All language subtitles for How the Earth Was Made HC 720p HDTV S01E11 Iceland EN

Earth, a 4.5- Billion-year-old planet,
still evolving.

As continents shift and clash, volcanoes
erupt, and glaciers grow and recede,

the Earth's crust is carved
in numerous and fascinating ways,

leaving a trail
of geological mysteries behind.

In this episode, Iceland, the world's
largest volcanic island, is explored.

This barren and alien landscape
generates one third of the world's lava.

Steam billows from the ground
and boiling water is thrust into the air.

It's a land of violent extremes
where fire meets its nemesis, ice,

and where clues
to understanding Iceland's formation

also provide a window into
the formation of the Earth itself.

In the middle of the north Atlantic Ocean
lies Iceland, a lone island,

only 300 miles wide.

A volcanic hotbed,

it holds some of the most diverse
geological wonders known to mankind.

To understand how it formed

and the dynamic forces
that are shaping this land,

scientists are scouring
the strange landscape for clues.

And the investigation starts here,
in the southwest of Iceland -

the Thingvillir plain.

This broad inland valley runs through
the centre of Iceland.

Giant cracks scar the valley floor,
leaving this unusual landscape behind.

Geologist Mike Poland
believes they're a major clue

in the mystery of Iceland's formation.

I'm standing
in a really spectacular place.

There's evidence
for volcanic activity all around.

This valley is covered in lava
and the plain is being ripped apart.

Everywhere I look, there's massive tears
in the ground, like this one right here.

This crack is getting bigger
and bigger every year.

In fact, this entire valley
is spreading apart

at about the same rate
that fingernails grow.

Now, imagine the forces that must be
involved to rip the land apart like this.

Something powerful is spreading
this valley at a rate of one inch a year.

A force so immense,
it's pulling the entire country apart.

But what force on Earth
could have such power?

In 1912, German climatologist
Alfred Wegener found an essential clue.

Browsing through maps,
he noticed that the great land masses

of the Americas and Eurasia
appeared to fit together.

This observation led Wegener
to propose a radical new theory,

that these great continents
had once been joined together.

So some unseen force
must have pushed them apart,

allowing water to rush
into the space between them,

creating the Atlantic Ocean.

It was inspired detective work
and a major step forward in the search

for what was pulling Iceland apart.

But with no method to prove
such a force existed,

Wegener's theory was ignored
for the next 40 years.

Then, in 1946, new evidence was
discovered to support Wegener's ideas.

The US Navy, using a technology
called sonar imaging,

mapped the Atlantic Ocean floor
for the first time.

The pictures revealed a 10,000-mile
network of underwater mountains,

separated by a giant tear which passes
through the centre of the Atlantic.

Scientists call this
the Mid-Atlantic Ridge.

This huge tear through
the Earth's crust is the boundary

between the American
and Eurasian plates,

and the tear runs right through
the centre of Iceland.

I'm actually standing
on what's essentially the ocean floor

where the Mid-Atlantic Ridge
comes onto land.

And it splits the North American plate
on this side

from the Eurasian plate on this side.

And the Mid-Atlantic Ridge starts
way south down by Antarctica,

comes all the way up
through the Atlantic

and splits this country right in two.

Scientists suspected this was pushing
the continents, and Iceland, apart.

They came up with a theory.

Deep below the ocean,

convection currents of molten rock
tear open the Earth's crust,

allowing magma to seep up
and push the continents apart.

But there was a problem.

It was so deep,
scientists had no way of proving

whether magma was seeping through
the crust at the centre of the ridge.

Until, in 1974,

Alvin, a human-operated submersible,

was launched by the Woods Hole
Oceanographic Institute.

With its ability to withstand
deep sea pressures,

scientists could finally travel down
to the depths needed

to reach the Mid-Atlantic Ridge.

It was by examining the tear
that runs through the centre of this ridge

that they spotted the evidence
they'd been looking for -

hot volcanic gases
billowing into the ocean.

Finding this told them that the
Mid-Atlantic Ridge was highly volcanic

and, like a giant wedge, was capable
of spreading great land masses apart.

Iceland's cracked Thingvillir valley is
a continuation of the Mid-Atlantic Ridge.

The same process that's pushing
America further away from Europe

is happening here on land.

Finally, here was a force
powerful enough

to explain why the cracks
are getting wider,

and Iceland is getting bigger.

As the... the ridge continues to spread,

it's going to add more
and more land to Iceland,

so, in a way, Iceland will... will start
getting longer and longer,

in... in an... in an east-west sense, as the
plates spread apart from one another.

So, in a way, Iceland is not getting
torn apart so much as it's getting built.

The investigation into how Iceland
is growing has revealed cracks

on the Thingvillir plain are widening
at a rate of one inch a year.

And hot gases prove that this
spreading force is volcanic,

forming the Mid-Atlantic Ridge,
which cuts right through Iceland.

Scientists concluded it's this
that's widening the country.

Convection currents of hot rock
pull the Mid-Atlantic Ridge apart.

Magma surges up to fill the cracks
and, as it approaches the surface,

it cools, hardens and forms new land.

Like a conveyor belt,
it continually pushes Iceland apart.

But something didn't add up.

Why wasn't Iceland
at the bottom of the ocean

like the rest of
the Mid-Atlantic Ridge?

There's something strange about the
amount of volcanic activity on this island.

This is not a normal section
of the Mid-Atlantic Ridge.

There's a tremendous amount
of volcanism

that's happening in this part of the ridge,

as opposed to the ridge
that's off in the Atlantic Ocean.

The hunt is now on to discover how
Iceland rose a mile and a half

off the ocean floor and became the
biggest volcanic island in the world.

Iceland.

There are more active volcanoes
concentrated here

than anywhere else on the planet.

Geologists are searching for what has
helped push Iceland off the ocean floor

and lights the fiery volcanoes
that rage across this barren land.

On the hunt for clues,

the investigation heads to one of
Iceland' s most active volcanoes, Hekla,

known locally as the Gateway to Hell.

Like all active volcanoes in Iceland,

Hekla sits alongside
the Mid-Atlantic Ridge.

Volcanologist Dr Pete La Femina
is taking a high-resolution scan

of the volcano to see if its geology
hides any clues about its inner workings.

This is a terrestrial
laser scanner,

and the laser produces a 3-D image
of the Earth's surface,

and that allows us to see
parts of Hekla volcano here

that we can't see with the naked eye.

His scan reveals a giant crack, or
fissure, running right through the centre

of the volcano, similar to those
found in the Thingvillir valley.

But this fissure doesn't just span
the width of the volcano,

it extends either side,
along a five-mile tear in the Earth.

It's this tear that's key to understanding
how Iceland's volcanoes erupt.

When Hekla erupted in the year 2000,

it wasn't just the volcanic cone
that exploded.

The earth actually ripped open along
the entire five-mile length of the fissure,

a weakness created by the stretching
along the Mid-Atlantic Ridge.

In the geological world,
these are known as fissure eruptions.

Forced open by the sheer volume
of magma pushing up from below,

the tear spewed out a terrifying 750
million cubic feet of molten rock an hour,

flooding the land with lava.

These fissure eruptions are so huge

they can change
the landscape drastically

in a matter of days,
leaving behind mountains like these.

You can see to the north here where
the Earth's surface actually opened up

during the fissure eruption

and lava erupted out.

This fissure starts to the north

and extends eight kilometres
through Hekla volcano here.

The sheer volume of magma produced

can be seen very well here
at Hekla volcano,

especially with these lava flows
that have draped the land's surface.

And, to me, this is really exciting

because you can see very large
volumes of eruptive material

produced over very short amounts
of time.

And Hekla is... is a beautiful place
to study that.

But what is creating
the vast quantities of lava

that are forced out
during these eruptions?

For many years,
the answer remained elusive,

until geologists found
incriminating evidence

locked inside the rocks.

The composition of the rocks here
in Iceland is quite different

than we see in other places.

By taking this rock back to the lab,

we can get a very good idea
of under what conditions it formed,

whether it formed deep within the Earth
or near the surface.

This rock was once molten lava which
erupted from one of Iceland's volcanoes.

Analysis of the chemicals in the rock
revealed unusually high concentrations

of rare Earth elements
lanthanum and cesium,

chemicals which are only found
in magma with a very deep origin.

It's the breakthrough scientists
had been searching for.

It was evidence that another,
much deeper, heat source

was combining with the Mid-Atlantic
Ridge to power the volcanoes of Iceland.

The rock evidence suggested
this second force lay hidden from view,

deep beneath Iceland's surface,

but it is possible to get a glimpse
of what's happening down there.

Scientists monitor the seismic
waves triggered by earthquakes

all over the world.

As the Earth's plates move,
they release shockwaves

called seismic waves
that pass through the Earth's crust.

These travel at a steady speed,
unless they hit a region of hot rock,

then they slow down.

POLAND: Now, as seismic waves
arrive in Iceland,

they're travelling very slowly
through the subsurface,

and this is somewhat unique to Iceland
and a few other places in the world.

It tells us that there's
a very hot column of rock,

perhaps even some... some
molten material beneath the surface.

These massive columns, or plumes,
are known as hotspots,

and are not unique to Iceland.

They are found beneath certain
volcanic areas in the world,

like Hawaii and Yellowstone.

Hotspots are these unwavering plumes
of... of hot material,

including molten rock, magma,

that stream up to the surface
from deep within the Earth.

The scientists finally had a snapshot
of the second force

that was helping to create Iceland.

The hotspot that lies beneath the island

is almost 100 miles wide
and 400 miles deep.

It channels rock slowly upwards

at temperatures over
1,700 degrees Fahrenheit.

It pushes against the crust,
heating the land from below

and forcing magma up
onto the surface as lava.

The investigation has identified the
two colossal forces that built Iceland -

the Mid-Atlantic Ridge
and the deeper Icelandic hotspot.

Millions of years ago, the
Mid-Atlantic Ridge drifted eastwards,

creeping towards
the fixed Icelandic hotspot.

Finally, they met

and have been locked together
in a deadly partnership ever since.

The result,
a truly formidable volcanic beast,

capable of creating magma
on a monumental scale.

As the mid-ocean ridge pulls apart,

there's decompression of the material
underneath it and that creates melting.

Decompression is simply removing
the pressure from a pile of rock.

It's much like opening a can of soda

or popping the cork off
of a champagne bottle.

The removal of so much pressure
makes the rock melt into liquid magma.

The hotspot is transporting heat
directly from the interior of the Earth

to the surface,
which also creates melting.

So this combination of decompression
of existing rock beneath the surface

and the direct transport of heat
from the centre of the Earth

create a huge amount of magma.

This incredible meeting
of the Mid-Atlantic Ridge and hotspot

began to build the island
beneath the waves,

pushing it upwards
and giving birth to Iceland.

Scientists have dated the island's
emergence to 20 million years ago,

but could only imagine
what this might have looked like.

But on November 14th 1963,
off the south coast of Iceland,

the world watched an action replay
of Iceland's spectacular birth.

A column of rock and ash
blasted out of the ocean,

18,000 feet into the sky,

so high it could be seen 70 miles away
in Iceland's capital city, Reykjavik.

A new island was forming
right in front of the world's eyes.

Scientists called it Surtsey,
after the Norse god of fire, Surtr.

Located 20 miles off the mainland,

the small island of Surtsey
is now a magnet for geologists.

It offers a wealth of forensic evidence
for Dr La Femina,

who is investigating
how Iceland first formed.

It's amazing to see Surtsey
for the first time.

I've seen pictures,
I've seen aerial photographs,

but to actually be here and get a chance
to... to go out and see it up close

and actually look at the geology,
it's just... it's just awe-inspiring.

This type of eruption
that formed Surtsey

has now been named after Surtsey,

we call them Surtseyan eruptions,
and they're very, very explosive.

The interaction of hot magma or lava
with the ocean

causes these very steam-rich and highly
explosive eruptions of ash and water.

When scientists first stepped foot
on the island in the summer of '64,

they found it hard to believe
that this was an island

whose age was measured in months,
not millennia.

In about nine and a half months,
this whole volcanic cone built up.

In addition, lava flows came out
of the volcanic centre here,

and we're seeing those,
these nice black cliffs in front of us.

Now geologists had an insight into
how early Iceland might have formed.

In only 20 million years,
Iceland grew from a tiny island

into a 40,000 square mile land mass
as big as the state of Kentucky.

The forces that power Iceland's
volcanoes have been revealed.

Cracks along Hekla volcano
unleash gigantic fissure eruptions.

And rare chemicals in the rock prove
that these eruptions were fuelled

by two separate forces,
the Mid-Atlantic Ridge and the hotspot.

Iceland grew to become
the world's largest volcanic island.

But volcanism alone doesn't explain
how the land of Iceland was formed.

The investigation will unearth
another, equally dramatic, force

that sculpted the distinctive shape
of the Iceland we know today.

A force which would challenge
the might of Iceland's volcanoes.

If Iceland was formed by fire alone,
it should look like other volcanic islands

such as Hawaii or Tahiti,
but something else was at work here

to transform this island
into the distinctive shape it is today.

Its shape is another clue
to Iceland's formation.

An extraordinary force
indented Iceland's northern coastline,

burrowing deep fjords
which extended far inland.

But what colossal force could cause
such a dramatic change

to Iceland's volcanic landscape?

There's an obvious suspect that's found
scattered across the island - ice.

As its name suggests,

Iceland has a long history
of being covered in ice like this.

Today it covers 10% of the island,
all year round.

And in the middle of the country
lies Europe's biggest icecap,

the mighty Vatnaj�kull.

Over 3,000 square miles in size,

Vatnaj�kull is so large it even has
its own climatic conditions.

Up to two thirds of a mile thick,

it squashes the land
like a giant slab of rock,

and at its edges, great tongues of
ice flow out through deep valleys.

Glacier expert
Dr Matthew Roberts is investigating

how ice can gouge out solid rock,

and discover the role it has played
in Iceland's past.

This is a GPS receiver,
just like in car satellite navigation.

It's used here to measure
glacier movement.

This will be left on the ice surface
for a few days and then I'll come back

and I'll analyse the data and discover
just how far the glacier has moved.

Dr Roberts' data reveals that this
whole glacier is sliding forward

at an astounding rate
of two feet per day.

This is an amazing,
ever-changing environment.

The ice around me is like an icy
sea that's been frozen in place.

As the ice flows
out of the confines of the valley,

it expands and spreads
to occupy a greater area.

Now, as it expands, crevasses form, and
large depressions just like the one here.

Here's a smaller crevasse that's formed.

Occasionally,
when these crevasses open,

as they begin to open,
sounds can be heard.

Also, the glacier occasionally
makes a groaning sound.

This is all signs that the glacier is alive
and moving forward very slowly.

Vatnaj�kull is one of the largest icecaps
in the northern hemisphere.

Flowing down the valleys,
the great mass of ice bears down

with the weight of 100 tons
per square foot.

Dr Roberts believes this moving giant
is a force capable of eroding solid rock,

and he's found crucial evidence
to prove it.

This is an excellent example
of the power of glacial erosion.

This boulder would have been trapped
beneath the base of the ice,

and as the ice flowed
over the surface of it,

it would have progressively eroded
the surface of the boulder to produce

these very distinctive marks
called striations in its surface.

We can even tell the direction
in which the ice was flowing.

If I take a rock, I can illustrate this.

Imagine this is the base
of the... of the ice

and material trapped inside the ice
is being dragged across

as the glacier moved to produce these
very distinctive marks in the surface.

This is just like sandpaper over wood.

The same erosive effect.

The erosive process that's happening
on this boulder is the same process

that's happening on a much larger scale
along the surface of these valleys.

ROBERTS: The glacier is responsible
for literally carving the landscape,

producing very distinctive
troughs and basins

which were formerly infilled
with solid rock.

This really testifies to the...
the erosive power of... of a glacier.

The ancient fjords on the north coast
are the same deep basin shape,

which means they must once
have been filled with ice.

Scientists now know that, around
one and a half million years ago,

changes in the Earth's orbit, and the tilt
of its axis, began to cool the planet.

An enormous ice sheet descended
from the north and shrouded Iceland

in a cloak of ice.

As the ice advanced and retreated,
it carved out deep fjords

and indented Iceland's
northern coastline.

Ice was a formidable force in Iceland,

and many volcanoes lay entombed
beneath it.

Fire and ice were now locked
in a titanic battle of supremacy.

Would the giant ice sheets
that carved the fjords

put out the fires
that created Iceland?

The first clue lies in this ancient valley,
five miles west of the glacier.

The valley floor is strewn
with hundreds of giant boulders,

but it's how they got here
that interests Dr Roberts.

These boulders provide a lot of insight
into how this landscape was formed.

The boulders are clustered together

and, interestingly,
these boulders are rounded,

which shows that they've been rolling.

Now, the boulders have been brought
together by some dynamical force.

You can also see smaller boulders
trapped in the centre.

And it's quite clear that flowing water
is the cause of this.

But this wouldn't have been water in the
stream that we see in the background.

This would have been water
produced by a much larger, faster flow

that would have inundated
this entire valley.

Dr Roberts has an extraordinary theory
about what happened here.

In ancient times, a cataclysmic flood
100 feet high cut through this valley.

It was so powerful that it rolled these
giant boulders like pebbles in a stream,

before dumping them
on the landscape.

But what could create
such a colossal flow of water?

Dr Roberts suspects the flood
came from the mighty Vatnaj�kull glacier

and is hunting for clues.

With such a huge area to cover,
Dr Roberts takes to the air.

His investigation leads him
to a crucial piece of evidence -

this strange bowl-like depression
on the surface of the ice.

This is an amazing location.

This giant depression in the... in the ice
has been formed as a pocket of water

has drained from beneath
the base of the icecap.

The beautiful concentric crevasses
that you see on the ice surface

have formed as the ice
has slowly crept into the hollow

that's been created
as the water has drained away.

Beneath the ice,
a dynamic process is happening.

Hot magma and steam are melting
the glacier from underneath.

The meltwater collects in a huge ice
basin, at the top of the volcano.

The basin slowly fills, but as it does,
the surrounding ice becomes unstable.

Cracks appear in the ice basin
and, as the hot water drains away,

it forms a tunnel which channels
the water to the edge of the glacier.

This would suggest that
volcanic eruptions still happen,

even under the enormous weight of ice.

Is this process the key to explaining
the ancient cataclysmic flood?

To answer this we must go to one of
Iceland's largest volcanoes, Grimsvotn.

Lying entombed beneath the ice
in the heart of Vatnaj�kull,

this massive volcano
violently erupts every ten years.

Here, fire and ice spectacularly collide,

with Iceland's volcanoes
emerging victorious.

Ice cannot suppress the invincible power
of Iceland's volcanoes,

which have now found a new way
to vent their anger.

During a huge eruption like this,
Grimsvotn can melt enough ice

to fill America's largest
man-made reservoir, Lake Mead.

But this vast volume of water
cannot be held back by the ice for long

and leads inevitably
to a massive glacial flood.

Such a force of nature struck Iceland
in 1996, with devastating consequences,

the floodwater taking out
everything in its path.

Bridges were torn down
and swept away,

and the highway
was submerged under water.

The flood itself reached
a... a peak discharge

of over 1.8 million cubic feet per second,
that's a remarkable discharge,

equivalent to the summertime discharge
of the River Amazon.

Imagine that sort of condition
over a relatively small area.

The sheer force of the water

carried icebergs
the size of four-storey buildings.

It's floods like these that can change
the landscape in a matter of days.

The erosive power of the flowing water
can result in tremendous amounts

of rock being eroded,

literally being fractured away by the
high water pressure that's being created.

So, literally, a landscape
can form before your eyes

during a very severe glacial flood.

The story of Iceland's bizarre landscape
is taking shape.

Striations on rock prove
that ice is a formidable force

that carved out
Iceland's unique coastline.

Boulders strewn in an empty valley
reveal cataclysmic floods of the past.

And depressions in the ice confirm

that Iceland's volcanoes
could not be suppressed.

But 12,000 years ago,
the great ice sheets retreated,

and Iceland was liberated
from their wintry grip.

Now, the effects of Iceland's volcanoes
would be felt on a global scale.

For thousands of years, Iceland's
volcanoes were locked in a titanic battle

with ice, but then, 12,000 years ago,
the giant ice sheets finally retreated.

This would open a new chapter
in Iceland's volcanic history,

as they were now free to wreak havoc.

But what effect would this have
on Iceland and its surroundings?

One of the most dramatic effects
can be found

in the south central region
of the island.

This alien landscape is known as Laki.

A row of strange craters
and solidified lava flows

that have bubbled up
from a huge tear in the earth.

A massive fissure eruption,

it stretches for an astounding
16 miles across the landscape.

Volcanologist Dr Thor Thordarson
is investigating Laki,

the site of one of the greatest eruptions
in recent history,

one which would have
devastating effects worldwide.

The Laki fissures which extend from
here in the southwest continue here

through the landscape as a row
of cones, up here, through Mount Laki,

which was split into two
during the eruption,

and continue further to the northeast

all the way to the margins
of the glaciers here.

Eyewitness accounts accurately date
the eruption to 1783.

This was one of the most
disastrous years in Icelandic history.

Fallout from the eruption caused
harvests all over the island to fail

and 75% of the livestock died,
plunging Iceland into a great famine

which killed ten thousand people.

But mysteriously, at the same time,

the rest of the northern hemisphere
reported freakishly cold weather.

Averaging 2.3 degrees
Fahrenheit below normal,

the northern hemisphere froze over.

THORDARSON: The North Sea
along the coast of Holland froze,

so people skated between villages
along the coast.

There was ice on the Mississippi
down by New Orleans in that winter.

For many years, it was thought the Laki
eruption and these climatic events

were unrelated,

but advances in geology found
it wasn't just a bizarre coincidence.

Comparing eyewitness accounts
with the geological remains,

Dr Thordarson has reconstructed
what happened.

He discovered that the eruption
started with a bang

on the morning of June 8th 1783.

It sent rocks flying high into the air
and ripped the earth open

along a one-mile tear.

But this was just the beginning.

Three days later, a second eruption
ripped open, then a third, fourth, fifth.

In total, the earth unzipped
along ten vast tears in the crust,

erupting lava continuously,
for over eight months.

The mammoth amounts of lava
that poured out of the ground here

would have buried Manhattan
to a depth of 830 feet.

But how an eruption
on this small, remote island

could cause climatic chaos

thousands of miles away
remained a mystery.

The evidence that would link Laki
with this worldwide catastrophe

was locked inside these boulders.

The story is in the rocks.

This rock here is part of the material,

the magma that came out
during the eruption.

These holes are called bubbles.

And they form as the magma
rises from deep within the ground

and approaches the surface,
and it really starts to boil.

The gas which is dissolved in the
magma at depth goes into the bubbles,

then it escapes into the atmosphere.

When this "bubble rock"
erupted onto the surface,

it would have poured gas out
into the Icelandic atmosphere.

Could this gas have caused
climatic chaos across the globe?

The identity of this gas can be found
in the microscopic structure of the rock.

If you look closely at this rock,
you can see a lot of white specks.

These little white specks are crystals
who grow in the magma at depth.

Sometimes these crystals, as they grow,
they will encapsulate pristine magma

and bring it up to the surface.

Like time capsules, the white crystals
contain untouched magma

from deep in the Earth,
locked away since 1783.

Dr Thordarson has analysed this magma

and found it to contain
poisonous sulfur dioxide.

And because there was
so much lava here,

it would have released
enormous amounts.

A staggering 100 million tons
of sulfur dioxide gas

was pumped into the atmosphere.

But how could gases released from Laki

cause bitterly cold weather
across the globe?

The answer lay in accounts

of a thick red fog
reported over Iceland in June 1783.

Within a few weeks, it had been blown
over London and Paris,

and by July it had dispersed across
the entire northern hemisphere.

Scientists now know that the red fog
was caused by the sulfur dioxide

which rose high into the air.

Mixing with water,
it created a sulfuric acid haze.

The haze blocked out the sun
and it sent temperatures plummeting.

As a result, the northern hemisphere
endured three bitterly cold winters,

which brought spring floods, famine
and widespread poverty to Europe.

Some historians have long believed
that these climatic conditions

triggered social and political unrest

which led to the French Revolution
in 1789.

But scientists now suspect Laki
had ramifications even further afield.

The cold temperatures in the north
changed air currents in the south,

causing dramatic climate changes.

India was hit by a terrible drought.

People say that more than half a million
people died from the drought in India.

Also, this change
in atmospheric circulation

caused a very cold summer in Japan.

It was cold and wet,
the rice harvest failed

and the result was the greatest famine
in Japanese history.

It is estimated that Laki killed
over two million people worldwide

and was one of the most
devastating volcanic eruptions

in the history of mankind.

The evidence has proven that
Iceland's recent volcanic history

has had a devastating effect on
the island, and the rest of the world.

Enormous lava fields reveal
that Laki was a gigantic eruption.

Bubbles in the rock indicate that huge
volumes of gas were released from Laki.

The white crystals reveal that this gas
was poisonous sulfur dioxide.

Evidence that Iceland's volcanoes

caused climatic mayhem
across the globe.

But eruptions like Laki may
not be confined to the past.

Some believe that the balance
between fire and ice is shifting

and has the potential to propel Iceland
into another hell on Earth.

The evidence is mounting
that Iceland has the potential

to be the most lethal island
on the planet.

A fearsome volcanic force lies
beneath it, creating powerful volcanoes

capable of generating gigantic lava flows
and altering global climates.

Yet many of Iceland's volcanoes
are covered in glaciers.

Fire and ice are held
in a delicate balance.

Scientists fear if this balance were
tipped in the volcanoes' favour,

Iceland could become even deadlier.

If the remaining ice were to melt,

what effect would it have on the activity
of Iceland's volcanoes?

The first clue in the investigation

lies in these innocuous looking
piles of rock and rubble.

They're found all over Iceland, and yet
these rocks don't come from a volcano.

They're moraines,

the geological term for rock piles
deposited at the mouth of a glacier.

These deposits are evidence
that the glaciers are shrinking.

Year by year, the glacier has melted
and retreated back up the valley,

leaving a moraine like this behind.

Dr Roberts has studied the
Vatnaj�kull glacier for the last ten years

and has noticed this dramatic trend.

The glacier has retreated
at a remarkable rate.

Since I've been visiting the area,
I've seen tremendous changes.

The ice has retreated annually

at a rate of about 200 feet per year.

This lake over here
used to be filled with ice.

I've seen the ice progressively melt,

this moraine has formed and this
whole valley has become almost bare.

Maybe in the next 20 years,

this whole glacier will disappear
and a lake will form in the valley.

Iceland's glaciers are melting
at an unprecedented rate.

With 5% of Iceland's icecaps
melting in the last 40 years,

the question that scientists
are keen to understand

is what effect this rapid melting will have
on the volcanoes that lie beneath.

The only other time that glaciers
have melted this quickly

is when Iceland came out
of the last Ice Age.

But what can past events tell us
about the future?

Geologist Professor Bill McGuire
is investigating

how volcanic activity changed
at the end of the last Ice Age,

and he's unearthed
some surprising results.

Around about
11 or 12,000 years ago,

you started to see quite rapid melting
of glaciers in Iceland and elsewhere,

and that triggered

a recognisable increase
in volcanic activity

because you were removing this
large mass of ice very, very quickly.

The rapid melting of ice kick-starts
volcanic eruptions beneath.

Volcanic eruptions are triggered
by the gas in the magma,

which expands to form bubbles,
and the bubbles drive the eruption.

It's rather like taking the cork
out of a... a bottle of champagne.

Now, if you have a very heavy weight
on top of a... a volcano,

if there's a heavy mass of water or ice,
that can help suppress eruptive activity.

But when ice melts quickly,

this downward pressure
is suddenly released,

and that's when the trouble starts.

As the ice melts, so the pressure
on the magma underneath is reduced,

the gas in the magma can form bubbles,
they can coalesce

and they can eventually drive the magma
upwards towards the surface

and trigger either explosive eruptions
or effusions of lava

that can spread out over huge distances.

Iceland's glaciers are melting rapidly.

This has led scientists to believe

that a devastating eruption on the scale
of Laki could happen again.

The question is when.

These are things
that we have to think about

and try to prepare ourselves to deal with
if they happen in our lifetime.

Is it possible that we can get
another eruption like this in Iceland?

Definitely.

The investigation has revealed

how the vast and violent island
of Iceland was formed.

Cracks in the Thingvillir Plain
and traces of chemicals in the rocks

revealed how the Mid-Atlantic Ridge
and hotspot joined forces

to create a colossal volcanic force.

Massive fissure eruptions
ripped the land open.

Haemorrhaging millions of tons of lava,
Iceland rapidly formed.

Deep northern fjords were evidence
that a giant ice sheet eroded the land

and entombed the volcanoes,
locking fire and ice in a titanic battle.

Boulders, strewn in an ancient valley,
revealed how fire emerged victorious,

unleashing cataclysmic floods.

And specks of sulfur in the rocks
showed how Iceland's volcanoes

have the potential
to cause global destruction.

Now glaciers, melting above some of
the world's most deadly volcanoes,

are increasing the threat
of future eruptions.

Over the last 20 million years,

Iceland's almighty volcanic force

has created a vast,
alien landscape.

Volatile
and unpredictable,

it may one day unleash
a massive eruption,

which could devastate both Iceland
and the wider world beyond.