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This is our planet, the Earth.
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It's an amazing ever-changing world,
full of natural wonders.
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But there's more to Earth than this,
much more.
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Because our planet
is unique in the solar system,
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perhaps even in the universe.
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Four and a half billion years
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have made it a world of
extraordinary landscapes
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and a home to life.
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My name's Iain Stewart
and I want to show you
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how our remarkable planet works.
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In this series, I'm going to
explore the four powerful forces
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that have come together
to create our world.
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The oceans,
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that have the power of life
and death over all living things.
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The atmosphere,
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the most fickle of forces.
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It drives our climate
and protects and nourishes us.
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Ice, it has carved the world we know
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and changed the course
of human evolution.
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But I'm going to start with volcanoes.
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They're terrifyingly destructive,
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but they're also the most
fundamental force on the planet.
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Volcanoes are part of a global system
that continually reshapes our world.
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They hold the key
to the origins of life on Earth.
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They saved the planet
from the biggest crisis it's ever faced.
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And they've even formed
a partnership with life
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that keeps our planet habitable.
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Ethiopia, eastern Africa.
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This is the Afar region, bandit country.
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So I've hitched a lift
with the Ethiopian military.
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I'm off to one of the hottest
and remotest places
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on the surface of our planet
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to see the most powerful force
on Earth in action.
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We've got plenty of equipment
because ahead of us
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there's some serious climbing.
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We've touched down on a dry,
brittle surface of recently cooled lava.
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once the helicopter leaves,
we're on our own for a couple of days.
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This place has no water,
no shelter, no life,
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except, I'm told, for a few snakes.
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But I think it's really
going to be worth it.
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I've come all this way to see one
of the most remarkable volcanoes
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anywhere on the planet.
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Erta Ale.
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The name means the smoking mountain
to the local Afar people.
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It's reckoned this volcano has been
continuously erupting lava
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for longer than any other on Earth.
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But no one's quite sure
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because it's only been properly
studied for the last 40 years.
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I've been lucky to see a lot
of volcanoes in my time
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and I've never seen one
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that has a permanent lake
of molten lava in its crater.
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But there's another reason
why this volcano is very special.
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And to see that,
I need to get down into the crater
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and see the lava up close.
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-How's that feel?
-That's fine.
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The rocks here are very sharp and
very brittle, so it's actually good
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that we're on an overhang
and that we're not going to
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-actually crash into them.
-Okay.
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Nervous?
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Yeah. Feeling a little bit nervous,
apprehensive really.
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You know, it's... You know,
first time you're ever going to abseil,
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you kind of didn't want it to be
down into an active volcano, but hey.
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Then the ledge is...
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This is my one now.
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-Sit back, sit back.
-After, after.
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Okay.
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That's it. That's good.
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It's a 30 metre vertical drop
to reach a wide terrace below.
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And the lava lake itself
is a little further down.
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I've waited until sunset
to take a closer look
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because the lava is
at its most spectacular at night.
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This is as close as I can safely get.
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Oh, wow. Crikey. That is magnificent.
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I mean, it's taken us
a hell of a journey to get here,
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but that makes it all worth it.
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I'm standing on the edge
of an active volcano,
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right next to a big pool of molten lava.
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What makes this lava lake
more than just pure spectacle
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is that it's a window that allows us
to look deep into the Earth
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and it helps us understand
the forces that shape our planet.
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Just take a look at the motion
of the lava lake speeded up.
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Something intriguing is happening.
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The movement of the lava
follows a very distinctive pattern.
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It wells up on one side of the crater
and forms a dark crust as it cools.
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Then this crust moves across
the surface of the lake
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driven by the churning action
of the lava below.
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Finally the crust sinks back down.
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As we'll discover,
this process of molten rock
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churning away below the surface
affects our entire planet.
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That's because this lava lake
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is connected to a gigantic source of
heat that lies deep inside the Earth.
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I think it's fair to say that
most of us go about our daily lives
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completely unaware
that underneath our feet,
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our planet is incredibly hot.
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I mean, we live on
a thin skin of cool rock,
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precariously located between
the cold freezer of space up there
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and a red hot furnace down there.
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And what a source of power
this furnace is.
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The Earth's heat does far more
than just fuel volcanoes.
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It created the first atmosphere
and the oceans.
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It continually reshapes
the planet's surface,
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builds great mountain ranges
and moves entire continents.
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And it created the conditions
for life on Earth to begin.
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In fact, you could say that
the whole history of the planet
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has been driven by the massive heat
trapped inside it.
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To understand where our planet's
inner heat comes from,
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we have to go back
four and a half billion years
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to the time of Earth's own birth.
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It was a period called the Hadean,
after Hades, the kingdom of hell,
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which is a good name because this
was a hot, hostile and violent world.
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You may not recognise it,
but this is our planet
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in its very earliest days.
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Little more than a few pieces of rock
colliding as they circle the Sun.
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These impacts were so violent,
they generated immense amounts of heat.
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And they also delivered vast quantities
of radioactive material to the Earth.
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Eventually, when the outer layers
of the planet cooled,
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these two powerful sources of heat
were trapped in a huge, hot core.
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The centre of our planet
is as hot as the surface of the Sun.
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This is the source of
Earth's vast heat energy.
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And it's what fuels
volcanoes to this day.
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Trapped within our planet,
Earth's hot core
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has been continuously releasing
unimaginable amounts of heat.
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It gives you some idea
how much when you realise that
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even after four and a half billion
years, there's still plenty left.
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Earth's inner heat makes
the planet's surface incredibly dynamic.
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It has created a restless
continually changing landscape
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unlike any other in the solar system.
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It's a world of destruction and renewal.
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This is Iceland,
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a place that offers
a great opportunity to see exactly
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how Earth's inner heat is continually
reshaping the planet's landscape.
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Molten rock usually lies hundreds of
kilometres underground
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but here, as in Ethiopia,
it's much closer.
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Yet the effect is very different.
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Sulphurous fumes and bubbling hot pools
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hint at the power
that is just beneath the surface.
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There are naturally heated pools
everywhere on the island,
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which makes going for a dip
something of a national pastime.
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These hot springs are fabulous
for relaxing in,
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providing you don't mind
sharing your bath.
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The mineral-rich water
is meant to have therapeutic qualities,
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but the people here
might not be quite so relaxed
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if they knew exactly
how the water gets heated.
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Right beneath us is a seething mass
of red hot molten rock.
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Just 20 kilometres beneath Iceland
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is a vast column of super-heated rock,
known as a plume.
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Recently, the shape of this
hot plume of rock has been mapped.
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It's 1 00 kilometres wide and
at least 600 kilometres deep.
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Created more than 50 million years ago,
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the plume is sustained by heat
continually rising up
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from the Earth's hot core.
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But this giant plume of
super-heated rock
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has done much more than just warm up
Iceland's hot springs.
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It also created Iceland itself.
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In 1 963, we got to see
how it must have happened.
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A volcano,just below the sea's surface,
blasted its way out of the water.
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A new island, Surtsey, was born.
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This is what Iceland must have looked
like 50 million years ago
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when it first burst above the surface.
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But what makes Iceland so unusual
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is not just that it sits
above a hot plume.
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This small island is also shaped
by the Earth's inner heat
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in another much more powerful way.
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This is Thingvellir.
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It's an important place
in human history because
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in AD 930,
a group of Icelandic chieftains
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gathered here
to sort out their disputes.
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This was the world's first parliament,
which then sat here
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for the next eight centuries.
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But there's another reason
why this is an important place.
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Although they didn't know it,
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those early pioneers of democracy
had set up their parliament
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in the shadow of
a most extraordinary rock face.
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From the air, you can begin to see
just how unusual this rock face is.
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It's a crack in the Earth's surface
that runs for hundreds of kilometres.
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But what we're looking at
is just a tiny part
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of something much, much bigger.
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This is the edge of a gigantic slab
of the Earth's crust,
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which runs unbroken
for 7,000 kilometres,
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right from this point,
under the Atlantic,
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across the USA,
all the way to California.
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It's what's known
as the North American Plate.
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The Earth's surface is broken up into
seven major chunks called plates.
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They're so enormous
that they can carry an entire continent
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and extend far under the sea.
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Strip away the Atlantic ocean
and you can see a long boundary
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between two of these plates
that runs along the ocean floor
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until it rises above the waves,
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cuts through Iceland,
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to eventually join up
with the rock face at Thingvellir.
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It's possible to see this plate boundary
from a completely different perspective.
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This is a very cold place
to go scuba diving.
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The water's just four degrees Celsius,
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but it's worth it
because I am actually swimming
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in the gap between the two giant plates
that run through Iceland.
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To my left, the North American Plate,
and to my right, Europe.
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These sheer rock faces
were once joined together,
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but driven by immense geological forces,
the land was split apart
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to create these deep chasms
which filled with water.
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It's hard to imagine a force
that can move continents apart,
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yet this is precisely what
the Earth's inner heat is able to do.
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It happens because hot rock rises,
heated by the Earth's core.
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Near the surface, the rock spreads
in two directions and goes sideways.
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It begins to lose heat.
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Eventually, the much cooler rock
sinks back down.
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Through this spreading process,
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the Earth's crust
is very slowly dragged apart
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and it's this that ultimately
causes the continents to move.
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The lava lake at Erta Ale
is an example of the same process
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but in miniature.
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As we've seen, the movement of hot lava
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drags the crust across
the surface of the lake,
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just as the continents
are pulled across the Earth's surface.
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To appreciate the idea
of continents moving,
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you have to step outside
human time scales
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and think in terms of
a completely different time frame.
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The continents here are drifting apart
at two centimetres every year.
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In my lifetime, we're talking
just a couple of steps.
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Even in a thousand years,
that's just 20 metres.
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It's only when you start to think
in terms of millions of years
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that you realise just what can happen.
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225 million years ago,
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our planet looked very different.
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All the continents were joined together
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in a single super-continent
called Pangaea.
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As the plates moved,
this super-continent broke up.
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New oceans formed as continents
drifted around the globe.
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It's this that has created the shape
of the world we know today.
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But the plates never stop moving.
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In the distant future,
our continents will once again
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be reunited in a new,
giant super-continent.
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We've seen what happens
when the plates move apart.
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But when they crash into one another,
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the effects are even more dramatic.
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The collision of the Earth's plates
is responsible
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for the most spectacular
mountain ranges on our planet.
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To see how they're created,
I've come to New Zealand's South Island.
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These stunning peaks run
500 kilometres along the west coast,
239
00:21:30,527 --> 00:21:33,439
forming a dramatic spine
down the island.
240
00:21:38,407 --> 00:21:40,523
According to Maori legend,
241
00:21:40,607 --> 00:21:44,566
these mountains are made
of the petrified bodies of four Gods
242
00:21:45,167 --> 00:21:48,682
who got stranded here
on a canoeing trip to Earth.
243
00:21:48,767 --> 00:21:51,884
As they were attempting
to return to the heavens,
244
00:21:51,967 --> 00:21:55,084
a big storm blew up
and capsized the canoe.
245
00:21:56,047 --> 00:21:57,446
They climbed on board
246
00:21:57,527 --> 00:22:01,236
and waited for someone to rescue them,
but no one came.
247
00:22:01,327 --> 00:22:04,524
As time passed,
they slowly turned to stone.
248
00:22:05,407 --> 00:22:09,400
As far as geology goes, there's
a slightly different explanation.
249
00:22:09,847 --> 00:22:14,477
It may not be as romantic as Maori
legend, but it's every bit as epic.
250
00:22:21,407 --> 00:22:25,719
What was to become New Zealand
was once a group of scattered islands.
251
00:22:27,887 --> 00:22:31,004
The collision of the Pacific
and Australian plates
252
00:22:31,087 --> 00:22:33,282
forced these islands together,
253
00:22:33,367 --> 00:22:37,565
creating the familiar outline of
New Zealand that we know today.
254
00:22:39,647 --> 00:22:43,242
Along the collision zone,
the land was buckled
255
00:22:43,327 --> 00:22:45,761
and a line of mountains rose up.
256
00:22:54,767 --> 00:22:58,726
New Zealand's mountains
are around five million years old.
257
00:22:59,167 --> 00:23:00,998
That may sound ancient,
258
00:23:01,087 --> 00:23:03,840
but it's just a geological
blink of an eye.
259
00:23:03,927 --> 00:23:08,557
Yet even in this short timescale,
these peaks have grown into giants.
260
00:23:09,607 --> 00:23:11,837
All the world's great mountain ranges
261
00:23:11,927 --> 00:23:15,237
form in this way
when continents collide.
262
00:23:15,327 --> 00:23:18,717
You can really get a sense of how
the surface of the Earth crumples
263
00:23:18,807 --> 00:23:21,037
when you look down from space.
264
00:23:22,327 --> 00:23:24,477
These are the European Alps,
265
00:23:26,807 --> 00:23:28,763
the South American Andes
266
00:23:31,767 --> 00:23:34,201
and the Himalayas of Central Asia.
267
00:23:39,167 --> 00:23:44,287
They're all relatively young, born out
of recent collisions between plates.
268
00:23:46,527 --> 00:23:49,917
Sometimes you can actually see
their growing pains.
269
00:24:01,407 --> 00:24:04,763
Earthquakes are
a horrific force of destruction.
270
00:24:06,207 --> 00:24:10,519
Entire cities can be wiped out
at terrible human cost.
271
00:24:18,767 --> 00:24:23,283
But this is what happens when our
planet builds its great mountain ranges.
272
00:24:26,767 --> 00:24:30,601
In october 2005,
a devastating earthquake
273
00:24:30,687 --> 00:24:34,077
hit the western Himalayas
in northern Pakistan.
274
00:24:39,127 --> 00:24:44,201
The area around the town of Muzaffarabad
was completely razed to the ground.
275
00:24:46,767 --> 00:24:48,644
But satellites measuring the height
276
00:24:48,727 --> 00:24:52,037
of the surrounding land
before and after the earthquake
277
00:24:52,127 --> 00:24:55,324
revealed that something else
had happened as well.
278
00:24:55,807 --> 00:24:57,525
The red and yellow colours
279
00:24:57,607 --> 00:25:00,758
show how the hills to the east
of the earthquake's epicentre
280
00:25:00,847 --> 00:25:04,806
had actually risen as much as
five metres during the earthquake.
281
00:25:08,687 --> 00:25:11,963
This process,
repeated thousands of times,
282
00:25:12,047 --> 00:25:16,518
has helped build the Himalayas into
the greatest mountain range on Earth.
283
00:25:18,247 --> 00:25:20,807
And it's just as well that
the Earth's inner heat
284
00:25:20,887 --> 00:25:23,162
continues to push mountains up.
285
00:25:30,887 --> 00:25:35,119
Because huge though mountains are,
they're continually under attack.
286
00:25:36,007 --> 00:25:40,159
Given enough time, there's a force
that can completely destroy them.
287
00:25:40,847 --> 00:25:45,841
It might seem unlikely, but that
force is nothing more than water.
288
00:25:46,487 --> 00:25:49,081
(THUNDER RUMBLING)
289
00:26:00,767 --> 00:26:04,680
Ironically, mountains create
the very rain that attacks them.
290
00:26:05,167 --> 00:26:09,718
They're high enough to disrupt the
atmosphere and create their own weather.
291
00:26:10,327 --> 00:26:12,045
The higher the mountains are pushed up,
292
00:26:12,127 --> 00:26:15,403
the higher the air is forced
to rise to cross them.
293
00:26:15,647 --> 00:26:21,085
So the air cools and condenses
into clouds, which produce rain.
294
00:26:28,367 --> 00:26:32,838
And it's surprising just how effective
the power of water can be.
295
00:26:32,927 --> 00:26:34,326
And forward!
296
00:26:36,487 --> 00:26:38,125
And forward!
297
00:26:51,767 --> 00:26:53,359
Hold on!
298
00:26:58,847 --> 00:27:00,963
It's only when
you're fighting the rapids
299
00:27:01,047 --> 00:27:04,835
that you can begin to understand
how powerful a river can be.
300
00:27:07,167 --> 00:27:09,601
This gorge is hundreds of metres deep
301
00:27:09,687 --> 00:27:14,477
and yet it was cut by the river,
relentlessly wearing away at the rock,
302
00:27:14,567 --> 00:27:16,797
and it's still getting deeper.
303
00:27:18,207 --> 00:27:20,243
Rivers don't just erode the rock,
304
00:27:20,327 --> 00:27:24,843
they also carry it from the mountains
to the sea in the form of silt.
305
00:27:26,127 --> 00:27:28,766
It happens on a massive scale.
306
00:27:30,527 --> 00:27:33,405
In South America,
the Amazon carries away
307
00:27:33,487 --> 00:27:37,400
over two billion tons
of the Andes every year
308
00:27:37,487 --> 00:27:40,320
and deposits it in the Atlantic ocean.
309
00:27:43,567 --> 00:27:45,717
And on the Indian subcontinent,
310
00:27:45,807 --> 00:27:48,799
the Ganges river that starts
high in the Himalayas
311
00:27:48,887 --> 00:27:53,324
grinds away around a billion
tons of rock every year,
312
00:27:53,407 --> 00:27:58,083
dropping it 3,000 kilometres downriver
in the Indian ocean.
313
00:28:02,607 --> 00:28:07,237
If it wasn't for the movement of the
plates building new mountain ranges,
314
00:28:07,327 --> 00:28:11,366
water would eventually erode away
all the land on our planet.
315
00:28:18,047 --> 00:28:22,120
It's hard to imagine, but if the plates
should ever stop moving,
316
00:28:22,207 --> 00:28:24,846
our planet would become a water world.
317
00:28:26,247 --> 00:28:29,125
It may take an unfeasibly long time,
318
00:28:29,207 --> 00:28:33,359
but eventually the land would be
worn down and washed out to sea
319
00:28:33,447 --> 00:28:38,316
and Earth would be covered
in a vast ocean several kilometres deep.
320
00:28:38,967 --> 00:28:43,802
So it's thanks to the collision of the
plates continually pushing the land up
321
00:28:43,887 --> 00:28:46,959
that we've still got terra firma
to stand on.
322
00:28:53,887 --> 00:28:58,119
our world is constantly reshaped
by a never-ending battle
323
00:28:58,207 --> 00:29:01,677
between the Earth's inner heat
that pushes the land up
324
00:29:01,767 --> 00:29:04,998
and the forces of erosion
that wear it down.
325
00:29:06,047 --> 00:29:07,719
But the Earth's inner heat
326
00:29:07,807 --> 00:29:11,720
has made a profound difference
to our planet in another way,
327
00:29:11,807 --> 00:29:15,117
perhaps the most important way of all.
328
00:29:22,807 --> 00:29:26,243
It began around four billion years ago.
329
00:29:32,927 --> 00:29:36,317
This is Rotorua
in the North Island of New Zealand.
330
00:29:40,167 --> 00:29:44,001
It's one of the most volcanically
active places on the planet.
331
00:29:45,007 --> 00:29:48,522
This is a landscape where
you can travel back in time.
332
00:29:48,927 --> 00:29:52,681
Rotorua is similar to how
the early Earth would have looked.
333
00:30:00,767 --> 00:30:03,565
In its early days,
the planet looked very different.
334
00:30:03,647 --> 00:30:07,799
Just like here, the ground was hot
with perpetual volcanic activity.
335
00:30:09,807 --> 00:30:13,356
Nasty chemicals brought up from below
stained the land.
336
00:30:15,127 --> 00:30:18,278
And noxious gases bubbled up
from steaming pools.
337
00:30:23,087 --> 00:30:26,557
To us, the young Earth
would have been a hellish place.
338
00:30:27,087 --> 00:30:31,922
But ironically, this volcanic activity
helped create the right conditions
339
00:30:32,007 --> 00:30:35,682
for the most important change
in the history of our planet.
340
00:30:36,807 --> 00:30:40,800
Ultimately, volcanoes provided
the surface of our young planet
341
00:30:40,887 --> 00:30:45,324
with warmth, water
and a potent cocktail of chemicals.
342
00:30:45,687 --> 00:30:49,646
And it was this combination
which inadvertently prepared Earth
343
00:30:50,207 --> 00:30:52,402
for an utterly remarkable event.
344
00:30:53,167 --> 00:30:55,362
No one's sure exactly how it happened,
345
00:30:55,447 --> 00:31:01,044
but around four billion years ago,
our planet saw the birth of life.
346
00:31:08,167 --> 00:31:10,317
These pools have a unique chemistry
347
00:31:10,407 --> 00:31:14,559
that is very similar to what would
have existed on the early Earth.
348
00:31:18,727 --> 00:31:22,606
Bruce Mountain has studied
these pools for many years.
349
00:31:22,687 --> 00:31:26,999
He's going to show me how the
first life on Earth might have begun.
350
00:31:27,087 --> 00:31:29,203
We don't have
a time machine to take us back
351
00:31:29,287 --> 00:31:31,278
so the only thing we can do
is look at things that
352
00:31:31,367 --> 00:31:33,835
we think are similar
to what they were like
353
00:31:33,927 --> 00:31:36,236
and these hot springs
are very, very close
354
00:31:36,327 --> 00:31:38,397
to those that would have been
found on the early Earth.
355
00:31:38,487 --> 00:31:39,966
So what's the temperature of this water?
356
00:31:40,047 --> 00:31:42,481
Well, the water's 75 degrees Celsius,
357
00:31:42,567 --> 00:31:45,400
so you'd definitely get
burned if you put your finger in there.
358
00:31:45,487 --> 00:31:49,116
And it's full of hydrogen sulphide,
which is quite poisonous.
359
00:31:49,207 --> 00:31:51,960
There's a bit of arsenic
in the water as well.
360
00:31:52,047 --> 00:31:55,244
Surely there can't be anything
living in there. What am I looking at?
361
00:31:55,327 --> 00:31:57,795
Oh, there's billions and billions
and billions and billions of organisms
362
00:31:57,887 --> 00:32:02,005
living in that water,
and they form these orange fibres.
363
00:32:02,087 --> 00:32:04,237
It looks like a fur
that's covering all the...
364
00:32:04,327 --> 00:32:06,079
-Yeah.
-...the rocks.
365
00:32:08,207 --> 00:32:11,085
For the microbes living within
the orange fibres,
366
00:32:11,167 --> 00:32:15,558
these toxic chemicals in the water
are a rich soup of nutrients.
367
00:32:18,527 --> 00:32:21,519
Pools like this were very common
on the early Earth.
368
00:32:21,607 --> 00:32:23,598
Fed by volcanic activity,
369
00:32:23,727 --> 00:32:28,642
they provided all the right chemicals
needed for the emergence of life.
370
00:32:30,927 --> 00:32:34,158
MOUNTAIN: Deep down below us,
there's a body of magma that's very hot.
371
00:32:34,247 --> 00:32:36,715
Now, the magma itself
is giving off gases like
372
00:32:36,807 --> 00:32:39,241
carbon dioxide and sulphur dioxide
373
00:32:39,687 --> 00:32:42,679
and that provides the food
for these bacteria to grow.
374
00:32:42,767 --> 00:32:46,077
So the volcanoes are like
a supply chain providing all this stuff?
375
00:32:46,167 --> 00:32:49,603
They're the heat engine
that drives the whole process.
376
00:32:55,087 --> 00:32:56,918
STEWART: Volcanic pools like this
377
00:32:57,007 --> 00:33:00,283
are one possible place
where life might have begun.
378
00:33:06,487 --> 00:33:08,398
But there is an alternative theory,
379
00:33:08,487 --> 00:33:12,639
as volcanoes created other places
where life could have started.
380
00:33:14,007 --> 00:33:15,998
Like hydrothermal vents.
381
00:33:18,367 --> 00:33:20,835
These too are the result
of volcanic activity,
382
00:33:20,927 --> 00:33:24,363
but they are found in
the deepest parts of the oceans.
383
00:33:26,567 --> 00:33:30,480
Today, they support
an extraordinary diversity of life.
384
00:33:31,727 --> 00:33:33,479
But four billion years ago,
385
00:33:33,567 --> 00:33:36,525
it's thought that the combination
of high temperatures and
386
00:33:36,607 --> 00:33:38,916
rich chemicals that the vents produced
387
00:33:39,007 --> 00:33:41,999
might have stimulated
the emergence of life.
388
00:33:50,807 --> 00:33:54,641
But the role of volcanoes went
beyond just kick starting life.
389
00:33:55,127 --> 00:33:59,439
They have played a critical role
in nurturing and protecting it, too.
390
00:34:03,727 --> 00:34:05,160
During Earth's infancy,
391
00:34:05,247 --> 00:34:08,603
the Sun wasn't burning
as brightly as it does today.
392
00:34:09,407 --> 00:34:11,716
In fact it was about 30% cooler.
393
00:34:12,447 --> 00:34:16,360
With a dimmer Sun
bathing the planet in weaker sunlight,
394
00:34:16,447 --> 00:34:19,484
Earth was actually
in danger of freezing.
395
00:34:19,567 --> 00:34:23,526
It was volcanoes that provided
the young vulnerable planet
396
00:34:23,607 --> 00:34:27,680
with a way to keep warm,
but not in the way that you might think.
397
00:34:27,767 --> 00:34:31,885
Earth wasn't warmed up
by all that hot lava spewing out,
398
00:34:31,967 --> 00:34:35,721
but by an extraordinary gas
that volcanoes pumped out.
399
00:34:36,127 --> 00:34:40,245
And that gas was carbon dioxide.
400
00:34:48,927 --> 00:34:52,806
Today we think of carbon dioxide
as a dangerous gas,
401
00:34:52,887 --> 00:34:55,481
causing havoc through climate change.
402
00:34:57,487 --> 00:35:01,924
But actually carbon dioxide
has always been vital to our planet
403
00:35:03,127 --> 00:35:07,996
because it traps heat in the atmosphere
that would otherwise be lost to space.
404
00:35:14,167 --> 00:35:18,080
To see just how critical
carbon dioxide is for Earth,
405
00:35:18,167 --> 00:35:20,635
take a look at our near neighbours.
406
00:35:24,127 --> 00:35:26,595
Mars is a frozen wasteland
407
00:35:26,687 --> 00:35:29,804
with an average temperature
of minus 60 degrees.
408
00:35:30,407 --> 00:35:32,238
That's because its atmosphere
409
00:35:32,327 --> 00:35:35,603
doesn't have enough carbon dioxide
to keep it warm.
410
00:35:38,007 --> 00:35:41,397
At the other extreme,
the temperature on the surface of Venus
411
00:35:41,487 --> 00:35:47,198
is hot enough to melt lead, not simply
because it's a bit closer to the Sun,
412
00:35:47,287 --> 00:35:49,323
but because Venus has an atmosphere
413
00:35:49,407 --> 00:35:52,877
with thousands of times
more carbon dioxide than Earth.
414
00:36:03,127 --> 00:36:06,722
The early Earth was much more
volcanic than it is today
415
00:36:06,807 --> 00:36:09,321
because its core was so much hotter.
416
00:36:10,647 --> 00:36:15,118
This provided enough carbon dioxide
to compensate for the weak Sun.
417
00:36:18,727 --> 00:36:23,084
It was volcanoes that prevented
the young Earth from freezing over,
418
00:36:25,487 --> 00:36:28,604
and so early life was able to survive.
419
00:36:29,247 --> 00:36:33,763
But even this was not the end of what
volcanoes have done for life on Earth.
420
00:36:33,847 --> 00:36:37,601
About 600 million years ago,
they also helped trigger
421
00:36:37,687 --> 00:36:40,884
the greatest evolutionary leap
in Earth's history.
422
00:36:42,927 --> 00:36:46,124
And a great evolutionary leap
was certainly needed
423
00:36:46,207 --> 00:36:50,803
because soon after life got started,
it got stuck in a bit of a rut.
424
00:37:00,367 --> 00:37:02,756
Shark Bay in Western Australia
425
00:37:02,847 --> 00:37:06,044
is home to some of
the oldest life forms on Earth.
426
00:37:08,047 --> 00:37:13,075
These strange domes are made up
from layer upon layer of bacteria.
427
00:37:13,927 --> 00:37:16,202
They're called stromatolites.
428
00:37:17,687 --> 00:37:19,917
For most of Earth's long history,
429
00:37:20,007 --> 00:37:22,999
this was the most advanced life
on the planet.
430
00:37:27,047 --> 00:37:29,163
For around two billion years,
431
00:37:29,247 --> 00:37:32,796
stromatolites ruled
our world unchallenged
432
00:37:33,687 --> 00:37:37,839
and there was nothing to suggest that
this was ever going to change.
433
00:37:40,087 --> 00:37:44,399
But Earth and the stromatolites
were to face a catastrophe,
434
00:37:44,487 --> 00:37:48,162
the most serious crisis
life has ever faced.
435
00:37:56,367 --> 00:38:01,157
Around 700 million years ago,
our planet started to cool.
436
00:38:12,767 --> 00:38:16,396
It was the beginning of an Ice Age,
but with a difference.
437
00:38:18,727 --> 00:38:20,763
No one is quite sure why it happened,
438
00:38:20,847 --> 00:38:23,281
but it seems that ice advanced
from the poles
439
00:38:23,367 --> 00:38:28,885
until the entire world was plunged
into an interminable frozen winter.
440
00:38:40,047 --> 00:38:43,278
It's been called the time
of snowball Earth
441
00:38:43,367 --> 00:38:47,121
because the whole planet would
have appeared as an icy ball.
442
00:38:50,167 --> 00:38:53,284
Travel out to Jupiter
and you can get some idea
443
00:38:53,367 --> 00:38:55,961
of what Earth might have looked like.
444
00:38:57,607 --> 00:39:02,556
Europa is one of Jupiter's moons.
It's completely covered in ice,
445
00:39:02,647 --> 00:39:06,276
just as Earth would have been
at the time of the snowball.
446
00:39:14,927 --> 00:39:16,599
But knowing what Earth looked like
447
00:39:16,687 --> 00:39:20,646
doesn't convey just how terrible
the conditions would have been.
448
00:39:20,967 --> 00:39:26,121
A blizzard high in the Alps in
mid-winter is as close as I can get.
449
00:39:30,127 --> 00:39:33,437
The conditions must have been
absolutely horrendous.
450
00:39:34,087 --> 00:39:37,636
I don't think I've been
ever as cold in my life.
451
00:39:39,007 --> 00:39:43,683
The temperature must be minus
20 degrees Celsius with the wind,
452
00:39:43,767 --> 00:39:49,399
but the thing is during snowball Earth,
things were much worse.
453
00:39:50,047 --> 00:39:51,275
(GROANS)
454
00:40:02,407 --> 00:40:06,878
Today, the average surface
temperature of the planet
455
00:40:06,967 --> 00:40:11,404
around the world is 1 5 degrees Celsius.
456
00:40:13,487 --> 00:40:15,318
During the time of the snowball,
457
00:40:15,407 --> 00:40:20,640
that average surface temperature
plummeted to minus 50.
458
00:40:20,727 --> 00:40:23,480
5-0 degrees Celsius.
459
00:40:25,887 --> 00:40:32,076
Those frozen conditions threatened
the very existence of life on Earth.
460
00:40:36,007 --> 00:40:38,521
The scary thing about snowball Earth
461
00:40:38,607 --> 00:40:42,759
is that our planet could have been
trapped in the freezer forever.
462
00:40:50,647 --> 00:40:54,037
Once ice had almost
completely covered the planet,
463
00:40:54,127 --> 00:40:58,120
most of the Sun's heat
was reflected back to space.
464
00:40:58,207 --> 00:41:01,438
It looked like the Earth
might never heat up again,
465
00:41:01,527 --> 00:41:03,483
but clearly something happened
466
00:41:03,567 --> 00:41:07,355
which rescued our planet
from the icy grip of the snowball.
467
00:41:12,607 --> 00:41:15,758
And what came to the rescue
was volcanoes.
468
00:41:18,367 --> 00:41:21,245
Even though ice covered
the entire planet,
469
00:41:21,327 --> 00:41:23,966
volcanoes continued to erupt,
470
00:41:24,047 --> 00:41:26,959
blasting through
the thick blanket of ice.
471
00:41:30,247 --> 00:41:32,761
It must have been an extraordinary time.
472
00:41:32,847 --> 00:41:36,635
The nearest we've experienced
was in 2004
473
00:41:36,727 --> 00:41:38,319
when an eruption was filmed
474
00:41:38,407 --> 00:41:41,558
bursting through an ice sheet
in central Iceland.
475
00:41:43,447 --> 00:41:46,245
This is what would have happened
during the snowball era,
476
00:41:46,327 --> 00:41:48,158
but on a global scale.
477
00:41:51,367 --> 00:41:54,837
The heat from volcanoes
would have melted holes in the ice,
478
00:41:54,927 --> 00:41:57,521
but that's not what saved our planet.
479
00:41:57,647 --> 00:42:02,880
It was the tons of carbon dioxide gas
they released that did the trick.
480
00:42:09,807 --> 00:42:12,401
As volcanoes continued to erupt,
481
00:42:12,487 --> 00:42:16,321
levels of carbon dioxide
steadily built up in the atmosphere.
482
00:42:18,487 --> 00:42:21,923
Until, around 630 million years ago,
483
00:42:22,007 --> 00:42:24,919
the layer of carbon dioxide
became so thick
484
00:42:25,007 --> 00:42:29,558
that it trapped enough heat to release
the planet from the grip of the ice.
485
00:42:34,367 --> 00:42:37,245
At last, a thaw began.
486
00:42:46,807 --> 00:42:49,605
Fierce storms pounded the planet
487
00:42:50,607 --> 00:42:53,167
as ice house became hot house.
488
00:42:53,727 --> 00:42:57,436
Temperatures swung from
minus 50 Celsius to plus 50
489
00:42:57,527 --> 00:42:59,597
in just a few hundred years,
490
00:42:59,687 --> 00:43:03,646
as Earth endured the most extreme
climate change in its history.
491
00:43:12,367 --> 00:43:16,440
Fortunately, over time
our planet's climate stabilised
492
00:43:16,527 --> 00:43:19,041
and Earth slowly returned to normal.
493
00:43:20,487 --> 00:43:22,398
It had been a close call,
494
00:43:22,487 --> 00:43:25,797
but a few pockets of life
had survived the snowball.
495
00:43:27,287 --> 00:43:29,243
We've got a lot to thank volcanoes for.
496
00:43:29,327 --> 00:43:32,000
They saved our planet
from a desolate fate
497
00:43:32,087 --> 00:43:35,397
as nothing more than
a lifeless frozen wasteland,
498
00:43:35,487 --> 00:43:37,443
but as if that's not enough,
499
00:43:37,527 --> 00:43:41,042
when volcanoes triggered
the end of snowball Earth,
500
00:43:41,127 --> 00:43:43,687
it set the stage for
the greatest leap forward
501
00:43:43,767 --> 00:43:45,962
in the history of life on our planet.
502
00:44:00,327 --> 00:44:02,318
I've come to South Australia
503
00:44:02,407 --> 00:44:06,525
to see what happened to the
evolution of life after snowball Earth.
504
00:44:08,207 --> 00:44:12,519
Palaeontologist Jim Gehling
is taking me to see some of the rarest
505
00:44:12,607 --> 00:44:15,246
and most ancient fossils in the world.
506
00:44:15,407 --> 00:44:17,557
The remains of the creatures
that finally ended
507
00:44:17,647 --> 00:44:19,842
the era of the stromatolites.
508
00:44:19,927 --> 00:44:21,724
Jim, where exactly are we going?
509
00:44:21,807 --> 00:44:24,480
We're going to a secret location
in the Flinders Ranges.
510
00:44:24,567 --> 00:44:27,035
This site is so valuable
511
00:44:27,127 --> 00:44:30,437
that we have to actually
be very careful about
512
00:44:30,527 --> 00:44:34,486
who we take in there and
who actually finds out about it.
513
00:44:34,567 --> 00:44:36,922
We're going to see one of
the most fantastic things.
514
00:44:37,007 --> 00:44:42,320
It's the place where you can get a
look at the very first fossil evidence
515
00:44:42,407 --> 00:44:44,557
of complex life on Earth.
516
00:44:49,847 --> 00:44:54,284
STEWART: The area we're about to visit
was once at the bottom of the sea.
517
00:44:54,367 --> 00:44:56,005
600 million years ago,
518
00:44:56,087 --> 00:44:59,682
the oceans were the only place
where life could be found.
519
00:45:01,727 --> 00:45:05,003
For a billion years,
all that the Earth had seen
520
00:45:05,087 --> 00:45:10,161
was microscopic single-celled creatures.
The best they could do was to form
521
00:45:10,247 --> 00:45:12,966
these domes of slime,
which we call stromatolites.
522
00:45:13,047 --> 00:45:17,563
So then in comes this snowball,
global glaciation and wipe out,
523
00:45:17,647 --> 00:45:20,002
and how did life get affected by that?
524
00:45:20,087 --> 00:45:23,124
Within a short time
after the end of the snowball,
525
00:45:23,207 --> 00:45:25,675
we see a revolution
in the history of life.
526
00:45:25,767 --> 00:45:30,079
We see a sudden increase in size and
complexity of the single cell creatures
527
00:45:30,167 --> 00:45:33,921
and soon after,
you find impressions on rocks
528
00:45:34,007 --> 00:45:38,285
of the very first large creatures,
things you can see with the naked eye,
529
00:45:38,367 --> 00:45:42,963
which we believe are
the oldest multi-cell creatures,
530
00:45:43,047 --> 00:45:44,844
the Ediacara fossils.
531
00:45:47,247 --> 00:45:49,203
STEWART: These fossils may represent
532
00:45:49,287 --> 00:45:52,962
the most important leap forward
in the history of life on our planet,
533
00:45:53,047 --> 00:45:55,880
but that doesn't mean
they're easy to spot.
534
00:45:55,967 --> 00:45:59,482
This is a very old surface
and if we clean it off
535
00:45:59,567 --> 00:46:02,684
and then push this putty
onto the surface,
536
00:46:02,767 --> 00:46:05,406
-you can actually see the impression...
-Look at that.
537
00:46:05,487 --> 00:46:07,637
...of a thing called Parvancorina.
538
00:46:07,727 --> 00:46:09,922
You know, it looks like
somebody's signet ring.
539
00:46:10,007 --> 00:46:12,237
-It's like a trademark.
-Exactly, yeah.
540
00:46:12,327 --> 00:46:14,283
And that's really all the fossil is.
541
00:46:14,367 --> 00:46:17,086
It's the impression of
this soft-bodied creature
542
00:46:17,167 --> 00:46:20,318
as it was preserved instantly
on the sea floor
543
00:46:20,407 --> 00:46:22,318
about 560 million years ago.
544
00:46:22,407 --> 00:46:24,602
These are nothing
like the fossils I'm used to.
545
00:46:24,687 --> 00:46:28,043
I mean, that...
I would never, ever have spotted that.
546
00:46:32,927 --> 00:46:36,158
Parvancorina wouldn't
attract much attention today,
547
00:46:36,247 --> 00:46:39,683
but this animal had made
a gigantic evolutionary leap.
548
00:46:41,767 --> 00:46:44,122
Unlike single-celled microbes,
549
00:46:44,207 --> 00:46:49,076
this was a complex creature with
a head, skin and internal organs.
550
00:46:56,367 --> 00:47:00,485
Under here we can actually see
the imprint of quite a large creature,
551
00:47:00,567 --> 00:47:02,558
at least the size of your hand.
552
00:47:02,647 --> 00:47:07,516
This is Dickinsonia and
it has got the finest segments
553
00:47:07,607 --> 00:47:09,245
that you can actually believe.
554
00:47:09,327 --> 00:47:11,443
-Oh, yeah. Just as it catches the light.
-So, can you see that?
555
00:47:11,527 --> 00:47:12,846
Once you get it the right angle
556
00:47:12,927 --> 00:47:16,203
you can actually see
the details of these body segments.
557
00:47:16,287 --> 00:47:19,245
There are about three there.
There's another one, there.
558
00:47:19,327 --> 00:47:21,363
It's like it was
impressed there yesterday.
559
00:47:21,447 --> 00:47:23,802
Every little detail is preserved
on these sands.
560
00:47:23,887 --> 00:47:25,445
It's beautiful.
561
00:47:27,207 --> 00:47:30,756
Dickinsonia could grow to
over a metre long.
562
00:47:30,847 --> 00:47:32,644
It's thought they lived on the sea floor
563
00:47:32,727 --> 00:47:35,400
soaking up nutrients through their skin.
564
00:47:39,727 --> 00:47:41,718
Here for the first time
we're seeing life
565
00:47:41,807 --> 00:47:44,526
that's become multi-celled, it's large.
566
00:47:44,607 --> 00:47:48,885
These are the creatures that gave rise
to the life that we know today.
567
00:47:50,367 --> 00:47:52,483
For around 50 million years,
568
00:47:52,567 --> 00:47:55,843
the Ediacarans lived in
an ocean free of predators.
569
00:47:56,727 --> 00:47:59,958
Slowly, they evolved into
more complex animals,
570
00:48:00,647 --> 00:48:02,638
but that came at a price.
571
00:48:03,087 --> 00:48:05,555
These new animals now came equipped with
572
00:48:05,647 --> 00:48:10,198
rigid skeletons and shells,
gripping claws and protective armour.
573
00:48:10,767 --> 00:48:14,885
The Earth had changed from
a soft, peaceful garden of Eden
574
00:48:14,967 --> 00:48:17,800
into a savage world
of predator and prey.
575
00:48:20,007 --> 00:48:24,603
This intense competition
now drove evolution at a frenetic pace.
576
00:48:31,607 --> 00:48:33,438
For more than two billion years,
577
00:48:33,527 --> 00:48:36,519
our world had been
dominated by microbes.
578
00:48:36,607 --> 00:48:43,240
Now, complex multi-celled life exploded
into many new shapes and sizes.
579
00:48:45,647 --> 00:48:48,684
Emerging from the sea,
animals and plants
580
00:48:48,767 --> 00:48:53,124
went on to conquer the land and the air.
581
00:48:58,567 --> 00:49:02,082
Volcanoes had ended the terrible time
of snowball Earth
582
00:49:02,167 --> 00:49:05,842
and in doing so, led to a great
evolutionary leap forward.
583
00:49:24,767 --> 00:49:28,680
But Earth's powerful volcanoes
had one further role to play
584
00:49:28,767 --> 00:49:30,997
in the story of life on Earth.
585
00:49:33,487 --> 00:49:35,079
It's a role that's still vital
586
00:49:35,167 --> 00:49:38,921
to the survival of complex life
like us to this day.
587
00:49:40,647 --> 00:49:46,563
It involves an amazing alliance,
a partnership between volcanoes and life
588
00:49:46,647 --> 00:49:49,639
that regulates
the temperature of the planet,
589
00:49:49,727 --> 00:49:53,356
and once again it happens
because volcanoes have the power
590
00:49:53,447 --> 00:49:55,438
to change our atmosphere.
591
00:50:03,207 --> 00:50:07,917
To show how this extraordinary
partnership works, I'm going to Sicily.
592
00:50:14,287 --> 00:50:17,802
This is my favourite place
on the entire planet.
593
00:50:17,887 --> 00:50:22,199
I'm 2,500 metres above sea level,
on the island of Sicily,
594
00:50:22,287 --> 00:50:25,677
and, as you can see,
this is pretty cold and windy,
595
00:50:25,767 --> 00:50:29,396
but the Phoenicians
called this place the Furnace.
596
00:50:29,487 --> 00:50:31,876
The Romans called it the Burning
597
00:50:31,967 --> 00:50:35,357
and for the Arabs,
it was the Mountain of Fire.
598
00:50:35,447 --> 00:50:37,483
We know it as Mount Etna.
599
00:50:40,607 --> 00:50:42,757
And even after thousands of years,
600
00:50:42,847 --> 00:50:46,556
it's still one of the most
active volcanoes in the world.
601
00:51:00,047 --> 00:51:04,040
It may be hard to believe that
volcanoes as destructive as Etna
602
00:51:04,127 --> 00:51:06,960
could ever develop
a partnership with life.
603
00:51:07,767 --> 00:51:11,919
But in fact working together,
they fine tune the Earth's temperature
604
00:51:12,167 --> 00:51:16,001
by controlling the amount of
carbon dioxide in the atmosphere.
605
00:51:21,647 --> 00:51:24,764
This process begins
in an unlikely place.
606
00:51:26,127 --> 00:51:29,642
The oceans,
with tiny creatures called plankton.
607
00:51:33,807 --> 00:51:36,605
They may be individually microscopic,
608
00:51:38,087 --> 00:51:41,204
but they're so abundant
that when they come together,
609
00:51:41,287 --> 00:51:43,437
they can be seen from space.
610
00:51:45,407 --> 00:51:49,320
Every year they proliferate
into huge blooms
611
00:51:49,407 --> 00:51:51,762
that colour the ocean green.
612
00:51:51,847 --> 00:51:54,361
And it's because the plankton
are so abundant
613
00:51:54,447 --> 00:51:57,883
that they can help regulate
the climate of the planet.
614
00:51:59,567 --> 00:52:02,877
The oceans absorb carbon dioxide
from the atmosphere
615
00:52:04,007 --> 00:52:06,760
and the plankton
use this carbon to grow.
616
00:52:09,367 --> 00:52:10,880
When the plankton die,
617
00:52:10,967 --> 00:52:15,324
they fall to the sea floor
and here, over thousands of years,
618
00:52:15,407 --> 00:52:18,046
they are slowly transformed into rock.
619
00:52:19,887 --> 00:52:23,243
In this way,
huge amounts of carbon dioxide,
620
00:52:23,327 --> 00:52:26,239
the very gas that keeps our planet warm,
621
00:52:26,327 --> 00:52:30,479
are removed from the atmosphere
and locked away on the sea floor.
622
00:52:34,287 --> 00:52:36,118
So if that was the end of the story,
623
00:52:36,207 --> 00:52:39,756
our planet would steadily
get colder and colder.
624
00:52:42,887 --> 00:52:46,960
Fortunately, volcanoes like Etna
don't allow that to happen.
625
00:52:48,807 --> 00:52:51,480
Etna is a special type of volcano.
626
00:52:51,967 --> 00:52:55,721
It's formed where two of
the Earth's plates are colliding.
627
00:52:55,807 --> 00:53:00,119
In this case, the African plate
with the European one.
628
00:53:00,687 --> 00:53:04,521
What happens is that one plate
gets forced down, or subducted,
629
00:53:04,607 --> 00:53:06,006
underneath the other.
630
00:53:06,087 --> 00:53:10,000
That action produces volcanoes
and subduction volcanoes
631
00:53:10,087 --> 00:53:13,841
produce some of the largest and most
powerful eruptions on the planet.
632
00:53:15,687 --> 00:53:20,317
Where the plates collide, the rock
on the sea floor containing carbon
633
00:53:20,407 --> 00:53:23,843
from the dead plankton
is carried deep into the Earth.
634
00:53:26,527 --> 00:53:29,837
As it descends,
this layer of rock is heated.
635
00:53:29,927 --> 00:53:33,363
So the rock melts,
releasing carbon dioxide.
636
00:53:36,367 --> 00:53:41,157
And gas is returned back into
the atmosphere during an eruption.
637
00:53:51,167 --> 00:53:53,840
The remarkable cycle is complete.
638
00:53:59,887 --> 00:54:02,321
It's uncanny how working together,
639
00:54:02,447 --> 00:54:06,235
life and volcanoes keep just
the right amount of carbon dioxide
640
00:54:06,327 --> 00:54:07,999
in our atmosphere,
641
00:54:08,567 --> 00:54:12,082
maintaining our planet
at a comfortable temperature.
642
00:54:15,847 --> 00:54:19,476
But this process that has
sustained all life on the planet
643
00:54:20,367 --> 00:54:22,403
comes at an enormous cost.
644
00:54:26,607 --> 00:54:29,963
Subduction volcanoes
are the most violent on Earth.
645
00:54:35,007 --> 00:54:37,521
You can see just how explosive they are
646
00:54:37,607 --> 00:54:41,395
by looking at one of the most
famous eruptions ever recorded.
647
00:54:42,727 --> 00:54:44,877
on May 1 8th, 1 980,
648
00:54:44,967 --> 00:54:48,562
Mount St Helens in the United States
was ripped apart.
649
00:54:52,567 --> 00:54:57,402
Within minutes,
2.8 billion cubic metres of the volcano
650
00:54:57,487 --> 00:55:00,684
were blasted out over
the surrounding countryside.
651
00:55:04,807 --> 00:55:08,959
For the last 25 years,
Mount St Helens has been fairly quiet.
652
00:55:13,487 --> 00:55:18,197
But inside its vast crater,
a giant cone of rock is growing.
653
00:55:19,967 --> 00:55:22,606
Forced up by the pressure from beneath,
654
00:55:22,687 --> 00:55:26,282
Mount St Helens is building
for another eruption.
655
00:55:36,287 --> 00:55:41,645
The irony is that subduction volcanoes
are so highly explosive and destructive
656
00:55:41,727 --> 00:55:43,683
because they're so gassy,
657
00:55:43,767 --> 00:55:47,316
yet it's the release of the gas
that's crucial to the Earth.
658
00:55:47,407 --> 00:55:51,559
That's the key to recycling carbon
that's locked in the rocks
659
00:55:51,647 --> 00:55:53,160
back into the atmosphere.
660
00:55:53,967 --> 00:55:58,882
The whole elaborate system
works like a finely tuned thermostat
661
00:55:58,967 --> 00:56:01,765
maintaining the right temperatures
for life.
662
00:56:06,527 --> 00:56:09,564
But, of course,
it must be hard to accept
663
00:56:09,647 --> 00:56:12,605
just how important volcanoes
are to our world
664
00:56:12,967 --> 00:56:15,845
when it's your own home
that gets destroyed.
665
00:56:22,207 --> 00:56:25,916
In 1 992, a few months
before I first came here,
666
00:56:26,007 --> 00:56:28,965
the volcano was spewing out
masses of lava.
667
00:56:30,487 --> 00:56:33,559
And I remember the news footage
of the farmer
668
00:56:33,647 --> 00:56:36,036
who lived in this house here,
669
00:56:36,127 --> 00:56:39,085
and with the lava coming up
to his front door,
670
00:56:39,167 --> 00:56:43,683
he sits down for a farewell meal,
drinks a final glass of red wine,
671
00:56:44,287 --> 00:56:47,279
daubs a sarcastic remark,
grazie governo,
672
00:56:47,367 --> 00:56:50,564
on the wall and
leaves his home to the lava.
673
00:57:13,607 --> 00:57:17,885
Ever since the planet formed
four and a half billion years ago,
674
00:57:20,647 --> 00:57:25,198
Earth's inner heat has been continuously
struggling to escape.
675
00:57:30,327 --> 00:57:35,162
We see the result as volcanoes,
but that's just one part of it.
676
00:57:42,167 --> 00:57:46,638
To me, nothing has been more important
to the history of our planet
677
00:57:46,727 --> 00:57:49,195
than the heat trapped inside it.
678
00:57:52,927 --> 00:57:55,441
No force on Earth is more dramatic,
679
00:57:55,527 --> 00:57:58,917
more destructive,
more violent than volcanoes,
680
00:57:59,007 --> 00:58:02,795
but they're so much more
than just a force of destruction.
681
00:58:02,887 --> 00:58:05,355
They're the life force of our planet.
682
00:58:05,447 --> 00:58:09,440
Quite simply, without volcanoes,
I wouldn't be here
683
00:58:09,527 --> 00:58:11,404
and neither would you.
684
00:58:16,607 --> 00:58:19,121
Next time, the atmosphere.
685
00:58:19,967 --> 00:58:21,923
It's immensely powerful,
686
00:58:22,767 --> 00:58:25,520
but, at the same time, highly sensitive.
687
00:58:28,807 --> 00:58:32,117
It's destructive
and yet it also protects us.
688
00:58:34,127 --> 00:58:39,247
Now it's changing fast with potentially
devastating consequences.