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male narrator:
Planet Earth is unique,
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an immense ball of rock
25,000 miles around.
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lt is a refuge,
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00:00:18,018 --> 00:00:21,228
1/3 land, 2/3 water,
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and with an atmosphere
rich in oxygen,
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it is the only known home
in the universe
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for living creatures.
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But this blue-green oasis
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has not always been
so welcoming.
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The planet bears the scars
of a traumatic past,
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a past
of extreme environments
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and extreme catastrophes.
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Over the course
of nearly 5 billion years,
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it has been a changing world,
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a world of fire,
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a world of ice,
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one of raging seas
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and poisonous skies.
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The life-forms
that now cling to its surface
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are the lucky survivors
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of a succession
of deadly mass extinctions.
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Forjust over 200 years,
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determined scientists
have explored the planet
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and unearthed its secrets.
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Their remarkable discoveries
have led them to tell
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an incredible story,
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the story
of "How The Earth Was Made."
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For thousands of years,
humans had no knowledge
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of the true age and origin
of the world.
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Butjust over 200 years ago,
all this would change.
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Scotland,
the Edinburgh coast:
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it was here,
one day in 1 788,
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that the discovery
of a small rocky outcrop
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would completely rewrite
the history of the Earth.
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Geologist Geoffrey Boulton
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is on his way
to the desolate Siccar Point,
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where this discovery was made
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by a maverick Scottish farmer,
James Hutton.
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Hutton was to become the father
of modern geology.
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- Hutton was a man
who was enthusiastic
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in the pursuit of truth,
a very inquiring mind.
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When he took over
his father's farm,
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he saw, underneath the soils,
rocks
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and wondered what these were.
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narrator: Hutton spent years
obsessed with understanding
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how the rocks of the Earth
were made.
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His intrepid field expeditions
took him all over Scotland,
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and they led him to realize
that extremely slow processes
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could create the rocks he saw
from layers of sediment.
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- He rode miles and miles
on his horse
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to go places where he thought
he could find
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exciting geological experiences
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even though he suffered terribly
from saddle sores.
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narrator: Hutton concluded
that rocks could take
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hundreds of thousands of years
to form.
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But his claims were speculative,
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and his radical ideas
flew in the face
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of the accepted version
of Earth history,
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provided by the church.
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00:03:21,743 --> 00:03:23,952
For generations,
the Christian church
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had been the sole authority
on all creation,
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based on the book of Genesis.
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And using
the biblical genealogies,
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church leaders
were now confidently claiming
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they knew the exact age
of the Earth itself.
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- Archbishop Ussher
in the 1 7th century
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had calculated that the Earth
was 6,000 years old,
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and indeed, he calculated
that it was made
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on October the 14th
in the afternoon.
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narrator: Hutton was convinced
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that the Earth
had to be much older.
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And when his explorations
led him to Siccar Point in 1 788,
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he would finally find the proof
he was looking for
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in the unusual formation
he discovered.
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- These rocks
are notjust any old rocks.
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They're very special rocks,
and the reason they're special
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is because of the story Hutton
was able to tell from them.
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narrator: Here,
two layered rock formations
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stand at right angles
to each other.
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- He knew these rocks
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had once been laid down
horizontally on the seafloor.
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They must then have been buried
under great depth
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to recrystallize.
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They must then have been tilted
on end by great Earth forces.
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Then they were eroded away
and truncated.
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Then these rocks
were deposited on top.
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And he realized that that would
not take hundreds of years
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nor thousands of years
but many millions of years.
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narrator: Hutton's discovery
was a turning point.
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From that day forward,
it was rock, not scripture,
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that would become the trusted
guide to the distant past.
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And over the next two centuries,
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the study of rocks
around the globe
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would lead
to the awesome revelation
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that this blue-green planet
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has been on
the most astounding journey...
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Ajourney that began
in a world of fire.
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lt is now believed
that the Earth
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was formed from collisions
among the countless meteors
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that made up
the early solar system.
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Back then, the surface
was an ocean of molten rock
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miles deep.
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Temperatures exceeded
8,000 degrees Fahrenheit,
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similar to the surface
of the sun.
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And huge meteorites rained down
in a relentless bombardment.
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The man who first proposed this
hellish origin for the planet
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was the Victorian scientist
Lord Kelvin.
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A British expert
in thermodynamics,
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Kelvin believed that the Earth
was slowly cooling down.
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The fires
of the planet's interior,
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visible in volcanic eruptions,
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suggested to him that the planet
had once been completely molten.
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Kelvin used thermodynamics
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to calculate a new age
for the Earth.
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He reasoned
that the molten planet
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would need
nearly 20 million years
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to cool
to its present temperatures.
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Kelvin was correct
about the Earth being molten
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but not about its age.
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His figure
was a colossal underestimate.
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Like all
1 9th-century scientists,
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Kelvin was unaware
of a key source of heat
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inside the early Earth
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that prevented the planet
from cooling as he predicted:
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radioactivity.
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ln the early Earth,
radioactive particles
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of uranium, thorium,
and potassium
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were in huge abundance.
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The heat produced from the decay
of these particles
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would keep the Earth
extremely hot
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for an extremely long time.
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But although these particles
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confounded
Kelvin's calculations,
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they would eventually
prove the keys
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to unlocking the true age
of the Earth.
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ln the 20th century,
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rare particles
of surviving radioactive uranium
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were collected together
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to create the first
atomic weapons.
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00:08:02,982 --> 00:08:05,901
But scientists had earlier found
a different application,
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using the radioactive particles
to accurately date the planet.
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ln 1 91 1 , a gifted 21-year-old
geology student, Arthur Holmes,
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used radiation
to revolutionize
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our understanding
of Earth history.
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After Holmes,
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geologists would talk
in billions,
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not millions,
of years.
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Radiometric dating
was simple in principle.
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lt was based on the discovery
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that traces of the radioactive
element uranium,
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found throughout
the rocks of the Earth,
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decayed into another element,
lead.
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Like sand trickling
through an hourglass
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over hundreds
of millions of years
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and at a steady rate,
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a sample of radioactive uranium
will decay to lead.
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By measuring the proportion
of uranium to lead
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in crystals trapped
in ancient rocks,
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Holmes could accurately
calculate their ages.
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Collecting data from samples
from all over the world
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would be a lifetime's work.
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But as Holmes grew older,
so did the Earth.
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lts calculated age
extended first to 1 billion,
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then 3 billion,
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then finally
to 4.5 billion years.
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Today 4.5 billion years
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is still the accepted age
for the Earth.
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Time on this incredible scale
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is known to those
in the business
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as deep time.
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- lt's difficult to imagine
how vast deep time is.
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But think of it this way.
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That's a grain of sand.
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lf it represented a year,
then the length of my finger
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would be equivalent
to the whole of my lifetime.
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From the tip of my finger
to my elbow
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would take us back
to the pilgrim fathers.
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From here to the rocky island
you see on the horizon
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would take us back
to the age of the dinosaurs.
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And if we were to turn round
and go to the equator,
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then it would be equivalent
to going back
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to the beginning of the Earth
4 1/2 billion years ago.
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narrator: The search for the age
of the Earth was over,
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and the results had opened
a window on the past.
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For the first time,
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scientists could put rocks
in the correct order,
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look deep into the Earth's past,
and tell its story.
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They would discover evidence
of an epic journey
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with many twists and turns.
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But the most significant step
may well have been taken
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within just a few hundred
million years of its birth,
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when the planet
became a water world.
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4.5 billion years ago,
the Earth was formed
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from the collisions
of millions of meteors
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in the young solar system.
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Temperatures were so high
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that the planet's surface
was a molten ocean.
198
00:11:06,123 --> 00:11:10,001
But even at that time,
Earth was beginning to cool.
199
00:11:10,127 --> 00:11:12,337
The radioactivity
that provided much of the heat
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00:11:12,463 --> 00:11:14,714
was slowly declining,
paving the way
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for the planet's
first radical change,
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its transformation
into a water world.
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The Barberton Hills,
South Africa:
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00:11:29,397 --> 00:11:31,398
this remote region is home
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to some of the oldest rocks
on Earth.
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00:11:36,737 --> 00:11:38,988
South African geologist
Gary Stevens
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00:11:39,115 --> 00:11:40,532
is on the lookout for some
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of these incredibly rare
survivors
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from the first billion years
of Earth history
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00:11:45,913 --> 00:11:48,998
whose unique shape
tells a story.
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- This area
of South African geology,
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00:11:53,212 --> 00:11:56,005
here on the eastern side
of Mpumalanga, is critical
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00:11:56,132 --> 00:12:00,468
for our understanding
of early Earth processes.
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00:12:00,594 --> 00:12:02,804
narrator: Gradual erosion
along the trickling creek
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00:12:02,930 --> 00:12:06,516
can occasionally expose
these primordial rocks.
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00:12:06,642 --> 00:12:09,144
- Here we have
an interesting rock.
217
00:12:09,270 --> 00:12:10,979
The rounded shape
of this rock over here
218
00:12:11,105 --> 00:12:13,022
is very different
than the rounded shape
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00:12:13,149 --> 00:12:17,402
of the rest of the rocks
in this river.
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00:12:17,528 --> 00:12:18,570
This is one of these
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00:12:18,696 --> 00:12:22,115
3.5-billion-year-old
pillow lavas.
222
00:12:22,241 --> 00:12:24,284
The rounded pillow shape
in the rock
223
00:12:24,410 --> 00:12:26,286
is a result of the lava
224
00:12:26,412 --> 00:12:28,246
that formed underwater
in an ocean
225
00:12:28,372 --> 00:12:31,958
approximately
3 1/2 billion years ago.
226
00:12:32,084 --> 00:12:34,377
narrator: Pillow lavas
are created today
227
00:12:34,503 --> 00:12:36,212
off the coast of Hawaii,
228
00:12:36,338 --> 00:12:41,176
where volcanic vents
erupt into the Pacific Ocean.
229
00:12:41,302 --> 00:12:44,345
This unique pillow shape
is only formed
230
00:12:44,472 --> 00:12:49,058
when lava solidifies
under deep water.
231
00:12:49,185 --> 00:12:52,937
All rocks found from the period
3.5 billion years ago
232
00:12:53,063 --> 00:12:55,148
have been pillow lavas.
233
00:12:55,274 --> 00:12:58,151
By 1 billion years
into the planet's existence,
234
00:12:58,277 --> 00:12:59,778
water had taken over.
235
00:12:59,904 --> 00:13:02,655
But geologists believe
that it had already been around
236
00:13:02,782 --> 00:13:05,116
a long, long time.
237
00:13:08,078 --> 00:13:11,456
4.4 billion years ago,
238
00:13:11,582 --> 00:13:15,418
the Earth was around
1 00 million years old.
239
00:13:21,759 --> 00:13:24,135
Meteors still crashed
into the planet,
240
00:13:24,261 --> 00:13:28,181
but gradual cooling of the core
had allowed most of the surface
241
00:13:28,307 --> 00:13:33,561
to solidify into a crust
of dark volcanic rock.
242
00:13:38,067 --> 00:13:41,319
And even then,
at this early stage,
243
00:13:41,445 --> 00:13:46,324
water was forming
on the surface.
244
00:13:46,450 --> 00:13:49,702
No rocks now survive
from this most early period,
245
00:13:49,829 --> 00:13:53,331
but tiny crystals
of zircon do.
246
00:13:53,457 --> 00:13:56,209
Uranium-carrying zircon
is one of the crystals
247
00:13:56,335 --> 00:13:58,044
that helped date the Earth.
248
00:13:58,170 --> 00:14:00,088
But these crystals
can also retain
249
00:14:00,214 --> 00:14:03,216
the chemical fingerprints
of water molecules,
250
00:14:03,342 --> 00:14:04,676
and these fingerprints
251
00:14:04,802 --> 00:14:08,012
are all over
the most ancient zircons.
252
00:14:10,558 --> 00:14:13,017
But the origin of the majority
of the planet's water
253
00:14:13,143 --> 00:14:14,978
remains a mystery.
254
00:14:15,104 --> 00:14:17,730
As the planet cooled,
the surface rocks
255
00:14:17,857 --> 00:14:21,234
began spewing out
tons of carbon dioxide.
256
00:14:21,360 --> 00:14:22,402
Some water vapor
257
00:14:22,528 --> 00:14:25,113
would have been vented
during this process,
258
00:14:25,239 --> 00:14:27,323
but some believe
it would not have been enough
259
00:14:27,449 --> 00:14:29,242
to cover the surface.
260
00:14:29,368 --> 00:14:31,286
- The rocks,
the material that accreted
261
00:14:31,412 --> 00:14:32,579
to form the Earth itself,
262
00:14:32,705 --> 00:14:36,040
would have been too dry,
too close to the really hot sun.
263
00:14:36,166 --> 00:14:38,293
We have this problem
of trying to understand
264
00:14:38,419 --> 00:14:41,504
where our water world
got all of its water.
265
00:14:41,630 --> 00:14:44,591
narrator: lmpact expert
Dan Durda supports the theory
266
00:14:44,717 --> 00:14:47,468
that the source
of most of the Earth's water
267
00:14:47,595 --> 00:14:49,345
was extraterrestrial.
268
00:14:49,471 --> 00:14:51,264
- The idea today
is that the Earth's oceans
269
00:14:51,390 --> 00:14:53,266
arrived from above.
270
00:14:53,392 --> 00:14:54,726
They were brought in
271
00:14:54,852 --> 00:14:56,936
in the water-rich asteroids
and comets
272
00:14:57,062 --> 00:14:59,147
which peppered the Earth
during the tail-off
273
00:14:59,273 --> 00:15:01,608
in its accretionary process.
274
00:15:01,734 --> 00:15:04,777
What l have here is a piece
of an actual meteorite.
275
00:15:04,904 --> 00:15:06,029
This is the material
276
00:15:06,155 --> 00:15:07,655
from which
the Earth itself formed.
277
00:15:07,781 --> 00:15:09,115
This primitive
little meteorite
278
00:15:09,241 --> 00:15:11,492
contains about 5% of water.
279
00:15:11,619 --> 00:15:13,953
lt's that water,
in objects like this,
280
00:15:14,079 --> 00:15:16,915
that was delivered to the Earth
to form the Earth's oceans.
281
00:15:17,041 --> 00:15:18,958
narrator: Scientists
are divided on this,
282
00:15:19,084 --> 00:15:21,252
but wherever the water
came from,
283
00:15:21,378 --> 00:15:22,545
when it did arrive,
284
00:15:22,671 --> 00:15:25,840
it changed the planet
dramatically.
285
00:15:25,966 --> 00:15:28,176
As it evaporated
off the surface,
286
00:15:28,302 --> 00:15:32,221
huge amounts of water vapor
rose to join the carbon dioxide
287
00:15:32,348 --> 00:15:37,644
in the young atmosphere,
forming thick blanketing clouds.
288
00:15:43,776 --> 00:15:45,902
This condensing water
would trigger
289
00:15:46,028 --> 00:15:50,365
the greatest downpour
the Earth would ever see.
290
00:15:50,491 --> 00:15:54,160
[thunder booming]
291
00:15:54,286 --> 00:15:56,913
As thunderstorms
rocked the skies,
292
00:15:57,039 --> 00:16:01,668
the rain began to fall
on the rocky surface below,
293
00:16:01,794 --> 00:16:03,795
and it kept on falling.
294
00:16:03,921 --> 00:16:05,213
[thunder booming]
295
00:16:05,339 --> 00:16:09,884
lt would rain
for millions and millions
296
00:16:10,010 --> 00:16:12,345
and millions of years.
297
00:16:12,471 --> 00:16:16,808
The result would be
a water world.
298
00:16:20,813 --> 00:16:23,272
4 billion years ago,
299
00:16:23,399 --> 00:16:27,360
the Earth was now
1/2 billion years old.
300
00:16:31,365 --> 00:16:36,369
Over 90% of its surface
had become a vast ocean.
301
00:16:40,374 --> 00:16:44,460
Small volcanic islands
poked out from the waves.
302
00:16:46,839 --> 00:16:49,382
The monstrous seas
were iron-rich,
303
00:16:49,508 --> 00:16:52,135
making them
an olive green color.
304
00:16:52,261 --> 00:16:55,471
Carbon dioxide
filled the skies so thickly
305
00:16:55,597 --> 00:16:57,223
that they appeared red.
306
00:16:57,349 --> 00:17:00,226
The dense atmosphere
produced enough pressure
307
00:17:00,352 --> 00:17:03,813
to crush a human body flat.
308
00:17:07,484 --> 00:17:09,610
And it was hot.
309
00:17:09,737 --> 00:17:15,033
Temperatures exceeded
200 degrees Fahrenheit.
310
00:17:15,159 --> 00:17:18,578
This toxic, hostile water world
would remain
311
00:17:18,704 --> 00:17:21,748
for another 1/2 billion years.
312
00:17:21,874 --> 00:17:26,127
But dramatic transformations
were on their way.
313
00:17:26,253 --> 00:17:27,920
Renewed volcanic activity
314
00:17:28,047 --> 00:17:30,590
would trigger the construction
of the continents
315
00:17:30,716 --> 00:17:34,093
by creating
a totally new kind of rock.
316
00:17:34,219 --> 00:17:38,264
Earth was about to become
a granite planet.
317
00:17:41,518 --> 00:17:45,772
3.4 billion years ago,
318
00:17:45,898 --> 00:17:49,358
the Earth was just over
a billion years old.
319
00:17:52,237 --> 00:17:55,740
Huge green oceans dominated.
320
00:18:05,125 --> 00:18:07,126
None of the crumbling
volcanic islands
321
00:18:07,252 --> 00:18:08,628
dotting the surface
322
00:18:08,754 --> 00:18:11,798
survived the punishing seas
for long.
323
00:18:11,924 --> 00:18:14,842
But everything
was about to change.
324
00:18:14,968 --> 00:18:17,804
An upsurge
in undersea volcanic activity
325
00:18:17,930 --> 00:18:20,640
was about to create
a tougher type of rock
326
00:18:20,766 --> 00:18:24,102
and give birth
to the continents.
327
00:18:24,228 --> 00:18:26,187
ln remote areas of the globe,
328
00:18:26,313 --> 00:18:29,107
the primeval cores
of these first continents
329
00:18:29,233 --> 00:18:32,527
have been exposed.
330
00:18:32,653 --> 00:18:34,946
South Africa:
331
00:18:35,072 --> 00:18:37,156
geologist Gary Stevens
is climbing
332
00:18:37,282 --> 00:18:42,453
on some of the oldest
continental rock on Earth.
333
00:18:42,579 --> 00:18:45,164
These rocks are special.
334
00:18:45,290 --> 00:18:47,208
- We're standing here
on an ancient granite.
335
00:18:47,334 --> 00:18:49,335
This granite
forms the nucleus
336
00:18:49,461 --> 00:18:52,296
of one of the world's
oldest continents.
337
00:18:52,422 --> 00:18:53,756
And we can see it here
338
00:18:53,882 --> 00:18:56,175
in the Barberton area
in South Africa.
339
00:18:56,301 --> 00:18:58,219
narrator: These eroded
outcrops of rock
340
00:18:58,345 --> 00:18:59,428
are the visible peaks
341
00:18:59,555 --> 00:19:02,348
of what is known
as the Kaapvaal craton,
342
00:19:02,474 --> 00:19:04,976
a titanic mass
of ancient granite
343
00:19:05,102 --> 00:19:06,727
underlying southern Africa,
344
00:19:06,854 --> 00:19:09,355
a remnant of the early Earth.
345
00:19:09,481 --> 00:19:12,024
3.5 billion years ago,
346
00:19:12,151 --> 00:19:15,319
granite was appearing
everywhere.
347
00:19:15,445 --> 00:19:17,822
An upsurge of volcanism
had fractured
348
00:19:17,948 --> 00:19:21,409
the crust of the Earth
underneath the vast oceans,
349
00:19:21,535 --> 00:19:23,911
allowing water
to plunge into the cracks
350
00:19:24,037 --> 00:19:27,039
alongside the molten lavas.
351
00:19:27,166 --> 00:19:30,293
The mixture of superheated water
and basaltic lava
352
00:19:30,419 --> 00:19:33,754
produced the new rock,
granite.
353
00:19:33,881 --> 00:19:35,506
lt rose from the depths
354
00:19:35,632 --> 00:19:39,135
to form the first
true continental crust.
355
00:19:39,261 --> 00:19:41,387
- This is why granite
is special and important.
356
00:19:41,513 --> 00:19:42,889
lt's light.
357
00:19:43,015 --> 00:19:46,058
This rock, granitic rock,
has a much lower density
358
00:19:46,185 --> 00:19:48,519
than this rock,
a basaltic rock.
359
00:19:48,645 --> 00:19:51,147
The difference in density
between these two rocks
360
00:19:51,273 --> 00:19:53,191
is greater
than the difference in density
361
00:19:53,317 --> 00:19:54,859
between water and air.
362
00:19:54,985 --> 00:19:57,570
This rock would be typical
for oceanic crustal material.
363
00:19:57,696 --> 00:19:59,864
This is typical
of the continents.
364
00:19:59,990 --> 00:20:01,741
Continents are light
and buoyant,
365
00:20:01,867 --> 00:20:04,702
oceanic crust
denser and heavier.
366
00:20:04,828 --> 00:20:07,413
lt literally floats
on the mantle.
367
00:20:10,042 --> 00:20:11,876
narrator: Granite crust
was not only light.
368
00:20:12,002 --> 00:20:14,212
lt was tough,
369
00:20:14,338 --> 00:20:18,549
tough enough to withstand
the erosive power of the oceans.
370
00:20:24,181 --> 00:20:26,307
For the next
couple of billion years,
371
00:20:26,433 --> 00:20:27,642
slowly but surely,
372
00:20:27,768 --> 00:20:32,772
the granitoid
proto-continents grew larger.
373
00:20:32,898 --> 00:20:36,692
On different parts of the globe,
granite crust appeared
374
00:20:36,818 --> 00:20:38,653
that would one day form
the hearts
375
00:20:38,779 --> 00:20:41,781
of the major land masses.
376
00:20:41,907 --> 00:20:45,618
The dominance of the oceans
was over.
377
00:20:45,744 --> 00:20:48,621
The continents had arrived.
378
00:20:51,166 --> 00:20:53,876
The slow expansion
of the granite proto-continents
379
00:20:54,002 --> 00:20:57,505
was to change more than just
the appearance of the planet.
380
00:20:57,631 --> 00:20:59,090
The shallow coastlines
381
00:20:59,216 --> 00:21:01,300
would bring life
to the sunlit surface
382
00:21:01,426 --> 00:21:05,680
and help trigger
the production of oxygen.
383
00:21:05,806 --> 00:21:08,266
Almost since the arrival
of the first oceans,
384
00:21:08,392 --> 00:21:11,227
it is believed that primitive
single-celled life-forms
385
00:21:11,353 --> 00:21:13,771
had appeared
deep beneath the waves,
386
00:21:13,897 --> 00:21:17,900
living off the heat produced
by the subsea volcanic fissures.
387
00:21:18,026 --> 00:21:21,362
But now they were evolving
and spreading upwards.
388
00:21:21,488 --> 00:21:24,657
On the continental coasts,
an organism was appearing
389
00:21:24,783 --> 00:21:28,035
that was to transform
the planet:
390
00:21:28,161 --> 00:21:30,788
the stromatolite.
391
00:21:30,914 --> 00:21:34,000
The stromatolite
would live off sunlight,
392
00:21:34,126 --> 00:21:38,629
and it would fill the atmosphere
with oxygen.
393
00:21:40,215 --> 00:21:44,385
This primeval organism
can still be found today.
394
00:21:53,103 --> 00:21:55,354
Western Australia:
395
00:21:55,480 --> 00:21:58,190
Martin van Kranendonk
is over 1 00 miles
396
00:21:58,317 --> 00:21:59,692
from the nearest town,
397
00:21:59,818 --> 00:22:03,821
heading across the outback
to a remote beach.
398
00:22:03,947 --> 00:22:05,114
- We're going down this track
399
00:22:05,240 --> 00:22:07,033
to one of the most unique places
in the world,
400
00:22:07,159 --> 00:22:08,784
where you've got
living stromatolites
401
00:22:08,910 --> 00:22:12,663
on the shoreline
here at Shark Bay.
402
00:22:12,789 --> 00:22:15,583
narrator: On the narrow,
sandy coast of Shark Bay,
403
00:22:15,709 --> 00:22:20,463
a multitude of stromatolites
fill the tidal shallows.
404
00:22:23,592 --> 00:22:26,010
Each of these unusual
rocky mounds
405
00:22:26,136 --> 00:22:31,515
are up to one foot across
and two feet high.
406
00:22:31,641 --> 00:22:33,893
lt was only in the 1 950s
407
00:22:34,019 --> 00:22:37,772
that the importance of Shark Bay
was realized.
408
00:22:37,898 --> 00:22:40,232
Following trips
to this remote site,
409
00:22:40,359 --> 00:22:42,568
Australian geologist
Phillip Playford
410
00:22:42,694 --> 00:22:46,447
was the first to discover
how stromatolites formed.
411
00:22:46,573 --> 00:22:49,450
Playford identified
a rare bacterial algae
412
00:22:49,576 --> 00:22:52,495
found in a slimy film
coating their surface
413
00:22:52,621 --> 00:22:55,998
as the creator
of the mounds themselves.
414
00:22:56,124 --> 00:22:57,833
- Stromatolites
are made up
415
00:22:57,959 --> 00:23:00,878
of very thin layers
of microorganisms
416
00:23:01,004 --> 00:23:04,423
that build up slowly,
layer by layer,
417
00:23:04,549 --> 00:23:05,841
year by year,
418
00:23:05,967 --> 00:23:08,636
as they use light energy
to gain their food,
419
00:23:08,762 --> 00:23:11,972
and as a waste product,
they precipitate rock.
420
00:23:12,099 --> 00:23:14,600
narrator: Other geologists
recognized the significance
421
00:23:14,726 --> 00:23:16,352
of Playford's findings.
422
00:23:16,478 --> 00:23:19,063
Patterns they had seen
in rocks billions of years old
423
00:23:19,189 --> 00:23:22,108
were in fact
fossilized stromatolites.
424
00:23:22,234 --> 00:23:23,401
Playford's discovery
425
00:23:23,527 --> 00:23:26,112
had sparked off
a fossil revolution.
426
00:23:26,238 --> 00:23:28,781
- Once people knew
that these kind of structures
427
00:23:28,907 --> 00:23:30,699
were made by living organisms,
428
00:23:30,826 --> 00:23:32,535
they went back
into the rock record
429
00:23:32,661 --> 00:23:35,079
and found that they found
the same kinds of structures
430
00:23:35,205 --> 00:23:38,457
and therefore could deduce
that life occupied planet Earth
431
00:23:38,583 --> 00:23:40,334
3 1/2 billion years ago.
432
00:23:40,460 --> 00:23:44,296
These are really the ancestors
of everything on Earth.
433
00:23:44,423 --> 00:23:47,258
We're actually looking at our
great-great-great-great-great-
434
00:23:47,384 --> 00:23:49,927
great-great-great-great-
grandmothers and grandfathers.
435
00:23:52,931 --> 00:23:56,642
narrator: The rock record shows
that by 2.5 billion years ago,
436
00:23:56,768 --> 00:23:59,728
stromatolites
were blossoming globally.
437
00:23:59,855 --> 00:24:03,899
All beaches on Earth
would've resembled Shark Bay.
438
00:24:09,281 --> 00:24:12,158
And as stromatolites
filled the shallows,
439
00:24:12,284 --> 00:24:17,288
they began to fill
the atmosphere with oxygen.
440
00:24:17,414 --> 00:24:18,706
- Planet Earth
in the solar system
441
00:24:18,832 --> 00:24:20,666
is the only planet
that has an atmosphere
442
00:24:20,792 --> 00:24:23,335
composed of a large amount
of oxygen.
443
00:24:23,462 --> 00:24:25,629
Geoscientists think
that that oxygen
444
00:24:25,755 --> 00:24:29,341
came only from the reaction
of stromatolites.
445
00:24:29,468 --> 00:24:33,179
narrator: The algae
turned sunlight into oxygen,
446
00:24:33,305 --> 00:24:37,683
a process known
as photosynthesis.
447
00:24:37,809 --> 00:24:39,768
Over a period
of 2 billion years,
448
00:24:39,895 --> 00:24:42,021
countless generations
of stromatolites
449
00:24:42,147 --> 00:24:46,358
pumped out over 20 million
billion tons of oxygen.
450
00:24:46,485 --> 00:24:49,195
At first, the gas dissolved
into the oceans,
451
00:24:49,321 --> 00:24:52,740
where it rusted out
billions of tons of iron.
452
00:24:52,866 --> 00:24:56,035
But eventually, it would also
fill the atmosphere
453
00:24:56,161 --> 00:24:58,704
and transform the planet.
454
00:24:58,830 --> 00:25:03,709
The planet's very appearance
was dramatically altered.
455
00:25:03,835 --> 00:25:09,006
As the iron left the oceans,
they changed from green to blue.
456
00:25:09,132 --> 00:25:11,175
When the oxygen moved on
to the atmosphere,
457
00:25:11,301 --> 00:25:14,386
it diluted the remaining
thick carbon dioxide
458
00:25:14,513 --> 00:25:17,014
and cleared the air.
459
00:25:26,358 --> 00:25:30,277
After nearly 2 billion years
of oxygenation,
460
00:25:30,403 --> 00:25:33,531
the blue planet was born.
461
00:25:37,035 --> 00:25:39,078
The Earth now had
its blue oceans
462
00:25:39,204 --> 00:25:41,205
and its blue sky.
463
00:25:47,504 --> 00:25:50,047
Relics of this great
transformative period
464
00:25:50,173 --> 00:25:54,927
survive today in immense layers
of iron-rich sediment
465
00:25:55,053 --> 00:25:56,095
originally deposited
466
00:25:56,221 --> 00:25:59,932
on the floors
of the ancient oceans.
467
00:26:00,058 --> 00:26:01,517
Scattered
all throughout the globe,
468
00:26:01,643 --> 00:26:04,520
the banded iron formations,
as they are known,
469
00:26:04,646 --> 00:26:08,148
are vital
for today's economies.
470
00:26:08,275 --> 00:26:13,112
They are the major source
of all the iron mined today.
471
00:26:14,990 --> 00:26:19,868
Following its oxygenation,
the Earth was more recognizable.
472
00:26:19,995 --> 00:26:22,621
But before it would become
the planet we know,
473
00:26:22,747 --> 00:26:26,375
a new cycle of cataclysmic
events would take place.
474
00:26:26,501 --> 00:26:28,294
Over the next billion years,
475
00:26:28,420 --> 00:26:31,463
deep movements
would wrench apart the crust,
476
00:26:31,590 --> 00:26:35,092
and life, which had just begun
to make its mark,
477
00:26:35,218 --> 00:26:37,928
would face
its toughest test yet.
478
00:26:49,274 --> 00:26:52,484
1 .5 billion years ago,
479
00:26:52,611 --> 00:26:56,739
planet Earth was almost
3 billion years old.
480
00:26:56,865 --> 00:26:59,241
For the first time
in its history,
481
00:26:59,367 --> 00:27:02,828
it was beginning to resemble
the planet we know.
482
00:27:02,954 --> 00:27:06,749
Newly arrived oxygen
had turned the oceans blue,
483
00:27:06,875 --> 00:27:08,334
and the continents had grown
484
00:27:08,460 --> 00:27:11,629
to cover nearly 1/4
of the surface.
485
00:27:11,755 --> 00:27:14,381
But their expansion
was not over,
486
00:27:14,507 --> 00:27:17,468
and beneath the oceans,
deep forces were at work,
487
00:27:17,594 --> 00:27:19,928
rearranging their positions.
488
00:27:20,055 --> 00:27:24,558
lmperceptibly,
the continents were on the move.
489
00:27:30,482 --> 00:27:34,151
Mark McMenamin is an expert
in plate tectonics,
490
00:27:34,277 --> 00:27:37,029
the study
of continental movement.
491
00:27:37,155 --> 00:27:42,660
Until the 1 960s,
this was radical science.
492
00:27:44,954 --> 00:27:47,498
- ln the 1 9th
and early 20th century,
493
00:27:47,624 --> 00:27:51,919
the consensus view was that
the continents were fixed.
494
00:27:52,045 --> 00:27:53,545
All geology was local,
495
00:27:53,672 --> 00:27:56,340
and the continents
stay in one place.
496
00:27:56,466 --> 00:27:59,885
narrator: But problems
for this view had been mounting.
497
00:28:00,011 --> 00:28:01,553
One of the greatest mysteries
498
00:28:01,680 --> 00:28:05,891
was the geographic position
of certain fossils.
499
00:28:06,017 --> 00:28:08,435
- Trilobites like the one
on my left here
500
00:28:08,561 --> 00:28:11,689
belong to the genus
Paradoxides.
501
00:28:11,815 --> 00:28:14,400
narrator: The Paradoxides
really was a paradox.
502
00:28:14,526 --> 00:28:17,695
lt was a freshwater creature
with a curious distribution.
503
00:28:17,821 --> 00:28:20,030
- This trilobite is found
504
00:28:20,156 --> 00:28:23,117
in the eastern part
of North America...
505
00:28:23,243 --> 00:28:24,910
- And also in Britain,
506
00:28:25,036 --> 00:28:28,539
on the other side
of the Atlantic Ocean.
507
00:28:28,665 --> 00:28:30,249
narrator: The freshwater
Paradoxides
508
00:28:30,375 --> 00:28:33,961
could not have swum
the vast salty ocean.
509
00:28:36,047 --> 00:28:37,423
And they were not
the only fossils
510
00:28:37,549 --> 00:28:41,427
showing bizarre
intercontinental distribution.
511
00:28:41,553 --> 00:28:44,888
Geologists struggled
for an explanation.
512
00:28:46,725 --> 00:28:51,603
ln 1 912, a radical new theory
would emerge from Greenland
513
00:28:51,730 --> 00:28:54,106
that would lay the foundations
for plate tectonics
514
00:28:54,232 --> 00:28:58,861
and shake Earth science
to its foundations.
515
00:28:58,987 --> 00:29:00,487
The new theory was put forward
516
00:29:00,613 --> 00:29:03,991
by a German weather scientist,
Alfred Wegener,
517
00:29:04,117 --> 00:29:06,034
a man who had spent
much of his career
518
00:29:06,161 --> 00:29:10,414
conducting atmospheric research
in Greenland's frozen wastes.
519
00:29:10,540 --> 00:29:12,291
But Wegener
had always been fascinated
520
00:29:12,417 --> 00:29:15,043
by the geologist's
fossil paradox,
521
00:29:15,170 --> 00:29:17,045
and he boldly claimed
that the answer
522
00:29:17,172 --> 00:29:19,339
was staring them in the face.
523
00:29:19,466 --> 00:29:22,968
- Ever since accurate world maps
were available,
524
00:29:23,094 --> 00:29:25,137
schoolchildren and others
have pointed out the fit
525
00:29:25,263 --> 00:29:27,973
between the east coast
of South America
526
00:29:28,099 --> 00:29:29,641
and the west coast of Africa.
527
00:29:29,768 --> 00:29:33,395
And this was always dismissed
in reputable scientific circles
528
00:29:33,521 --> 00:29:36,315
as just a coincidence
of no meaning.
529
00:29:36,441 --> 00:29:37,983
And so many
disappointed children
530
00:29:38,109 --> 00:29:41,779
were turned away and told
that their idea was wrong.
531
00:29:41,905 --> 00:29:43,906
narrator: Wegener proposed
that the continents
532
00:29:44,032 --> 00:29:46,450
had indeed
once been joined together
533
00:29:46,576 --> 00:29:49,495
and had subsequently
drifted apart.
534
00:29:52,207 --> 00:29:54,208
His observations in Greenland
convinced him
535
00:29:54,334 --> 00:29:58,879
this continental drift
was possible.
536
00:29:59,005 --> 00:30:02,424
- l think that his inspiration
was meteorological.
537
00:30:02,550 --> 00:30:05,010
Perhaps he saw
breakup of ice floes
538
00:30:05,136 --> 00:30:08,222
and made what we would call
an extrapolation
539
00:30:08,348 --> 00:30:13,310
to the hard rock part
of the planet.
540
00:30:13,436 --> 00:30:15,229
narrator: But few geologists
could accept
541
00:30:15,355 --> 00:30:18,899
the radical theories
of a mere meteorologist.
542
00:30:19,025 --> 00:30:22,486
- There was complete rejection
of what Wegener was saying.
543
00:30:22,612 --> 00:30:27,032
This is a tall order,
to take a gigantic continent
544
00:30:27,158 --> 00:30:29,368
and shove it
through the ocean floor
545
00:30:29,494 --> 00:30:31,578
to get it
halfway across the globe.
546
00:30:34,958 --> 00:30:36,333
narrator: Throughout his life,
547
00:30:36,459 --> 00:30:39,711
Wegener fought to gain evidence
for his theory.
548
00:30:39,838 --> 00:30:44,383
But his brave attempts
eventually led to his demise.
549
00:30:44,509 --> 00:30:49,096
ln 1 930, his last expedition
to Greenland ended in tragedy
550
00:30:49,222 --> 00:30:53,433
when he lost his way
in a snowstorm.
551
00:30:53,560 --> 00:30:56,395
- ln an icy situation
on a glacier,
552
00:30:56,521 --> 00:30:59,898
it's difficult to find your way.
553
00:31:00,024 --> 00:31:02,860
Separated
from both his base camp
554
00:31:02,986 --> 00:31:05,362
and the other members
of his expedition,
555
00:31:05,488 --> 00:31:09,199
he basically got lost
and died of exposure.
556
00:31:11,244 --> 00:31:13,036
narrator: Wegener was dead,
557
00:31:13,162 --> 00:31:17,374
but his theory
of continental drift lived on.
558
00:31:21,212 --> 00:31:23,589
The breakthrough came
after the U.S. Navy
559
00:31:23,715 --> 00:31:26,466
produced a global map
of the ocean floor,
560
00:31:26,593 --> 00:31:28,927
originally commissioned
for submarine warfare
561
00:31:29,053 --> 00:31:30,762
during World War ll.
562
00:31:30,889 --> 00:31:32,306
[sonar pinging]
563
00:31:32,432 --> 00:31:39,146
This detailed map revealed one
of the Earth's greatest secrets:
564
00:31:39,272 --> 00:31:41,857
the fractured network
of submarine mountains,
565
00:31:41,983 --> 00:31:44,109
volcanic rifts, and trenches
566
00:31:44,235 --> 00:31:49,114
that split the oceans
into enormous plates of crust.
567
00:31:49,240 --> 00:31:51,366
These plates would be
the building blocks
568
00:31:51,492 --> 00:31:54,620
for the new science
of plate tectonics.
569
00:31:54,746 --> 00:31:57,289
The rifts and trenches
would provide a solution
570
00:31:57,415 --> 00:31:59,291
to how continents drift
571
00:31:59,417 --> 00:32:05,213
by proving that the ocean floors
are continuously being recycled.
572
00:32:05,340 --> 00:32:08,383
- Plate tectonics
is completely driven
573
00:32:08,509 --> 00:32:14,097
by the destruction of the old
and the creation of the new
574
00:32:14,223 --> 00:32:15,682
narrator: Deep below
the surface,
575
00:32:15,808 --> 00:32:19,311
mobile mantle rock is in
continuous circular motion,
576
00:32:19,437 --> 00:32:21,313
following convection currents
of heat
577
00:32:21,439 --> 00:32:24,316
generated
deep within the planet.
578
00:32:24,442 --> 00:32:26,568
Where these currents rise,
the rifts form,
579
00:32:26,694 --> 00:32:28,320
and the plates are pushed apart,
580
00:32:28,446 --> 00:32:32,282
with new ocean crust
created in the gap.
581
00:32:32,408 --> 00:32:35,118
Where the mantle currents
sink back down into the Earth,
582
00:32:35,244 --> 00:32:37,829
they drag old oceanic plate
down with them
583
00:32:37,956 --> 00:32:39,665
towards the interior.
584
00:32:39,791 --> 00:32:43,835
As the ocean plate moves,
so do the continents.
585
00:32:43,962 --> 00:32:49,007
- That oceanic plate drags
the continent along with it.
586
00:32:49,133 --> 00:32:52,302
The process is like
an escalator or a conveyor belt.
587
00:32:54,138 --> 00:32:56,014
narrator: The process
of ocean creation
588
00:32:56,140 --> 00:32:58,100
is visible today
on a rocky island
589
00:32:58,226 --> 00:33:00,560
in the middle of the Atlantic:
590
00:33:00,687 --> 00:33:02,562
lceland.
591
00:33:02,689 --> 00:33:05,524
lceland lies
on the Mid-Atlantic Ridge,
592
00:33:05,650 --> 00:33:09,695
a 1 0,000-mile-long range
of subsea volcanic mountains
593
00:33:09,821 --> 00:33:13,490
that mark one of the deep rifts
in the Earth's crust.
594
00:33:15,785 --> 00:33:18,328
- lceland is really like a peak
of this mountain chain.
595
00:33:18,454 --> 00:33:22,207
lt's like huge volcano
sitting on top of it.
596
00:33:22,333 --> 00:33:23,917
narrator: Seismologist
Páll Einarsson
597
00:33:24,043 --> 00:33:26,586
studies the volcanism
of this remote island,
598
00:33:26,713 --> 00:33:30,882
volcanism that is helping
to expand the Atlantic Ocean.
599
00:33:35,263 --> 00:33:38,682
Occasionally, an unusual type
of volcanic eruption on lceland
600
00:33:38,808 --> 00:33:42,561
confirms
the plate-tectonic process:
601
00:33:42,687 --> 00:33:45,147
a fissure eruption.
602
00:33:45,273 --> 00:33:48,275
A fissure eruption
is a wall of fire.
603
00:33:48,401 --> 00:33:50,569
They can be 25 miles long
604
00:33:50,695 --> 00:33:53,822
and spew lava
hundreds of feet into the air.
605
00:33:53,948 --> 00:33:55,574
- People fear eruptions.
606
00:33:55,700 --> 00:33:57,993
They respect the volcanoes.
607
00:34:04,208 --> 00:34:05,751
narrator: The fissures
mark the path
608
00:34:05,877 --> 00:34:09,963
of the deep plate boundary
that is creating the Atlantic.
609
00:34:10,089 --> 00:34:11,757
All across the island,
610
00:34:11,883 --> 00:34:14,092
running from northeast
to southwest,
611
00:34:14,218 --> 00:34:17,262
are the remains
of these fissure eruptions,
612
00:34:17,388 --> 00:34:21,767
scarring the rocky landscape
with shallow canyons.
613
00:34:21,893 --> 00:34:25,896
These canyons are very slowly
widening lceland.
614
00:34:31,694 --> 00:34:34,446
At their base,
new crust is being created,
615
00:34:34,572 --> 00:34:37,949
pushing Europe
and America apart.
616
00:34:38,076 --> 00:34:40,702
- So here we are
located in the fissure
617
00:34:40,828 --> 00:34:42,704
between the two
continental plates,
618
00:34:42,830 --> 00:34:44,998
the two crustal plates.
619
00:34:45,124 --> 00:34:47,959
Here on my left,
we have the North America plate,
620
00:34:48,086 --> 00:34:51,463
and on the other side,
we have Europe.
621
00:34:51,589 --> 00:34:54,091
This fissure here
is in a lava flow
622
00:34:54,217 --> 00:34:56,593
that's only
about 8,000 years old.
623
00:34:56,719 --> 00:34:57,844
So in 8,000 years,
624
00:34:57,970 --> 00:35:00,472
that's how much
the two plates have moved.
625
00:35:00,598 --> 00:35:03,809
- The rate
of continental drift
626
00:35:03,935 --> 00:35:07,979
averages about 2.5 centimeters
per year,
627
00:35:08,106 --> 00:35:10,649
the rate at which fingernails
typically grow.
628
00:35:10,775 --> 00:35:14,111
narrator: 2.5 centimeters,
one inch per year,
629
00:35:14,237 --> 00:35:16,404
means that in one
human lifetime,
630
00:35:16,531 --> 00:35:20,534
America and Europe will move
just six feet further apart.
631
00:35:22,578 --> 00:35:25,831
But over millions of years,
this speed of movement
632
00:35:25,957 --> 00:35:28,542
was enough
to shift the continents
633
00:35:28,668 --> 00:35:31,253
thousands of miles.
634
00:35:35,466 --> 00:35:37,843
Using plate tectonics
as their guide,
635
00:35:37,969 --> 00:35:39,928
geologists
such as Mark McMenamin
636
00:35:40,054 --> 00:35:41,972
have reconstructed
the epic story
637
00:35:42,098 --> 00:35:44,683
of continental movement
from the beginning.
638
00:35:44,809 --> 00:35:48,061
From samples taken from
present-day continental margins,
639
00:35:48,187 --> 00:35:50,730
they've compared fossils
and microfossils
640
00:35:50,857 --> 00:35:53,900
and matched up distinctive types
of ancient rocks
641
00:35:54,026 --> 00:35:57,362
to reconstruct
where the continents used to be.
642
00:35:57,488 --> 00:35:59,114
- lt's a tricky task.
643
00:35:59,240 --> 00:36:00,615
lt's kind of like Humpty Dumpty.
644
00:36:00,741 --> 00:36:02,200
You've got all of these pieces.
645
00:36:02,326 --> 00:36:04,661
You need to use
whatever clues you can,
646
00:36:04,787 --> 00:36:06,746
whatever fingerprints you can,
647
00:36:06,873 --> 00:36:11,251
to put one continental margin
against the other.
648
00:36:11,377 --> 00:36:12,961
narrator: They are now confident
649
00:36:13,087 --> 00:36:15,255
that they can trace
the movement of the continents
650
00:36:15,381 --> 00:36:18,466
back over a billion years
651
00:36:18,593 --> 00:36:21,511
to a time of a mass
continental collision.
652
00:36:25,183 --> 00:36:27,809
As the oceans between them
were swallowed up,
653
00:36:27,935 --> 00:36:30,437
the large land masses
drew together
654
00:36:30,563 --> 00:36:35,692
in what was to become
a supercontinent, Rodinia.
655
00:36:39,405 --> 00:36:41,907
lt is believed that Canada
and the U.S.A.
656
00:36:42,033 --> 00:36:46,661
formed
the supercontinent's heart,
657
00:36:46,787 --> 00:36:50,540
with other continents
bunched around them.
658
00:36:53,002 --> 00:36:57,923
But Rodinia was unlike
any continent seen today.
659
00:36:58,049 --> 00:37:02,385
lt was a desolate,
lifeless place.
660
00:37:02,511 --> 00:37:04,804
- lt would've been very much
like being in the desert.
661
00:37:04,931 --> 00:37:07,599
lt would've been similar
to parts of the Sahara,
662
00:37:07,725 --> 00:37:09,267
Death Valley.
663
00:37:09,393 --> 00:37:11,937
There would have been
no plants, no forests,
664
00:37:12,063 --> 00:37:14,397
no grasslands.
665
00:37:17,235 --> 00:37:20,862
Rodinia would have been
a barren continent.
666
00:37:28,120 --> 00:37:30,413
narrator: Rodinia
may have been lifeless,
667
00:37:30,539 --> 00:37:32,874
but it was to have
a profound effect
668
00:37:33,000 --> 00:37:35,502
on life in the oceans.
669
00:37:35,628 --> 00:37:37,420
ln the oxygenated waters,
670
00:37:37,546 --> 00:37:39,297
primitive life-forms
were blooming
671
00:37:39,423 --> 00:37:43,426
alongside the stromatolites.
672
00:37:43,552 --> 00:37:45,971
But the huge supercontinent
was about to give them
673
00:37:46,097 --> 00:37:48,848
a tremendous shock.
674
00:37:48,975 --> 00:37:51,643
Rodinia was to trigger
what is now known
675
00:37:51,769 --> 00:37:53,687
as "snowball Earth,"
676
00:37:53,813 --> 00:37:58,650
the biggest freeze
the world has ever seen.
677
00:37:58,776 --> 00:38:02,404
By around 700 million years ago,
Rodinia's position
678
00:38:02,530 --> 00:38:04,948
was blocking the currents
that brought warm water
679
00:38:05,074 --> 00:38:07,200
from the equator to the poles.
680
00:38:07,326 --> 00:38:10,996
Without this heat,
the polar regions froze.
681
00:38:11,122 --> 00:38:13,790
The resulting ice
reflected more of the sun's rays
682
00:38:13,916 --> 00:38:15,667
away from the Earth,
683
00:38:15,793 --> 00:38:17,877
and in a catastrophic
snowballing effect,
684
00:38:18,004 --> 00:38:19,879
temperatures dropped
still further,
685
00:38:20,006 --> 00:38:23,008
and the ice advanced
to cover the Earth.
686
00:38:28,431 --> 00:38:32,350
Surface temperatures
fell below minus 40 degrees.
687
00:38:32,476 --> 00:38:35,353
The oceans were covered
in an ice sheet
688
00:38:35,479 --> 00:38:38,023
almost a mile deep.
689
00:38:38,149 --> 00:38:41,526
The only life on Earth,
marine bacterias and algae,
690
00:38:41,652 --> 00:38:45,238
were trapped beneath
in the darkness.
691
00:38:45,364 --> 00:38:48,366
The result was disaster.
692
00:38:48,492 --> 00:38:50,869
All but a tiny fraction
of organisms
693
00:38:50,995 --> 00:38:53,705
were driven to extinction.
694
00:38:53,831 --> 00:38:57,167
The whole planet was dying.
695
00:39:06,344 --> 00:39:12,223
650 million years ago,
climate changes triggered
696
00:39:12,350 --> 00:39:15,435
by the formation
of the supercontinent Rodinia
697
00:39:15,561 --> 00:39:17,145
had left the surface
of the Earth
698
00:39:17,271 --> 00:39:21,483
covered with a sheet of ice
one mile thick.
699
00:39:21,609 --> 00:39:26,863
Temperatures hovered below
minus 40 degrees Fahrenheit.
700
00:39:26,989 --> 00:39:30,241
Marine organisms,
the only life on the planet,
701
00:39:30,368 --> 00:39:32,660
had almost been wiped out.
702
00:39:32,787 --> 00:39:37,540
The future of life on Earth
hung in the balance.
703
00:39:43,756 --> 00:39:45,256
But beneath the ice,
704
00:39:45,383 --> 00:39:50,178
the supercontinent
was in turmoil.
705
00:39:50,304 --> 00:39:54,766
Vast volcanic eruptions
were splitting Rodinia apart.
706
00:39:54,892 --> 00:39:57,102
- lt's thought
that the accumulation of heat
707
00:39:57,228 --> 00:39:58,853
at the base
of the supercontinent
708
00:39:58,979 --> 00:40:02,524
is what eventually leads
to its undoing.
709
00:40:02,650 --> 00:40:05,610
lt's like putting a blanket
over the Earth.
710
00:40:05,736 --> 00:40:07,904
The heat that's generated
in the Earth's interior
711
00:40:08,030 --> 00:40:10,490
will accumulate
underneath that blanket.
712
00:40:10,616 --> 00:40:14,619
narrator: The heat would spell
the end of the snowball.
713
00:40:14,745 --> 00:40:16,371
As Rodinia ruptured,
714
00:40:16,497 --> 00:40:18,790
carbon dioxide
released by the eruptions
715
00:40:18,916 --> 00:40:21,960
created a temporary
greenhouse effect.
716
00:40:22,086 --> 00:40:25,672
The ice sheets drew back.
717
00:40:25,798 --> 00:40:30,927
Rodinia had broken
into giant fragments.
718
00:40:31,053 --> 00:40:37,142
And the icy grip on life
was broken.
719
00:40:37,268 --> 00:40:40,520
As shallow seas opened up
in Rodinia's wake
720
00:40:40,646 --> 00:40:42,981
and oxygen levels increased,
721
00:40:43,107 --> 00:40:44,858
the primitive organisms
were free
722
00:40:44,984 --> 00:40:48,987
to take their next
great step forward.
723
00:40:49,113 --> 00:40:54,409
They would become complex
and a lot more dangerous.
724
00:40:57,455 --> 00:40:59,831
The Canadian Rockies:
725
00:40:59,957 --> 00:41:02,667
these remote mountains
are home to a rare record
726
00:41:02,793 --> 00:41:05,712
of this key event
in the evolution of life,
727
00:41:05,838 --> 00:41:09,090
the so-called
Cambrian explosion.
728
00:41:09,216 --> 00:41:11,301
- For the first time
in the history of life on Earth,
729
00:41:11,427 --> 00:41:13,470
we have some
of the highest oxygen levels
730
00:41:13,596 --> 00:41:17,182
that we've had since the Earth
was actually formed.
731
00:41:17,308 --> 00:41:18,475
Life bloomed.
732
00:41:18,601 --> 00:41:21,352
We see animals
unlike we've ever seen before.
733
00:41:21,479 --> 00:41:23,354
narrator: Paleontologist
Paul McNeil
734
00:41:23,481 --> 00:41:25,857
is hiking up
to a remote mountain quarry
735
00:41:25,983 --> 00:41:29,068
known as the Burgess Shale.
736
00:41:29,195 --> 00:41:31,488
The astonishing fossils
in this quarry
737
00:41:31,614 --> 00:41:33,948
are a window on the world
as it existed
738
00:41:34,074 --> 00:41:37,327
over 500 million years ago.
739
00:41:37,453 --> 00:41:38,620
- lf you surveyed
all the people
740
00:41:38,746 --> 00:41:40,038
who study the history of life,
741
00:41:40,164 --> 00:41:41,539
you get
almost unanimous agreement
742
00:41:41,665 --> 00:41:43,041
that this is one
of the most important
743
00:41:43,167 --> 00:41:44,334
fossil sites in the world.
744
00:41:49,840 --> 00:41:51,883
narrator: The man who discovered
the Burgess Shale
745
00:41:52,009 --> 00:41:55,094
was an American,
Charles Doolittle Walcott,
746
00:41:55,221 --> 00:41:58,139
the president
of the Smithsonian lnstitute.
747
00:41:58,265 --> 00:42:01,559
This fanatical fossil hunter,
who was born into poverty,
748
00:42:01,685 --> 00:42:04,187
had lived the American dream.
749
00:42:04,313 --> 00:42:06,606
Armed only
with a high school diploma,
750
00:42:06,732 --> 00:42:08,233
he had fought his way
to the top
751
00:42:08,359 --> 00:42:11,945
of the American
scientific establishment.
752
00:42:12,071 --> 00:42:15,406
But it was his tenacious
fossil-hunting expeditions
753
00:42:15,533 --> 00:42:18,117
in the most remote mountains
of North America
754
00:42:18,244 --> 00:42:22,372
that would lead to his
most stunning achievement.
755
00:42:22,498 --> 00:42:24,249
- This is the actual location
756
00:42:24,375 --> 00:42:28,002
where Walcott first made
his amazing discovery.
757
00:42:28,128 --> 00:42:32,006
As the legend goes,
it was August 31 , 1 909,
758
00:42:32,132 --> 00:42:36,344
riding along this very trail
with his wife in a snowstorm.
759
00:42:36,470 --> 00:42:39,430
And as they were riding along,
a large slab of rock came down,
760
00:42:39,557 --> 00:42:42,392
blocked the trail,
and they couldn't get by.
761
00:42:42,518 --> 00:42:45,395
Now, being a gentleman,
as all paleontologists are,
762
00:42:45,521 --> 00:42:47,605
he immediately
leapt off his horse,
763
00:42:47,731 --> 00:42:49,148
flipped over the slab of rock,
764
00:42:49,275 --> 00:42:52,235
and found an incredibly
well-preserved fossil.
765
00:42:52,361 --> 00:42:53,653
lt was down on the trail.
766
00:42:53,779 --> 00:42:55,113
Where did it come from?
767
00:42:55,239 --> 00:42:57,365
Nowhere but up there.
768
00:42:57,491 --> 00:42:58,908
narrator: The source
of the rockfall
769
00:42:59,034 --> 00:43:04,664
was a section of the cliff
no more than 1 00 feet across,
770
00:43:04,790 --> 00:43:06,457
a small area that became
771
00:43:06,584 --> 00:43:10,378
the celebrated
Burgess Shale quarry.
772
00:43:17,428 --> 00:43:19,637
Walcott, often aided
by his own family,
773
00:43:19,763 --> 00:43:23,516
eventually extracted
over 60,000 fossils.
774
00:43:23,642 --> 00:43:24,892
And since Walcott,
775
00:43:25,019 --> 00:43:27,312
a further 1 00,000
have been excavated
776
00:43:27,438 --> 00:43:31,190
from this uniquely rich
cliff face.
777
00:43:31,317 --> 00:43:33,651
- Quarrying the rocks
out of the mountain
778
00:43:33,777 --> 00:43:35,612
requires a tremendous amount
of work,
779
00:43:35,738 --> 00:43:38,823
a lot of backbreaking labor.
780
00:43:38,949 --> 00:43:40,325
But it's also
extremely exciting,
781
00:43:40,451 --> 00:43:42,285
because every time
you split open a rock,
782
00:43:42,411 --> 00:43:43,995
you never know
what you're gonna find.
783
00:43:44,121 --> 00:43:45,663
Most of the time,
you find nothing,
784
00:43:45,789 --> 00:43:48,416
but every once in a while,
you find a new animal,
785
00:43:48,542 --> 00:43:50,209
one that's never
been seen before,
786
00:43:50,336 --> 00:43:52,503
one that's been revealed
for the first time
787
00:43:52,630 --> 00:43:54,047
in 1/2 billion years.
788
00:43:54,173 --> 00:43:55,840
narrator: The thousands
of fossils
789
00:43:55,966 --> 00:43:57,175
found in the Burgess Shale
790
00:43:57,301 --> 00:44:00,303
reveal that starting
500 million years ago,
791
00:44:00,429 --> 00:44:04,682
life exploded with staggering
diversity and complexity.
792
00:44:04,808 --> 00:44:06,184
- The preservation
of these fossils
793
00:44:06,310 --> 00:44:07,560
is actually incredible
794
00:44:07,686 --> 00:44:10,897
in that they're actually
preserved in three dimensions.
795
00:44:11,023 --> 00:44:13,566
You can excavate
through the fossils themselves,
796
00:44:13,692 --> 00:44:15,401
see the internal organs,
797
00:44:15,527 --> 00:44:19,238
remove the organs,
see the digestive tract.
798
00:44:21,158 --> 00:44:23,534
This is fantastic preservation.
799
00:44:23,661 --> 00:44:25,411
Oh, look,
it's starting to crack,
800
00:44:25,537 --> 00:44:28,998
and there goes a piece.
801
00:44:29,124 --> 00:44:33,336
What we have here
is an actual anomalocaris.
802
00:44:33,462 --> 00:44:35,296
These guys
were up to a meter in length.
803
00:44:35,422 --> 00:44:38,675
That actually made them
the T. rex of the Cambrian.
804
00:44:46,475 --> 00:44:49,769
narrator: ln the Cambrian seas,
the oxygen-rich shallow waters
805
00:44:49,895 --> 00:44:54,315
were teeming
with complex organisms.
806
00:44:54,441 --> 00:44:57,026
And creatures were feeding
not just on plants
807
00:44:57,152 --> 00:44:59,487
but on each other.
808
00:45:03,367 --> 00:45:05,535
- The Cambrian is actually
one of the most special times
809
00:45:05,661 --> 00:45:06,786
in the history of life.
810
00:45:06,912 --> 00:45:08,996
We see more different types
of animals
811
00:45:09,123 --> 00:45:11,582
than we see in the rest
of the entire history
812
00:45:11,709 --> 00:45:13,626
of life on Earth.
813
00:45:13,752 --> 00:45:15,378
narrator: From this time
onwards,
814
00:45:15,504 --> 00:45:18,965
with a biological arms race
driving their evolution,
815
00:45:19,091 --> 00:45:22,093
creatures would become
increasingly complex,
816
00:45:22,219 --> 00:45:25,263
with the development
of hard shells, skeletons,
817
00:45:25,389 --> 00:45:29,684
eyes, and teeth.
818
00:45:29,810 --> 00:45:33,688
Modern animals
had arrived on Earth.
819
00:45:40,654 --> 00:45:42,780
The high level of oxygen
that had triggered
820
00:45:42,906 --> 00:45:46,117
this explosion of life
in the seas
821
00:45:46,243 --> 00:45:48,327
was also making
a final modification
822
00:45:48,454 --> 00:45:50,747
to the atmosphere.
823
00:45:50,873 --> 00:45:53,166
Over the next 1 00 million years,
824
00:45:53,292 --> 00:45:57,670
oxygen reached
today's high levels,
825
00:45:57,796 --> 00:46:00,631
a level dense enough
to allow an ozone layer
826
00:46:00,758 --> 00:46:04,469
to form
in the upper atmosphere.
827
00:46:04,595 --> 00:46:10,600
This layer was to free
life-forms from the oceans.
828
00:46:10,726 --> 00:46:13,102
Previously,
powerful ultraviolet light
829
00:46:13,228 --> 00:46:17,148
would destroy any organism
not protected by the water.
830
00:46:17,274 --> 00:46:22,320
Now the ozone layer
would act as a UV shield.
831
00:46:29,620 --> 00:46:32,246
400 million years ago,
832
00:46:32,372 --> 00:46:36,501
the Earth is more
than 4 billion years old.
833
00:46:36,627 --> 00:46:38,753
Over the next 1 00 million years,
834
00:46:38,879 --> 00:46:42,632
the continents
would once again converge.
835
00:46:42,758 --> 00:46:45,760
And this time,
thanks to the ozone shield,
836
00:46:45,886 --> 00:46:49,680
life was free
to leave the oceans
837
00:46:49,807 --> 00:46:52,266
and conquer the land.
838
00:46:52,392 --> 00:46:57,104
Planet Earth had become a world
of tropical swamps.
839
00:47:00,108 --> 00:47:06,072
South Georgia, U.S.A.,
the Okefenokee Swamp.
840
00:47:07,616 --> 00:47:09,367
- The Okefenokee
is believed to be
841
00:47:09,493 --> 00:47:11,369
what we would call an analogue,
842
00:47:11,495 --> 00:47:13,371
a modern analogue,
or an environment
843
00:47:13,497 --> 00:47:15,540
that's very similar
to the wetlands
844
00:47:15,666 --> 00:47:19,585
that existed on Earth
in the past.
845
00:47:19,711 --> 00:47:24,757
narrator: Fred Rich is an expert
on prehistoric swampland.
846
00:47:26,468 --> 00:47:30,221
Geologists like him believe
that this freshwater swamp
847
00:47:30,347 --> 00:47:32,723
closely mimics
the surface of the continents
848
00:47:32,850 --> 00:47:34,892
300 million years ago
849
00:47:35,018 --> 00:47:39,021
in a period known
as the Carboniferous.
850
00:47:39,147 --> 00:47:42,066
- The Carboniferous
was an unusual time
851
00:47:42,192 --> 00:47:45,361
because it was the first period
in Earth history
852
00:47:45,487 --> 00:47:48,739
when large plants
occupied Earth's surface,
853
00:47:48,866 --> 00:47:53,619
40, 50, 70 feet high,
that grew in dense groves
854
00:47:53,745 --> 00:47:56,414
and produced
a vast forest canopy
855
00:47:56,540 --> 00:47:59,083
and a steamy tropical jungle
atmosphere
856
00:47:59,209 --> 00:48:03,754
that was something entirely new
on the face of the Earth.
857
00:48:03,881 --> 00:48:06,215
narrator: This dense
tropical swampland
858
00:48:06,341 --> 00:48:10,553
would dominate the Earth
for the next 60 million years.
859
00:48:14,182 --> 00:48:15,600
The evidence is present
860
00:48:15,726 --> 00:48:20,021
on all of today's continents
in the form of coal.
861
00:48:22,608 --> 00:48:24,984
The coal we use for fuel
was formed
862
00:48:25,110 --> 00:48:28,905
from millions of years' worth
of accumulated plant matter,
863
00:48:29,031 --> 00:48:33,409
most of which existed
less than 300 million years ago.
864
00:48:38,874 --> 00:48:41,125
And it formed
because of the unique way
865
00:48:41,251 --> 00:48:44,503
freshwater swamps decompose.
866
00:48:47,549 --> 00:48:50,134
- Okefenokee is derived
from a Native American word
867
00:48:50,260 --> 00:48:52,803
that means
"land of the trembling earth."
868
00:48:52,930 --> 00:48:55,514
lt's not very easy
to walk through the swamp,
869
00:48:55,641 --> 00:49:00,186
because the subsurface
is soggy plant remains.
870
00:49:00,312 --> 00:49:01,520
narrator: The freshwater
871
00:49:01,647 --> 00:49:03,731
prevents the vegetation
from decaying,
872
00:49:03,857 --> 00:49:08,152
allowing huge amounts
to build up over time.
873
00:49:08,278 --> 00:49:10,863
- Beneath me is not
the regular sort of soil
874
00:49:10,989 --> 00:49:12,782
that you would have
in your backyard.
875
00:49:12,908 --> 00:49:16,118
The soil that you see here
is the plant material
876
00:49:16,244 --> 00:49:21,832
that accumulated last year
or perhaps five years ago.
877
00:49:21,959 --> 00:49:23,918
lt's leaves, stems, twigs.
878
00:49:24,044 --> 00:49:26,170
There's still a good bit
of water in this.
879
00:49:26,296 --> 00:49:29,632
But if we put this under
a tremendous amount of pressure
880
00:49:29,758 --> 00:49:30,716
and add some heat,
881
00:49:30,842 --> 00:49:33,344
by covering over
with layers of rock
882
00:49:33,470 --> 00:49:35,888
and leaving it in the ground
for millions of years,
883
00:49:36,014 --> 00:49:38,057
eventually it will change
to this.
884
00:49:38,183 --> 00:49:39,642
This is a piece
of bituminous coal,
885
00:49:39,768 --> 00:49:44,105
and it's around the order
of 200 million years old.
886
00:49:44,231 --> 00:49:45,356
narrator: As the dead plants
887
00:49:45,482 --> 00:49:47,817
were transformed to coal
on land,
888
00:49:47,943 --> 00:49:50,653
the shallow waters
surrounding the continents
889
00:49:50,779 --> 00:49:52,697
were preserving
millions of generations
890
00:49:52,823 --> 00:49:55,074
of dead marine organisms
891
00:49:55,200 --> 00:50:00,496
that would become
our other major fossil fuels,
892
00:50:00,622 --> 00:50:03,207
oil and gas.
893
00:50:03,333 --> 00:50:08,546
Every year, mankind mines
almost 5,000 megatons of coal,
894
00:50:08,672 --> 00:50:11,382
30 billion barrels of oil,
895
00:50:11,508 --> 00:50:14,969
and 3,000 billion cubic meters
of gas.
896
00:50:15,095 --> 00:50:17,555
This fertile period
of Earth history
897
00:50:17,681 --> 00:50:21,934
has given us much of the energy
we use today.
898
00:50:22,060 --> 00:50:24,687
Without it,
the lndustrial Revolution
899
00:50:24,813 --> 00:50:26,939
may never have happened.
900
00:50:29,693 --> 00:50:32,737
Plants were not alone
in making a new life on the land
901
00:50:32,863 --> 00:50:35,906
300 million years ago.
902
00:50:36,033 --> 00:50:39,869
As time went on,
first enormous insects...
903
00:50:46,251 --> 00:50:49,378
Then ambitious amphibians
904
00:50:49,504 --> 00:50:53,049
and finally early reptilians
left the seas
905
00:50:53,175 --> 00:50:56,802
to take their first steps
on the muddy shorelines.
906
00:50:56,928 --> 00:51:01,390
The U.S. east coast back then
would have teemed with monsters:
907
00:51:01,516 --> 00:51:03,768
three-foot millipedes on land,
908
00:51:03,894 --> 00:51:05,770
two-foot dragonflies
in the air,
909
00:51:05,896 --> 00:51:10,566
and proto-alligators
patrolling the nearby waters.
910
00:51:12,819 --> 00:51:16,322
The world was over
4 1/4 billion years old,
911
00:51:16,448 --> 00:51:18,115
and for the first time,
912
00:51:18,241 --> 00:51:23,746
the surface was host
to a complete modern biosphere.
913
00:51:33,632 --> 00:51:35,966
But the all-conquering
life-forms
914
00:51:36,093 --> 00:51:40,471
were about to experience
a hell on Earth.
915
00:51:40,597 --> 00:51:42,306
Forces deep within
916
00:51:42,432 --> 00:51:44,266
were about to give
life on the surface
917
00:51:44,392 --> 00:51:46,811
its sternest test ever.
918
00:51:46,937 --> 00:51:49,313
Enormous volcanic eruptions
919
00:51:49,439 --> 00:51:51,857
would herald the biggest
mass extinction
920
00:51:51,983 --> 00:51:54,985
in the planet's entire history.
921
00:52:02,494 --> 00:52:06,247
250 million years ago:
922
00:52:06,373 --> 00:52:08,415
for hundreds of millions
of years,
923
00:52:08,542 --> 00:52:09,667
life on the surface
924
00:52:09,793 --> 00:52:13,420
had faced numerous challenges
to its survival
925
00:52:13,547 --> 00:52:17,258
but nothing on the scale
of what was about to happen.
926
00:52:21,263 --> 00:52:23,848
ln what would one day
become Siberia,
927
00:52:23,974 --> 00:52:27,893
the Earth's crust
became a volcanic morass.
928
00:52:28,019 --> 00:52:32,189
The cause was a rare
mantle plume eruption.
929
00:52:32,315 --> 00:52:34,441
No one knows for sure
why they occur,
930
00:52:34,568 --> 00:52:37,695
but occasionally,
huge masses of hot mantle
931
00:52:37,821 --> 00:52:41,574
from deep within the Earth
surge upwards,
932
00:52:41,700 --> 00:52:45,327
melting and smashing
the crust above.
933
00:52:45,453 --> 00:52:49,373
The eruptions continued
for over 1 million years.
934
00:52:49,499 --> 00:52:55,921
They spewed out over 1 million
cubic miles of molten rock,
935
00:52:56,047 --> 00:53:02,094
enough to bury the modern U.S.A.
in a layer over 1 ,000 feet deep.
936
00:53:02,220 --> 00:53:04,722
Clouds of poisonous gases
spread out
937
00:53:04,848 --> 00:53:07,016
and shrouded
the entire globe.
938
00:53:12,022 --> 00:53:14,940
lt was too much
for most species of life.
939
00:53:15,066 --> 00:53:19,069
Over 95%
were driven to extinction.
940
00:53:23,325 --> 00:53:25,534
lt was the most
cataclysmic event
941
00:53:25,660 --> 00:53:28,662
the planet
has ever witnessed.
942
00:53:31,833 --> 00:53:37,796
The planet that emerged
from the chaos was much changed.
943
00:53:37,923 --> 00:53:40,758
A new supercontinent,
the great Pangaea,
944
00:53:40,884 --> 00:53:43,344
now dominated.
945
00:53:45,263 --> 00:53:48,265
And the climate
was altering dramatically.
946
00:53:48,391 --> 00:53:50,559
Over the next 200 million years,
947
00:53:50,685 --> 00:53:54,605
oxygen and carbon dioxide
would rise to new peaks.
948
00:53:54,731 --> 00:53:56,106
And under these conditions,
949
00:53:56,233 --> 00:53:58,776
the animals
that had survived the extinction
950
00:53:58,902 --> 00:54:01,987
were to evolve
into the most infamous creatures
951
00:54:02,113 --> 00:54:04,949
ever to walk the Earth...
952
00:54:05,075 --> 00:54:06,492
[screeching roar]
953
00:54:06,618 --> 00:54:08,535
The dinosaurs.
954
00:54:12,749 --> 00:54:14,667
Utah, U.S.A.
955
00:54:17,921 --> 00:54:21,757
Paleontologist Reese Barrick
is on the hunt for dinosaurs.
956
00:54:24,010 --> 00:54:26,887
ln this dusty corner
of the western U.S.A.,
957
00:54:27,013 --> 00:54:30,140
the rocks are packed
with their bones.
958
00:54:30,267 --> 00:54:32,810
- Almost 1/3 of the history
of life on this planet
959
00:54:32,936 --> 00:54:34,853
was dominated by dinosaurs.
960
00:54:34,980 --> 00:54:38,107
lt really, truly is
a dinosaur planet.
961
00:54:38,233 --> 00:54:41,235
We have, from the bottom
of this slope,
962
00:54:41,361 --> 00:54:43,988
sediments that are
1 50 million years.
963
00:54:44,114 --> 00:54:46,073
And as you go up the slope,
you actually end up
964
00:54:46,199 --> 00:54:49,952
in the Cretaceous
at 125 million years.
965
00:54:57,002 --> 00:54:58,168
How we doin', Barb?
966
00:54:58,295 --> 00:55:00,004
- Doin' great.
- Find anything fun?
967
00:55:00,130 --> 00:55:03,173
- A small rib
and some interesting fragments.
968
00:55:03,300 --> 00:55:05,175
- Well, that's a start
for the day.
969
00:55:05,302 --> 00:55:07,011
narrator: Compared
to modern creatures,
970
00:55:07,137 --> 00:55:09,013
dinosaurs were enormous.
971
00:55:09,139 --> 00:55:12,433
The average mammal today
is smaller than a dog.
972
00:55:12,559 --> 00:55:15,853
The average dinosaur
was larger than a grizzly bear.
973
00:55:15,979 --> 00:55:18,981
[dinosaur roaring]
974
00:55:22,319 --> 00:55:24,903
- Marvin, excellent.
Look at that.
975
00:55:25,030 --> 00:55:28,532
That is a spectacular
therizinosaur claw.
976
00:55:28,658 --> 00:55:31,660
This animal's gonna have to be
300 kilograms,
977
00:55:31,786 --> 00:55:33,412
so it's about the size
978
00:55:33,538 --> 00:55:35,789
of a National Football League
lineman.
979
00:55:35,915 --> 00:55:37,166
[chuckles]
980
00:55:37,292 --> 00:55:39,084
These are absolutely fantastic
981
00:55:39,210 --> 00:55:42,171
because they're
very well-preserved bone.
982
00:55:42,297 --> 00:55:44,423
A perfect claw.
983
00:55:44,549 --> 00:55:47,926
Absolutely brilliant, Marvin.
Nice job.
984
00:55:50,722 --> 00:55:53,098
narrator: The first recorded
dinosaur fossil find
985
00:55:53,224 --> 00:55:56,226
was a bone discovered
by young Mary Ann Mantell
986
00:55:56,353 --> 00:55:59,271
in England in 1 822.
987
00:55:59,397 --> 00:56:02,441
Her husband, Dr. Gideon Mantell,
was intrigued
988
00:56:02,567 --> 00:56:04,026
and set about determining
989
00:56:04,152 --> 00:56:06,862
what type of creature
it belonged to.
990
00:56:10,075 --> 00:56:13,994
The fossil was unlike anything
he'd ever seen.
991
00:56:17,207 --> 00:56:18,957
After much research,
992
00:56:19,084 --> 00:56:21,585
he decided
it was in fact a tooth
993
00:56:21,711 --> 00:56:25,381
from an enormous lizard.
994
00:56:25,507 --> 00:56:27,966
He named the beast lguanodon,
995
00:56:28,093 --> 00:56:31,804
after the iguana lizard
he thought it resembled.
996
00:56:31,930 --> 00:56:35,599
Over the next few decades,
across Europe and the U.S.A.,
997
00:56:35,725 --> 00:56:38,519
more and more huge bones
were unearthed,
998
00:56:38,645 --> 00:56:41,188
and given their similarity
to modern lizards,
999
00:56:41,314 --> 00:56:44,608
the name dinosaur,
meaning "terrible lizard,"
1000
00:56:44,734 --> 00:56:45,943
was coined.
1001
00:56:46,069 --> 00:56:49,238
[dinosaur roaring]
1002
00:56:53,785 --> 00:56:55,661
But many paleontologists today
1003
00:56:55,787 --> 00:56:58,956
believe one of the reasons
dinosaurs grew so large
1004
00:56:59,082 --> 00:57:00,791
was that they weren't
cold-blooded
1005
00:57:00,917 --> 00:57:03,794
like today's lizards.
1006
00:57:03,920 --> 00:57:06,964
They were lukewarm-blooded.
1007
00:57:07,090 --> 00:57:08,465
This gave them the advantages
1008
00:57:08,591 --> 00:57:12,761
of both cold-blooded lizards
and warm-blooded mammals.
1009
00:57:12,887 --> 00:57:15,556
- Dinosaurs
were able to be active
1010
00:57:15,682 --> 00:57:17,641
and collect food
all year long,
1011
00:57:17,767 --> 00:57:19,476
and yet they could put
a greater amount
1012
00:57:19,602 --> 00:57:21,228
of the food that they ate
towards growing
1013
00:57:21,354 --> 00:57:23,981
as opposed
to just heat generation.
1014
00:57:24,107 --> 00:57:25,858
narrator: But another reason
for their size
1015
00:57:25,984 --> 00:57:28,735
may have been the sweltering
oxygen-rich environment
1016
00:57:28,862 --> 00:57:31,905
that came to dominate
the dinosaur era,
1017
00:57:32,031 --> 00:57:35,284
an environment triggered
by volcanism.
1018
00:57:43,293 --> 00:57:46,670
Starting around
1 80 million years ago,
1019
00:57:46,796 --> 00:57:49,840
a new upsurge
in volcanic activity
1020
00:57:49,966 --> 00:57:53,177
split apart
the supercontinent.
1021
00:57:53,303 --> 00:57:56,221
The continental fragments
began their long journeys
1022
00:57:56,347 --> 00:57:59,683
into the positions
they occupy today.
1023
00:57:59,809 --> 00:58:04,229
North America, South America,
Africa, and Europe
1024
00:58:04,355 --> 00:58:07,357
all went
their separate ways.
1025
00:58:07,484 --> 00:58:12,696
The Pangaean supercontinent
was no more.
1026
00:58:12,822 --> 00:58:15,782
Each of the new continents
still carried dinosaurs,
1027
00:58:15,909 --> 00:58:20,329
and the steamy volcanic climate
seemed to suit them.
1028
00:58:21,581 --> 00:58:24,958
lt was global warming
gone wild.
1029
00:58:25,084 --> 00:58:32,216
CO2 levels increased over 500%,
and temperatures soared.
1030
00:58:32,342 --> 00:58:34,635
ln the greenhouse conditions
this created,
1031
00:58:34,761 --> 00:58:40,390
huge tropical forests spread
across many of the continents.
1032
00:58:40,517 --> 00:58:42,434
- The increasing amount
of tropics
1033
00:58:42,560 --> 00:58:44,311
meant that there was a lot more
lush vegetation,
1034
00:58:44,437 --> 00:58:46,730
which means there's a lot more
food for dinosaurs,
1035
00:58:46,856 --> 00:58:49,107
which allowed them
not only to specialize
1036
00:58:49,234 --> 00:58:50,359
and evolve to specialize
1037
00:58:50,485 --> 00:58:52,236
on different types
of plant materials
1038
00:58:52,362 --> 00:58:55,614
but allowed them
to get extremely large.
1039
00:58:58,451 --> 00:58:59,743
narrator: Many scientists
believe
1040
00:58:59,869 --> 00:59:01,620
that evolving
for millions of years
1041
00:59:01,746 --> 00:59:04,206
in this warm oxygen-rich world
1042
00:59:04,332 --> 00:59:06,500
allowed
the lukewarm-blooded dinosaurs
1043
00:59:06,626 --> 00:59:09,253
to reach their enormous sizes.
1044
00:59:09,379 --> 00:59:12,923
Huge dinosaurs may have been
a biological response
1045
00:59:13,049 --> 00:59:16,218
to a volcanically
overactive planet.
1046
00:59:17,804 --> 00:59:20,305
But size would not save
the dinosaurs
1047
00:59:20,431 --> 00:59:23,433
from what was to come.
1048
00:59:23,560 --> 00:59:25,185
Their time on Earth would end
1049
00:59:25,311 --> 00:59:28,188
in sudden,
unstoppable devastation.
1050
00:59:43,413 --> 00:59:48,834
1 00 million years ago,
1051
00:59:48,960 --> 00:59:52,546
planet Earth
was ruled by dinosaurs.
1052
00:59:52,672 --> 00:59:55,674
[dinosaur screeching]
1053
00:59:57,927 --> 01:00:02,264
Huge beasts filled the land,
the sea, and the air.
1054
01:00:05,059 --> 01:00:11,732
They lived in a sweltering world
defined by overactive volcanism,
1055
01:00:11,858 --> 01:00:13,358
and before it was finished,
1056
01:00:13,484 --> 01:00:16,153
this volcanism
would bring to the surface
1057
01:00:16,279 --> 01:00:20,198
some of the planet's
most wondrous riches:
1058
01:00:20,325 --> 01:00:21,950
diamonds.
1059
01:00:28,082 --> 01:00:30,208
Kimberley, South Africa:
1060
01:00:30,335 --> 01:00:33,712
Jock Robey is chief geologist
at De Beers,
1061
01:00:33,838 --> 01:00:36,757
the largest diamond company
in the world.
1062
01:00:36,883 --> 01:00:39,509
- Diamond is simply
the high-pressure form
1063
01:00:39,636 --> 01:00:42,137
of the element carbon.
1064
01:00:42,263 --> 01:00:46,475
This is a typical eight-sided
crystal called an octahedron.
1065
01:00:46,601 --> 01:00:50,145
Uncut, it is worth $2,000
a carat.
1066
01:00:50,271 --> 01:00:53,857
As a cut stone, it would
probably sell for $80,000.
1067
01:00:53,983 --> 01:00:55,359
narrator: For thousands
of years,
1068
01:00:55,485 --> 01:00:57,277
diamonds
had been found worldwide
1069
01:00:57,403 --> 01:00:59,529
washed up in sandy riverbanks,
1070
01:00:59,656 --> 01:01:04,034
but their source
had remained a total mystery.
1071
01:01:04,160 --> 01:01:06,328
lt was not until 1 869
1072
01:01:06,454 --> 01:01:08,622
when huge unique
diamond discoveries
1073
01:01:08,748 --> 01:01:10,248
were made in South Africa
1074
01:01:10,375 --> 01:01:13,377
that their remarkable origin
was revealed.
1075
01:01:13,503 --> 01:01:15,379
- What is special
about the diamonds
1076
01:01:15,505 --> 01:01:17,172
found in the Kimberley area
1077
01:01:17,298 --> 01:01:19,257
was, here,
for the first time ever,
1078
01:01:19,384 --> 01:01:23,387
they found the source rock
of diamonds.
1079
01:01:23,513 --> 01:01:26,473
This is a piece of rock
mined from the kimberlite,
1080
01:01:26,599 --> 01:01:30,560
and as we turn it,
it contains a diamond.
1081
01:01:30,687 --> 01:01:32,854
narrator: The diamond-bearing
rock was extracted
1082
01:01:32,980 --> 01:01:35,732
from strange
vertical formations.
1083
01:01:35,858 --> 01:01:39,319
- As the miners were digging,
they found that the diamonds
1084
01:01:39,445 --> 01:01:42,072
were contained in a body of rock
1085
01:01:42,198 --> 01:01:44,700
that had a shape
of an ice cream cone:
1086
01:01:44,826 --> 01:01:48,078
slightly broader at the surface,
yellow in color,
1087
01:01:48,204 --> 01:01:51,623
tapering down
to a narrower point.
1088
01:01:57,547 --> 01:01:58,964
narrator: Henry Carvill Lewis,
1089
01:01:59,090 --> 01:02:01,466
a visiting American
mineralogist,
1090
01:02:01,592 --> 01:02:03,927
put together the pieces.
1091
01:02:04,053 --> 01:02:05,762
He realized these diamond mines
1092
01:02:05,888 --> 01:02:10,642
were actually the mouths
of ancient volcanoes.
1093
01:02:10,768 --> 01:02:13,437
The miners were digging down
into their roots,
1094
01:02:13,563 --> 01:02:17,232
through the diamond-bearing
magma that remained.
1095
01:02:19,944 --> 01:02:22,988
But these were clearly not
normal volcanoes.
1096
01:02:23,114 --> 01:02:25,782
They were
over three times deeper,
1097
01:02:25,908 --> 01:02:27,784
extending nearly 1 00 miles
1098
01:02:27,910 --> 01:02:30,787
beneath the surface
of the continent.
1099
01:02:30,913 --> 01:02:34,291
Uniquely intense pressures
and temperatures at this depth
1100
01:02:34,417 --> 01:02:37,502
make it the only place
that diamonds can form,
1101
01:02:37,628 --> 01:02:39,588
and the diamonds
could only be brought up
1102
01:02:39,714 --> 01:02:42,215
by uniquely intense eruptions.
1103
01:02:42,341 --> 01:02:45,051
The diamond-bearing magma
exploded out of the Earth
1104
01:02:45,178 --> 01:02:48,305
at over 300 miles an hour.
1105
01:02:48,431 --> 01:02:51,016
- lmagine the force
and the power of this volcano
1106
01:02:51,142 --> 01:02:53,310
to cut those sheer
vertical walls
1107
01:02:53,436 --> 01:02:55,812
and blow this up
another thousand meters.
1108
01:02:55,938 --> 01:02:58,398
This is the power
of these volcanoes.
1109
01:03:06,407 --> 01:03:08,658
narrator: When the Pangaean
supercontinent split apart
1110
01:03:08,785 --> 01:03:10,494
over 1 00 million years ago,
1111
01:03:10,620 --> 01:03:12,829
scientists believe
the enormous upheaval
1112
01:03:12,955 --> 01:03:15,707
triggered these supereruptions.
1113
01:03:15,833 --> 01:03:18,418
Because supercontinental
breakups are rare,
1114
01:03:18,544 --> 01:03:21,671
so are the diamonds
they bring to the surface.
1115
01:03:21,798 --> 01:03:24,966
The diamonds that erupted
into the dinosaur world
1116
01:03:25,092 --> 01:03:29,513
would survive unblemished
until the present day.
1117
01:03:29,639 --> 01:03:33,475
But the dinosaurs
would not be so lucky.
1118
01:03:40,650 --> 01:03:44,986
65 million years ago,
1119
01:03:45,112 --> 01:03:47,072
the planet was lush.
1120
01:03:47,198 --> 01:03:50,992
Vegetation was thick
on the surface.
1121
01:03:51,118 --> 01:03:54,871
Living things were prospering
like never before.
1122
01:03:54,997 --> 01:03:56,540
But the dominant dinosaurs
1123
01:03:56,666 --> 01:03:59,709
were about to be wiped
from the face of the planet.
1124
01:03:59,836 --> 01:04:01,628
[dinosaur roaring]
1125
01:04:01,754 --> 01:04:04,381
- Dinosaur bones
are found continuously
1126
01:04:04,507 --> 01:04:06,508
throughout
the sedimentary record
1127
01:04:06,634 --> 01:04:09,261
from 230 million years ago
1128
01:04:09,387 --> 01:04:11,388
right up
to 65 million years ago,
1129
01:04:11,514 --> 01:04:14,850
and then, instantaneously,
they vanish.
1130
01:04:16,769 --> 01:04:18,144
narrator: Not only dinosaurs
1131
01:04:18,271 --> 01:04:23,066
but over 70% of species
on Earth disappeared.
1132
01:04:23,192 --> 01:04:26,361
From plant life upward,
something terrible had happened
1133
01:04:26,487 --> 01:04:29,739
to the entire ecosystem
of the planet.
1134
01:04:33,744 --> 01:04:36,079
This mass extinction
remained a mystery
1135
01:04:36,205 --> 01:04:39,457
for generations
of paleontologists.
1136
01:04:39,584 --> 01:04:42,127
But it is a mystery no longer.
1137
01:04:44,630 --> 01:04:46,756
Colorado, U.S.A.:
1138
01:04:46,883 --> 01:04:49,009
Dan Durda is taking samples
1139
01:04:49,135 --> 01:04:55,098
from an exposed layer of rock
exactly 65 million years old.
1140
01:04:55,224 --> 01:04:58,268
Scientists now believe
that it holds the answer.
1141
01:04:58,394 --> 01:05:01,229
For Dan Durda,
this powdery rock
1142
01:05:01,355 --> 01:05:03,940
is an indication
that the dinosaurs perished
1143
01:05:04,066 --> 01:05:06,943
in a sudden
astronomical catastrophe.
1144
01:05:07,069 --> 01:05:10,822
- Dinosaurs and 75% of all
the other plants and animals
1145
01:05:10,948 --> 01:05:13,783
that lived with them,
this layer is their tombstone.
1146
01:05:13,910 --> 01:05:17,370
This thin layer of clay
is the important evidence
1147
01:05:17,496 --> 01:05:20,624
of a violent event
in the history
1148
01:05:20,750 --> 01:05:22,083
of life on the planet.
1149
01:05:22,209 --> 01:05:24,419
narrator: The evidence
held in the tombstone layer
1150
01:05:24,545 --> 01:05:25,712
is a huge amount
1151
01:05:25,838 --> 01:05:30,133
of an exceptionally rare
element, iridium.
1152
01:05:30,259 --> 01:05:32,302
The remarkable concentration
of iridium
1153
01:05:32,428 --> 01:05:34,930
was discovered accidentally
in 1 980
1154
01:05:35,056 --> 01:05:37,515
by a father-and-son team
of scientists,
1155
01:05:37,642 --> 01:05:41,394
Luis and Walter Alvarez.
1156
01:05:41,520 --> 01:05:43,146
On the planet's surface,
1157
01:05:43,272 --> 01:05:47,150
iridium is usually found
in very small concentrations.
1158
01:05:47,276 --> 01:05:50,320
Most of this rare element
originates from space rock
1159
01:05:50,446 --> 01:05:52,822
deposited from the multitude
of small meteors
1160
01:05:52,949 --> 01:05:56,660
vaporizing in the upper
atmosphere every day.
1161
01:05:56,786 --> 01:05:58,745
The Alvarezes
were looking for variations
1162
01:05:58,871 --> 01:06:01,539
in the strength
of these tiny meteor showers,
1163
01:06:01,666 --> 01:06:03,959
but when they realized
this huge concentration
1164
01:06:04,085 --> 01:06:06,503
was held in the infamous
tombstone layer,
1165
01:06:06,629 --> 01:06:09,881
they proposed a radical
new theory for the extinction:
1166
01:06:10,007 --> 01:06:12,300
death from above.
1167
01:06:12,426 --> 01:06:18,181
The dinosaur planet had been hit
by an enormous meteor.
1168
01:06:18,307 --> 01:06:21,518
Their theory remained
controversial for over ten years
1169
01:06:21,644 --> 01:06:23,353
until the final piece
of the puzzle
1170
01:06:23,479 --> 01:06:27,023
was discovered in Mexico:
1171
01:06:27,149 --> 01:06:31,528
a hidden crater
over 1 00 miles across.
1172
01:06:31,654 --> 01:06:34,531
- ln 1 990, the Chicxulub
impact crater was discovered,
1173
01:06:34,657 --> 01:06:36,533
and its age,
when finally dated,
1174
01:06:36,659 --> 01:06:39,285
turned out to be precisely
65 million years old.
1175
01:06:39,412 --> 01:06:40,453
lt turned out to be,
1176
01:06:40,579 --> 01:06:43,081
it was the smoking gun
for the Alvarez theory.
1177
01:06:43,207 --> 01:06:45,709
narrator: Worldwide,
the tombstone layer
1178
01:06:45,835 --> 01:06:50,213
contains an estimated
200,000 tons of iridium.
1179
01:06:50,339 --> 01:06:56,052
This translates to a meteor
over six miles in diameter.
1180
01:06:56,178 --> 01:07:00,223
lts impact on the planet
would have been devastating.
1181
01:07:00,349 --> 01:07:01,850
- You've got to imagine
Mount Everest
1182
01:07:01,976 --> 01:07:05,979
flying at you across the sky
at 20 kilometers per second.
1183
01:07:18,534 --> 01:07:20,410
Several thousand
cubic kilometers
1184
01:07:24,582 --> 01:07:26,833
and launched
around the entire planet,
1185
01:07:26,959 --> 01:07:29,419
slowly raining back down
through the atmosphere
1186
01:07:29,545 --> 01:07:31,212
to settle across
the surface of the Earth
1187
01:07:31,338 --> 01:07:34,257
as a thin layer
of dust and debris.
1188
01:07:37,053 --> 01:07:38,762
narrator: But the meteor
was not alone
1189
01:07:38,888 --> 01:07:41,264
in wreaking destruction.
1190
01:07:41,390 --> 01:07:44,309
Today in lndia,
ancient lava flows exist
1191
01:07:44,435 --> 01:07:45,685
that are so thick,
1192
01:07:45,811 --> 01:07:49,314
whole temples have been carved
into their layers.
1193
01:07:49,440 --> 01:07:51,983
The lavas were the result
of a massive eruption
1194
01:07:52,109 --> 01:07:54,027
that was occurring
simultaneously
1195
01:07:54,153 --> 01:07:55,737
with the meteor strike.
1196
01:07:55,863 --> 01:07:57,238
Although not as extensive
1197
01:07:57,364 --> 01:07:59,574
as the earlier
Siberian eruptions,
1198
01:07:59,700 --> 01:08:01,868
these lava flows
in western lndia
1199
01:08:01,994 --> 01:08:06,122
could have buried the U.S.A.
to a depth of over 600 feet.
1200
01:08:06,248 --> 01:08:09,209
The huge clouds of toxic dust
they produced
1201
01:08:09,335 --> 01:08:12,295
would have rivaled
those of the meteor.
1202
01:08:12,421 --> 01:08:14,214
65 million years ago,
1203
01:08:14,340 --> 01:08:16,424
the meteor impact
and the eruptions
1204
01:08:16,550 --> 01:08:19,803
would have been
a deadly double blow.
1205
01:08:19,929 --> 01:08:21,930
Whichever had
the stronger effect,
1206
01:08:22,056 --> 01:08:23,890
the combination
of these events
1207
01:08:24,016 --> 01:08:26,935
sounded the death knell
for the dinosaurs.
1208
01:08:27,061 --> 01:08:30,063
[dinosaur roaring]
1209
01:08:31,816 --> 01:08:34,651
A dust cloud lingering high
in the upper atmosphere
1210
01:08:34,777 --> 01:08:39,155
and blocking the sun
devastated the life below.
1211
01:08:39,281 --> 01:08:41,157
The huge dinosaurs,
1212
01:08:41,283 --> 01:08:43,743
along with most other
major species,
1213
01:08:43,869 --> 01:08:45,203
were extinct.
1214
01:08:45,329 --> 01:08:47,122
The new world
that was to follow
1215
01:08:47,248 --> 01:08:50,792
would be the world
of the mammals
1216
01:08:50,918 --> 01:08:53,128
and the world of man.
1217
01:08:59,802 --> 01:09:03,096
50 million years ago,
1218
01:09:03,222 --> 01:09:06,724
life was slowly recovering
after the cataclysmic extinction
1219
01:09:06,851 --> 01:09:10,019
that obliterated
the dinosaurs.
1220
01:09:10,146 --> 01:09:15,483
The Earth had been around
for over 4.4 billion years,
1221
01:09:15,609 --> 01:09:17,986
but only now
were the first mammals,
1222
01:09:18,112 --> 01:09:22,031
our ancestors,
beginning to flourish.
1223
01:09:22,158 --> 01:09:24,367
Long before humans arrived,
1224
01:09:24,493 --> 01:09:28,663
the continents continued to move
and crash into one another.
1225
01:09:28,789 --> 01:09:32,167
Slowly but surely, the surface
started to look familiar
1226
01:09:32,293 --> 01:09:34,377
as plate tectonics and erosion
1227
01:09:34,503 --> 01:09:38,006
created the dramatic landscapes
we see today.
1228
01:09:45,014 --> 01:09:49,893
The Swiss Alps:
1229
01:09:50,019 --> 01:09:52,687
some mountain chains
can be explained
1230
01:09:52,813 --> 01:09:57,567
by volcanic eruption of rock
from the depths of the Earth.
1231
01:09:57,693 --> 01:10:00,445
But the greatest,
including the Alps,
1232
01:10:00,571 --> 01:10:02,572
contain no volcanoes.
1233
01:10:02,698 --> 01:10:05,575
They appear to have risen
as if by magic
1234
01:10:05,701 --> 01:10:08,328
up from the plains beneath.
1235
01:10:10,998 --> 01:10:13,958
This famous range
runs through the heart of Europe
1236
01:10:14,084 --> 01:10:18,963
and reaches over three miles
above sea level.
1237
01:10:19,089 --> 01:10:25,386
How was such a huge mass of rock
pushed up so high?
1238
01:10:32,311 --> 01:10:34,270
Adrian Pfiffner is an expert
1239
01:10:34,396 --> 01:10:37,732
on the structure
of the Alpine chain,
1240
01:10:37,858 --> 01:10:39,943
and he knows the answer.
1241
01:10:40,069 --> 01:10:41,986
- The scene we see
in front of us
1242
01:10:42,112 --> 01:10:45,573
is the result of a collision
between two continents,
1243
01:10:45,699 --> 01:10:49,744
the African continent
and the European continent.
1244
01:10:53,582 --> 01:10:55,500
narrator: A close study
of the Alpine rocks
1245
01:10:55,626 --> 01:10:57,502
can provide clear evidence
1246
01:10:57,628 --> 01:11:00,171
of how the mountains
were formed.
1247
01:11:00,297 --> 01:11:03,091
The secret is revealed
in quartz crystals
1248
01:11:03,217 --> 01:11:05,260
that are extremely small.
1249
01:11:05,386 --> 01:11:10,306
- These slices are about
25 thousandths of a millimeter.
1250
01:11:10,432 --> 01:11:11,641
At that thickness,
1251
01:11:11,767 --> 01:11:14,811
you see through
one single grain.
1252
01:11:14,937 --> 01:11:16,521
narrator: The tiny crystals
in the rock
1253
01:11:16,647 --> 01:11:18,690
reveal massive deformation.
1254
01:11:18,816 --> 01:11:23,111
- The quartz grains
have been really stretched,
1255
01:11:23,237 --> 01:11:25,029
elongated and flattened.
1256
01:11:25,155 --> 01:11:29,200
You need large stresses
in order to deform these rocks.
1257
01:11:29,326 --> 01:11:31,160
One process that is doing this
1258
01:11:31,287 --> 01:11:35,456
is actually the collision
of two continental plates.
1259
01:11:35,582 --> 01:11:37,875
narrator: For the last
45 million years,
1260
01:11:38,002 --> 01:11:40,461
as the continents
have continued to move,
1261
01:11:40,587 --> 01:11:46,342
the African plate and subplates
have been grinding into Europe.
1262
01:11:46,468 --> 01:11:48,761
The continental crust
along the collision point
1263
01:11:48,887 --> 01:11:51,306
experiences extreme pressure,
1264
01:11:51,432 --> 01:11:55,518
and the solid rock itself
is warped and buckled.
1265
01:11:55,644 --> 01:11:58,271
- lf you assume that my hands
are two plates
1266
01:11:58,397 --> 01:12:00,356
which are squeezing
the rocks in between,
1267
01:12:00,482 --> 01:12:03,484
you can see that some
of the material escapes upwards
1268
01:12:03,610 --> 01:12:06,237
and leads to the building
of a mountain chain.
1269
01:12:06,363 --> 01:12:09,866
narrator: The twisted folds
of the rock strata are exposed
1270
01:12:09,992 --> 01:12:17,540
as the mountains are slowly
squeezed higher and higher.
1271
01:12:17,666 --> 01:12:20,418
One famous Alpine mountain
1272
01:12:20,544 --> 01:12:22,462
demonstrates clearly
this collision
1273
01:12:22,588 --> 01:12:27,759
of the African and European
continental plates:
1274
01:12:27,885 --> 01:12:30,720
the Matterhorn.
1275
01:12:30,846 --> 01:12:35,683
The Matterhorn is the child
of two continents.
1276
01:12:38,062 --> 01:12:40,104
- What's amazing
about the Matterhorn is,
1277
01:12:40,230 --> 01:12:42,357
the top pyramid
of the Matterhorn
1278
01:12:42,483 --> 01:12:45,902
is a piece of Africa,
and it lies on Europe.
1279
01:12:46,028 --> 01:12:48,404
narrator: ln the formation
of this classic mountain,
1280
01:12:48,530 --> 01:12:52,533
the two continental plates
have actually overlapped.
1281
01:12:52,659 --> 01:12:54,327
- You can think of a car crash.
1282
01:12:54,453 --> 01:12:56,621
lf two cars crash
with each other,
1283
01:12:56,747 --> 01:12:59,082
maybe one car
slides over the other one.
1284
01:12:59,208 --> 01:13:01,584
The two continents
moved together,
1285
01:13:01,710 --> 01:13:04,962
and Africa
moved on top of Europe.
1286
01:13:05,089 --> 01:13:07,340
narrator: Plate tectonics
are responsible
1287
01:13:07,466 --> 01:13:10,426
for all the Earth's
mountain ranges,
1288
01:13:10,552 --> 01:13:12,762
and over millions of years
of growth,
1289
01:13:12,888 --> 01:13:14,722
the only thing
that has stopped them
1290
01:13:14,848 --> 01:13:18,434
grinding inexorably skywards
is erosion...
1291
01:13:21,230 --> 01:13:24,941
Erosion by snow, wind, and rain.
1292
01:13:25,067 --> 01:13:30,113
- This is the action of water
that is eroding the mountains.
1293
01:13:30,239 --> 01:13:33,324
Now, this might seem to be
something very small,
1294
01:13:33,450 --> 01:13:36,077
but actually, if you look
at the entire Swiss Alps,
1295
01:13:36,203 --> 01:13:39,622
50 million tons
is eroded every year,
1296
01:13:39,748 --> 01:13:42,125
and this corresponds
to a small mountain
1297
01:13:42,251 --> 01:13:45,336
roughly 1 ,000 meters high,
one every year.
1298
01:13:49,174 --> 01:13:51,134
narrator: The height
of mountains around the world
1299
01:13:51,260 --> 01:13:54,679
are determined
by these two opposing forces---
1300
01:13:54,805 --> 01:13:57,640
uplift and erosion---
1301
01:13:57,766 --> 01:13:59,809
changing them by fractions
of an inch,
1302
01:13:59,935 --> 01:14:03,688
up or down, each year.
1303
01:14:03,814 --> 01:14:06,649
But plate movement
and water erosion
1304
01:14:06,775 --> 01:14:09,861
can also create
the opposite of a mountain.
1305
01:14:09,987 --> 01:14:11,237
Under the right conditions,
1306
01:14:11,363 --> 01:14:14,657
the surface itself
can be cut away,
1307
01:14:14,783 --> 01:14:18,286
sometimes spectacularly.
1308
01:14:23,041 --> 01:14:25,751
The Grand Canyon:
1309
01:14:25,878 --> 01:14:29,505
over 1 mile deep,
1310
01:14:29,631 --> 01:14:35,052
1 0 miles wide,
1311
01:14:35,179 --> 01:14:39,432
277 miles long,
1312
01:14:39,558 --> 01:14:42,268
and still growing.
1313
01:14:42,394 --> 01:14:44,145
- One of the great stories
of exploration
1314
01:14:44,271 --> 01:14:45,646
is when the first Europeans
1315
01:14:45,772 --> 01:14:48,399
saw the Grand Canyon
in the year 1 541 ,
1316
01:14:48,525 --> 01:14:50,693
and a couple of those men
came over to the rim,
1317
01:14:50,819 --> 01:14:52,445
they saw the river down below,
1318
01:14:52,571 --> 01:14:55,406
and they thought
it was six feet wide.
1319
01:14:55,532 --> 01:14:57,533
The explorer sent
a couple of his men down,
1320
01:14:57,659 --> 01:14:59,202
and they came back later
and said,
1321
01:14:59,328 --> 01:15:01,579
"The canyon is deeper
than it looks."
1322
01:15:04,625 --> 01:15:06,209
narrator: Wayne Ranney
is an expert
1323
01:15:06,335 --> 01:15:08,377
on this geological phenomenon,
1324
01:15:08,504 --> 01:15:13,341
its unique scale the consequence
of titanic forces of nature.
1325
01:15:16,678 --> 01:15:19,514
Over the course
of the last 6 million years,
1326
01:15:19,640 --> 01:15:22,266
this spectacular canyon
has been carved
1327
01:15:22,392 --> 01:15:25,478
by the slow, winding
Colorado River
1328
01:15:25,604 --> 01:15:28,606
in combination
with dramatic uplifting
1329
01:15:28,732 --> 01:15:31,359
of the Colorado Plateau.
1330
01:15:34,404 --> 01:15:35,905
Plate tectonic processes
1331
01:15:36,031 --> 01:15:38,908
have pushed the whole plateau
upwards.
1332
01:15:39,034 --> 01:15:43,746
lt now lies over 8,000 feet
above sea level.
1333
01:15:43,872 --> 01:15:45,957
- This uplift probably occurred
1334
01:15:46,083 --> 01:15:49,085
with the Pacific plate coming
into the North American plate
1335
01:15:49,211 --> 01:15:50,962
and wrinkling the crust,
1336
01:15:51,088 --> 01:15:53,881
much like if you took
a throw rug on a hardwood floor
1337
01:15:54,007 --> 01:15:56,008
and pushed it
along the hardwood floor.
1338
01:15:56,134 --> 01:15:58,094
When the edge of that rug
reaches the wall,
1339
01:15:58,220 --> 01:16:00,012
you'll see this big bow-up
in the rug,
1340
01:16:00,138 --> 01:16:01,597
and that's exactly
what's happened
1341
01:16:01,723 --> 01:16:04,767
to the western edge
of North America.
1342
01:16:04,893 --> 01:16:06,269
narrator: The river
looks too small
1343
01:16:06,395 --> 01:16:08,938
to cut a canyon so deep,
1344
01:16:09,064 --> 01:16:11,732
but its height above sea level
1345
01:16:11,858 --> 01:16:16,070
means that the force of gravity
gives it great power.
1346
01:16:19,283 --> 01:16:20,950
- All you have to do
is look at big rivers
1347
01:16:21,076 --> 01:16:23,035
like the Amazon
or the Mississippi.
1348
01:16:23,161 --> 01:16:25,037
They have much more
volume of water
1349
01:16:25,163 --> 01:16:26,581
than the Colorado River does,
1350
01:16:26,707 --> 01:16:28,374
and yet they don't cut
large canyons,
1351
01:16:28,500 --> 01:16:30,668
because their landscape
is not elevated.
1352
01:16:30,794 --> 01:16:33,671
So uplift brings the rocks
into an elevation
1353
01:16:33,797 --> 01:16:35,506
where the river
can then saw down
1354
01:16:35,632 --> 01:16:36,799
through all of those layers
1355
01:16:36,925 --> 01:16:41,554
and create the canyon landscape
we see today.
1356
01:16:41,680 --> 01:16:43,973
narrator: Plate tectonics
combined with erosion
1357
01:16:44,099 --> 01:16:45,808
have sculpted
many of the features
1358
01:16:45,934 --> 01:16:47,893
on the surface of our planet,
1359
01:16:48,020 --> 01:16:51,314
and as a general rule,
the mostjagged, tallest peaks
1360
01:16:51,440 --> 01:16:52,815
and the deepest canyons
1361
01:16:52,941 --> 01:16:55,651
are the youngest
of these grand structures,
1362
01:16:55,777 --> 01:17:00,823
all formed within
the last 50 million years.
1363
01:17:00,949 --> 01:17:03,326
But the final touches
have been added
1364
01:17:03,452 --> 01:17:08,331
by yet another
major force of nature.
1365
01:17:08,457 --> 01:17:11,167
2 million years ago
in east Africa,
1366
01:17:11,293 --> 01:17:12,877
ancestors of modern humans
1367
01:17:13,003 --> 01:17:18,674
were taking their first steps
on Earth.
1368
01:17:18,800 --> 01:17:21,844
At the same time,
down from the North Pole,
1369
01:17:21,970 --> 01:17:26,349
enormous icy glaciers
began to descend.
1370
01:17:26,475 --> 01:17:30,603
The Earth was about to enter
the ice ages.
1371
01:17:35,984 --> 01:17:40,529
2 million years ago,
ancestors of modern humans
1372
01:17:40,656 --> 01:17:44,533
had begun to spread
out of Africa.
1373
01:17:44,660 --> 01:17:48,746
But the Earth around them
was cooling down.
1374
01:17:48,872 --> 01:17:50,539
Before long, much of the planet
1375
01:17:50,666 --> 01:17:54,043
would be coated
in huge glaciers.
1376
01:17:54,169 --> 01:17:57,421
The ice ages had arrived.
1377
01:18:00,592 --> 01:18:02,677
The grand freezings
were triggered
1378
01:18:02,803 --> 01:18:05,221
when overflowing volcanoes
in Panama
1379
01:18:05,347 --> 01:18:09,058
created the land bridge
joining North to South America
1380
01:18:09,184 --> 01:18:13,646
and radically altered
global ocean currents.
1381
01:18:13,772 --> 01:18:18,693
The polar seas
cooled significantly.
1382
01:18:18,819 --> 01:18:21,779
The result was that pronounced
dips in global temperature
1383
01:18:21,905 --> 01:18:24,615
could now tip the planet
into ice ages
1384
01:18:24,741 --> 01:18:28,077
lasting tens of thousands
of years.
1385
01:18:34,710 --> 01:18:36,752
lceland:
1386
01:18:36,878 --> 01:18:39,213
the Langjökull glacier.
1387
01:18:41,091 --> 01:18:43,718
ln the highest,
coldest parts of the planet,
1388
01:18:43,844 --> 01:18:47,972
glaciers still reign supreme.
1389
01:18:51,309 --> 01:18:54,937
Few venture out
in these hostile terrains,
1390
01:18:55,063 --> 01:18:58,774
but glacier climatologist
Finnur Pálsson and his team
1391
01:18:58,900 --> 01:19:01,736
regularly battle
the freezing elements.
1392
01:19:03,530 --> 01:19:05,698
- When you're doing
glacier fieldwork,
1393
01:19:05,824 --> 01:19:08,617
conditions can be very bad.
1394
01:19:08,744 --> 01:19:14,290
narrator: Outside, it is below
minus 20 degrees Fahrenheit.
1395
01:19:14,416 --> 01:19:18,961
- l like to work
in harsh conditions.
1396
01:19:19,087 --> 01:19:21,797
Difficulty is something
you need to tackle.
1397
01:19:21,923 --> 01:19:25,634
narrator: Finnur is keeping tabs
on the growth of the glacier.
1398
01:19:25,761 --> 01:19:29,805
At present,
it is over 350 square miles,
1399
01:19:29,931 --> 01:19:32,433
the size of New York City.
1400
01:19:32,559 --> 01:19:34,268
And although it may look static,
1401
01:19:34,394 --> 01:19:37,688
in fact,
it is in constant motion.
1402
01:19:37,814 --> 01:19:44,987
Glaciers are formed initially
by snowfall on high areas.
1403
01:19:45,113 --> 01:19:47,490
The compacted ice
is then dragged down
1404
01:19:47,616 --> 01:19:50,493
by the force of gravity.
1405
01:19:50,619 --> 01:19:54,497
The glaciers move
like slow-motion rivers.
1406
01:19:54,623 --> 01:19:56,081
- You can think of ice
1407
01:19:56,208 --> 01:19:59,168
as soft material
like toothpaste.
1408
01:19:59,294 --> 01:20:02,004
lt flows.
1409
01:20:02,130 --> 01:20:06,467
lf you make a big blob
of toothpaste on a plate,
1410
01:20:06,593 --> 01:20:11,013
it will slowly sink down
and flow away to the edges.
1411
01:20:11,139 --> 01:20:14,433
narrator: Finnur and his team
in lceland regularly check
1412
01:20:14,559 --> 01:20:17,937
on the incremental movement
of the ice.
1413
01:20:21,900 --> 01:20:24,735
- This is a satellite
positioning system.
1414
01:20:24,861 --> 01:20:27,988
We can calculate
the position of this point
1415
01:20:28,114 --> 01:20:30,366
with an accuracy
of about two centimeters
1416
01:20:30,492 --> 01:20:33,536
to calculate how fast
the glacier moves.
1417
01:20:33,662 --> 01:20:35,704
narrator: Finnur's measurements
tell him
1418
01:20:35,831 --> 01:20:41,544
that this glacier is moving
at over 1 50 feet per year.
1419
01:20:41,670 --> 01:20:43,045
ln today's mild temperatures,
1420
01:20:43,171 --> 01:20:46,423
glacial advance is kept in check
by glacial melting,
1421
01:20:46,550 --> 01:20:48,384
but if global temperatures
were to drop
1422
01:20:48,510 --> 01:20:50,886
byjust a few degrees
for a long period,
1423
01:20:51,012 --> 01:20:53,347
then the glaciers
would grind slowly forward,
1424
01:20:53,473 --> 01:20:57,017
and the Earth would enter
another ice age.
1425
01:20:57,143 --> 01:21:00,020
The existence of ice ages
was first discovered
1426
01:21:00,146 --> 01:21:04,525
by 1 9th-century Swiss geologist
Louis Agassiz.
1427
01:21:04,651 --> 01:21:07,444
As he explored
the Swiss Alps in the 1 830s,
1428
01:21:07,571 --> 01:21:09,321
Agassiz couldn't help but notice
1429
01:21:09,447 --> 01:21:13,576
the immense boulders
scattered over farmland
1430
01:21:13,702 --> 01:21:17,580
and the bizarre towers of gravel
capped by stones
1431
01:21:17,706 --> 01:21:22,877
that stood guard over some
of the mountain valleys.
1432
01:21:23,003 --> 01:21:26,255
To explain how the rocks
arrived at these positions,
1433
01:21:26,381 --> 01:21:29,258
he speculated that they had been
carried and deposited
1434
01:21:29,384 --> 01:21:33,345
by ancient glaciers that had
once filled the Alpine valleys
1435
01:21:33,471 --> 01:21:37,474
and covered
the Northern Hemisphere.
1436
01:21:37,601 --> 01:21:39,810
lnitially ridiculed
by his peers,
1437
01:21:39,936 --> 01:21:42,521
Agassiz's ice age theory
became accepted
1438
01:21:42,647 --> 01:21:45,274
as telltale signs
that these huge glaciers
1439
01:21:45,400 --> 01:21:47,401
had indeed covered
the continents
1440
01:21:47,527 --> 01:21:50,946
were found
all over the globe.
1441
01:21:51,072 --> 01:21:53,240
The evidence is everywhere.
1442
01:22:00,790 --> 01:22:03,125
New York's Central Park:
1443
01:22:03,251 --> 01:22:06,045
this oasis of green
in the middle of Manhattan
1444
01:22:06,171 --> 01:22:09,632
exposes part
of the island's ancient bedrock.
1445
01:22:09,758 --> 01:22:12,259
Many large outcrops
are visible,
1446
01:22:12,385 --> 01:22:15,387
and they contain the footprints
of the glaciers.
1447
01:22:19,476 --> 01:22:21,393
Climate expert Joerg Schaefer
1448
01:22:21,519 --> 01:22:25,689
is looking for subtle traces
of this frozen world.
1449
01:22:25,815 --> 01:22:27,316
- lt's actually
something l bet
1450
01:22:27,442 --> 01:22:28,776
that most New Yorkers
do not know.
1451
01:22:28,902 --> 01:22:30,361
You see the ice age
is everywhere
1452
01:22:30,487 --> 01:22:33,238
if you open your eyes.
1453
01:22:33,365 --> 01:22:37,159
narrator: Look closely,
and the superhard bedrock
1454
01:22:37,285 --> 01:22:40,996
is marked with scores
of tiny parallel lines
1455
01:22:41,122 --> 01:22:43,540
fractions of an inch deep.
1456
01:22:43,667 --> 01:22:47,336
- So this point here is actually
one of the most amazing spots
1457
01:22:47,462 --> 01:22:50,965
of evidence for an ice age
in the middle of New York City.
1458
01:22:51,091 --> 01:22:53,842
narrator: The grooves
were caused by small rocks
1459
01:22:53,969 --> 01:22:57,471
caught under the massive weight
of a moving glacier.
1460
01:22:57,597 --> 01:22:59,848
- These little rocks
basically cut like a knife
1461
01:22:59,975 --> 01:23:02,935
into this very hard bedrock.
1462
01:23:03,061 --> 01:23:05,312
This is clear proof that, once,
1463
01:23:05,438 --> 01:23:08,023
an enormous ice sheet
was moving in this direction
1464
01:23:08,149 --> 01:23:10,150
in the middle of New York City.
1465
01:23:14,656 --> 01:23:19,076
narrator: The glaciers
that hit New York were massive.
1466
01:23:19,202 --> 01:23:20,869
They rolled down from the Arctic
1467
01:23:20,996 --> 01:23:25,708
and buried Manhattan
under a huge depth of ice.
1468
01:23:25,834 --> 01:23:27,584
- To give you an idea
about the thickness
1469
01:23:27,711 --> 01:23:30,879
of the Laurentide ice sheet
in the Manhattan area,
1470
01:23:31,006 --> 01:23:33,424
it was at least twice as thick
1471
01:23:33,550 --> 01:23:36,093
as the Empire State Building
is high today.
1472
01:23:36,219 --> 01:23:39,054
narrator: Over the last
2 million years,
1473
01:23:39,180 --> 01:23:41,682
as the climate fluctuated,
1474
01:23:41,808 --> 01:23:46,228
the huge ice sheets
waxed and waned.
1475
01:23:46,354 --> 01:23:49,023
With every pass,
they gouged and crushed
1476
01:23:49,149 --> 01:23:51,942
and reshaped
the land beneath them.
1477
01:23:54,320 --> 01:23:58,407
As the last glaciers retreated
1 0,000 years ago,
1478
01:23:58,533 --> 01:24:01,618
they left behind
a bruised and battered landscape
1479
01:24:01,745 --> 01:24:06,790
and created features
we still see today.
1480
01:24:06,916 --> 01:24:09,418
ln the U.S.A.,
Cape Cod and Long lsland
1481
01:24:09,544 --> 01:24:11,628
are built on immense piles
of boulders
1482
01:24:11,755 --> 01:24:16,759
dropped from the retreating edge
of the North American ice sheet.
1483
01:24:16,885 --> 01:24:20,387
And the great weight of the ice
formed huge depressions
1484
01:24:20,513 --> 01:24:23,140
that now make up
the Great Lakes.
1485
01:24:23,266 --> 01:24:24,850
ln the warmer climate
1486
01:24:24,976 --> 01:24:27,352
that followed
the last glacial retreat,
1487
01:24:27,479 --> 01:24:34,985
early humans had free reign
over the surface.
1488
01:24:35,111 --> 01:24:39,573
ln this brief period,
a fraction of a fraction of 1%
1489
01:24:39,699 --> 01:24:41,742
of the history of the Earth,
1490
01:24:41,868 --> 01:24:47,122
the entire history of human
civilization has taken place.
1491
01:24:47,248 --> 01:24:50,793
Human ingenuity
has reshaped our planet.
1492
01:24:50,919 --> 01:24:52,669
From our perspective,
1493
01:24:52,796 --> 01:24:56,590
our achievements
are breathtaking.
1494
01:24:56,716 --> 01:25:00,552
But will we continue
to survive and prosper?
1495
01:25:00,678 --> 01:25:02,554
- Humans have, with technology,
1496
01:25:02,680 --> 01:25:05,265
dominated the planet
more completely, perhaps,
1497
01:25:05,391 --> 01:25:08,143
than any other animal
in the history of life,
1498
01:25:08,269 --> 01:25:10,646
but we've done it
for such a short period of time
1499
01:25:10,772 --> 01:25:13,649
that we've got
a long ways to go.
1500
01:25:13,775 --> 01:25:16,652
narrator: Over the past
4.5 billion years,
1501
01:25:16,778 --> 01:25:20,322
the Earth has been
on the most incredible journey.
1502
01:25:20,448 --> 01:25:24,243
Over the eons of its existence,
the planetary environment
1503
01:25:24,369 --> 01:25:28,664
has undergone
immense transformations.
1504
01:25:28,790 --> 01:25:30,874
And since the arrival of life,
1505
01:25:31,000 --> 01:25:33,502
these transformations
have in many ways
1506
01:25:33,628 --> 01:25:37,506
determined which organisms
will survive
1507
01:25:37,632 --> 01:25:42,177
and which will be swept aside.
1508
01:25:42,303 --> 01:25:45,389
lf this turbulent past
is any guide to the future,
1509
01:25:45,515 --> 01:25:47,349
life and humans in particular
1510
01:25:47,475 --> 01:25:50,018
will face further battles
for survival
1511
01:25:50,145 --> 01:25:54,189
as the planet continues
along its path of change.
1512
01:25:54,315 --> 01:25:56,692
- Life is highly dependent
on the Earth.
1513
01:25:56,818 --> 01:26:01,530
What the Earth gives us
is what we have to deal with.
1514
01:26:01,656 --> 01:26:04,158
- lt's hard to separate
completely
1515
01:26:04,284 --> 01:26:07,870
the processes of geology
and the processes of life.
1516
01:26:07,996 --> 01:26:11,665
Life in some ways
drives geology,
1517
01:26:11,791 --> 01:26:13,667
and geology creates
the environments
1518
01:26:13,793 --> 01:26:17,171
in which life thrives.
1519
01:26:17,297 --> 01:26:22,384
narrator: Our first major
challenge will be the climate.
1520
01:26:22,510 --> 01:26:24,553
At the start
of the 21st century,
1521
01:26:24,679 --> 01:26:27,181
we may worry
about global warming,
1522
01:26:27,307 --> 01:26:29,057
but most scientists recognize
1523
01:26:29,184 --> 01:26:32,561
that we are in a gap
between ice ages.
1524
01:26:32,687 --> 01:26:34,897
Our whole civilization
has occurred
1525
01:26:35,023 --> 01:26:39,318
in a brief warm period,
1 0,000 years so far.
1526
01:26:39,444 --> 01:26:42,279
This warmth has proved crucial.
1527
01:26:42,405 --> 01:26:43,864
- lt's definitely not
a coincidence
1528
01:26:43,990 --> 01:26:46,909
that civilizations developed
over this period of time,
1529
01:26:47,035 --> 01:26:49,912
because the climate
is so favorable to our species
1530
01:26:50,038 --> 01:26:52,289
to develop and flourish.
1531
01:26:52,415 --> 01:26:54,958
The period we live in the moment
climate-wise
1532
01:26:55,084 --> 01:26:57,044
over the last, let's say,
1 0,000 years
1533
01:26:57,170 --> 01:26:59,296
is exceptionally stable.
1534
01:26:59,422 --> 01:27:01,215
lt's almost unbelievably stable
1535
01:27:01,341 --> 01:27:03,425
if you look
into the geological record.
1536
01:27:03,551 --> 01:27:06,470
lt certainly will not
stay forever like that.
1537
01:27:06,596 --> 01:27:08,430
narrator: Even
if our industrial economies
1538
01:27:08,556 --> 01:27:09,806
effect a global warming
1539
01:27:09,933 --> 01:27:11,600
over the next
couple of centuries,
1540
01:27:11,726 --> 01:27:14,269
they can do no more
than delay the inevitable.
1541
01:27:14,395 --> 01:27:16,063
The continents'
current positions
1542
01:27:16,189 --> 01:27:17,940
keeping the polar oceans cool
1543
01:27:18,066 --> 01:27:23,403
mean that in just 1 5,000 years,
a new ice age may occur.
1544
01:27:23,529 --> 01:27:27,824
- The New York area is going
to be completely changed
1545
01:27:27,951 --> 01:27:29,952
by the next cycle of glaciation,
1546
01:27:30,078 --> 01:27:32,412
and at some point,
glaciers are going to move down
1547
01:27:32,538 --> 01:27:37,417
and grind New York
into the North Atlantic Ocean.
1548
01:27:39,837 --> 01:27:42,798
narrator: But even if we survive
the big freezes,
1549
01:27:42,924 --> 01:27:45,509
there will be
greater challenges to come.
1550
01:27:45,635 --> 01:27:47,970
As plate tectonics
move the continents
1551
01:27:48,096 --> 01:27:49,721
and end the ice ages,
1552
01:27:49,847 --> 01:27:51,807
coastal regions
will be engulfed,
1553
01:27:51,933 --> 01:27:56,520
and whole countries
will disappear.
1554
01:27:56,646 --> 01:27:59,314
200 million years from now,
1555
01:27:59,440 --> 01:28:03,151
a new supercontinent,
Pangaea Ultima,
1556
01:28:03,278 --> 01:28:04,861
is due to take shape
1557
01:28:04,988 --> 01:28:09,449
as first the Mediterranean
and then the Atlantic Ocean
1558
01:28:09,575 --> 01:28:11,618
are swallowed up.
1559
01:28:11,744 --> 01:28:14,538
- There will be continents
eventually colliding
1560
01:28:14,664 --> 01:28:16,498
with the east coast
of North America,
1561
01:28:16,624 --> 01:28:19,543
so New York, in the long run,
will be destroyed
1562
01:28:19,669 --> 01:28:21,712
in a continent-to-continent
collision
1563
01:28:21,838 --> 01:28:25,007
and will be completely crushed
1564
01:28:25,133 --> 01:28:27,843
and thrust upward
as a new mountain range.
1565
01:28:27,969 --> 01:28:29,803
narrator: The Earth
will once again
1566
01:28:29,929 --> 01:28:32,389
be thrown into deadly turmoil.
1567
01:28:32,515 --> 01:28:34,599
Oxygen levels
and surface temperatures
1568
01:28:34,726 --> 01:28:36,226
could fluctuate wildly
1569
01:28:36,352 --> 01:28:38,729
and lead to new
mass extinctions.
1570
01:28:38,855 --> 01:28:41,606
But even the trauma
of supercontinental disruption
1571
01:28:41,733 --> 01:28:44,067
is nothing compared
to what will follow.
1572
01:28:44,193 --> 01:28:45,944
Everything will grind to a halt
1573
01:28:46,070 --> 01:28:50,574
when the plate-tectonic engine
finally stops.
1574
01:28:50,700 --> 01:28:53,327
- The maintenance
of habitability on this planet
1575
01:28:53,453 --> 01:28:57,706
is involved
with the plate-tectonic cycle.
1576
01:28:57,832 --> 01:29:00,375
lt's not an infinite cycle.
1577
01:29:00,501 --> 01:29:02,044
There is an end in sight.
1578
01:29:02,170 --> 01:29:03,462
lt's billions of years from now,
1579
01:29:03,588 --> 01:29:05,881
but we know, eventually,
the system will wear out.
1580
01:29:06,007 --> 01:29:07,758
narrator: The fires
in the depths
1581
01:29:07,884 --> 01:29:10,218
that have dominated activity
on the surface
1582
01:29:10,345 --> 01:29:13,055
will one day use up their fuel,
1583
01:29:13,181 --> 01:29:19,895
and the story of planet Earth
will be over.
1584
01:29:20,021 --> 01:29:22,939
Without its burning heart,
the Earth will share
1585
01:29:23,066 --> 01:29:26,026
what many believe
was the fate of Mars.
1586
01:29:28,321 --> 01:29:31,239
The atmosphere and oceans
will be stripped away,
1587
01:29:31,366 --> 01:29:35,202
and the surface will become
a bone-dry barren desert.
1588
01:29:35,328 --> 01:29:38,205
The planet will be dead.
1589
01:29:41,209 --> 01:29:45,128
But this is a picture
of an incredibly distant future.
1590
01:29:45,254 --> 01:29:47,422
For at least
the next billion years,
1591
01:29:47,548 --> 01:29:50,092
as the Earth continues
its epicjourney,
1592
01:29:50,218 --> 01:29:54,054
some form of life
should continue.
1593
01:29:55,556 --> 01:29:58,642
But the human species,
which has walked the Earth
1594
01:29:58,768 --> 01:30:00,685
for over 2 million years
1595
01:30:00,812 --> 01:30:03,730
and mastered it
only in the last 1 0,000,
1596
01:30:03,856 --> 01:30:05,440
may be in danger.
1597
01:30:05,566 --> 01:30:08,151
As the environment transforms,
1598
01:30:08,277 --> 01:30:11,738
Earth could well become unfit
for humans.
1599
01:30:11,864 --> 01:30:14,199
lf that happens
in the distant future,
1600
01:30:14,325 --> 01:30:16,535
rather than be forced
to face extinction
1601
01:30:16,661 --> 01:30:18,412
like our predecessors,
1602
01:30:18,538 --> 01:30:21,123
technology may allow us
to leave Earth
1603
01:30:21,249 --> 01:30:23,792
in search of new homes,
1604
01:30:23,918 --> 01:30:28,588
other blue-green planets
on which to make a new start,
127338
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