NOVA

In the heart of Africa

are two of the world's most dangerous volcanos.

Within their craters, molten lava steams and boils.

Over centuries

these volcanoes have erupted many times,

but when will they erupt again?

It's a crucial question,

and no one knows the answer

because these are among the least-studied volcanoes

in the world.

Now an international team of scientists

has come to investigate these giants,

to predict future eruptions and save lives.

Everything we do to understand

this volcano is very important to avoid another disaster.

Today,

they're flying to a volcano called Nyamuragira

in a region rife with dangerous militias.

After many active years,

this volcano has stopped erupting.

The fire in its crater appears to be gone.

We need to collect some really critical data up there

to understand what might happen in the future.

Will Nyamuragira erupt again?

And if so, when?

The people who live here are at risk.

Can scientists find a way to protect them

before time runs out?

Right now,

I just want to get things set up and going,

so we can just get as much as possible

in this really short time that we have here.

Can they solve the mystery

of "Volcano on the Brink"?

Right now, on "NOVA."

Major funding for "NOVA" is provided by the following:

In a remote region of central Africa

lies one of the most active yet least explored volcanoes

on the planet:

Nyamuragira,

as spectacular as it is mysterious.

The volcano sits on the eastern border

of the Democratic Republic of Congo, the DRC,

near the shores of the vast Lake Kivu.

Fewer than 20 miles from the volcano

is the town of Sake.

Its residents are all too familiar

with the threat of its frequent eruptions.

Market traders Terese Kalume and Mama Noya

have spent their entire lives here

and witnessed the effects for themselves.

Nyamuragira eruptions blanket large areas of farmland

in scalding-hot, choking ash,

destroying crops, killing livestock,

and bringing famine.

At the moment, there is just such a break.

It's been five years since the last major eruption.

Has the volcano gone extinct,

or will it erupt again, more deadly than before?

It's this question

that an international group of scientists

has come to investigate.

To do that, they have to be transported to the volcano

by a United Nations peacekeeping team.

For British geologist Chris Jackson,

it's a field trip like no other.

It's actually in a fairly dangerous

part of the the area,

so the only way to get there is

with a military helicopter.

My heart's racing just at the thought

of getting on that helicopter.

Few people have visited Nyamuragira...

For good reason.

This region of the DRC was the center

of one of the bloodiest wars of modern times.

Fueled by a long colonial history,

vast mineral wealth, political tensions,

and international pressures,

millions were killed and injured.

Although the war is officially over,

widespread unrest continues.

Violent militia and rebel groups are operating in nearby forests,

so the helicopter flies fast at treetop level

to stay out of their gunsights.

Even at this speed,

the helicopter provides a great vantage point

to see one of the most volcanic places

on earth.

American volcanologist Kayla lacovino

has studied volcanoes across the planet,

but the volcanism here

is on a scale she's never experienced.

I thought I knew

what this landscape was going to look like,

but there's really way more volcanoes,

way more melt here than I expected.

It's... the amount of magma production in this region

is insane.

As they reach Nyamuragira,

they can see it's a giant shield volcano,

so called because successive lava flows

have spread widely across the landscape,

giving its surface a sloping, shield-like shape.

The volcano rises to over 10,000 feet,

surrounded by old lava flows

that blanket almost 600 square miles.

At the summit,

the main caldera created by previous eruptions

is over a mile across, with 300-foot-high walls

and, at its center, a 600-foot-deep crater.

Usually such an active volcano near so many people

would be covered in monitoring equipment,

but because it's remote and dangerous,

Nyamuragira has none.

This is a rare opportunity

to gather data for predicting future eruptions.

We're hoping to land on top of the volcano,

right next to its active crater.

We need to collect some really critical data up there

to understand what might happen in the future.

This is one of Africa's most active volcanoes,

and it has a very complex history.

During the past 100 years,

it's erupted from its flanks at least 30 times,

flooding the surrounding farmland in molten rock,

though this hasn't happened

for the past five years.

In 2014,

for the first time in almost a century,

a small lava lake developed in the center of the crater.

So, the first thing the scientists want to check

is whether that lava lake is still there.

We're banking round now.

There's just sheer cliffs

right down to the lava lake, which,

from what I can see at the moment, seems to...

seems to be crystallized,

so seems to have turned into rock.

But does this

have anything to do with the volcano's behavior?

With the lava lake apparently gone,

will the volcano return

to its cycle of huge, destructive eruptions?

Belgian geologist Benoît Smets,

who works with local scientists,

specializes in geo-hazards.

I think we should first follow

the, the cracks... Okay.

And then turn right right, try to avoid them. Okay, cool.

He discusses plans with Aldo Kane,

a former Royal Marine,

who's in charge of the expedition's safety.

Across the caldera, this is where the gas escapes,

so it's quite dangerous.

Okay, all right, we'll get everyone out,

and then we'll get a bit of a brief then.

Okay.

It's not just the volcano that worries Aldo.

Just to be aware there are armed groups

operating in and around the, the slopes of the volcano.

If you do see someone that's not from our group,

then get on the radio, let me know.

There is a path and tracks going through here,

so they are using it, it is accessible to them,

so keep your eyes peeled.

Any armed groups that saw them fly in

could be heading to the summit, so they can't stay long.

So, we've got two hours, so we need to be back here,

everyone at the chopper ready to go in two hours.

- Cool? - Okay, sounds good.

Thanks, Aldo.

The urgent question for the team

is whether the current break in large-scale eruptions

is coming to an end.

Kayla believes that the plume of gases released by the volcano

will yield vital clues.

I want to find a place

where I can actually get inside the plume

and put the gas box,

and that can tell me more about the different chemicals

that are coming out of the plume.

Monitoring the changes in that gas chemistry

is what tells us whether the system is changing,

whether it's moving towards an eruption,

whether there's new, new magma being input at the very base.

The gases really tell the whole story.

Most volcanoes have a magma chamber,

a reservoir of molten rock deep underground

that fuels eruptions.

As the magma rises up towards the surface,

it releases a mixture of gases.

A sudden increase in one gas, called sulfur dioxide,

often signifies an imminent eruption.

Kayla wants to discover the concentration of sulfur dioxide

in the gas plume, but it won't be easy.

I'm really... yeah, I feel, I feel like

we're really pushed for time here.

There is a lot of gas coming out of here.

The problem for me is that once it gets to the top,