For over 4.5 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, Italy.
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.
In June 1995,
the volcano of Soufrire
burst into malignant life.
It 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 Soufrire 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.
It's exceptionally viscous.
And it just builds up
and up and up,
forming this big dome structure.
It'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.
Mark Davies can't just watch
from the safety
of the helicopter.
He must get as close as he can
to the flow.
It's incredibly dangerous.
At any moment,
and without warning,
the volcano might erupt again,
and he'd have
no chance of escaping.
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
6cm in 3 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.
It contains big, huge blocks
within it,
sometimes the size of houses.
It 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, I wouldn't want
to know, myself.
This is how Montserrat used to be
before the catastrophe--
an 8-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.
It, 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.
This is the operations center
for the volcano observatory.
It's monitoring
the whole of the volcano.
It'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.
And the greater the chance
of a violent eruption.
But the technique
is only a best guess.
It'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.
If the eruption stops tomorrow,
the dome is still up
on top of the volcano.
It's still unstable, and it will
still retain its heat.
And it might stay like that
for 5 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.
Montserrat's disaster
is caused by something
that happened
over 4 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.
Its 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.
It's a chondrite--
a type of stony meteorite--
and it's been wandering
around the solar system
for about 4,500 million years.
It's stuff like this
that the Earth is made of--
space junk glued together.
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.
It 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.
Internal 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.
It had an iron core
surrounded by molten rock.
On the surface,
a thin crust was developing.
It 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 9 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.
In 1963, this act of creation
could be seen by all.
Some 10 billion square feet
of lava
erupted off the coast of Iceland
to form the new island
of Surtsey.
It 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.
It'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 9 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.
In the Yukon province, the chief
scientist is Charlie 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.
To send shock waves
deep into the crust,
200 pounds of explosive
are buried in the ground.
We're digging 3 holes
for the geophones that we're
going to be putting in here
so that we can have
a 3-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.
10, 9,
8, 7,
6, 5,
4, 3,
2, 1.
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.
It 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.
It 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 3 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 Idaho Falls,
Princeton microbiologist
Tullis Onstott
is hoping to take a closer look
at their descendants.
Hey, thanks.
What I 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.
It contains gases
that are toxic to us.
And yet they still manage
to survive.
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.
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.
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.
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.
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?
In 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.
The impressive thing
about the place
is how red it is.
In 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.
Initially, 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.
After 2 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.
In a secret location
Buick discovered
are some of the world's
oldest and rarest fossils.
What I've done is step back
more than 3-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.
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 2.
It took 65 million years.
2 continents we know today
were shaped by another upheaval
that hit the remains of
the supercontinent in the south.
In 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.
Iguazu 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.
In 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.
In fact, in the waterfalls,
one can see
steps of the waterfalls
which shows the individual
lava flows in this pile.
Imagine 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 I need.
On the other side of the world,
across the Atlantic Ocean,
is the world's
most ancient desert.
It dominates most of
the southern African country
of Namibia.
I'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.
The Atlantic Ocean,
which now divides Africa
and South America,
owes its very existence
to this geological cataclysm
that tore Pangaea apart.
The supercontinent
looked like this,
made up of
the present-day continents
of Africa, South America, India,
Antarctica, and Australia.
The cracking started here
and split the continent
into the present-day continents
of South America and Africa.
In geological terms,
it happened incredibly fast.
The crack opened northward at
a speed of 2 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
5 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 2 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.
Atlantis, Alvin.
The valve is open.
The light is on.
The hatch is shut.
Oxygen's on.
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
4 miles beneath our feet.
Lindsay Parson heads a team
at the Southampton
Oceanographic Centre.
These are really
some of the most amazing images
that I 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.
It'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.
The pressure
is an immense
2 tons per square inch.
Water is superheated
to over 700 degrees.
It'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--
6-foot-long tube worms
and strange fish.
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.
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.
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.
Individual snapshots
are processed by computer
and a photomontage created.
That information is turned
into 3-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.
Iceland.
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 Iceland 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.
Ice and fire is a deadly mixture.
In 1996, part of the mid-ocean
ridge erupted under the ice cap.
It 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.
In the catastrophic flood
that followed,
10 square miles of land
was drowned.
This time the damage
was only to roads and bridges.
But in Iceland,
the earth is always menacing.
In 1975, the Krafla volcanic
eruptions began,
lasting 9 years.
14 square miles of basalt
spewed out,
in some places widening
the land itself by 28 feet.
In 1973, the town of Heimaey
was almost overwhelmed
when the nearby volcano
woke from a 5,000-year sleep.
5 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.
It 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 Island 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 Island 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 10cm 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.
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.
It'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.
It'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.
I'm gonna attempt to scoop
a sample of molten lava--
hopefully with a hammer
so I 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.
Thornber is risking his life.
But unless scientists can learn
how to forecast eruptions,
volcanoes will continue to be
an uncontrollable threat.
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.
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.
Okay, we're at 227 Azimuth.
18 degrees ''L''.
This is starlit.
Culmination's at 74 degrees.
We're rotating clockwise.
Okay, you'll be clear to fire.
We're at 21.
Going down.
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 2.5 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.
The hot spot is currently moving,
or manifesting itself,
at Lo'ihi,
which is a submarine seamount
to the south
of the Big Island of Hawaii
and still more than 3,000 feet
beneath the surface
of the ocean.
It may be another 100,000 years
before we see Lo'ihi surface.
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.
It is more than 80 feet deep,
and it's splitting away
at 3 inches a year.
Eventually, the whole side
of the mountain will fail
and collapse into the sea.
It 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.
In 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 Indian 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 5 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.
It was formed
in the bottom of the ocean.
So 50 million years ago,
the tops of these mountains
were at the bottom of the sea.
It'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.
This is the only place
where 2 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.
I can't quite feel it
just standing here on a piece
of Himalayan rock--
The earth that I'm standing on
is actually moving up
at about 10mm a year
and is moving to the north at
an even faster rate than that,
maybe 15mm a year.
The reason
why we can measure this
is because of these
fantastic receivers.
They use 4 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
1 mm of accuracy
in the horizontal
and more like 5 mm in the vertical.
That way, I 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.
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.
You can think of this river
in 2 different ways.
One is that this land is still
and the river is cutting down.
The other way-- and, I 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.
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.
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.
It seems this area is continuing
to rise faster than the high peaks.
One day this riverbed
will be taller than Everest.
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.
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 India and China
at 2 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.
The crux of the matter is
that we need to know
how that total convergence
is partitioned over the faults.
If all 60mm 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.
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.
In some places,
only 4 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.
It 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 1.5 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.
You can't have an earthquake
without a fault.
And I'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.
In other words, this ground here
is attached
to New York and Iceland.
The ground here is attached
to Hawaii and Japan.
At this part of the fault,
the plates are stuck.
They should be moving
at 2 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.
In 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 I was last here.
All over the road here.
And I have a machine
in the field,
and I 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.
It consists of a rod
that is attached firmly
to that side of the fault,
passes through the fault
into the box here.
Inside the box is a computer
that's been measuring things.
Now, I 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.
It records the movement
of the fault every minute,
to about 1/1,000
of an inch.
So let's download the data
and have a look.
There we are.
Well, it looks
as though we have had
about 7mm of creep,
like this site usually has.
But the interesting thing is,
it's all limited to
a very short period of time.
If 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 5mm
in the space of a couple of hours.
And it continues to slip
in the next few days.
In other words,
a whole year's budget of slip
occurs within the space
of a few days.
That might not seem much--
5mm--
but it's affecting
a long section of the fault,
maybe 5 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.
San Francisco is home
to 2.5 million people
and lies right on the Hayward fault.
In its 200 years' history,
it's been hit by 3 killer quakes.
Scientists know
the slippage on the fault
has begun to slow down--
a warning sign.
But when will it strike?
In 1989, 67 people died
in an earthquake
at Loma Prieta,
part of San Francisco.
No one had foreseen it coming.
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.
As the world population grows,
so does the danger.
There are now more than
100 cities around the world
with population of over 2 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
11 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.
At 4:24 in the morning
on the 17th of January 1994,
the suburb of Northridge
was shaken to its foundations.
A blind fault had fractured
11 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.
When it goes, like Northridge did,
seismic waves
are spread all over the basin
as big ripples
shaking all the buildings.
It'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.
When the sand-and-water
combination is shaken together,
it turns liquid for 5 minutes
after the shocks,
causing tall buildings
to destabilize and fall.
It'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.
In 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?
It'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.
Ice 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.
If this keeps happening,
sea levels will rise.
A rise of only 15 inches
would spell catastrophe
for low-lying countries
and low-lying cities.
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 Ice Age,
when we had changes of 100
or 200 meters in sea level
over a few tens of thousands
of years.
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.
When sea levels rise
around coastal volcanoes
such as Etna,
they have
a rather interesting effect.
If 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.
In modern times,
we haven't really experienced
the full terror
of a volcanic catastrophe.
If Bill McGuire's theory
is right,
such an event could hurry in
the new Ice Age
because nature can wield
a 2-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 3 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.
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.
I'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.
It'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.
The ice ages affected and
shaped the landscapes.
But sometimes the clues
are so gigantic,
it's hard to recognize them.
In 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.
This rock, the size of
a 3-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.
In 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.
It ends in a sheer cliff
400 feet high,
and it's in the shape
of an enormous horseshoe.
It's like the gorge below
Niagara Falls.
But this, Dry Falls,
is fully 2 Niagaras high and 3 wide.
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?
100 miles to the east,
geologist Joseph T. Pardee
had described
an enormous Ice 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.
In 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.
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.
This discharge was
10 times the flow
of all the world's rivers.
That's almost beyond belief.
In 1926, a freak flood created
a 100-foot-deep canyon
200 miles away
in the Walla Walla Valley.
It 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.
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.
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.
It'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.
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.
It'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 6 Apollo missions.
Man, does this thing
have steep walls.
They said 60 degrees.
Now, I tell you, I can't
see to the bottom of it,
and I'm as close to the edge
as I'm gonna get.
That's the truth.
I can't believe
we came over those mountains.
The largest impact feature
on the moon,
the Imbrium basin, is more
than 1,000 kilometers across
and was produced by the impact
of a comet or asteroid
more than 100 kilometers across.
Yeah, those are
pretty big mountains
to fly over, aren't they?
The basin is surrounded
by mountains
more than 5 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.
Look at that.
Guess what we just found.
I think we found
what we came for.
Crystalline rock, huh?
Yes, sir. You better believe it.
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.
200 space rocks
large enough
to cause global devastation
are known to be on
Earth-crossing orbits,
and there may be many more.
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 6-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-winter like conditions
that would threaten
civilization as a whole.
The geological record
shows impacts brought
catastrophe and devastation
which wiped out many species.
There have been 5 key mass
extinctions in Earth's history.
Best known are the dinosaurs.
Why did they simply disappear
from the face of the Earth?
India 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.
It'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.
Iridium 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 110 miles wide
was detected off the coast
of Mexico's Yucatn Peninsula.
It, too, was created
65 million years ago.
It was formed
by a 10-mile-wide cosmic killer
which closed on Earth at
more than 60,000 miles an hour.
It struck with the violence
of the world's entire
nuclear arsenal
exploding 1,000 times over.
It 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 Indian Ocean.
The exact opposite point
in those days
was the island of India.
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.
In 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.
In 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.
It 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.
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.
If we turn our back
for one moment,
the geological cycle of erosion
and deposition will take over.
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.
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.
In 5 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.
It 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.
It will be the end
of our amazing Earth.