Original subtitles

Our planet is home to some spectacular natural wonders.

Yet exactly how and why they form is still a mystery.

But now, new camera technologies are revealing their inner workings

in stunning detail.

My name is Dr Helen Czerski

and I'll be looking at how these extraordinary images

are transforming our understanding of the natural world.

In this programme, we look at the latest scientific insights

into the destructive power of volcanoes.

A volcano is a place where the fiery innards of the Earth intrude

into our world, here on the surface.

And they're a reminder of the dynamic nature of the earth

beneath our feet.

Now, thermal imaging is revealing why eruptions can last months

or even years.

High-speed cameras are showing us why certain volcanoes

wreak more havoc than others...

..and eyewitness footage captured on mobile phones

is giving us vital clues as to why some eruptions

are almost impossible to predict.

We can now catch on camera the complex processes crucial

to knowing how and when these forces of nature

are going to blow.

In September 2014, a sunny Saturday morning hike

suddenly turned deadly for hundreds of visitors on Japan's Mount Ontake.

With almost no warning, the volcano erupted,

spewing forth billowing ash clouds, travelling too fast to outrun.

This mobile phone footage captured by hiker

Kuroda Terutoshi...

..shows the terror of the tourists trapped on the mountain.

He and his friends scramble down the mountain, looking for shelter.

But within seconds, they're enveloped by the ash cloud

and small rocks from the eruption are raining down around them.

With no warning is issued, hundreds of people were in danger.

Rescue operations quickly swung into action.

Kuroda and many others had a lucky escape.

But 58 people lost their lives that day,

most through falling rocks or gas inhalation.

It was the worst volcanic disaster in Japan for 90 years.

Ontake has been closely monitored since the 1980s.

So across Japan, the question was asked,

why wasn't this eruption predicted?

There's a vital clue in Kuroda's footage.

The colour of the ash cloud is almost white,

indicating that it's not magma being erupted.

Instead, what we're seeing is steam.

The eruption on Mount Ontake was a rare event

called a phreatic eruption - it's a steam explosion.

It happens when groundwater seeps into the volcano

and meets really hot rock.

It's similar to when you pour water on to a pan of really hot oil

and it starts to spit and steam.

Inside the volcano, when the water reaches the very hot rock,

it evaporates to form steam, and then, as it expands,

it pushes out on the rocks around it with explosive force,

making a really violent eruption.

They're very hard to predict because they happen so quickly.

So it's just as well that there aren't very many of them.

To predict an eruption,

you need to understand what's going on deep below the surface.

Nowhere more so than at Nyiragongo in East Africa...

..where a million people live in the volcano's shadow.

During the last eruption in 2002,

lava flows destroyed much of the town.

147 people were killed and thousands left homeless.

Nyiragongo is so deadly because its lava is the fastest in the world,

travelling at up to 60kmh and decimating everything in its path.

In recent years, many scientists, like Dario Tedesco,

have been studying the lava,

trying to understand why it flows so fast

and whether future eruptions can be predicted.

It's really completely different from other volcanoes.

It really is unique.

There are so many secrets on this volcano that you don't get from

the other volcanoes.

And Nyiragongo offers a unique opportunity

because sitting in its crater is the world's largest lava lake.

Usually magma, the molten rock inside a volcano

collects in reservoirs far below the earth's surface,

where it's almost impossible to study.

But here, it's sitting right out in the open.

Dario's team are trying to collect a sample of fresh lava from the lake

but it's a long way down.

The crater is deep enough to bury the Empire State Building.

They stop halfway.

As the lake is so active,

they decide to get a sample from a safer distance 600 metres away.

But while they're setting up,

Dario spots someone else much closer to the boiling hot lake.

It is dangerous, in my opinion.

It is a little crazy.

I mean, I won't do that.

It seems an extraordinary risk.

But back in the lab,

analysis of samples like these by geologist Tom Darrah is giving real

insight into why it's so deadly.

The composition of Mount Nyiragongo lavas are both complex

and mysterious.

The lava I'm holding my hand from Mount Nyiragongo

is effectively a time capsule of the Earth's history.

When the sample is heated and analysed,

scientists discover a composition of the chemicals strontium

and neodymium, that's only found in one other place...

..ancient asteroids.

They think this lava contains traces of the ancient rocks that formed

the Earth four billion years ago.

The only way it could have this signature is if its origins lie deep

within the planet.

The gases that we analysed tell us that this volcano is sourced

from a very deep location within the Earth.

The source has to be somewhere well below the Earth's crust.

In fact, scientists believe there's a huge upwelling of intense heat,

a mantle plume, rising up from deep under this part of East Africa.

It's the way this hot spot interacts with the Earth's mantle

that generates a magma that's very low in silica.

And it's this unusual composition that makes Nyiragongo's lava

so fluid and so deadly.

With further study of the lava,

they hope to find ways to predict how the next eruption will happen

and where the lava might flow.

How dangerous an eruption is depends on the composition of the magma.

There are two main types of eruption.

If it's effusive, the magma rises up and flows out as liquid lava.

But in an explosive eruption,

the magma breaks into tiny fragments of hot ash that explode violently

out of the top.

Explosive eruptions cause far more volcanic deaths,

while effusive eruptions can destroy homes and property.

So knowing which type to expect is critical.

And that comes down to changes deep underground at a micro scale.

It may sound surprising but one of the things that's most important

for volcanic eruptions is the presence of bubbles.

Inside a volcano, there are gases from deep in the Earth's mantle

dissolved in the liquid magma.

But as the magma rises up, the pressure drops and bubbles form.

It's like what happens when you take a bottle of fizzy water

and take the lid off. Because you're reducing the pressure,

lots of bubbles suddenly form and they rise up to the surface

because they're less dense than the fluid around them.

But while these bubbles are just pushing gas

and a little bit of water out with them,

in a volcano, they're driving out red-hot magma.

How much magma comes out and whether you get a gentle effusive eruption

or a violent explosive eruption

depends mainly on the magma's viscosity.

And I can show you the effect that the viscosity has

using these two bottles of fluid.

This one is fizzy water, with lots of dissolved gas inside it.

This one is lemonade and it's got sugar in it as well,

which means that it's still got the same dissolved gas in it

but it's thicker, it's more viscous.

These sweets are going to act as nucleation sites,

so places for the bubbles to form.

So I'm going to drop these into the bottles and have a look at what

happens. So I drop them in...

You can see that lots of bubbles form.

The bubbles are rising because they're less dense.

They're quite big. They dragged a little bit of fluid up with them.

This one is similar to an effusive eruption.

But there's a big difference in what happens if I do the same thing

with the more viscous fluid.

Drop in these...

and you can see that things are much more violent.

The bubbles are much, much smaller.

They've dragged loads and loads of liquid up with them.

It's all escaped from the bottle and because the liquid is more viscous,

the bubbles find it harder to escape from it and they drag more of

the liquid up with them when they escape

and this is the equivalent of an explosive eruption,

when you have much more viscous magma.

In 2010, an explosive eruption in Iceland wreaked far more havoc

than anyone had predicted.

Eyjafjallajokull spewed thousands of tonnes of ash,

up to 10km into the atmosphere and out across Europe.

But it was no ordinary ash.

For the first time in British aviation history,

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

The particles were so fine they could blow into aircraft engines

and melt, causing potentially fatal breakdowns.

Fears over the ash led to the biggest shutdown of airspace

since the Second World War.

100,000 flights were grounded and millions of passengers stranded.

The Icelandic eruption wasn't particularly big or powerful.

So why was it one of the most disruptive in living memory?

Volcanologist Emma Liu thinks the answer lies with how the ash was formed.

The reason Eyjafjallajokull's eruption caused so much disruption

was because of how much fine grain volcanic ash it produced.

Normally when this type of magma erupts,

it produces something like you see in Hawaii.

You get large particles like this, which don't travel very far.

I have actually some ash from the Eyjafjallajokull eruption.

You can see it's very fine grained, like a powder.

The thing that was different is that this volcano erupted

from beneath the glacier.

The magma was able to mix with cold water from the glacier

and it's this interaction that caused the magma to cool

much more quickly.

Volcanic ash is actually a glass,

a volcanic glass created when molten magma cools to a solid.

But as Emma has been discovering, when glass is cooled quickly,

it behaves in a very unusual way.

So this is a Prince Rupert's Drop.

They've been known since the 17th century,

when King Charles II was given one of these drops by his nephew,

Prince Rupert of Bavaria.

It's formed by dripping molten glass into water.

When the glass cools quickly in water,

the outside of the drop cools very fast, forming a hard outer shell.

But the inside, it cools more slowly,

and as it cools, it contracts,

pulling in on the outer shell, like stretching an elastic band.

So we think that what happens when the glass is cooled quickly

to form a Prince Rupert's Drop,

it's similar to what happens when magma is cooled rapidly

when it comes into contact with water, like glacier ice

or lakes. All this stored energy inside the drop

gives it very unusual fracture properties.

You can hammer...

..and it still won't break.

But it has a weak point.

It's only by using an ultra-high speed camera,

filming at 130,000 frames per second,

that we can see just what's happening.

By breaking the tail and releasing all the stored energy very quickly,

and you can see when the glass exploded,

it produced this very fine powder,

which is just like the volcanic ash that would have been released

into the atmosphere.

Using an electron microscope,

Emma can compare particles from the Prince Rupert's Drop

with ash from Eyjafjallajokull.

So both are very angular, very blocky in shape.

They show the same beautiful, brittle fracture patterns,

which tell you a lot about how the fracture actually formed.

The similarities between the natural ash particles and the fragments

of a Prince Rupert's Drop suggest they were formed in similar ways.

Emma's work could be crucial in understanding

what will make some future eruptions so much more dangerous than others.

This is a map of every active volcano in the world.

Some of them, like Hawaii,

are thought to sit over mantle plumes like Mount Nyiragongo,

but most active volcanoes in the world sit at subduction zones,

and those are places where one tectonic plate

is sliding underneath another one,

and you get a line of volcanoes along the back.

And that's the case, for example, down the western coast of South America, here,

where the plate's sliding underneath South America.

And when you look at the whole of the Pacific, you can see a pattern.

There's a ring of volcanoes all the way around here.

This is where 75% of the world's active volcanoes are

because this is where the most subduction zones are.

And it's called the Pacific Ring of Fire.

Papua New Guinea's Mount Tavurvur sits right inside this ring of fire.

In 2014,

holiday-maker Phil McNamara was filming the volcano when he caught

on camera the extraordinary power of an explosive eruption.

Watch out for the shock, it's coming.

CRACKING

Holy smoking Toledos!

This incredible footage has been seen more than 18 million times online.

It shows this volcano explosively erupting and the lovely thing

about it is, you can see the shock,

you can see the pressure wave that's travelling out as the air that's

pushed out from the volcano barrels into the air in front of it

so quickly.

The pressurised magma inside the volcano exploded so violently

that it compressed the atmosphere around it

and that's the line you can see expanding out.

And that pressure front is travelling faster than the speed of sound,

but even though it's travelling so quickly,

it still takes time to reach the holiday-maker on the boat.

Watch out for the shock, it's coming.

CRACKING There it is, all that time to come this distance.

Holy smoking Toledos!

The Tavurvur eruption was over in days

but some eruptions last for months

or longer. Now, new camera advances are helping reveal why.

In 2011, Puyehue-Cordon Caulle in Chile

erupted for the first time in 50 years.

The plume was 14km high

and thousands of local residents had to be evacuated.

But six months later, it was still erupting.

And volcanologist Hugh Tuffen joined an expedition

led by John Castro to find out more.

I just had to get out there.

It was a unique opportunity, as this was a very rare type of eruption.

My specialism is rhyolitic magma.

We almost never watch rhyolitic eruptions taking place.

There's actually only been two worldwide in my whole lifetime.

The jungle they trekked through, normally lush and green,

was covered in ash from the eruption.

But it was the lava that Hugh was most interested in.

It was the first time in our lives that we'd ever seen a rhyolitic lava

flow in action.

This was an amazing thing.

Rhyolite is very, very thick viscous magma that is rich in silica.

Its viscosity makes this lava the slowest moving on earth,

travelling just a few metres a day.

This was as far from a river of red lava as you could get.

This was like a glacier of creaking and groaning lava that was almost

imperceptibly moving.

Because the volcanic gases become trapped in this thick magma,

rhyolitic eruptions are some of the largest on earth.

Whoa! That was like textbook.

And Hugh believed it might also explain something else.

One of the unsolved mysteries of rhyolites

is how the gas escapes from this very, very thick magma.

There has to be some way of the gas getting out.

If they could discover how the gas escaped,

they might be able to work out how long the eruptions would last -

crucial information for the thousands of people living nearby.

One night, as he was filming the expedition, Hugh had a revelation.

It gradually got darker and darker, and as it did so,

then the vent really came to life.

I had a switch on the camera which meant that we could go from watching

visible light to infrared light.

We could suddenly see bombs of lava that were being ejected on these

long lazy paths before they landed on the ground.

The thermal cameras saw through the steam and vapour

and showed the hot bombs as bright white pixels.

But it also showed them stopping and starting in cycles.

It seemed as though there were valves

through which gas and ash was able to escape very rapidly.

But then these were blocking up.

And then a new valve was opening up right next to it.

Wow, look. It's just cleared itself again now.

It was a beautiful thing to watch, but also very scientifically useful,

as we can then work out how fast the bombs are moving

and this all links in

to how the gas is able to escape from the magma at the vent.

Hugh's thermal imaging had revealed that after each ejection of bombs,

the volcanic vents were sealing up again, trapping the gases inside.

And that's why the eruptions lasted so long.

To actually see all these secrets being revealed by Puyehue

was quite something.

Around the world, hi-tech cameras are giving us new insights

into how volcanoes work.

Stromboli in Italy is one of the most active volcanoes on earth,

spewing forth ash and steam daily.

But it's also emitting a gas called sulphur dioxide.

It's a crucial indicator of volcanic activity.

But it's completely invisible to the naked eye.

Now, scientists from Manchester are using an ultraviolet camera that can

see these invisible emissions.

By capturing the gas on camera,

they can work out the total volume of all the gases emitted,

giving them vital clues as to how an eruption will evolve

and how long it might last.

At volcanoes like Yasur in Vanuatu,

scientists from Rome are trying to unlock the secrets of dangerous

high-speed lava bombs.

But because they are ejected at supersonic speeds,

they've been almost impossible to study.

Now, by filming at speeds of up to 1000 frames per second,

the scientists can see their precise velocity and path.

This gives them critical information

about how far the bombs might travel...

..and how hazardous the eruption might be for anyone living in its path.

The difficulty with studying volcanoes is you don't know

when they're going to be active,

so it's very difficult to be there at the right time.

And that's why cameras are now an essential tool

for studying volcanoes, because they can be there all the time.

There's plenty of data like this.

This is live data from Kilauea volcano in Hawaii

and there's lots of different webcams,

there's thermal images showing the crater,

there's overviews of the crater, lots of different angles,

and this is broadcast in real-time to scientists around the world,

so they can watch what's happening, and even better than that,

if something interesting does happen,

they can then go back and look at what led up to that event.

So there's a video here from the last 48 hours of the same volcano

and you can see that as daylight comes,

the activity of the volcano changes with time.

And it's data like this that's going to be essential in the future

for taking the next step in understanding these connections

to the innards of our planet.

Volcanoes have long been feared as fiery and unpredictable demons.

But now we're seeing very intricate details and invisible processes

as never before, our knowledge is improving rapidly.

They still hold many secrets but we are coming closer than ever

to understanding how they work and when they're going to erupt.