Original subtitles

Volcanoes are sleeping giants,

woe betide us, should they awake.

Millions of people live in their shadows,

and very close to a looming catastrophe.

But, even giants, far away and long forgotten,

can suddenly come alive.

Looking at history,

we come to understand that active volcanoes

also need to be reckoned with in the future.

Volcanologists, climate researchers, geologists,

they all want to learn from previous catastrophes

in order to save lives in the future.

In a way, they're like Beauty and the Beast.

Can we protect ourselves from this danger?

We can't always predict these events.

People will die.

Istanbul is Europe's largest metropolis.

More than 14 million people live here.

But, few of them know that the eruption of a volcano

has shaped this city's destiny.

History shows what's in store

for many cities around the world.

Because, no matter how far away the volcanoes are,

no one's truly safe.

In the year 541 AD, Istanbul is still called Constantinople.

A foreign plague decimates the population

of the Byzantine capital.

Millions of people die.

Emperor Justinian, and the entire country,

are desperate.

An invisible foe has taken over the empire.

Your Majesty, the air we breathe is so bad,

the pestilence has spread to the city.

What do you plan to do?

Those who are righteous have nothing to fear.

Then, ask the heavens what we've done.

The city is full of corpses.

What is the true reason?

The answer to this riddle

might be found one and a half millennia later,

and more than 3,000 kilometers further north.

A small international team of researchers

has put up their tents in eastern Greenland.

They are here to research the climate of the past.

Johannes Freitag, of the Alfred Wegener Institute,

hopes to retrieve information from the ice

on how the climate has changed

over the last millennia.

Good to see you.

Good to see you.

He is in search of sudden climate changes.

Greenland is an inhospitable place.

Even in summer, the temperatures cool down

to minus 18 degrees Celsius.

But here, far from civilization,

is the perfect place for ice core drilling.

Because the ice here is very thin,

100,000 years of climate history are deep frozen

in only half a kilometer depth.

The exact location of the drilling site is key.

If there are any anomalies in the upper layers,

it needs to be relocated.

It goes down until this layer.

Here you can see the melted layer.

It's refrozen melt water from last summer.

And so, below here, there's massive ice.

The fine layers are like growth rings.

It's important not to destroy them during the retrieval.

An annual layer measures about half a centimeter.

So, the researchers are slowly stepping back in time.

But, the work has to be broken off every now and then.

The drill can't heat up, or it would melt the ice.

The layers have been reached,

from around the time of the plague.

Does the ice give any indications about the trigger

of the disease?

30.

50.

The electrical conductivity

of the drilling core confirms the suspicion.

In the sixth century AD,

the ice suddenly points to a shift.

There was a sudden increase

in the atmosphere's sulfur content.

Very clear.

That's rare.

This mus be a volcanic peak.

It is quite high,

and present in 10 centimeters of the ice.

That equals about two years.

We don't know the time period for sure right now,

because we don't have the exact determination

of the age of the ice.

Volcanoes are fed by the hot inner core

of the Earth.

Driven by this heat,

magma rises out of the Earth's mantle in slow currents,

and accumulates under its thin crust.

The molten rock also transports a whole mix

of poisonous gases to the top.

Could the mysterious epidemic stand in close relation

to the eruption of a volcano?

Before the city was struck by the unknown disease,

the sky darkened.

There are precise accounts,

dating back to the year 536 AD.

For months, the sun has been weak,

in summer as in winter.

Everyone fears it might never come back.

The wine is sour, the harvest is lean.

There is so much snow that the birds are dying.

It is as though Hell had crept

out of the depths of the Earth.

Historian, Mischa Meier, of the University of Tübingen,

has analyzed the accounts to understand what exactly

happened back then.

During the sixth century AD,

the population is already very wary of anything it sees

as abnormal.

This is due to a fatalistic view of the world

that was quite popular back then.

It was sort of, waiting for the world to end attitude

that fostered any thoughts of the coming doom.

Any sign would do.

And, this unusual weather obviously fit in quite nicely.

Scholars had predicted the end of the world

to occur at the beginning of the sixth century.

And, every change in the environment was seen

as a sign of the coming last judgement.

And, indeed, change was coming,

but much different than people back then expected.

They are testimonies of an almost forgotten catastrophe.

Its cause, a seemingly insolvable mystery.

The Earth itself keeps destroying life

on its own surface,

because volcanoes spew out, not only ashes,

into the Earth's atmosphere,

but sulfuric gases as well.

During massive eruptions, they catapult sulfur

as high as one kilometer into the air.

Once there, the sulfur mixes with water.

This creates a layer of clouds, made up of sulfuric acid,

that barely lets in any sunlight.

A more recent example shows the effects this can have.

In 1815, in Indonesia, the Tambora volcano awakes.

Its actual eruption only lasts for three hours.

In this short time, ashes and ash flows

kill about 10,000 inhabitants.

But, its cloud claims many more deaths around the world.

By this time, the world had already grown so close

that the word about the catastrophe has spread to Europe.

Shortly afterwards, the sulfur reaches our continent.

The clouds color the sky a deep red.

There are breathtaking sunsets,

that have been captured by William Turner,

and are preserved until today.

But this beauty, is the harbinger of a catastrophe.

What follows, are cold spells, bad harvests,

and the biggest famine of the 19th century.

The number of victims of Tambora's sulfur clouds

can only be estimated.

On a global scale, the volcano probably cost 10 times

the amount of lives than the eruption in Indonesia.

In Germany, many people are forced to flee their home.

The ice cores from Greenland are analyzed

in the Alfred Wegener Institute in Bremerhaven.

Will the suspicion of a volcanic eruption

in the sixth century, the century of the mysterious disease,

be confirmed?

There are hundreds of samples stored in cold chambers.

It is one of the largest ice core storages in the world.

Until now, the volcano that poisoned the climate

in the sixth century hasn't yet been found.

We want to reconstruct the climate

on the entire planet to piece together the puzzle.

That is why we have ice cores from all over the world.

The analysis of the core from Greenland

confirms it.

The traces of sulfur actually do stem

from the sixth century.

At the same time the cold spell reached Constantinople,

a previously unknown volcano covers the northern hemisphere

with a cloud of sulfur.

But, the scientists have a suspicion.

Could it be that, within a few years,

there wasn't just one, but in fact two eruptions?

And indeed, the laboratory analyses show

that a few centimeters further there is another indication

of sulfur.

A second volcano had poisoned the climate

just a few years after the first.

And, the epidemic follows this eruption.

The eruption left traces on the North and the South Pole.

The volcano that spit them out,

must therefore be found in the middle, close to the Equator.

In El Salvador, hidden away from the world until now,

lies the Ilopango.

The traces of its last eruption

have long since been overgrown by the tropical rain forest.

Robert Dull, of the University of Austin Texas,

has specialized in the study of past ecosystems.

He is convinced that the Ilopango is responsible

for the climate chaos in the sixth century.

And, he is looking for evidence to prove his theory.

The volcano is, basically, the lake.

What you see here, is an outline of the entire area

that was erupted, all at once, when this volcano erupted

15 hundred years ago.

So, instead of just having a single vent,

where lava would come up through a single vent,

we have many vents,

and all of that material was expelled explosively at once.

The eruption must have been immense.

It buried the entire area under

a several meter high layer of ashes.

Volcanic ash doesn't have a lot in common with regular ash.

It is finely scattered rock.

The force of the explosion ripped apart

huge amounts of lava, and turned it into dust.

We find an ash that's light in color like this,

it's very exciting for someone like me,

because what it tells us

is that it's both high in silica

and that it was erupted explosively in a geologic instant.

Might have been a day, might have been two days,

but a huge amount of material was erupted all at once,

which tells us of the strength, and magnitude,

and shear immensity.

Robert Dull tries to reconstruct

exactly what happened during the eruption.

He interprets the geological traces

that are invisible to most people.

As long as the giant is asleep,

nothing tells of the danger lying beneath.

Even back then, the volcano was a crater lake.

Its magma chamber lies underneath.

The pressure in it slowly increases

until it reaches a critical point.

The gases that are freed in the molten rock

start to ascend.

Steam, created by the heat of the magma chamber,

settles over the landscape, like fog.

Until suddenly, the roof of the chamber flies up

like the cork of a bottle of champagne.

As the eruption column falls back into itself,

pyroclastic streams flow over the earth.

The ash clouds, as hot as 700 degrees Celsius,

destroy everything in their way.

Not only do they flow over the edge in huge sheets,

but they flow through the valleys and up mountainsides,

and there's some estimates that they flowed

as high as 15 hundred meters in some places,

up hillsides, according to geologists working in this area.

So, you can't outrun these events.

You cannot outrun a pyroclastic flow.

You can't hide from a pyroclastic flow.

You die in a pyroclastic flow.

It's unlikely that anyone in a radius

of 1,000 square kilometers survived this inferno.

Today, only the ashes show just how big the eruption was.

The size of the eruption, by measuring the thickness,

not only right by the crater itself,

but as we get further and further away,

the more measurements we have

the more accurately we can estimate the size

of the eruption itself.

In order to discover the world's biggest volcanoes,

one can't solely rely on the search on land.

The ship, Bedeor,

carries a team from the Kiel Research Institute GEOMAR,

that will examine the ocean floor around Cape Verde.

There is a steel pipe

on the underside of the two ton weight,

which is supposed to be jammed into the sea bed.

That way, it is possible to extract a drilling core

of about nine meters,

but only if it doesn't hit a spot on the ground

that is too hard.

The gravity core has to sink down

to about three and half kilometers,

until it reaches the seabed.

At a speed of one meter per second,

this can take up to an hour.

Time and again, sediment coring continues to unveil

previously unknown volcanic eruptions.

Important information, in order to understand

the impact of volcanoes on the history of the Earth.

The actual success of the team was uncertain,

but at eight in the morning,

hope turns to certainty.

The drilling has succeeded.

The drill sleeve contains everything

that has swept over the ocean floor for centuries,

even volcanic ash.

Volcanologist, Steffen Kutterolf, collects samples

of this ash from all over the world.

He is eager to discover the frequency

of big volcanic eruptions.

Once we find 10 layers of ash in a core,

we examine in what direction the ashes flew.

Only with the information of dissemination at hand,

is one able to make other predictions,

like the volume that came out of this eruption.

The sediment cores have a big advantage.

Other than sulfur, ash can be traced back

to a particular volcano.

It is like a fingerprint.

Every volcano, and every eruption is unique.

In the GEOMAR Institute in Kiel,

there are samples from all around the world.

The ashes of the ocean floor can, therefore,

be traced back exactly to a particular eruption.

Steffen Kutterolf has brought in several sediment samples

of the Pacific Ocean floor,

close to Central America's coast.

The type of crystals in the ashes alone,

can reveal their possible origin.

The volcanologist has a suspicion.

The mineral is typical for the last big eruption

of the Ilopango Volcano.

The exact composition reveals that the ashes are indeed

from El Salvador.

Even though he has found them hundreds of kilometers

further away on the Pacific Ocean floor.

By doing so,

we could place the marine ash layers that we found

and had previously been undiscovered

in correlation with the eruption of the Ilopango.

Now, we have a result of an expansion

of 1.2 million square kilometers,

which is about four times the size of Germany.

This proves that the eruption of the Ilopango

catapulted more ash and gas into the atmosphere

than any other volcano has, in the last 2,000 years.

Today, buildings cover the ash in many places.

As a matter of fact, the capital of San Salvador

was built on it,

16 kilometers away from the, still, active volcano.

No one is prepared for a possible eruption of the volcano,

especially not on the scale of the amount of ash

a previous eruption suggests.

The country has other, more pressing, problems.

There are, however, 6 million people

living in a radius of 100 kilometers around the volcano.

Anywhere between North America, Central America,

and South America,

no country is more densely populated than El Salvador.

What does that mean?

There's land scarcity, there's not enough room

for all these people to live.

So, to think of moving an entire city, like San Salvador,

even to ask people to move off the flanks of a volcano

that we know is active, is very very difficult,

because that's all they have.

Therefore, it is even more important

to examine the early eruptions of the Ilopango.

Robert Dull wants to get an impression

of the area around the crater lake.

He hopes to find regional indications

of the last big eruption of the volcano,

because the dispersion of the ashes

reveal which areas might be in danger in the future.

Generations have settled in this area

without even knowing about the volcano's existence.

The giant has been dormant for several centuries,

and no one remembers the big eruption.

Was it really a trace of sulfur from here

that was found in the ice cores?

If you look across this valley now,

you can see it's a broad, relatively flat valley

that's quite rich with all the volcanic materials

it's fallen over thousands of years of development

in rich agricultural soils.

So, you can see why people were attracted to this region

in the first place.

Agriculture has erased the traces

of the eruption even further.

This makes it almost impossible to determine the exact time

of the eruption.

Volcanic ash is made up of inorganic material,

like stone or fragments of glass.

Their age is indeterminable.

Robert Dull has to rely on the remains of living beings

that died during the eruption.

Wood is a great help here.

It was carbonized in the scorching ash,

but didn't burn up completely,

due to the lack of oxygen.

That is how it is possible to narrow down the exact time

of the eruption.

It's a time capsule.

It's a precise moment in time

that's captured in this ash.

So, when we dig these pieces of wood out,

the smallest pieces that we find,

the big tree trunks that we find,

any piece of wood that we're able to pull

out of this ash,

can then directly be associated with the time

of the eruption.

These are rare moments of joy

for Robert Dull and his colleagues.

Because the carbonized wood has chemical substances

that steadily decompose over the years,

the tree's time of death can be determined

by measuring the decomposition in the laboratory.

These samples have helped us narrow the dating range

from 120 years down to more like 20 years.

And, we've really been able to pinpoint,

and say, yes, Ilopango was not a fifth century eruption,

it happened in the early sixth century AD.

Following the eruption,

there was a cold spell of 15 years

that reached all the way to Constantinople.

Once there, the unknown disease spreads further.

In desperation, people turn to religion.

Emperor Justinian even mandates forced baptisms

to appease the alleged wrath of God.

But, to no avail.

More and more residents fall sick and die.

The disease spreads from Asia,

all the way through the east Roman Empire and Europe.

It's trace goes all the way to Munich,

and the suburb Ascheim.

So many people died within a short period,

that several bodies had to be put into the same grave.

But here, time has erased almost all traces.

The only surviving evidence could possibly be found

in the people's teeth.

Holger Scholz, of the

Institute for Microbiology of the German Armed Forces,

hopes to solve the riddle by using forensic methods.

Special suits protect the samples against contamination,

because one skin flake, alone, is all it takes

to soil the last DNA samples before their analysis.

The scientists manage to isolate the genetic substance.

It belongs to a bacteria

that caused the deadliest infectious disease

in the history of human kind,

Yersinia pestis, or the plague.

The cooling off that happened back then,

left a further weakening of the population.

There were extreme famines,

and that meant that people didn't have enough to eat.

Even rodents, that are an important factor

for the transmission of the plague,

retreated to the cities

where there was still some food left,

and that is obviously how humans came into more contact

with the pathogens.

The plague's bacterium actually feeds

off the blood of rodents.

The connection to humans is created by fleas.

Once the flea changes its host,

it transmits the pathogen,

and the risk of an infection increases

with every animal a human has contact with.

There was terrible hygiene.

The immune system was severely weakened.

And all that, furthered the expansion of the pathogen,

which in turn cost the lives of millions of people.

Far away, the Ilopango in El Salvador

changes the climate.

Famine ensues.

The population becomes more vulnerable to the plague.

The disease can strike anyone.

It blurs the lines between the rich and the poor.

Panic and chaos ensues.

There is no more food.

The emperor cannot uphold law and order.

The fact that the emperor, himself,

was struck with the plague,

obviously increased the insecurity immensely.

And, if one is seeing this as one of God's plans,

it was clear that the emperor is being punished,

and therefore was losing the grounds of his legitimate rule.

Even the emperor,

who was godlike in the eyes of the population,

is struck by the plague.

In view of the span of a human life,

volcanic eruptions that trigger climate chaos

are comparatively rare.

So rare in fact, that the risk is often forgotten.

But they have, nevertheless,

been present throughout history.

In 2014, danger came very close.

The Bárdarbunga volcano in Iceland

had been belching out lava for several months.

And, it still pumps about 35,000 tons

of sulfur dioxide into the air.

No one knows, yet, how the eruption will develop,

and when it is going to come to a halt.

The volcano is located under Europe's largest glacier.

Once the lava comes too close to the ice,

there's a possibility of a hydrogen explosion.

If this were to happen, the gases would rise up,

even higher.

And, Iceland is close to western Europe.

The sulfur could make it all the way to Germany,

even without such an explosion.

One look into history reveals the possible consequences.

The winter of 1784 was one of the hardest ever

to hit central Europe.

In the following spring,

melt water and ice flooded down the rivers.

The flood breaks bridges,

causing many stretches of land to disappear.

There are severe floods in Würzburg and other cities.

Cologne reports a water level of almost 14 meters,

the highest water level ever measured.

Even at the start of the eruption,

volcanic gases drift to western Europe.

John Grattan, a geographer at the University of Wales,

has assembled accounts of contemporary witnesses.

On the 23rd of June, 1783, people across western Europe

woke up to a changed world.

Forests being stripped of their leaves,

and there's an intense smell of sulfur in the air.

The cause of the disaster

was the Icelandic volcano, Laki,

a giant gap in the earth,

that produces more than 6,000 cubic meters of lava

per second.

Within eight months,

it releases approximately 120 million tons

of sulfur dioxide, which travels to western Europe

and changes the local climate.

There are very clear descriptions

of people struggling to breathe,

of an uncomfortable pressure

palpitated through their hearts,

of mysterious agues and fevers,

of outbreaks of terrible diarrhea of the bloody flocks.

There are theories that imply

that the Laki eruption is co-responsible

for the French Revolution.

Ever since then, Laki has been dormant.

But, what would happen if the giant awakens again?

Today, the atmosphere is a lot more polluted

than during the eruption of Laki.

Calculations show, that today,

430,000 people die prematurely,

due to the effects of dust particles.

Industrial plants and traffic pollute the environment,

not only through emissions of carbon dioxide,

but also through very small particles in the air.

Volcanic gases would burn the atmosphere even further.

Scientists have calculated

that if this were to happen,

there would be 140,000 more deaths per year.

The purpose of the

Federal Office of Citizen Protection and Disaster Assistance

in Bonn,

is to organize quick aid in times of crisis.

Christoph Unger is in charge of the institution.

He and his co-workers develop strategies

to prepare for multiple instances of crisis.

Are we prepared for a volcanic eruption

happening far away?

At the moment we are not preparing

for gases or dust particles in the air

that might reach Germany.

But the consequences of a volcanic winter

are comparable to today's weather extremes.

The onset of a cold spell could have far reaching effects,

as the example of the Münsterland shows.

In 2005 there is a snow storm,

leaving up to half a meter of snow.

Power poles fall over under the weight.

And, there are entire stretches of land

that are plunged into darkness.

250,000 people are without electricity.

Some, even for several days.

And that, was relatively harmless.

A blackout of a larger area would be disastrous.

No radio, no TV, no computers.

There's hardly any cash left,

so you can't buy anything.

Gas stations need electricity to pump gasoline.

Security systems wouldn't work.

It would have a huge impact on our social life.

In the last years,

Germany has repeatedly had to fight with cold weather

and high water levels,

but not to the extent as after the Laki eruption

in the 17th century.

In such a catastrophic case,

the danger of infectious diseases would increase.

What would happen if 30% of the population fell sick?

We have a problem with supply.

Because, the supply chains would break.

There'd be very different kinds of problems in security

in vulnerable institutions,

where there wouldn't be enough personnel at hand,

and there's even the question of

who would be vaccinated, when.

Who will receive the very short supplies of vaccines?

This would lead to an immense impact on all areas

in society, as a whole.

The residents of Constantinople

don't fare any different.

And not knowing the cause of the disease,

makes them even more afraid.

More and more,

the city is overwhelmed with the plague.

It isn't just the people that fall sick,

but the system itself that is beginning to fail.

Panic ensues.

Civilization unravels.

There simply wasn't enough population

and military capacity

to protect these regions and these cities,

because the plague had decimated too many of them.

And it isn't just the effects

on the people's health.

The plague kills soldiers and taxpayers.

Trust in the power of the state has been gravely damaged.

Even after 100 years, the empire cannot defeat the onslaught

of the Arabs.

And that is how the eruption of the Ilopango

might have also heralded the end of antiquity itself.

Since the time of Emperor Justinian,

the world population has grown to over 7 billion people.

And, more than half of them live in cities,

and depend on transport, trade, and telecommunication.

Can you protect all these people against a volcanic eruption

with a global effect?

There are about 15 hundred active volcanoes worldwide,

but only 100 of them are under local surveillance

by observatories,

and the last eruption of the other volcanoes

isn't even known.

But, even if the volcanoes are well monitored,

an eruption is still hard to predict.

Even experienced scientists can make horrendous mistakes.

In 1993, an international team of researchers

perform measurements on the peak of the Colombian volcano,

Galeras.

They are in good spirits.

Nobody seems to be bothered by the mist

that covers the view on the crater.

Suddenly, the volcanologists are taken aback

by a hydrogen explosion.

Rocks and small particles fly up in the air.

One part of the group is still on the inside of the crater.

There is no hope for these nine people.

Others are severely injured.

A joyous trip has turned into a nightmare.

Only two months later, the volcano erupts again.

This time, it also hits the scientists' research station

that was seen as secure, at the time of the first eruption.

So, even in modern times,

even in the developed world and rich countries,

the level of preparedness is not adequate

to handle such a large, sudden event.

And, no matter how many instruments we have

measuring small earthquakes and measuring Earth's elevation

as it rises, in anticipation of an earthquake,

we can't always predict these events.

So, even if scientists know

that a volcanic eruption is about to happen,

do they know the course of the eruption?

In 1980, Mt. St. Helens announced another eruption

through several small earthquakes.

It is located on the west coast of the USA,

close to the major cities of Portland and Seattle.

Richard Waitt, of the US Geological Survey,

witnessed the eruption.

As so many others, he was convinced that he knew

what was going to happen.

By late March, this word, bulge,

was on everybody's lips.

So, it got big enough that, and the volcano steep enough

that many people suspected,

at some point it's gonna start landsliding.

What was expected, though, is that there be

a series of small landslides

and that would be a warning

and people could get out.

The eruption was announced in the media,

and drew more and more onlookers to the area.

But then, Mt. St. Helens erupts in a totally unexpected way.

An earthquake let's the entire north slope slide down.

The mountain explodes, due the the loss of pressure.

Mud and small stones rush down the hillside.

No, that was not anticipated.

It went over one ridge, down into a valley,

over the next ridge,

and just kept going out and out,

20 kilometers, 30 kilometers maybe.

I don't even know how far it went.

But, way out.

And, nobody anticipated anything like that.

Ash, clouds, and mudslides overrun

the fleeing people.

57 people died.

Among them, are scientists that miscalculated the impact

of the eruption.

The surrounding area is covered in dust.

540 million tons of volcanic ash are dispersed

over an area larger than the Netherlands.

Only weeks later, the immensity becomes clear.

There is a huge hole in the volcanic cone.

The desertificated area, in front of the opening,

is over 600 square kilometers large.

As a comparison,

the eruption of the Ilopango, in 540 AD,

was about 10 times as large.

So, we do know that modern science can help us

predict, somewhat, when these events will occur.

But, we've never been tested on the level of Ilopango.

We've never had a massive eruption, of this size,

near a densely populated urban center.

Never.

So, what happens when this happens near Seattle?

What happens when this happens in Naples?

Will our technology be good enough to get everybody out?

There are more than 67 large cities,

worldwide, located close to an active volcano.

That means there are about 116 million people

living dangerously close to these giants.

There are already 37 million of them,

living in the area of Tokyo,

in the shadow of Mt. Fuji.

Its last big eruption happened more than 300 years ago.

Geologically speaking, this is the blink of an eye.

If it were to erupt, its ashes would destroy

the entire infrastructure of the city.

The situation in Seattle isn't much better.

Scientists see Mt. Rainier as one of the sleeping giants

that could erupt at any time.

Even in Europe, it's dangerous.

Mt. Vesuvius, alone, could destroy Naples entirely.

But there's an even larger magma chamber

in the Bay of Naples.

The Soufriere Hills Volcano, located close to Plymouth,

the capital of the Caribbean island of Montserrat,

can provide a glimpse into the possible effects

of an eruption happening close to a city.

Before the city was buried under its ashes,

several times, there were 4,000 people living here.

Hardly anyone has stayed.

Today, Plymouth is a ghost town.

Volcanic eruptions are a global threat.

But, their awakening also offers new possibilities,

because with every one of these eruptions,

scientists learn more about them.

One such example is Mt. St. Helens.

Even if every giant is unique,

a few of the results taken from here

can be applied to other volcanoes as well.

This is a birthplace of modern volcanology

in many ways,

especially some of the extraordinary events.

This landslide, there's probably four or 500 volcanoes

around the world now,

that have had a landslide, we know of,

because of this.

I mean, this is what opened the door to understanding that.

Only a few years ago,

a young geologist developed a ground breaking method.

It enables us to predict a volcanic eruption

more precisely.

Today, experts from the US Geological Survey

fly to the top of the mountain several times.

Down here, it's about 30 degrees in the shade.

But, on top, the scientists have to deal

with very cold temperatures.

Angela Diefenbach monitors the volcano from the air.

The most important point for her,

is that the method is simple, flexible,

and affordable enough for developing countries,

where a lot of volcanoes are not monitored

on a regular basis.

You can use a point and shoot camera,

or a smart phone camera.

You just want to make sure you have good lens

characteristics.

So, you don't want,

like a GoPro camera wouldn't be that good

for this type of work,

because you have a lot of radial distortion,

and that translates into your model.

Currently, there is a plug of cold lava

that keeps the volcano shut.

This so-called lava dome is dangerous,

because it stores pressure underneath it.

Any change in the surface could be a sign

of a possible eruption.

Angela Diefenbach shoots her photos

from a precisely chosen angle.

The brilliance of the idea is that the photos form a basis

on which her computer generates an exact 3-D replica

of the volcano.

If she, then, compares the data to earlier flights,

the smallest changes become visible immediately.

This method can even be applied during an eruption,

because it is often in the last moment

that one can predict how the giant is truly going to act.

This particular lava dome doesn't pose much of a threat,

because it erupted very slowly and it was relatively cool

when it erupted.

But, other lava domes, other volcanoes,

tend to collapse,

either from big explosions or by gravitational forces.

And, when they collapse, they produce pyroclastic flows,

which are very dangerous to people.

Mt. St. Helens is a very well monitored volcano,

but there are many sleeping giants all over the world

that can hardly be researched.

There is a huge, seething lava lake

in the Democratic Republic of Congo, for example.

The Nyriagongo lies in the middle of an area

that is torn apart by civil war.

And, even if the giants lie in sparsely populated regions,

like the Tavurvur in Papua New Guinea,

their load of sulfur can reach any corner of the world.

This is why Angela Diefenbach's method is so beneficial.

It helps to assess the risks.

But scientists can nevertheless, only warn in time.

They cannot stop an eruption from happening.

In the midst of big cities,

life seems to be as safe as ever,

but history shows that some things aren't as they seem.