All language subtitles for Rise of the Continents 4of4 Eurasia 720p HDTV_Subtitles01.ENG

MUSLIM CALL TO PRAYER

Istanbul.

For more than 2,000 years it stood at
the crossroads between East and West.

The point where Europe ends

and Asia begins.

The two continents divided
by the Bosphorus Straits.

This is one of the great journeys.

Stepping off the continent,
leaving Europe behind.

But crossing the Bosphorus
isn't all that it seems.

This notion that Europe and Asia are
separate is a bit of a nonsense.

From a geological perspective,
they're both part of
the same vast landmass.

Eurasia stretches from
the Atlantic coast of Portugal

all the way through
to Russia's Pacific coast,

making it the biggest continent
on the planet.

To reveal how this mighty continent
formed, I want to reach back in time.

Because, if you know where to look,
there are clues to its ancient past

written into the world around us.

Its landscapes...

..wildlife...

Hey! Is that karimeen?

..and the very rock
from which it's built.

The tiniest detail can reveal
the history of a vast continent.

Evidence that shows
how Eurasia was assembled

in a series of
monumental collisions...

This just kicked off
just as we got here.

..catastrophic impacts

that created the conditions
for civilisations to rise,

changed the course
of life on Earth...

..and left an indelible mark
on the landscape...

Just a wall of rock and ice.

..a mountain range spanning
the entire continent.

The story of how that formed was
the story of how Eurasia formed.

A continent forged in a series of
collisions that continue to this day.

And because the process
that built Eurasia is still active...

Whoo-ho-ho!

..the largest continent
on the planet

is merely the start of
something far bigger.

The first clue to uncovering
Eurasia's past can be found
here in Istanbul.

For centuries, the city's
strategic location
at the heart of the continent

has made it a major centre for trade.

Turkish delight. Lovely!

With honey and pistachios.
Pistachios?

Yes, honey and pistachios.
It's lovely.

Just as it does to this day.

We have a present for
your mother-in-law.

There's a joke there, I'm sure.

That's the thing
about these bazaars -

they still sell
the traditional things

that they've been selling since
this city was in its infancy.

Look at this.
Exotic foods there, spices.

Metals, spice men...jewellery,
precious stones like this, ceramics.

If you want it, it's here.

Now smell, please.

Wow!

But there's one product that's shaped
Istanbul's history like no other.

In a way, this city is here
because of this stuff - silk.

Look at it, it's just gorgeous.

If you go back to the sixth century,

this is one of the most expensive,
most sought-after commodities,

partly because it comes
all the way from China

and also because how it was made
was this closely guarded secret.

The story goes that a delegation
of monks would smuggle back

a couple of silkworm inside
a bamboo cane, brought it back here

and then this place, Istanbul, just
took off as a hub of silk production.

And the fabric gave its name
to the Silk Road,

the network of ancient trade routes
that runs across
the entire continent,

connecting China through Istanbul
and onto Europe.

And the Silk Road is crucial
to the story of Eurasia today

because beneath it lies evidence

that reveals the origin of
the continent itself.

Evidence that can be found
500 kilometres southeast of Istanbul,

where the Taurus Mountains reach
the shores of the Mediterranean...

..in a place that's been both
a staging post on the Silk Road

and a site of pilgrimage
since the days of Ancient Greece.

This whole landscape
is steeped in myth.

Just over the back is Mount Olympus,
the home of the Greek gods.

Actually, it's one of about
20 Mount Olympuses

that are scattered across
the ancient world.

But the mountain that I'm climbing
now is unique - Mount Chimera.

It's named after this mythological
creature that's got
the tail of a snake,

the body of a goat and a lion's head.

Oh, yeah - and it breathes fire.

These are the eternal flames.

In Turkish they're called Yanartas,
which is just "flaming rock".

Look at them. Today they're
maybe half a metre high

but in ancient times
they were much higher,

so that if you were out at sea,
you could see this place
as a lighthouse.

But my favourite story, though, is,
because we're so close to Olympus,

this could be the source of
the first Olympic flame.

It's such a surreal scene.

But what fuels these flames
is far more ancient.

And analysing it takes you back
tens of millions of years

to the time Eurasia formed.

Fossilised sea creatures.

Plankton.

Three to four kilometres
into the Earth.

Do you see this black residue here?

It's soot - essentially carbon.

That tells us that these flames
are burning an organic compound.

In this case, natural gas or methane.

A geochemical analysis of
these flames indicates

that that gas is coming from
carbon-rich rocks deep underground.

Much of it from fossilised
sea creatures, plankton.

To transform plankton into gas,

you have to take the long-chain
hydrocarbons that make up the cells

and you have to break them
into smaller and lighter bits.

This process happens spontaneously
at around 140 degrees...

..temperatures that can be generated
by burying the rock

three to four kilometres
down into the Earth.

The best way to do that

is to pile layer upon layer upon
layer of sediment on top of it.

And the place where that process
happens all the time

is the bottom of the deep ocean.

The gas here shows that
millions of years ago

this region of Turkey was underwater.

But the evidence of a lost ocean
doesn't stop there.

It can be found all along
the ancient Silk Road.

This is Eurasia as we know it today

and here we are down here
in southern Turkey.

Some of the biggest oil and gas
fields on the planet occur
east of Turkey

in a belt through Central Asia
to Afghanistan.

But east and west of that too
there's evidence of a former ocean.

There's precious stones that started
off as rocks on the ocean floor.

Things like jade which occur
in Pakistan, in Burma and in China.

And then marble occurs in Greece,
Italy and other parts of Europe.

You also get metals that are formed
on the bottom of the ocean,

metals like copper that
you get found in Cyprus.

But the final evidence,
the best evidence

is fragments of the rock
that I'm sitting on.

These are fragments of ophiolite.

Ancient ocean crusts

which you find formed in a kind of
belt all the way across this region.

What all these lines of evidence
add up to

is the fact that there was
once a vast ocean

that stretched the entire length
of this continent.

The continent of Eurasia
as we know it today

didn't exist 200 million years ago.

Where the south of the continent,
Italy, Arabia and India, are today

there was a 90 million
square kilometre ocean.

The Tethys.

Western Europe was lost
beneath its waves...

..and Britain was a collection
of tropical islands

off its northwestern shores.

Wrapped around its long
arcing coastline,

all the Earth's landmasses
were joined together

into one vast supercontinent.

Called Pangaea, it was a land
dominated by the dinosaurs...

..just as fearsome marine reptiles
ruled the Tethys.

Today, all those creatures
are now extinct.

And the Tethys Ocean itself
has long since disappeared.

But what destroyed the Tethys

and led to the extinction of many
of the creatures that lived in it

is the same geological process that
led to the formation of Eurasia.

Because the story of Eurasia

is essentially the story
of how the Tethys died.

The mystery of how Eurasia formed
from the death of the Tethys

involves one of the greatest
mass extinctions in Earth's history,

the rise of its ancient civilisations

and will reveal the continent's
ultimate fate.

And clues to how that happened

can be found in the southernmost tip
of India.

These are the gentle backwaters of
Kerala in southern India.

A place famed for its spices,
especially black pepper.

One of the key staging posts

on another of those ancient trading
routes that crisscross Eurasia.

For centuries,
Kerala's lakes and waterways

supported a traditional way of life,

a floating existence
that still survives to this day.

I'm here to find
something truly ancient,

something that's lived
in waters like these

for over 100 million years.

A creature that provides
a direct link

back to the most important event
in the formation of Eurasia...

..and is, for the local fishermen,
these waters' most prized catch.

A fish known here as karimeen.

Hello!

How're you doing? Hi there.

The karimeen is tasty.
Very, very tasty.

Is there a lot? Is it all over?

All over.

So how do you catch it?

Do you jump in?

Catch it.

You make it sound so easy.

First, two of the fishermen
use a line

to scare the fish into the mud
at the bottom of the lake.

Then the others swim behind,
making a noise to startle the fish...

..before plucking them from
the mud with their bare hands.

Hey! Is that karimeen? Yay!

Fantastic! Number one.

That's fast.

Very nice.

Put it in there.

This is it. This is what all
the action was for. A karimeen.

Latin name Etroplus suratensis.

A fish whose anatomy reveals
the evolution of entire continents.

IAIN'S VOICE ECHOES:
..the anal fin...

..shape of the skull...

It's a type of fish called a cichlid.

They're marked out by a couple
of anatomical quirks

that make them distinctive.

One of them is right at the back.

It's at his rear end, basically,
the anal fin.

Now, in most cichlids, the anal fin's
got three or four spines

but this species has many more.

The other characteristic
is at the front end.

It's in the distinctive shape
of the skull

which relates to the swim bladder,

that sac that controls
the buoyancy of the fish.

There's only one other group of fish

that share these distinctive
characteristics.

The closely related
Paretroplus cichlids.

And they live over
4,000 kilometres away...

..in Madagascar.

Now, Etroplus can tolerate
slightly salty conditions

but they're essentially
a freshwater fish,

so one thing's for sure
is they didn't swim here.

Instead the answer is that
it's not the fish that moved.

It was India.

This is a reconstruction of how
the Earth's landmasses looked like

120 million years ago,

just before the emergence of
the first cichlid fishes.

You can see up here, China and
Siberia fused together.

And you can see the area here
that's going to become Britain

and this in here in blue is
the Tethys Ocean.

Then down here past the equator
into the southern hemisphere,

tucked snugly in beside Madagascar,
is India.

If I press "play" here I can simulate
how the landmasses then move.

What you find is that
in 90 million years,

India and Madagascar split.

Then suddenly, 25 million years
after they separated,

India more than doubled its speed.

That's dramatic stuff.

That's a mini-continent, something
like 3,000 kilometres across,

just speeding across the globe,
crashing into Eurasia.

Fantastic! I never tire of
watching this. It's great.

India's journey north was a key
moment in the formation of Eurasia

because, as it moved, it closed
the ocean in front of it,

spelling the beginning of the end
for the Tethys.

But the big question is
what caused it to speed up,

because that led to one of

the most catastrophic events
in Earth's history.

You can see evidence of that
cataclysm in the hills
outside Mumbai,

a place known as the Deccan Traps.

The Deccan.

It's one of those words
for a geologist that
conjures up these images.

This iconic landscape.
Stepped plateaus and things.

And yet this kind of gentle
landscape holds in it

one of the cataclysmic geological
events in the planet's past.

There's telltale signs
in that cliff face there.

You see, it looks like a set of
bands. They're layers of lava.

Molten rock that came out, solidified

and then built up
layer upon layer upon layer

over tens, hundreds of thousands
of years to form these hills.

68 million years ago,
this landscape was very different.

Eruption after eruption poured
1.3 million cubic kilometres of lava

across southern India.

Enough to cover the UK in a layer
of rock five kilometres thick.

All over these hills, there's gems
like these just carved into the lava.

But there is no volcanic activity
in India today,

so the question is where's
the source of these eruptions?

And how did it speed India up?

This whole cave is carved out of
a type of lava called basalt.

IAIN'S VOICE ECHOES:
Ilmenite... magnetite...

latitude.

It's got really fine crystals.

About 10% are minerals
called iron oxides - rust.

It gives us this reddy browny tint.

Minerals like ilmenite
and magnetite.

And that's the clue, because
these iron oxides are magnetic.

Just after the lava solidifies,

its temperature drops
below 585 degrees

and the magnetic fields of
the iron oxide crystals

align themselves with
the planet's own field.

The thing about the Earth's
magnetic field is that it changes

depending on your position
on the planet,

where you are between the South Pole
and the North Pole.

In other words, your latitude.

It's a property
known as its inclination

and it means that the basalt
contains a record of its position

at the precise moment it solidified,

which allows you to pinpoint
exactly where it formed.

Today, this temple is at a latitude
of 18.7 degrees north.

But the thing is, the magnetic
inclination of the rock itself

tells us that it formed at a latitude
of about 20 degrees south.

In other words, this lava formed
in the southern hemisphere.

So the thing is that the source of
this volcanism isn't to be found

deep beneath my feet here.

Instead it's several thousand
kilometres in that direction.

If you trace India's journey
back to the point it crossed
20 degrees south,

you arrive directly
over a mantle plume.

A huge column of superheated rock

that rises up from near
the Earth's core.

As India moved over the plume,
it triggered the Deccan eruptions.

But deep underground
it had another impact...

..something that can explain
India's dramatic acceleration.

Continents flow around the mantle
like vast ships.

Just as a hull of a ship
lies below the water line,

so the bulk of a continent, maybe 80%
of it, extends deep into the Earth.

Today, the Indian continent

is half the thickness of
the other great landmasses.

It's thought that that's because

as the Indian Plate moved across
that mantle plume

it melted away the base of
the continental plate.

According to that idea,
that huge loss of mass,

combined with the lubricating effect
of that molten rock,

and also maybe an extra push
from the mantle plume,

caused India to double its speed,
propelling it towards Eurasia.

It was a geological cataclysm.

But the implications for life
are even more dramatic,

because the Deccan eruptions
contributed

to one of the greatest turning points
in the history of life on Earth.

As the plume burnt its way up
through the continent,

it pumped billions of tonnes
of ash and toxic gas

directly into the atmosphere.

Over hundreds of thousands of years,

this slowly choked the planet
and poisoned the oceans,

wiping out 50% of all life.

And for the dinosaurs
it led to a drawn-out decline

until it's thought an asteroid
finally finished them off.

But the end of the dinosaurs
turned out to be our gain,

because, as one group
of animals died out,

so another rose to take their place.

The mammals.

In a way, the extinction was
curiously selective.

I mean, you and I would
never have survived.

In fact, no land vertebrate larger
than 25 kilograms made it through.

But back then our distant ancestors

had just the right mix of
characteristics to survive.

And there's one modern mammal

that's thought to have similar
adaptations today.

Because what's worked in the past

also works on the mean streets
of Mumbai.

The city has such a large
rat problem,

it employs a small army
of rat-catchers,
like Rakesh Daji Mittal.

So we think of humans as being
the most successful mammal,

but I reckon we're looking at
the ultimate one here - rats.

They've certainly got all
the essential traits for survival.

They're small enough - they can
get into nooks and crannies

and just keep themselves
tucked away from harm.

And, in food, they're voracious
eaters. They eat anything.

And that not having to rely on
a single source of food
is really useful.

It's...

And I guess the main thing is sex.
These things breed like...

rats, really,

which is why the rat-catchers of
Mumbai are struggling to keep up.

If it's a question of who's going to
survive the next apocalypse,

my money's on them.

It's curious to think

that it might have been
characteristics possessed
by the humble rat

that enabled our distant
ancestors to survive

where the dinosaurs had perished.

And that it was the movement of India
that ultimately paved the way

for us to inherit the Earth.

As it continued north,
India left the mantle plume behind.

But, now travelling twice as fast,
it crashed into the rest of
Eurasia...

..changing the face of the continent

and sealing the fate of
the Tethys Ocean.

and sealing the fate of
the Tethys Ocean.

But the demise of the Tethys

would have another major impact
on human history...

..shaping the rise of
Eurasia's civilisations.

Morning, Max. Hello, sir.

Hey! Welcome aboard.

It's small, isn't it?

To see how that lost ocean influenced
our past and still affects us today,

you need to take a closer look at
the most obvious result of the
collision.

FAINT MUSIC
Where's the music coming from?

Where's your tape deck? Your CDs?

Ah!

I love the music.
I just can't get over the music.

Giorgio Moroder - lovely!

Ha-ha!

What a place you have here.

Ah! Ah-ah-ah!

It's a long way down.

It is a very, very long way down.

These are the Himalayas,
the greatest mountain range on Earth.

Ah! Now we see the mountains.
Here they are.

The Dhaulagiri's over there,

Manaslu's over here and
Annapurna's ahead of us.

All three of those are
over 8,000 metres.

26,500 feet. That's three of the top
ten mountains in the world.

The mountains look solid
and immovable.

Ah! That's majestic.

Just a wall of rock and ice.

But that is just an illusion.

These peaks are in fact
a slow-motion car crash

playing out over millions of years.

Ah!

And still we climb.

Whoo-hoo!

It's absolutely stunningly beautiful,

but when you look at the mountains,
as a geologist you see so much more.

It's almost like you see through
the obvious snow and rock

to the inner workings.

You can see the process of
mountain building almost in action.

I can see some folds.

So, Max, that's those folds up there.

See the rocks kind of wrapped around
this enormous fold structure.

You can see that it comes across,
swings down like a big Z shape.

It's not just the shape of them
that's spectacular -
it's the sheer size.

You see these Zs up there? Z.

We call them Z-shape folds.

It's very technical, geology.

These folds, some the size of
entire mountains,

were created as India ploughed into
the rest of the continent,

the immense power of the collision
twisting and contorting solid rock,

as if it were Plasticine.

Ah, yeah.

I love it! Love it!

You might think these contorted rocks
are pieces of the land

scrunched upwards as the two
continents ploughed into each other.

But the reality is
far more surprising.

This is one of the great rivers
of Eurasia, the Kali Gandaki.

It starts up there
in the north in Tibet

and flows down through the wilds of
Mustang Province of northern Nepal,

down through here
to India in the south.

For millions of years, it's been
carving its way down
through the Himalayas

to produce what down there is one of
the deepest gorges in the world.

And it's in rivers like these
that you can find clues

to the origin of the rock from which
these mountains are formed.

Curious stones, called saligrams
by the locals,

who worship them as manifestations
of the Hindu god Vishnu.

What I'm looking for is hard,
black nodules,

kind of black lumps of shale

that's fallen out of the cliff
and then been washed around

and I'm hoping that at the heart of
one of these nodules

we're going to find a saligram,
because often they enclose them.

Need to break them open
and reveal them.

What's lovely is that when you
reveal them, if you get it,

you're exposing something
that last lived in the Jurassic,

100-odd million years ago,
sort of exposed back to the world.

And the other thing that's lovely,
if you find one,

is you're the first person in
the world to ever find that.

Cos it's been hidden away
for 100 million years or so

and then you break it open.

It's your fossil.

So, if you see any, tell me.

You're looking for a natural weakness
and once you get that...

This'll be the one.

This'll be the one.

This geology lark's
harder than it looks.

The funny thing about it is,
all the way up that road

there's guys selling these things.

They get them from the rock
and sell them to all the tourists

and I thought no, no,
I'm going to find them for real.

How much for this?

350. 350 rupees, OK. One...

This is going to be a bargain.
There's 300... OK?

OK. OK.

Now this... This is a saligram.

Look at that.
Absolutely beautiful.

Geologists know it better
as an ammonite.

It's the fossilised remains

of an extinct member
of the squid family.

The modern-day version
would be the nautilus.

The body would be in here
and the head

and tentacles would sit out here.

The thing is, just like
the modern-day nautilus,

these creatures didn't live in the
mountains - they lived in the ocean.

That's the thing about geology.

It's not really the rocks themselves
that are important -

this is a rather boring black mud -
but it's the stories they tell.

I mean, these ammonites were
swimming around in Jurassic seas

when dinosaurs roamed the land,

when Eurasia was really
coming together.

That's what the story
of the rocks tell.

The walls of this valley,
2,700 metres above sea level,

are brimming with the remains of
ancient sea creatures.

Marine fossils have been found
right across the Himalaya,

including right at the top
of Mount Everest.

It's astonishing to think that
rocks that started out

at the bottom of the Tethys Ocean
are now the roof of the world.

When India collided with Eurasia,

the ocean floor at the margins of
the Tethys was thrust upwards...

..forming an immense barrier
across the continent.

And it's by creating that barrier

that the Tethys has had a profound
effect on the course of human
history,

and still does to this day.

Because mountains this high
can't help but interfere
with the climate.

THUNDER RUMBLES

That is one angry sky
up there, isn't it?

That's the thing about mountains -
they create their own weather,

and the bigger they are,
the bigger the weather they create.

Somewhere round that cloud and mist

there's the Himalayas,
the biggest on the planet,

so it's no real surprise, then,
that it produces

one of the most important weather
systems on the planet - the monsoon.

THUNDER ROLLS

WIND AND RAIN

The winds that bring the moist air
rise up along these slopes

and just dump rain and snow
on those hills

and you get these brutal downpours
like these,

running up to the wet season,

that dump water in the gorges
and rivers up there,

create mudslides and landslides that
just chuck it down, chuck material.

If you can just see, there's a river
down there that's flooded,

that's full of mud and dirt that's
been taken out of that mountain
range.

This is one of the most dynamic
active environments in the world.

But also one of the wettest.

THUNDER RUMBLES

THUNDER STILL RUMBLES

These sediment-laden waters
flow down from the mountains

and out onto the plains of India,
Pakistan and China...

..and, combined with
the monsoon rains,

water and nutrient-rich soils
from the Himalayas support
three billion people.

Nearly half the world's population.

But the formation of Eurasia has had
a much wider impact on civilisation.

Because India's collision was
only the beginning of the end
for the Tethys.

Arabia also moved north, creating
the Zagros and Taurus Mountains

that run through Iran and Turkey.

Italy and Greece collided with
northern Europe, building the Alps...

..and completing a mountain chain
that spans the entire length of
Eurasia...

..and marks the final resting place
of the once-great Tethys Ocean.

And, just as the Himalayas support
Asia's population today,

so this immense chain of mountains
created the conditions

for the first civilisations
to rise across the continent.

Oh, wow! Look at this.

Isn't that magnificent?

Many of the great Eurasian
civilisations sprung up

in the shadow of the mountain chains
that spanned the continent.

They occupied fertile river valleys
that grew up

on the back of sediment the water
washed down from mountains.

Following the line of the mountains
and connected by trade routes,

a chain of empires developed
across the continent.

But the mountains themselves
also provided a sanctuary

for numerous city states, like
the Pisidian city of Termessos

in the Taurus Mountains
of southern Turkey.

If you were a society that lived
in the mountains

then you had to work with
the geological cards
you'd been dealt.

This is a fragmented landscape.

Cities like this are physically
hemmed in and isolated from the
neighbours.

But isolation also means
independence

and cities like this could become
crucibles of invention and
innovation.

Empires like the Greeks
and the Romans

that had mountains at their heart
became successful,

because they were able
to harness that ingenuity.

So, in a way, Eurasia's long history
of civilisation

goes back not thousands,
but millions of years

to the formation of the mountains
at the heart of the continent.

Eurasia as we know it was complete
around 20 million years ago.

The landmasses that formed it had
moved into their current positions.

And with the closing of the Tethys,

western Europe, including Britain,
emerged from beneath the waves.

But the formation of Eurasia is
really just the beginning
of this story,

because the process that built it
is still active today.

And by understanding that process

it's possible to chart the
astonishing future that awaits
the continent.

This is the Mediterranean Sea,
instantly recognisable on a map.

In the west, it connects
to the Atlantic Ocean

through the narrow
Straits of Gibraltar

and then in the east it's
the shores of Turkey and
the Middle East that end it.

But, just like the Tethys before it,
the Med too is closing,

as the vast African Plate
moves north.

And where it collides with Eurasia
beneath the southern tip of Italy

it's created a cluster of volcanoes
that rise up from the ocean floor.

This is Strombolicchio.

It's actually the solidified throat
of an ancient volcano.

200,000 years ago that rock was
molten, rising up to spew

and explode out of a volcano that
would have risen above our heads.

And then, around that time, that
volcanic activity switched
to the south

and this thing just crumbled and
collapsed back down into the sea,

so all that's left is
a solid volcanic neck.

The innards, the guts of
an ancient volcano.

Today, the tiny island of
Strombolicchio

lies two kilometres north
of Stromboli...

..Italy's most continually
active volcano...

Grazie.

..in a place you can see Eurasia's
destiny taking shape.

The thing about volcanoes is that
they're windows into the inner Earth.

This particular one is a window
into the most important process

driving the movement
of the continent.

The only trouble is
that to understand it,

I have to get right up there.

The summit towers some 900 metres
above sea level...

..casting a long shadow
over the island

and the villages that cling
to its shores.

Ha!

Look at it steaming away.

Oh, that's perfect!

This just kicked off
just as we got here.

They call it "puffing" here -
a big puff, and you can see
all the boulders

just rolling down the hill
and the smoke there.

We've arrived.

BLAST
Hey! Hey!

Look at that.

That's Stromboli for you.

Isn't that magnificent?!

This volcano's been doing this,
exploding like this,

every ten, twenty minutes really
for the last 2,000 years.

Whoa!

That's a good 'un.

That's a cracker!

It's so hard to get an idea
of the intensity of that,

but those orange balls that are
getting kicked out there

are actually metre-sized boulders.

And the temperature of that must be
500, 600 degrees.

Extraordinary! You really don't want
to be much closer than this.

Well, I do, but...

What makes Stromboli special
is it doesn't really produce
that much lava.

Unlike volcanoes like Hawaii and Etna
that spew out these huge lava flows,

this volcano's eruptions are
almost exclusively explosive.

And at night, when the sun goes down
and the fireworks really start,

you really understand why it's called
the Lighthouse of the Mediterranean.

Stromboli's regular
explosive eruptions

create one of the planet's
most astonishing spectacles.

But more than that, they're a clue
to understanding the process

shaping the fate of the continent.

Whoo-ho-ho-ho!

IAIN'S VOICE ECHOES:
..viscous and sticky...

..trapped gases...

..so explosive...

..the Tethys destroying itself...

This crater rim is just
littered with blocks

that have been thrown out of
that vent down there.

Stuff like that.

This material is actually made
of a rock called andesite.

Andesite is quite a light grey rock
and that's cos it's got a lot of
silica in it.

Because it's got a fair amount
of silica in it,

it tends to make the magma
quite sticky and viscous

and that means it traps gases.

It's just lots and lots of bubbles
in this rock.

And it turns out that
it's those bubbles

that's the reason why those
eruptions are so explosive.

As the magma rises to the surface,
the gas trapped inside expands

until the bubbles burst
and the rock explodes.

But the gas responsible

isn't one you'd immediately
associate with a volcano.

It's water vapour,

or steam.

This rock actually explains
where the water comes from

to drive those steam eruptions.

You might think the steam
comes from sea water

sinking into the volcano,

but actually the water's
already in the rock.

Look at this. This is an andesite
without all those bubbles

so that you can see all the beautiful
crystals, called pyroxene.

Pyroxene crystals form at depths
of five to ten kilometres.

And as they grow they encase
tiny quantities of magma,

locking it away and carrying it up
to the surface.

Now, if you could look
into those tiny specks

of the original magma
that formed this rock,

you'd find that there was
water in them.

In other words, the water was
actually in the magma

deep down in the mantle.

The only way water could be found
so deep in the inner Earth

was if something carried it there.

In this case,

it was dragged down in the rock
that forms the ocean floor itself.

Because Stromboli is a volcano

powered by
a process called subduction.

Subduction generally happens when
ocean crust meets continental crust.

The ocean crust rocks are denser
so they sit lower in the mantle

and when they collide,

the ocean crust gets pushed under
the lighter continental crust

descending down into the mantle.
BANG

So that eruption up there
actually started off

about 100 kilometres
beneath our feet.

Down there, water gets forced out
of those ocean rocks

and causes the rocks
around them to melt,

which rise up and eventually
burst out as volcanoes.

Subduction is the ultimate fate
of all ocean crust.

But it isn't a consequence of
the continents moving.

Subduction is the engine that drives
the movement in the first place.

As the ocean crust descends
beneath the continental crust,

it doesn't break off - it's still
attached to all that ocean floor.

And it's that vast slab of rock
heading down into the mantle

that pulls the ocean crust and in
turn hauls the landmasses behind it,

dragging the continents across
the face of the Earth.

Maybe it's because we live in the
land that it's tempting to think

that it's the landmasses moving
around that closed the oceans.

That it was the northward movement
of India that destroyed the Tethys.

But actually it's the exact opposite.

It was the Tethys that pulled
the continents together,

destroying itself in the process.

It was subduction that built Eurasia.

And it's subduction that's shaping
its ultimate destiny.

For 300 million years subduction
has been gradually,

inexorably closing the Tethys,
creating Eurasia.

And as time goes on
it'll close the Med too.

Africa will continue northwards,
this whole area will emerge as land

and these islands will be the peaks
of the Mediterranean mountains.

A great mountain chain at the heart
of a new supercontinent.

As Africa ploughs northwards,

France and Germany become
ever more mountainous.

And those peaks would look out
over a vast desert

covering the whole of central Europe
and Asia.

It's thought that 250 million years
in the future

all of those continents will once
again be joined together as one,

with Eurasia right at the heart of
it.

Australia joins up with
southern China.

The Americas crash into
the shores of Africa.

And Britain is swept up
towards the North Pole.

The formation of this vast new land,
the planet's grand cycle,

that epic break-up

and movement of the continents
across the face of the Earth

will begin once again.

Subtitles by Red Bee Media Ltd