Iceland Erupts: A Volcano Live Special Volcano Live

Two years ago,

an ash cloud from an Icelandic volcano paralysed Northern Europe.

But was this just a freak event or could it happen again?

I'm travelling to the source of the ash cloud to find out.

I'll be meeting the scientists

who are monitoring the biggest volcanic threats.

I'll descend deep underground to discover

the effects of tectonic activity.

And I'll meet the people who live and work

in the most volcanically active country on Earth.

We may not have any active volcanoes in Britain,

but we're not immune to their effects.

What can we learn from Iceland about living with volcanoes?

Here in Britain,

we tend to think of large-scale natural disasters

as something that happen in other countries

less safe and benign than ours.

But in 2010, something happened to remind us

that we're not immune from the forces of nature.

A volcano erupted over 1,000 miles away in Iceland,

but in a matter of hours it brought our modern, high-tech world

to a juddering halt.

For the first time in British aviation history,

all flights in and out of the UK have been cancelled.

Ten million flights pass through European airspace every year.

At Heathrow alone, they deal with over 1,000 planes a day.

Air traffic controller Jonathan Astell was on duty

the day the ash cloud arrived.

We know that putting volcanic ash through an engine of an aircraft

is a bad thing to do. In this case, it was very much like glass,

which, if you throw a box full of bottles through an aircraft engine,

that's not going to be good.

It's going to melt, it's going to really do some serious damage.

'In a matter of hours,

'European aviation authorities were forced to shut the skies.'

I've never worked so hard

for so few aircraft flying. It was just incredible.

And at one point it felt like it would never end.

But not all Icelandic eruptions bring Europe to a standstill,

so what was it that made this one so disruptive?

And most importantly, could it happen again?

To find out, I'm heading for the country where all this began.

MUSIC: "Play Dead" by Bjork & David Arnold

It's called "the Land of Fire and Ice,"

and I was trying to avoid using that term,

but when you're up here looking at it, that's exactly what it is.

The scale of this landscape

is just astonishing.

Nature's had a field day on this island.

I'm on my way to the site of the 2010 eruption

to see what it looks like two years on.

Well, this is it.

This is the culprit.

Eyjafjallajokull.

We're flying directly around the crater now.

You can smell the sulphur in the air.

And it's strange.

I thought that there would be somehow more evidence,

that the landscape would still be blackened.

I mean, there was tons and tons -

untold amounts - of ash that poured out of this crater,

and yet now there's so little sign of it up here.

And it looks so benign and so beautiful now.

A great shining, pure white glacier.

It's just an incredible sight.

The eruption was on a scale that we hadn't seen in living memory.

No-one died in 2010, but as events unfolded,

the Icelandic president had a stark warning for the rest of the world.

Unfortunately, what we have seen in the last few days

could only be a beginning of an experience

which might be repeated throughout the 21st century

because the scientific evidence points towards larger eruptions

in the near future.

So I think we should, all of us, throughout Europe and the world,

start planning in a calm and rational way for that eventuality.

If there are bigger eruptions to come,

I want to know when they might arrive

and what the consequences could be

for both Iceland and Europe.

So, from Eyjafjallajokull, I'm setting out to visit

a few of Iceland's 15 other active volcanoes,

some of which have produced big eruptions in the past,

and others which threaten to erupt again in the near future.

Since Iceland was settled just over 1,000 years ago,

on average there's been a volcanic eruption every five years.

And one of the biggest and most devastating of those eruptions

has changed the landscape of one corner of Iceland for ever.

I think this is the strangest,

most otherworldly landscape...

..I've ever seen.

It's just great, chaotic lumps and piles of rock

covered in this thick, khaki-grey moss.

It's just weird.

It's almost as if some giant

crumbled up pieces of cake all over the plains,

and they've gone mouldy.

This lumpy plain was formed in 1783 by an enormous eruption

from a volcanic fissure called Laki.

At over 20 kilometres wide,

it's part of the biggest single lava flow on the planet.

'To hear how it all happened, I'm meeting Henrik Olufsen,'

a guide here in southern Iceland.

This lava has its origin from Laki,

and the fissures opened and it took only four days

for the lava to run down, about 34 kilometres down to the lowlands.

So it's, erm... You can't imagine how powerful it was.

And that was ongoing for eight months.

This map shows how the eruption spread

from a fissure in the hills

and fed two enormous lakes of lava which expanded across the plain

and began to close in on a small farming community.

These pictures from Hawaii in 2011

show a fissure eruption in full flow.

The lava fountains that burst from this short fissure

were up to 50 metres high.

It gives some idea of what the eruption in Iceland

must have looked like.

Although in 1783, the fissure was 25 kilometres long

and the fountains of lava were 500 metres high,

as tall as skyscrapers.

Lava from the fissure spread over a vast area

as far as the eye can see.

How do we know so much about this eruption

and the effects that it had?

There was a pastor here, in this area.

His name was Jon Steingrimsson.

And he wrote some description about this eruption.

Both from the geological side and also from the human side.

The pastor described the scene as the lava poured out

and made its way towards his village on the coast.

TRANSLATION: "My companions and I walked towards the fissure.

"There, a flood of fire flowed with the speed of a great river,

"swollen from meltwater on a spring day.

"In the middle of this fiery river, great cliffs

"and slabs of rock were swept along,

"tumbling about like large whales swimming, red hot and glowing."

As the lava flow advanced towards their homes,

the pastor gathered his congregation

and gave what has become a famous sermon,

known in Iceland as the Fire Mass.

He inspired the villagers to face up to their situation without fear.

His church was near here.

Was it in a village that was eventually engulfed in the lava?

Actually, the lava stopped two kilometres from the church

where he was holding this great speech called Fire Mass,

where he was trying to urge people to carry on and believe in life.

Presumably, for the people, terrified in the church,

they must have looked at their pastor and thought, somehow,

-he had a direct connection to God.

-Yeah.

But lava was only part of the problem.

The eruption also produced huge amounts of sulphur dioxide

and fluorine, which poisoned the water

and contaminated food for people and animals alike.

As crops failed and livestock began to die,

famine swept across huge swathes of Iceland.

25% of the population of Iceland died because of hunger,

and most of the island was totally covered with ash.

And there was also a mist.

You know, they hardly had sunlight for many months.

The events of 1783 are an important chapter in Icelandic history.

10,000 people died during the Laki eruptions,

and it's a story which is still taught in school here.

The courage shown by the pastor, Jon Steingrimsson,

has also come to symbolise the attitude of Icelanders

to the volcanoes around them.

Is it something that's still referred to today?

-Is it still talked about today?

-Absolutely.

It was a huge catastrophe for Icelanders,

and we have to have this knowledge about it

so we can learn and, you know, carry on.

You're living, kind of, in the shadow of danger all the time.

As an Icelander, is that sense of potential impending doom

always slightly at the back of your mind?

No. To be honest, no.

If you understand it, if you have... If you respect it,

you should not be afraid.

So it's quite important for us to know about those things,

because they will happen again, I can tell you.

In 2010, it was a cloud of volcanic ash that made its way to Europe.

But in 1783, the continent was engulfed

by a huge cloud of sulphur dioxide.

If a similar eruption happened again today,

that toxic gas could have devastating consequences,

particularly in densely populated areas like London.

People would start to really struggle to breathe,

the air quality would deteriorate dramatically.

We'd probably struggle to see St Paul's across the river here.

And so I would say that the disaster potentially could be

greater in the 21st century than it was in the 18th century,

and in the 18th century they thought it was the end of the world,

so you can see that people... It's going to be bad.

In the summer months, hot weather and air pollution

often combine to reduce air quality in modern cities across Europe.

Add volcanic gases to the mix

and the result is a thick fog laced with sulphuric acid.

At that point, people with fragile health or breathing problems

can really begin to suffer.

Professor John Grattan has found evidence in historical records

showing that the arrival of volcanic fog from Iceland

had similar effects over large swathes of Europe

in the 18th century.

On the 23rd of June 1783,

people across Western Europe woke up to a changed world.

There are descriptions of people waking up

and looking out their window at their gardens and seeing

that their fruit had fallen to the ground,

forests being stripped of their leaves,

and there was an intense smell of sulphur in the air.

And they say that in the morning and in the evening,

as the sun rises and sets,

it's blood-red, like a red-hot pewter plate.

And somebody describes it as "like a red-hot salamander",

and people are really, really worried by this.

There are very clear descriptions of people struggling to breathe,

of an uncomfortable pressure, palpitations of the heart,

of "mysterious agues and fevers",

of outbreaks of terrible diarrhoea, "the bloody flux".

As the summer advances and the smell of sulphur gets more intense,

people start to die.

People start to die in ones and twos, then in great numbers.

There are descriptions of so many farmhands dying in the fields

that the farmers were afraid they wouldn't be able

to get their harvest in in time before the summer ended.

Within the parishes we've looked at in England,

we're looking at about 30,000 extra deaths -

a doubling of the death rate -

and it certainly seems to be higher than that in France.

The research so far suggests about 250,000,

so we're getting up towards 300,000 that we can be certain of,

and nothing like that's ever been seen before, or frankly, since.

It's quite natural at this time to invoke God.

There are sermons which tell people

that we think this is the end of the world, boys and girls,

and you'd better start to take note of your soul.

This is Armageddon, and you'd better take note of it.

This was one of the largest eruptions in Icelandic history,

but the earth only sees events of this size

every few hundred years.

So it may be several generations before we have to face up

to problems like this in Europe.

The colossal volcanic scar from the Laki eruption

now stands as a monument to the lives that were lost,

and this is just one of many fissures

which cut across this landscape.

The fissures in Iceland are part of a network of rifts

that cross the entire planet.

These are the boundaries between the tectonic plates,

and they're home to 80% of the world's volcanoes.

Iceland straddles one of those plate boundaries,

where for 50 million years, the North American

and Eurasian plates have been moving in opposite directions.

The results of this violent tug of war

are clearly visible in the landscape.

As the plates pull apart,

magma rises from the Earth's mantle to fill the gap.

Millions of years of eruptions have piled lava flow upon lava flow

to create an entire country.

So the rift that splits this island in two

is the birthplace of Iceland itself.

And in the future, Iceland will continue to grow,

which makes it vital that scientists understand

exactly how the process works.

Here in the south-west of the country,

a recently explored site represents a unique opportunity to study

one of these volcanoes not just on the surface, but from the inside.

I've come here with Bjorn Oddsson,

a volcanologist who's keen to get a first look

at this geological one-off.

We're joining a team of mountaineers

who are making final preparations for our extraordinary descent...

..a real life Journey To The Centre Of The Earth.

They've rigged up a mechanical lift

which will lower us directly into what was once

the fiery mouth of this volcanic vent.

I for one am slightly apprehensive.

-Now, you've never been down here either?

-No, I've never been here.

Are you a little bit nervous about this slightly Heath Robinson

piece of kit that we're descending into the bowels of the earth in?

-No, I think it will work.

-I hope so!

-I hope so too.

'Crossing the gantry to the lift

'feels a little bit like walking the plank,

'and the gaping hole beneath is impossible to ignore,

'but finally we're ready to descend.'

SHE GASPS

It will be not so bad!

SHE LAUGHS

That's my nerves as well.

OK, we're getting into a very narrow bit here.

'It's a strange feeling,

'being slowly swallowed up by the mouth of a volcano.'

-It's a very kind of organic-feeling space, this, isn't it?

-Yes.

It feels almost alive, the shapes of the rock.

-It's just like it happened yesterday.

-Yeah!

And what's amazing, just looking at the walls is,

you can kind of see the bits of magma

left on the side of the chamber.

When it was plastered on the wall, it was not fully solidified,

so in time it re-melts and drops down, and freezes.

So these sort of chocolate-like drips stuck to the walls,

that's the magma, the remnants of the magma?

Yes, that's the remnants.

Gravity pulls it down and forms these candle-like forms.

That's incredible.

'As we descend further, the throat of the volcano begins to widen out.

'We're lowered into a vast open chamber.'

'From top to bottom, it's 150 metres -

'taller than St Paul's Cathedral.

'We're now deep inside the body of this volcano,

'in a space that would once have flowed with liquid magma.'

So, is this the only place in the world that you know of

that you can descend down into a volcano?

Yes, as I know.

And this is very special,

because all the magma has drained away from here to the surface.

So in normal circumstances,

this immense cavern that we're standing in now...

-It would be full of magma.

-It would be full of magma.

Yes, or lava, afterwards.

Tell you what's so extraordinary,

that I really wasn't expecting, was the colour.

It's just a riot of every colour you can think of.

That's due to many reasons.

Iceland and Icelandic mountains were built up with many lava layers

in many events of volcanic eruption,

and we see both ash and lava

from different types of volcanic eruptions.

So this is like an open book.

You can read the story of this mountain.

'In the damp air of the cave,

'chemical reactions have changed the colour of the rocks

'like the rust on a piece of iron.

'But as well as a beautiful sight,

'the colourful shapes in the walls have a greater significance.

'Like tree rings, the lava layers record

'the history of eruptions here,

'as they piled up one on top of another.

'And running vertically through the walls,

'this band of black rock marks the feeding channel

'that supplied magma from deep beneath our feet.'

-What you see here is like a wall of fire.

-Right.

But this is just a wall of fire frozen underground.

'It cuts across this cave,

'and it runs along the entire length of the fissure

'underneath the volcanic ridges on the surface,

'which it created a few thousand years ago.'

And we can see the direction of these lines

is parallel to all the mountain ridges we see on the surface.

Most volcanic eruptions in Iceland are on fissures,

so Iceland is pulled apart,

and on one side we see the North American plate,

on the other side we see the Eurasian plate.

So we're sort of standing in the middle of those two tectonic plates?

Yes, of these two continents.

Does that mean effectively what we're doing is standing

in a kind of no man's land between the two?

We are in Iceland!

SHE LAUGHS

Good answer.

'This volcanic cathedral provides a fascinating new perspective

'on Iceland's central rift,

'and research here should help scientists like Bjorn

'to understand better how the opening of that rift

'controls Iceland's volcanic activity.

'The last eruption on this part of the rift was 3,000 years ago,

'but other parts of the rift have opened up much more recently,

'as the inhabitants of an island

'just off the south coast of Iceland can testify.'

This is Heimaey,

and the entrance to its harbour is protected by dark, looming cliffs -

a clue to events which rocked this place to its foundations

almost 40 years ago.

Does this volcano come as a complete surprise to you,

or did you have any warning?

There was no warning whatsoever until 10 o'clock yesterday evening.

-Which was the earthquake.

-Yes.

'Lava entering the sea causes the water to virtually boil,

'and sends clouds of steam thousands of feet up into the air.'

On the morning of January 23, 1973,

a fissure a mile long opened up

and split this part of the island in two.

Great fiery fountains of lava lit up the night sky,

alerting the people in this town

that they had to escape, and quickly.

Today on Heimaey, evidence of that volcanic eruption is easy to find.

This was the stuff that was coming out of that fissure.

It is actually a sort of ash, but it's more like gravel,

and it was literally raining down.

But of course, it wasn't cool, inert stuff like this -

it was at about 1,000 degrees Celsius.

And this wasn't all that was coming out of that fissure.

There were enormous lumps of lava like this.

This is called a lava bomb, and these were being thrown out.

Great molten lumps of rock that came thudding into the ground.

So to be here when that happened

must have felt like being in a living hell.

To the 5,000 inhabitants of this tiny island,

it felt like the end.

The volcano threatened to engulf everything,

and although it was a heart-wrenching decision,

they knew immediately that they had to leave.

It was pure luck that the night the volcano erupted,

the harbour was full of fishing boats, and on a normal night,

all the men and all the boats would have been out at sea.

But there'd been a huge storm the night before

that had kept men and boats at home, so when the volcano erupted,

suddenly there was a means of escape

from what must have seemed at the time an inescapable fate.

Most of the population was evacuated to the mainland by boat,

but Heimaey's natural harbour makes it

the most profitable fishing port in the whole of Iceland,

and no-one was willing to abandon this place for good.

Determined to preserve their way of life,

about 100 men stayed behind

to try and save as many homes as they could.

At first, they concentrated on clearing ash,

hoping to stop roofs collapsing.

But the ash kept falling and many houses were soon completely buried.

Where a whole neighbourhood once thrived,

just a single chimney now emerges from the ash.

After a month, the eruption showed no sign of abating.

And a huge lava flow advanced towards the town,

consuming everything in its path.

And when the lava finally reached the coast,

it began to threaten the most valuable part of the island.

The harbour entrance in Heimaey was just a few hundred metres wide.

But as lava added new land to the coast,

there was a real chance that the gap might be closed forever.

For those who had stayed behind, like local welder Halle Tryggvason,

that was the moment the real fight back began.

TRANSLATOR: We knew we had to save the harbour,

because our livelihood depends on being able to sail out to sea.

If we're going to live on this island, we have to be able to fish.

Our town and way of life wouldn't last long without the fishing industry.

That's just the way it is.

It seemed impossible that anything could be done to save the harbour.

But something that had happened ten years earlier

provided a glimmer of hope.

Just a few kilometres from Heimaey,

an underwater volcano broke the surface in 1963

to create a brand-new island called Surtsey.

As lava flowed into the sea,

one volcanologist had watched as it cooled and hardened on contact

with the water, creating a barrier which diverted the flows behind it.

Ten years later, he realised that what he'd witnessed

could be the key to saving Heimaey's harbour

and he proposed that they spray seawater

directly onto the advancing lava.

I was put to work welding pipes together.

As soon as we began spraying cold seawater on the lava,

it started hardening and gradually heaping up.

We noticed that the lava was losing ground

and actually being diverted, so everyone was saying, "It's working.

"Spray more on it. Spray more."

Halle and the rest of the team worked around the clock.

A huge network of pipes was put together

and extra pumps were shipped in to get water right into the heart

of the lava flow.

An unbelievable amount of sea water was sprayed onto the lava

to try and stop its advance.

Huge amounts. Constantly.

I have no idea how much, but it would be fun to know.

Incredibly, cooled by the water,

a huge barrier of solidified lava was built up alongside the harbour.

This new wall of rock stopped the lava flow 200 metres short

of the cliffs on the far side.

Today that gap remains, and access to the harbour has been preserved.

By taking on the volcano,

the people of Heimaey had maintained their livelihood.

And to this day, they continue to harvest the rich fishing grounds

of the northern Atlantic.

It must have been a really fantastic feeling

that somehow, against all odds, you were doing it.

A volcano isn't exactly an ordinary kind of adversity. Not at all.

So it was amazing to see our plan actually working.

It's incredible that we were able to stop the lava

and save our town, as well as our harbour.

It was miraculous. It just worked.

By standing up to the eruption, the people of Heimaey had shown

a typically Icelandic resilience to the volcanoes around them.

As Iceland's Prime Minister told me,

the people of all of Iceland live with fire beneath their feet.

It was a life-changing event for the population of this island.

But as with the vast majority of Icelandic eruptions,

only a small area was affected.

When Eyjafjallajokull erupted in 2010,

the effects extended way beyond southern Iceland.

So what is it about this volcano that made it capable

of causing an international incident?

To find out, I'm heading to the summit,

using specially adapted Jeeps to cross the glacial ice.

Why is it necessary to have such big tyres?

Is it just to make you feel a bit more macho?

A little bit like that, yes. No! THEY LAUGH

We climb 1,500 metres before arriving at the crater's edge.

Again, I've joined Bjorn Oddsson

who's part of the team that made a surprisingly discovery

about the 2010 eruption.

'We've come as close to the edge of Eyjafjallajokull's main crater

'as we dare.

'Beyond here, the walls of this new gash in the ice'

are extremely unstable,

tumbling down to the steaming vent below.

So, we are standing here on the Eyjafjallajokull volcano

and we're going to look into the crater with a thermal camera

and see the heat it's still generating two years later.

When the magma is erupted, it's close to 1,100 or 1,200 degrees in Celsius.

-Wow.

-And by the time it cools down

and I would guess that just below the surface it's around boiling point.

-Several metres down, you would find 600-800 degrees in Celsius.

-Wow.

Because it takes a really long time to cool down.

Does that mean that the volcano is still sort of in eruption mode,

-if you like? Could it still go any minute?

-It still can go any minute.

But it will probably be like this for many years

and the core beneath will be warm.

-Even though we're 1,500 metres up and it's freezing?

-Yes. Even though.

SHE LAUGHS Even though.

I think the abiding memory that everybody has of this eruption

were those vast, towering ash clouds that then got dispersed

not just across Iceland, but all the way to northern Europe.

Why ash? Why did this volcano generate so much ash?

That's due to the volcanic happening under ice,

so it produced a lot of meltwater and the interaction between lava

and ice breaks up all the lava and forms ash,

which is transported into ash plumes and dispersed in the atmosphere.

Meltwater in the summit crater interacts with the lava

emerging from the vent.

The resulting steam explosions rip the magma into tiny fragments,

better known as ash.

If it would happen on dry land, then we would see lava flowing around.

-Right.

-But when we mix water and magma, it turns explosive.

And all the product is ash but not lava.

During the eruption, a quarter of a million cubic metres of ash

was blasted high into the atmosphere.

Long-lasting high pressure over the Atlantic

created strong northerly winds,

which carried the ash towards continental Europe.

In many eruptions,

the supply of magma runs out after a couple of days.

But not here.

In 2010, Eyjafjallajokull continued to pump out ash for over a month.

What was it that made this eruption go on so long?

Was it something particular about this volcano?

Access of a huge amount of magma.

It seems like the magma from the last eruption has been resting

-under the volcano...

-Wow.

-..since 1821.

So, hang on a second. Let me see if I can understand this properly.

-You're saying that the last eruption here was in 18...?

-1821.

-1821.

And the magma came up, as we expect, up the sort of chimney,

if you like, up to the crater, but some of it got sort of stuck

on the way, went down a little channel or a little tunnel

-and just sat there?

-Yes.

And then, 2010, you have another great boiling up of original magma,

if you like, at the bottom of the chamber,

that starts to travel up. The old magma wakes up and goes, "Hang on a second, what's going on?"

-And that comes up with it?

-Yes.

-You scientists are quite clever, aren't you?

-Yes. THEY LAUGH

So when Eyjafjallajokull came to life once more in 2010,

the old magma was stirred up and it too emerged from the crater,

adding to the volume of ash

and extending the eruption for much longer than expected.

-Is this our picnic?

-This is our picnic.

So, during the eruption, all this area was covered by ash.

-So this would've been black?

-All black, several metres.

-Right.

But it's two years since, so we had two years of winter snow.

So maybe 10, 15 metres of snow on top of it,

-so we don't see any ash here right now.

-'The ash might all be buried now,

'but Bjorn has brought a sample with him

'to explain what it tells us about the eruption.'

-This is the very ash that came out of this volcano in 2010?

-Yes.

-Wow.

-And in the beginning, it was this fine-grained ash,

so you can feel it in your fingers.

-It's a little bit muddy.

-Yeah.

And this is the fine grain that gets highest in the atmosphere

and is carried most way from the volcano.

-So this would have been the stuff that caused all the disruption in Europe?

-Yes.

-Right.

-And with time, it got more coarse grained, the eruption.

-Right.

So it changes with time.

And this ash here we see is more like sand, it doesn't stick together.

Oh, it is, it's completely different.

-It's much grittier, isn't it?

-Yes.

This is affecting the local more than the finer ones.

Right, because this would have been too heavy to have a blown all that way.

Until 2010, this was considered a dormant volcano.

And people had been living and working in its shadow for generations.

Helga Haraldsdottir has a small farm beneath Eyjafjallajokull

and I've come to see how she coped with the eruption here

two years ago.

So, can you tell me what happened on that morning

when the eruption started? What did you hear and see?

We just saw these big, big gushes of ash coming up

and going east over the mountains.

So it was at that point it was going away from you.

Yes, it was going away.

And we immediately started to prepare,

trying to tighten all the houses, getting animals inside...

..and prepare for it.

Helga's photographs, taken when the eruption began,

show westerly winds taking the ash away from her land.

But after just two days,

the winds swung around to bring the ash cloud straight towards her farm.

This big dark, brownish cloud

getting probably three, four kilometres higher

and just coming crawling down here over the hills.

-So it was sweeping down across here?

-Sweeping down from the glacier.

And in the end, we just disappeared into it.

Everything was pitch black and we didn't see anything.

Even though you understood what it was,

it must still have been quite frightening.

-Yes, it was. You really don't know what to expect.

-Yeah.

You never know how you're going to react to it, really.

It was just like Christmas snowing, except it was black.

It was not that heavy, but it was like a fine, fine sand,

got into your eyes, into your mouth.

I mean, it sounds perhaps a rude question,

but did you not think that buying a farm right underneath a volcano

was possibly unwise?

-No, I don't think so.

-KATE CHUCKLES

I don't think anybody considered Eyjafjallajokull was an active volcano.

-Really?

-It hadn't erupted for 200 years

and we didn't really think it would go off.

THEY LAUGH

Wasn't your first reaction just to run away? I mean, what did you do?

No, my first reaction was, "Get all the horses inside!"

We were getting everything inside and, well, it was that close

we were putting the last horse ass inside the door

when heaven falls upon us.

-Was it covered in ash?

-It was absolutely pitch black, everything.

It was from five centimetres thick and then,

as it went closer to the volcano, it just got thicker and thicker.

Helga and her family, along with the other local farmers,

were evacuated.

They could only visit once a day to feed their animals

and had to wear masks to keep out the ash.

The eruption had come at the worst possible moment,

because April here is the start of the lambing season.

It's a part of the year that can be stressful at the best of times.

But for Helga, in 2010 it was a nightmare.

Even with the animals inside,

the thick ash cloud still crept in through windows and doors.

Did you notice any adverse health effects from this ash on you

or indeed your animals?

I couldn't see any on the adult animals,

but we lost the first six or seven lambs.

-Wow.

-So I think it was just the amount of ash in the air,

it was too much for them.

I always slaughter some lambs in the autumn,

and I noticed they had black spots in the lungs.

Some tiny, tiny and others large.

Then I killed one, a two-year-old

and she had brownish stripes in her lungs as big, thick as my finger.

-Wow.

-Just going through the lungs.

Are you worried that given the state of your sheeps' lungs,

that your lungs might not be so great either?

-Yeah, I think I got some ash down there but...

-You're coping.

Yeah, I can then use it as an excuse when I can't run any more!

So, once this ash cloud had passed,

what were you left with? What did the farm look like?

Well, everything was kind of in greyish, dark colours.

We had about five to seven centimetres thick ash over everything.

Then when it rained, it got into this disgusting mud

and then when it dried up again, it was just like a concrete

over everything.

-What did you think you could do?

-Nothing. You couldn't do anything.

You just had to wait and see what will happen.

And we took the point early on that we're just going to try

to stick with it, see how it goes.

But we were not going to throw in the towel yet.

So what happened to all the ash? Did you literally have to scrape it up?

-No, no, no. It's just sitting under the grass.

-Yeah.

Looking at the area around the farm now,

it's hard to believe it was once blanketed by thick, black ash.

-God, it is beautiful here.

-Yes, it is.

-Oh, look at your lambs.

-HELGA CALLS IN NATIVE TONGUE

'This year's lambing season has just begun

'and life on Helga's farm has returned to normal.'

-Have these just been born? They look very young.

-Yes.

They are adorable!

-Have you ever thought, "Actually, I just want to move"?

-No. No.

It's the best spot in Iceland.

-Really?

-Yes.

It's way, way colder just ten kilometres to the east or west

over the winter, so it's the best spot in Iceland.

And if Eyjafjallajokull was to decide to erupt again next year,

-would you still feel the same?

-Yes, I think so.

I would just be a little bit more prepared what to do!

The people of Iceland have had to live with volcanic eruptions

since the country was settled in the ninth century.

Since then, there's been a pattern,

a peak in the level of activity, which comes every 140 years.

Scientists believe that the next peak could come as soon as 2030.

But events over the last couple of years

suggest that things might have already begun to pick up.

In March, 2010, there was a spectacular lava eruption

just a few kilometres from Eyjafjallajokull.

In May, 2011,

another explosive eruption happened at a volcano called Grimsvotn.

And later the same year, there was a burst of geothermal activity

beneath the glacier at Katla, one of Iceland's biggest volcanoes.

Now that geothermal activity heated up the ice

and caused a flood of water to come pouring off the volcano

and down this river valley, taking out the bridge

and causing mass devastation as it made its way to the sea.

Katla is just 20 kilometres from Eyjafjallajokull,

but it's much, much bigger.

And in Iceland,

many people are worried that an eruption here could be next.

The time for Katla to erupt is coming close.

I don't say "if", but I say "when".

So I think it is high time for European governments

and airline authorities all over Europe and the world

to start planning for the eventual Katla eruption.

I'm heading for the summit of Katla

to see how scientists are using the latest technology

to keep a close eye on this volcanic giant.

Crossing the vast summit icecap, we're joined by Dr Benni Ofeigsson,

the man in charge of monitoring efforts here on Katla.

He leads us to a rocky outcrop rising out of the icy plain,

the highest point for miles around.

-We are actually at the edge of the caldera rim.

-Right.

The caldera is a depression that is formed

when a magma chamber is emptied.

So what we're looking at here is snow and ice covering

that kind of classic volcano crater,

and the caldera stretches in which direction?

If you look...

look around here, we see the edge of the caldera rim.

-So all the high points.

-The high points here

are at the edge of the caldera rim. All the way around.

-I mean, it's absolutely enormous.

-It's enormous.

It's about ten kilometres diameter.

-And how thick is the ice on top of it?

-About 750 metres.

-Wow.

Calderas mark the top of the very biggest volcanoes in the world.

And they're formed by what are known as super eruptions.

The explosions that created Katla's caldera several hundred years ago

were 50 times bigger than Eyjafjallajokull in 2010,

depositing ash layers in Russia some 2,000 miles away.

Fortunately, not every eruption here is quite that big.

But Katla has seen plenty of activity

in the last few hundred years.

So, how active is this volcano?

-Well, it has been erupting roughly once or twice every century.

-OK.

-So the last time it had a great eruption?

-It was in 1918.

It was about three times bigger than the Eyjafjallajokull eruption.

In 1918, there was a huge ash eruption at Katla,

which also unleashed a torrent of meltwater many times larger

than the flood last year.

It ripped huge chunks from the glacier

and carried them like icebergs towards the coast.

-That is almost a century ago.

-Yes.

-So does that mean it's kind of overdue?

-Well, I wouldn't say that.

Volcanoes aren't overdue, they change patterns

on a regular basis or an irregular basis, actually.

They are irregular and complex things.

It might erupt in 10 years, it might erupt in 50 years.

It might erupt in a few weeks.

KATE CHUCKLES NERVOUSLY

OK. Shall we get this job done, then?

The length of time between eruptions at Katla varies a lot,

'so the only way to anticipate the next episode of activity

'is by carefully monitoring its behaviour.

'Bolted to the rock, these GPS instruments use satellite technology

'to accurately report their position every second of the day.

'They show that the surface of this enormous volcano

'is almost constantly on the move.'

-It looks to the uninitiated eye that it's moving quite a lot.

-Yes, it is.

It is moving quite a lot.

What we are looking at now is volcanic unrest

and that's a long-term indicator

that something is... could potentially happen.

And it could potentially happen at short notice.

'This shifting of the ground is often seen at active volcanoes,

'but it doesn't necessarily mean an eruption is on the way.

'What Benni is really looking out for is evidence that shows

'whether the pressure is building in Katla's magma chamber

'deep beneath our feet.'

How does magma accumulating - kilometres below us, presumably -

how does that affect a GPS instrument

right up here on the surface?

You have a magma chamber below a volcano

and there is magma coming into that magma chamber.

It increases the pressure in the magma chamber, so you're basically...

-..increasing it in size.

-Right. So you...

It's like blowing up a balloon, so you see it on a surface,

-you see an uplift and away.

-Ah.

So Benni won't issue any warnings until he sees clear movement

up and away from the magma chamber over a period of days or weeks.

Only that would suggest that Katla is building up

to a really big eruption.

When Katla does erupt again,

the consequences could be a lot more serious

than the ash cloud that reached us two years ago.

In Iceland, the population is well aware of that threat

and of the dangers posed by all the other volcanoes around them.

I've now met...

a whole series of locals,

scientists that are involved in how eruptions work

and monitoring the volcanoes,

and then just the regular people who live alongside them

and with the consequences of them.

And there's a sense of acceptance,

but not resignation. It's very different.

Um...

And a sense of...

This is just who we are and where we are.

And it's very much part of us.

There's a lot we can take from the Icelandic attitude

to the volcanoes in their midst.

We can't stop volcanic eruptions happening,

but we can learn from them.

And it's a lesson we should take seriously.

Because there is no doubt that Iceland's volcanoes will erupt again.

It's just a matter of when.

Subtitles by Red Bee Media Ltd