Episode 1 Expedition Volcano

Hidden in the heart of Africa,

deep in the Congo,

is one of the most spectacular volcanoes on Earth.

Nyiragongo.

It is also one of the most deadly.

It's ferocious.

It feels very alive.

It last erupted in 2002...

..devastating the nearby city of Goma.

The Earth's molten core enveloping an African town.

There are few places on Earth

where an active volcano threatens so many people,

in a country already shattered by decades of violence.

Now there's an uneasy peace,

so a team of international and local scientists are on a mission

to explore this rarely visited volcano...

..to try and predict when it will next erupt.

This is some of this really fast moving lava.

30, 40, even more miles per hour.

The team are also investigating the surprising ways this volcano affects

all aspects of life here.

Their search for answers will take them deep inside the crater...

I've just come over the edge.

..and into great danger.

If any of this rock goes here, that's it for both of us.

On a remote jungle road,

the team of scientists is heading towards a highly active volcano...

..Nyiragongo.

It lies on the Democratic Republic of Congo's

eastern border with Rwanda.

To the south, just seven miles away, is Goma,

a city of almost a million people.

Last time Nyiragongo erupted, Goma was taken by surprise.

The expedition hopes to find new ways of predicting the next eruption

so the city has enough warning to evacuate.

The team have brought an array of equipment to investigate this

volcano like never before.

-Just take care that the men take the heavy bag.

-Yes.

Leading the science team is Belgian volcanologist Benoit Smets.

Actually, that's the one I'm worried about.

-The seismometer?

-I don't want someone to drop it.

Americans Professor Jeff Johnson and Dr Kayla Iacovino

have brought specialist kit

that can identify warning signs of an impending eruption.

I think it'll be good.

Is this like normal fieldwork?

Is this what you always bring?

I think, for me, this kind of

highlights the range of things we do in geology, right?

Joining them are two British scientists,

humanitarian Dr Xand van Tulleken

and geologist Professor Chris Jackson.

For me, I'd literally have a notebook and a pencil, a compass.

-A little hammer?

-A little hammer!

Sun's out down here. Did you have a good night last night?

Absolutely hammered it down.

Really come down. Big, big...

Former Royal Marine Aldo Kane is in charge of getting everyone and

everything to the top of the volcano,

and he's hired in 140 local porters to help.

So we've got science kit, expedition kit, rigging kit, food, water.

Nearly four tonnes of kit that's going up the hill today.

Nyiragongo's crater rim is 2,000 vertical metres above the jungle

and only accessible on foot.

But Chris and Xand both know

how important getting the expedition to the top is...

..because yesterday they travelled

in through the city that lies at the foot of this volcano.

Goma is little known outside the Congo,

but it's an extraordinary city

that owes its very existence to Nyiragongo.

It's all made of lava, isn't it?

Yeah, this is all lava rock directly from Nyiragongo,

the volcano we're going to go and visit.

It's amazing to think that there's such a threat posed by that volcano,

yet because of that volcano

you can build houses and some sort of infrastructure,

so there's a gift and a curse, really, there with the volcano.

I guess I was expecting one thing

-and it's actually quite a lively town, isn't it?

-Yeah.

Today, Goma is growing rapidly,

but it has been rebuilt, literally from ashes,

because in 2002 it was shattered by the eruption of Nyiragongo.

-NEWS CORRESPONDENT:

-The red river keeps flowing,

pouring out of the volcano and down towards Goma.

With little warning, the city was overrun by lava.

Daylight and some of the first pictures reveal a black blanket of

lava covering entire neighbourhoods.

SIREN

Nyiragongo impacts life here in many unexpected ways...

..and it's this that Xand will be investigating.

I'm a doctor and I have a particular interest in humanitarian medicine.

I'm fascinated by this relationship to the volcano,

how the volcano affects every aspect of daily life here,

how people here cope with the constant threat of eruption,

and what another eruption would do to the people living here.

Nyiragongo has erupted twice within the last 40 years.

There's little doubt it will again,

with the same catastrophic consequences.

Chris has studied volcanic landscapes across the world.

For him, predicting eruptions is

both a scientific and humanitarian challenge.

For a geologist, this is incredibly exciting,

to be joining an expedition like this to do cutting-edge,

critical science for the people

living in the shadow of this giant volcano.

After six hours, the team are

reaching the upper slopes of Nyiragongo.

The weather's closed in and it's cold.

But their reward is a view of one of Earth's great natural wonders.

HE LAUGHS

Oh, my goodness.

So, this is the coolest thing I've ever seen, but you all seem pretty

psyched as well and, like, this is for you another day in the office,

isn't it? You're like, "Yeah, another day, another volcano."

No?

I think this might be the coolest thing I've ever seen.

-Really?

-There's literally

nothing like this in the world.

There are six lava lakes, permanent lava lakes, on Earth.

You are standing looking into one of those six.

Of those six lava lakes, they are all babies compared to...

Yeah, they are.

All other global lava lakes could fit into this lava lake

with tons of room left over.

This lava lake is enormous.

The sheer size of it, I think, is just hard to even fathom.

The crater rim is a vast

1.2 kilometres in diameter.

Inside is a permanent cauldron of molten rock

that is 260 metres across,

more than twice the length of a football pitch...

..and it constantly churns at over 1,000 degrees.

It's ferocious.

It feels very alive.

And even when we're silent,

there's that constant roar.

It just doesn't let up at all.

As a structural geologist, we're

often left with what's at the Earth's surface, so we're looking at

rocks, we're describing the rocks, we're measuring the rocks,

we're mapping the rocks, and we may then use also some other geophysical

techniques to look down into the Earth,

but we don't need to kind of image it.

We're actually seeing right down into the lava lake.

But the team haven't come this far just to admire the view.

Tomorrow, they plan to abseil into the crater

to study the lava lake up close.

From where we are here, to get down there is over 400 metres.

So that's, what, four times Big Ben?

That is full-on.

That's where we hope to camp, down there on that second level.

Are you all like, "Yeah, I can't wait,"

first light, you're going to be down there?

You are super-psyched to get down there?

Well, I don't know. This is terrifying.

That, to me... When I look at the lava lake, I don't see danger

so much. It's an amazement. It's not a fear.

I'm afraid of the getting down there.

That's terrifying. That is absolutely terrifying.

Understanding the lava lake's behaviour is crucial,

because it could be linked to forces deep inside the volcano...

..and may provide warning signs of an eruption.

But as Chris and Xand bed down for the night,

it's the descent into the crater, rather than volcano science,

that's playing on their minds.

Whether it's going to be the physical aspect or the mental aspect

that's most challenging, that's probably what I'm going to have

the most sleeplessness about tonight.

There's a lot of risk there that you can't modify.

-Yeah.

-You can wear a helmet and stuff,

but if you're going to get hit by a big rock,

-it's going to be bad.

-That's it.

Hello. Sorry, were you doing a video diary?

We're doing a big diary sesh. Now we've got the man himself.

Now, we've been talking about risk, Aldo.

When is something too risky to not do it?

We've done as much as we can

to mitigate all of the known risks that we can mitigate against,

and then the rest of it is just risky.

LAUGHTER

You were really doing well there.

It was really convincing until you said that.

For Xand, this is only a brief visit to the crater.

Now he's seen the volcano,

he's heading back down

to investigate the complex ways it impacts life in Goma.

First light on the crater rim.

The priority is to get down to the lava lake as soon as possible.

Even though the current weather conditions are miserable,

at this altitude it can get a lot worse.

The temperature is slightly warmer in there,

but it can change like that,

and it can go down to freezing.

My team were down there yesterday and were caught out in a hailstorm.

OK, it's just started with the heaviest hail.

Torrents streamed down the loose crater wall,

creating the climber's enemy - rock fall.

OK, there are waterfalls coming all down the side of the volcano.

And the waterfalls are knocking massive rocks

coming flying towards us.

For Aldo, the risk of bad weather means a change of plan.

What we want to do is cut the amount of people that are going down into

the volcano to essentials only.

And, Kayla, I was speaking to you earlier on and you mentioned you can

do a lot of your stuff up on the top here,

so I'm happy to keep you up here

and not take you down there because of that.

I can do all of the work that I need to do, basically, on the rim.

There are definitely some mixed emotions behind

me not being able to go down.

There's a bit of relief because it is so dangerous to do

and there's also a bit of disappointment because, you know,

what an amazing experience

to spend a couple of nights in the crater next to the lava lake.

It's something I could never have dreamed of being able to ever do.

Later, the weather clears,

and Aldo decides to get the team down.

I can feel my heart rate going up just putting the harness on.

-Wait till you look over the edge.

-Yeah.

Last bit before we go down, kicking rocks off,

if you do kick a rock off, big shout, "Rock!"

-OK.

-If one of these rocks hits someone on the head,

it'll kill them, even with these helmets on.

OK. I think I'm ready.

You should enjoy the view first before we go over,

-because after that you're going to be fairly busy.

-OK.

Nyiragongo's crater has three levels.

Tier one is a small outcrop around 250 metres below the rim.

A sheer 80-metre drop below is tier two,

where the team will be camping.

And finally, tier three, the bottom level that surrounds the lava lake.

-How are you feeling?

-A blend of excitement and nerves,

I'll be honest with you, yeah.

Climbing down is the most dangerous part of the expedition.

Doubly so for Chris...

Nice and gently, Chris.

..because he's not an experienced climber.

How does it feel?

Better now. I've just come over the edge.

And in such a remote location, if anything goes wrong,

there are no rescue teams.

-Sorry.

-Try not to do that because there are sections, if you do that,

that the whole slope will go.

-Yeah.

-All of this is just waiting to fall.

That wind's just picked up.

Yeah, yeah, I can feel it.

Be careful not to kick anything.

If you kick anything, it's coming down on my head.

Yeah, OK.

Everything's moving.

Nothing is stable.

Rock!

Oh, Jesus.

Sorry.

Have a look back up.

Oh, yeah.

Yeah.

Yeah, that's good, that's good.

-Ow.

-You OK?

-Yeah.

As the weather holds, the rest of the team also start the descent.

Just watch your feet coming down.

Halfway down, Aldo spots a small but potentially deadly problem.

Super sharp rock.

-You see that?

-Wow.

What's happened there?

That's where the rock fall has come down and chopped this rope.

Has it gone through the fabric to the core?

It's not chopped it completely.

The inner core still looks like it's usable,

but it will have lost a lot of its strength.

I'm going to change over onto this,

and then we'll put a backup on this.

After three hours on the ropes,

Chris has almost reached tier one.

That's where we are heading to, to the base camp down there.

-OK.

-OK?

But he needs to get to tier two

if he's going to have a bed for the night.

Goma isn't totally unprepared for Nyiragongo's next eruption.

The city does have a volcano observatory.

Its job is to keep an eye on volcanic activity...

..and warn people about the dangers of living in this landscape.

Xand is on his way to a small village just outside the city

to meet with two scientists...

..Dario Tedesco and Mathieu Yalire,

who work there.

This region comes with its own unique threats,

and the scientists are warning the villagers about one of them.

We've assembled the whole village around an area that, to me,

looks completely normal, but is apparently extremely dangerous,

and then we're going to do a demonstration.

EQUIPMENT BEEPS

Seeping from the ground is an invisible but lethal gas,

so the observatory scientists use goats to warn local people,

especially children, about its presence.

The animal is led into an innocuous-looking patch of ground.

At first, nothing happens,

and the goat appears fine.

But then, it collapses.

Bring him up.

-Bring him up.

-With bottled oxygen to hand,

it's a simple job to bring the animal round.

There we go.

OK, OK. There we go.

How's he doing? Oh, he's good, he's back.

Good job. Good job, young man.

There you go.

Well, my first goat resus.

That is a very happy ending. Lovely.

Although it looks traumatic, the goat makes a full recovery.

It collapsed because it was

suffocated by the invisible, odourless gas, carbon dioxide.

This gas seeps up slowly through cracks in the rocks.

It comes from the volcanic system that underlies this whole area.

Because carbon dioxide is heavier than air,

it forms deadly pools in thousands

of shallow depressions that litter this region...

..making them a particular hazard for children.

This seems like an incredibly dangerous thing

to have near a village.

We call these areas mazuku.

Mazuku?

Mazuku means

-evil wind.

-Evil wind?

Evil wind, yeah.

I mean, it's one thing to have your parents say,

"Don't go and play in the hole,"

but it's another thing to see the goat pass out in the hole

and realise how dangerous it is, I think.

I started with a very clear idea that volcanoes are dangerous

because they're boiling hot and they throw out rocks and lava,

and actually this is a much more dangerous threat.

It's not evident. It's secret.

And because it's so un-obvious,

it gets the most vulnerable people in the community.

Back on the rock face, Chris is still descending.

Just ready for first. It's going to be Chris, over.

Make yourself comfy.

He's about to be lowered by Aldo and his team

down a final 80-metre free-hanging drop to the campsite below.

Clear now.

-Thank you.

-Rock!

Steady.

-OK.

-Chris is down.

-Thanks. Cheers, man.

-Spot on.

-That is very good.

-Oh, too intense.

-Don't look back.

-Don't look back.

Don't look back.

So, I've made it down to tier two.

Daz is just sorting out the ropes to be sent back up for the next victim.

The first thing I noticed as soon as I come down to this level,

these giant chasms,

maybe a metre, maybe two metres wide.

You can see in the distance the campsite that's been set up.

The tents are pitched between two potentially fatal hazards.

The vertical drop down to the lava lake is less than 30 metres away.

Just behind the tents

lies a field of fallen rocks from the crater wall.

Despite the danger, for Chris, it is out of this world.

If I was to compare this environment anywhere else, I'd say Mars.

There's just blacks and whites and reds -

very simple colours everywhere.

There is no vegetation whatsoever.

There doesn't seem to be anything living down here.

One of the reasons is actually what I'm smelling. It's sulphur.

And all around us

there's these vents which are spewing out sulphur into the air.

As evening falls, the rest of the team descend...

..with Aldo the last...

..chancing his luck in complete darkness.

Tomorrow, the science can begin.

The next morning, down on tier two...

..Benoit is up first, sorting out his experiment.

Nyiragongo is very important for me

because this volcano is very dangerous.

It threatens a lot of people.

Everything we do to understand this volcano is very important to avoid

another disaster like in 2002.

Benoit wants to monitor the lava lake level

throughout the time in the crater.

He wants to work out what's going on inside Nyiragongo.

Unlike most volcanoes, Nyiragongo erupts from fissures in its flanks.

But like all volcanoes,

it erupts when pressure builds in its magma chamber.

If the team could measure that pressure,

it would provide a warning signal of an eruption.

The problem is the magma chamber is over a kilometre underground,

so it's impossible to measure pressure changes directly.

But Benoit suspects

those pressure changes may affect the behaviour of the lava lake.

Here, we have the chance to have this big lava lake,

and you can see the lava lake as a magmatic chamber at ground surface.

The plan is to use time-lapse photography

to record any changes in the lake level.

But when it spends half its time hidden by clouds of gas,

it's tricky to see,

so Benoit has built his own infrared cameras to overcome this problem.

I made these boxes myself.

My box is made of a microcomputer

that will control everything,

a real-time clock

to have an accurate time,

and a camera.

It's a small camera like you have in your smartphone.

And it'll take every ten seconds,

and by comparing these pictures

I will be able to see the variations of the lava lake level.

The next day, Benoit returns to his cameras to see if they've worked,

and, more importantly,

whether they can reveal anything about pressure in the magma chamber.

Whoa.

We've got a beautiful lava lake level drop compared to yesterday

at the same time. It's great.

So we recorded something special.

The home-made technology works.

Over the last 24 hours,

the cameras recorded a small drop in the lake level.

This suggests pressure in the magma chamber does affect the lava lake.

It's not about having the lava lake level high or low,

it's understanding these movements to predict

big events like a flank eruption.

We have the opportunity to measure the pressure change

by looking at the lava lake level.

At the moment, the volcano is stable,

so there are only small changes in pressure.

If the volcano was building towards an eruption,

Benoit would expect to see huge variations in level,

40 metres or more.

His cameras can spot these changes,

but they're not designed to be left in the crater...

..so the team need to find a way to permanently monitor the lake level

to provide Goma with a warning.

Despite the threat of a volcanic eruption, Goma is a growing city.

Each new house is built on old lava flows.

This brings with it a potentially fatal health problem.

I didn't... I didn't bring any safety goggles,

so I've got my sun specs instead.

Every house starts with a stonemason

like Heritier, chiselling out a long drop toilet.

Problem is, cooled lava is an incredibly hard rock.

I've been doing this for about 30 seconds and I'm winded.

Heritier's job is tough but necessary,

because without toilets,

there's a deadly side-effect of living on lava.

Long drop toilets work really well if you have a long drop toilet.

And the problem here is that there have been loads and loads of things

in Goma that have moved people out of Goma or moved people into them

where they don't have toilets.

We have refugee movement, violent conflict, and volcanic eruptions.

And so if you have people without access to toilets,

what you have is massive spread of infectious diarrhoeal illness,

particularly cholera.

This is one of the world hotspots for cholera.

An estimated 13,000 refugees have died in the last week,

mostly from cholera, and the bodies line the streets.

In 1994, more than a million people crossed the border,

which is just a few miles in that direction,

from Rwanda, Rwandan refugees,

and they stopped in Goma and in the surrounding countryside.

A team of nurses are desperately trying to save the dying.

There's a scramble to set up drips of rehydration fluids and salts.

I've worked in cholera epidemics,

and it's almost impossible to

describe the amount of diarrhoea that's produced.

So in a cholera treatment centre,

you have sloping floors and you have beds with holes in them,

so people go to the toilet directly onto the floor

and you're just washing it into a central gutter.

It's unbelievable, the quantities of fluid that you need to replace.

We are talking about 20 litres,

sometimes more, per day, of diarrhoea.

So it can kill you within hours.

The added layer of tragedy on top of that number of deaths

is that, in this region, digging graves is virtually impossible,

as you can see. Very, very hard to do.

The cholera outbreak in 1994

was caused by a mass movement of people

with no access to decent sanitation,

so human waste polluted Goma's main water source.

Goma's population has now grown to almost a million people,

so when Nyiragongo next erupts

there will be a mass evacuation

in numbers that haven't been seen since 1994.

SIREN

Practice drills have recently been introduced to test the response of

police, charities, and medical aid to an eruption.

But the danger is that hundreds of thousands of people

fleeing their homes

will find themselves without access to a toilet,

leading to another epidemic.

This town, Goma,

is one of the first places I ever heard about when I started studying

tropical medicine. I guess I thought that I knew a fair bit,

and what I really love, and what's been very interesting and amazing,

is that I really didn't understand anything at all.

I guess you wouldn't think that

a bacteria getting inside you and giving you diarrhoea

would be determined by a volcano.

Up on the volcano rim, Kayla is starting her investigation.

She's studying the gases

that constantly vent from the lake's surface...

..because they can provide another way

to tell what's happening in the magma chamber.

The real power in gas measurements is that it can tell us about

the entire system miles and miles beneath your feet.

So that's where the action is. That is the driving force of volcanism.

It's controlled deep down in the guts of the volcano.

All lava contains gases,

but when an eruption is building, those gases change.

The one that alarms volcanologists is sulphur dioxide,

because it often signals that lava is moving up towards the surface.

With a simple device called a gas box, Kayla can detect its presence.

Sulphur dioxide is the kind of gas that bubbles out of the magma

in the really shallow part of the system,

so just beneath the lava lake.

If we see, all of a sudden,

a huge spike in the amount of sulphur dioxide

that's coming out of the crater,

that could be something that happens before an eruption.

After 12 hours, Kayla returns to find out what's been recorded.

So, I'm just looking at the data now, and I'm pretty happy.

So, these are sulphur dioxide. We're getting some readings there.

Less than one part per million, but there is some reading there.

So maybe not an immediate eruption.

This low sulphur dioxide reading

means no new magma is rising up through the volcano.

For the moment, Goma is safe.

The problem is, gases on their own are an unreliable warning indicator.

Sampling them depends on weather conditions and wind direction.

But the team are hoping to test another piece of technology

that could provide a better way to warn of an eruption.

When Nyiragongo erupted in 2002, lava flows split the city in three,

killing around 100 people

as the rest of the city fled for their lives.

So is that where the lava got to?

Yeah, exactly. The lava came and stopped...

Xand's meeting local journalist Caleb Kabanda

to find out what it was like

and if there are any lessons to be learned.

You couldn't get to, like, the top of a big building?

The lava has been flowing for two days now.

It shows no sign of stopping.

So you come back that morning, and what does the city look like?

As if the people of Goma had not suffered enough,

this was a day that brought them more death, more tragedy.

Fireballs filled the sky after a petrol station here exploded.

Fuel cans leapt into the air.

Walking through Goma, having heard Caleb's story,

it's hard to think back to 2002 and imagine lava flowing through these

streets, knocking buildings down, destroying everything.

But what's even harder to imagine is how little time it took for the city

to be inundated, how it seemed to be caught unawares.

No matter how much warning the science team can provide,

Goma's residents still need to know how much time they have to evacuate

once the lava starts flowing from the volcano.

Back in the crater, the team are now focusing on how quickly

the lava could reach Goma.

That's down to how fast it will flow during the next eruption.

To find out, they'd ideally study

the chemical composition of lava from the lake.

But collecting samples is simply too dangerous.

There is, though, another possibility.

During preparations for filming,

Aldo witnessed a new vent opening up

that sent rivers of lava running across tier three,

the crater floor.

We were supposed to be heading down,

but this aggressive vent here is

constantly boiling and the, er...

You can see there the lava bombs that are getting blown out of there

are probably 40, 50 metres into the air.

For Aldo, it was terrifying.

Just so many...

Now the vent is simply smoking.

But the lava flows it left are just a few months old.

They could be what the scientists need.

So the plan is to descend to tier three.

First, they need to check if the lava is cool enough to walk on.

We're about to launch a thermal camera fitted to a drone

that the Belgian science team have brought along, and it's going to be

flown over T3, the lowermost level next to the lava lake,

specifically to look at where there may be hot rocks or magma

underneath a thin crust.

So if we go over the fumaroles, we know they are about 60 degrees.

So this would be, like, something we can use for...

What's its max?

-500.

-500.

-Yeah.

-Don't go over the lake!

-No!

It's flying back this way.

Yeah, there's something really hot there.

It could be this vent.

I have a problem with the drone.

I cannot control it.

Is the drone... Have you got control?

-No.

-Maybe you can move, try to keep the signal.

Yeah, I think here.

Just watch the...

So we're, kind of, almost over

the area that we'll be running the ropes in and abseiling down.

Was that safe enough for tomorrow?

I think that's fine as long as we don't go too close to the vent,

which was really hot, but everything else was OK.

I'm coming back, because I cannot control the drone.

The wind is too strong.

I've got visual.

The crater floor is just about safe enough to walk on.

But, by chance, Chris has discovered

that it's not just the bottom of the crater that's warm beneath the feet.

I've walked only ten metres away from the camp to take a pee,

which is the minimum distance we have all agreed we should go

before we actually use the toilet, and I've found out

something remarkable about the rocks just around us.

I'm going to pour some water on here in a live experiment

to show you just how changeable and hostile this environment is.

The water boils straightaway

as it hits the rocks here,

produces this horrible sulphuric acid smell or sulphur smell which

has gone straight in my nostrils,

so I think this isn't going to be my toilet place of choice any more.

While Chris heads off to find a new location,

at the edge of the cliff face

Aldo is preparing the climb down to tier three

for petrologist Olivier Namur.

He thinks samples from the recent lava flow will reveal

if the next eruption will be fast flowing or slow moving lava.

I'm interested in the composition of the lavas

and the evolution through time,

so I've been sampling old lavas in the last couple of days

and I will be sampling this very young lava

that erupted last year on tier three.

I think it's about 100 metres, so, that's...

I think where we are now is about the height

of the white cliffs of Dover.

Yeah, thereabouts.

I've never been down here before.

This is going to be my first time.

The descent isn't straightforward.

There's an initial short abseil,

then a sloping field of fallen boulders where the crater wall has

collapsed, followed by a final

vertical drop down to the crater floor.

It all has to be rigged safely,

so Aldo goes first.

So brittle.

-RADIO:

-Go ahead.

That's both Daz and I on boulder field, over.

Whoa, there's some big chunks of rock there, mate.

About 150 metres away from the lava lake at the minute, but...

I reckon, Daz, about 80 metres?

So it's about 80 metres straight down there.

At the foot of the cliff,

recent rock fall is clear evidence of its fragility.

Oh, man, look at these rocks.

Just precariously balanced.

If any of these rocks decide to go...

..then that's it.

As Aldo drops over the edge,

Daz, his climbing buddy, keeps an eye on him.

Any false move could create a lethal rock fall.

Even up on the camping level, Benoit can see the risk Aldo is taking.

Mate, right here.

So, I've just arrived on tier three.

The lava lake is about 100 meters that way

and that is the route I've just abseiled down.

It is...

..without doubt,

one of the most dangerous things I've ever done.

My mouth is dry...

..and my heart rate is up.

All the classic signs of...

..100% pure, unadulterated fear.

Time to get out.

It is super sketchy.

I think it's the most sketchiest thing that

I've seen since being in here.

I don't know what you're used to, but...

..not entirely sure I would go back down there.

If you think it's not a good idea, we'll not take the risk.

I mean, we are here to do good science

and collect exceptional data, but not taking stupid risks.

I know you well enough to know

that if that situation down there is...

..you're fearful of that, then...

No, it's too dangerous.

Let's forget about going to tier three.

The team abandon the planned descent to the crater floor,

but there is still a possible source of fresh lava.

During the recent eruption, the vent threw out lava bombs,

and some may have landed on the boulder field

halfway down to tier three.

If they can find any, Olivier will have his sample of lava.

For the rock samples, we can have some spatters.

-Yeah, but only...

-..coming from the vent in the boulder field.

It's not ideal.

It's not ideal but it's better than nothing.

The team quickly get to work.

No-one wants to hang around here too long.

I mean, you're standing hammering a cliff

which is clearly already unstable.

Yeah, this is true but this is the only way to get these samples.

Olivier soon finds what he was looking for - new lava bombs.

What have you got?

It's a very fine grained lava.

This should be enough.

It's quite fresh. I think that will tell us quite a lot about

the recent activity of the volcano.

They are quite nice.

After one happily uneventful hour,

he has enough samples

and, for an experienced geologist,

they contain an unmistakable message,

but it's not good news.

Let me show you one of the samples that I collected

from the active vent.

We can see that these samples are a glassy black matrix.

We can see a lot of bubbles here around,

and a few tiny white crystals.

We know that the composition of these volcanoes are low in silica,

very low, below 40%.

This makes this lava very fluid, so they have low viscosity,

they will be flowing like water

along the flanks of the volcano, rather than mud.

And on top of that, because they have only a few crystals,

that decreases again the viscosity of this lava.

Because they have only a few crystals, they are very fluid.

So I suspect that if there is a new eruption, with this composition,

it might be flowing even faster than during 2002.

In 2002, lava flowed into Goma

at reported speeds of up to 40 kilometres per hour,

reaching its centre in fewer than ten hours.

Olivier's samples have revealed that next time, it could be even faster,

so the city may have even less time to evacuate.

That makes the need for an effective warning system more pressing.

Tomorrow, the team have the last piece of kit to test.

Nyiragongo creates a unique set of problems for

the people who live in its shadow.

But there's another side to this city -

the character that's defined by the volcano.

It's symbolised by a local invention

that is found nowhere else in Africa -

a deceptively simple wooden scooter called a chukudu.

Xand wants to find out the story behind them.

Since I arrived in Goma, I've seen hundreds of these things.

They're all over the place.

They're usually carrying massive, massive loads.

They're real feature of the landscape here.

But seeing them up close, I mean,

carving a perfectly circular wheel out of hardwood with a machete is...

I don't think it looks easy, but it's a lot harder than it looks.

Can I try? OK.

Like that? OK.

I'm not very good at this.

You made it look... You made it look very easy.

I got a little bit off there.

How did you learn to do this?

How much weight could this chukudu carry?

You don't have a tape measure.

What colour can I get it in?

The chukudus tell...

..almost tell the story of the whole region

just captured in this one thing.

You have people doing a kind of extraordinary job

under unbelievably difficult circumstances.

You don't find these anywhere else

and that's because this is a totally unique place.

There isn't really another landscape like it.

It's very difficult to farm. It's very difficult to move stuff around.

You do see this extraordinary

level of work and resilience and willingness to try and imagine

a better future and work towards it.

This is almost a symbol of resistance

and a very, very big part of people's identity here.

Back inside the crater, the team return to their main challenge...

..detecting signs of an impending eruption.

Earlier, Benoit established

that sudden, erratic changes in the lava lake level

usually happen before an eruption,

so the key to an early warning system is monitoring that level.

American volcanologist Jeff Johnson thinks he can do this by listening

to the sounds Nyiragongo produces.

But not just any sounds.

This is a custom-built microphone,

and it's capable of recording sounds

beyond the threshold of human hearing.

Jeff's microphone is designed to pick up very low-frequency sound,

what's known as infrasound.

Volcanoes speak at low frequencies.

They generate sound that we can hear,

but they also generate this world of infrasound...

..a unique voice print that we want to recognise and understand

so that when that tone changes in the future,

we will be able to understand what's going on.

The theory is that, like a sliding trombone,

as the level of the lava lake rises and falls,

the infrasound tone changes.

Using infrasound is at the cutting edge of volcano science,

and Chris is keen to see how it works.

So we're listening to sounds coming from the lava lake, is that right?

We're trying to hear the lava lake with these sensors?

The infrasound is detecting motions

that occur both at the lava lake surface

and also inside this bowl, that can be vibrating.

You don't think of a caldera this big as being an air mass

-that may be going up and down.

-No.

But that's what we have discovered,

the crater actually acts as a musical instrument.

First, the microphones need to be installed.

To detect the infra sound tone,

Jeff and Chris place groups of them

at several locations around the crater,

as close to the edge as they dare.

Go from here to there.

-Yeah.

-And from here to there.

OK.

It's not long before they are producing results.

So we've collected some data.

It looks like a bunch of wiggles on a screen to me.

What noise is the volcano making?

Right, so, we can't hear infrasound,

but we can speed it up and we can make it audible.

Here's an example of the infrasound being sped up...

-RATTLING

-..by a factor of 40.

This, to me, is exciting.

I see the data, it's good, good quality, and I am happy.

Different infrasound tones

correlate with different levels of the lava lake.

Installing a network of microphones within the crater would mean

the level can be monitored remotely,

and any dramatic changes in the lake level used as a warning.

So it would be fair to say that infrasound could help better

protect the people of Goma from a volcanic eruption?

So, I'm a scientist and I'm naturally cagey about

answering a question like that but, yes, I do believe

that infrasound is a fundamental tool for volcano monitoring

and, not too far down the road, we will be able to use

infrasound monitoring here to better forecast Nyiragongo's next eruption.

The science team are packing up, ready to head out of the crater.

It's a time to reflect on what's been achieved.

The volcanoes can live for millions of years and we're here for a couple

of weeks, but we're getting the beginnings of an idea of what

this volcano is capable of doing.

Their work has revealed that, for the moment, Nyiragongo is quiet,

but when it does next erupt,

the lava is likely to reach Goma faster than ever.

They've also established that infrasound could be a way

to remotely monitor the lake level,

a key warning sign of an eruption.

Nyiragongo is not an easy volcano to study.

It is a massive headache in terms of getting people and equipment here.

The motivation for it is very clear.

There are a million people living very close to this volcano

so, despite all the problems, it's worth it.

The expedition has also worked with a local volcano observatory

to help prepare the people of Goma for the dangers of living

in this highly volcanic landscape.

I've been thinking more and more

about how people here can manage to do the impossible thing

of living with this volcano that is such a constant threat to this city.

On the one hand, the volcano

is deeply connected to deadly epidemics,

to the destruction of houses, the destruction of communities.

And, of course, you can't quite live with that idea.

It's hard to hold it in your head.

But the work the scientists are doing in predicting the eruption

will give people time, maybe to not save their property or their houses,

maybe not to save their land, but at least to save themselves,

and that does give you a hope of rebuilding.

Next time, the team move on

to an even bigger and more violent volcano...

..and discover how these volcanoes affect every aspect of life here,

from endangered wildlife to the conflicts this region has suffered.