust and ash into the air,
plunging the world into darkness.
Nitrogen, sulfur, and oxygen in the atmosphere
combined to form acid rain as the Earth cooled.
ln this cosmic winter,
75% of all living things perished.
When the skies cleared, the dinosaurs had gone.
Human time span is so short,
it's hard to understand that we will be undone by forces
that play out over millions of years.
ln Utah, the shells of countless millions of marine creatures
which lived and died here
have been exposed where the San Juan River
creates a great tear in the Earth's crust.
The river has revealed a lost world.
200 million years ago,
the shallow seas once lapped the shores
of the giant supercontinent Pangaea,
which stretched unbroken from pole to pole.
50 million years ago,
this entire region underwent a cataclysmic change.
Erosion began relentlessly stripping away
layer upon layer of rock.
The tectonic forces
which squeezed, compressed, and lifted the land
were locked in an endless battle with erosional forces,
carving fantastic landscapes.
Water is the strongest force of all.
lt cuts through solid rock to create deep canyons.
With terrible patience,
it will scour away the stone and shape the rocks.
One day, in an unimaginably distant future,
Antelope Slot Canyon will be as wide and as deep
as the Grand Canyon itself.
The thousand-foot-high sandstone pillars, buttes, and mesas
that rise above the plains
are the memorials to millions of years of the geological battle.
But they, too, will disappear.
Nothing can withstand erosion.
Sculpting the surface, gouging out the deepest ravines,
cutting down the tallest mountains,
nature finds its own equilibrium.
RAMPlNO: The small mining town of Kolmanskop,
abandoned just a few decades ago,
is already being invaded by the sand dunes.
Eventually it will be entirely covered.
lf we turn our back for one moment,
the geological cycle of erosion and deposition will take over.
NARRATOR: Professor Rampino knows
from his work in the Namibian desert
how the tectonic dance will end.
Scientists may argue about the short and medium term,
but the further ahead they look,
the clearer the vision becomes.
The sand in this dry riverbed in Namibia
is part of an endless cycle of erosion and deposition.
The sand is formed by erosion of granite outcroppings
and carried downstream by rivers to the coast
and picked up by ocean currents, moved along the Namibian shore
to form the long beaches of Namibia.
Some of the sand is blown inland to form dunes.
The sands can be consolidated into sandstone
and then be eroded again to form new sands,
part of a cycle from granite, to sand, to sandstone,
and back to sand again.
On a human time scale, not much happens.
But on a geological time scale,
all that we've done and all that we've made will be destroyed.
NARRATOR: So, at the end, Earth has no future.
Through millennia to come,
the unfamiliar continents will form and move on
as the plates continue their wanderings.
Rivers will change their courses,
oceans will empty and fill,
and mountains erode and rise again.
But our sun is aging.
ln five billion years, it will run out of energy.
As gravity tightens its grip, it will collapse on itself,
the temperature rising to 100 million degrees.
lt will expand uncontrollably,
engulfing Mars, Venus, and the Earth.
The seas will boil away, the atmosphere evaporate,
as Earth becomes a charred ember.
Then the sun will cease all nuclear fusion and die.
lt will be the end of our amazing Earth.