Episode 2 Kate Humble: Into the Volcano

'I'm standing on the rim

'of one of the most active volcanoes on the planet.

'It's so powerful, it once blew the top off this entire island.'

This is Marum, with its truly breathtaking lava lake.

But to understand how this volcano is behaving,

we need to get off the rim of this crater

and descend towards that fiery inferno.

'I've travelled over 10,000 miles to join a team of scientists

'as they attempt to get under the skin of this volcano.'

I can feel the heat now.

'It's a challenge fraught with risk.'

Ooo! Sorry! Oh, Tim, sorry!

It's OK, no problem.

'But it could give us an insight into its inner workings

'never achieved before.'

That's enough to kill you pretty quickly, actually.

It can pump out more sulphur dioxide than anywhere else on earth

in a toxic plume of gas that engulfs the island and its people.

So I'll also be finding out how it affects the lives of the islanders.

LAUGHTER

What's so funny exactly?

Is this volcano building towards another major eruption?

-Oh, my God, it's really warm! Argh!

-Whoa!

I'm flying above the island of Ambrym in the Vanuatu archipelago.

This island is home to one of the most dynamic

and exciting volcanoes in the world.

It's called Marum.

And we're here to try and understand how this volcano works.

What its personality is.

Ambrym is one of the islands in the Vanuatu chain

that sits on the edge of the Pacific Ring of Fire.

Its volcano contains one of just five lava lakes in the world.

A permanently-bubbling cauldron of molten rock that makes it unique.

I've joined Professor Shane Cronin,

who has been monitoring this volcano for a decade.

I'd say it's dark and brooding.

You've got this black ash, the lava, the shapes.

He's here to find out if its behaviour is shifting.

It brings me back time and time again to understand its moods,

its changes, its effects on people.

And what makes this volcano particularly unusual and special?

One of the things about it that's so unusual is it's always erupting.

It's not always throwing material in the air,

but it's almost always erupting.

There's almost always something going on.

Magma is always there. It's alive, it's pulsing.

And to understand the breadth of those changes,

we do need to get a feel for that personality.

When its moods shift, what might indicate a mood shift

and what might indicate a hazard for the people living on the island.

'This whole island is a volcano.

'Its landscape scarred by the string of violent eruptions

'which have frequently forced entire villages to be evacuated.

'So, what's it like for the 7,000 people

'who live their lives on the slopes of an active volcano?'

Hi.

-I'm Kate.

-Hello, Kate. Welcome to Ambrym.

Thank you. Oh, how beautiful!

-They smell lovely. Thank you so much!

-It's a pleasure.

Look at this fantastic village!

'As soon as we arrive, we're greeted Vanuatu-style.'

Is this a normal occurrence when you come to an island like this?

Well, on an island like this, when a plane comes,

or when a cargo boat comes in, you know, it's a big occasion.

-They look cute, don't they?

-They do. They look amazing.

TRIBAL SINGING

-Hello!

-Say hello.

-CHILDREN: Hello!

How are you? Hello?

LAUGHTER

What's so funny exactly? Hm?

LAUGHTER

It's very, very strange just dropping into a community like this.

You come in across this thick, dense vegetation

covering this incredibly rugged landscape.

And that's all because of the volcano

that totally dominates this island.

But then you get to a place like this

and it feels so benign and friendly

and you can't believe that just up there

is a great boiling pit of lava.

And the impact on these villages will be enormous.

-It's like Christmas.

-Yeah.

LAUGHTER

Wow! Santa's sack!

'Ambrym is so remote that planning a trip to the heart of its volcano

'is a bit like a military operation.

'Everything we need has to be flown in and carried with us

'on the eight-hour hike to the summit in a few days' time.'

You like to pack light.

Yeah, I know. You volcanologists!

I thought you just needed one little hammer.

'I'm joining Shane and geologist Chris Firth...'

-You got everything?

-Yeah. It looks like it.

I don't recognise any...

'..as they attempt something they've never tried before.'

I've got somebody else's bags entirely!

'Abseiling right into this volcano

'to find out if it's becoming more threatening.

'But before we embark on our arduous journey to the top,

'we'll be spending a few days in the village of Ranvetlam

'so we can gather some crucial evidence

'about the forces at work deep below us.'

So this is where you'll be staying.

It's beautiful.

'Here, like everywhere on Vanuatu, pigs are part of village life.'

I love pigs.

LAUGHTER

-They roam around the village.

-They do?

-Yes.

Just completely free?

Yeah. But they belong to someone.

-OK. So you're saying, don't steal one.

-No.

-No.

LAUGHTER

The threat of an eruption is ever-present on Ambrym,

so Chris and Shane want to gauge the level of risk

Marum poses to the people living here.

Volcanoes are highly volatile and unpredictable,

but Shane helped devise a scale of risk for Ambrym's volcano

that's internationally recognised.

We're here to find out if Marum's hazard level needs to be increased

and the islanders warned of any imminent danger.

CHILDREN SING

So, Shane, can you give me a sort of geological lie of the land?

So we are located right up here, by Ranvetlam at the moment.

So we're in that northern Ambrym and Marum is here.

And we are north of the caldera.

So the central part of the island, this caldera system

is where the bulk of the magma is right here.

This volcano, if not unique, certainly unusual

is the fact that it has this open lava lake, doesn't it?

-Yeah.

-And not even one, but more than one.

-Right.

-Which is certainly unique amongst volcanoes.

This volcano is more or less in a constant state of eruption.

So when you look at the eruptive history of it

and see a lava lake here, lava lake there, it comes and goes,

the whole thing is always in a state of flux.

Do you know yet whether it could then go into

a more violent, eruptive stage than simply being a lava lake?

The best example we have of that is about 2005.

In 2005, this was the biggest point source

-of sulphur dioxide on the planet.

-Wow!

So that's the sort of thing we will be looking for

in terms of trying to understand the state of the volcano

is how much gas is coming out of it,

how vigorous, or how active the lava lake happens to be

and what other features and signs we see of different types of activity.

'In a couple of days, I'll be coming face to face with Marum,

'and I'm already feeling anxious.'

We've sent a team ahead to the summit.

They're battling the elements and setting up camp.

Sound of a good bolt is if it's singing to you.

Hear that ding-ding?

Beautiful.

A team of six specialists is making the crucial preparations

for us to abseil into the volcano

so we can collect the evidence we need to find out if it's changing.

The weather up there is highly unpredictable.

And until they've finished building base camp, we can't join them.

So for the next few days, I'll be finding out

more about the island and its volcano

to help us when we get there.

Of all the Vanuatu islands,

Ambrym is the most notorious for black magic.

Marum is believed to hold the spirits of the islanders' ancestors.

And the complex systems of belief here

are deeply connected to the power of the volcano.

So here, Kate, look, they are just weaving coconut leaves together

-to go on top of the housing.

-Ah!

And I love the fact they, um...

'I've asked anthropologist Haidy Geismar,

'who has worked here over many years,

'to help us understand how the volcano shapes what people believe.'

The volcano is an intrinsic part of the environment.

It affects the crops, it affects the soil, the fertility of the soil

and the very ways in which people live.

Are there lots of stories, are there lots of legends,

I don't know, songs, carvings, that reflect the volcano, or not so much?

Knowledge in Vanuatu is very placed in particular locations.

And stories don't float around,

they belong to places and people from particular places.

We've heard one story which talks of a mysterious cave on the coast.

A place believed to have the power to kill.

We want to know if this power might be linked to the volcano.

-Morning.

-Morning.

-Chief Harry, Kate.

-Hello.

-Shane. This is Chief Harry. He's the chief of Ranvetlam.

-Oh, OK.

'Chief Harry has local knowledge that might be of help to us.'

You know when you want something where...

Only find them in the 18th, 19th century.

So this cave which is down by the sea,

they discovered it in the 18th, 19th century.

They saw that every time anything went inside, it died.

So it's a place that people have known about

these powers for quite some time

and sometimes in the past, they have used them malevolently.

If you take someone's leftover food and put it inside the cave,

-then that person would die.

-Wow!

HE SPEAKS IN LOCAL DIALECT

So Menuhin is a language word which means breathing.

It means you become short of breath.

-It pulls away your breath.

-OK.

If people are short of breath,

-it sounds like carbon dioxide.

-Right.

I mean, a lot of people are killed by carbon dioxide in volcanic areas.

-Yeah.

-It's a silent killer.

'Traditional beliefs in this village go hand in hand

'with a desire to better understand the volcano using science.

'And even though the cave is taboo,

'the importance of Shane's work here is well recognised.'

THEY SPEAK IN LOCAL DIALECT

So I'm allowed to take my measuring instruments down.

OK. Just don't take part of my breakfast down.

-Yeah.

-Otherwise I'm going to be suspecting your motives.

'Shane's convinced Harry is talking about a volcanic vent.

'A deep crack in the earth which is releasing

'potentially-deadly amounts of carbon dioxide.

'If he's right, it could be a clue to Marum's current behaviour.'

Do you think this is it here, Shane, in front of us?

-I think this is the place.

-Oh, wow!

-It looks like it.

Oh, horrible!

LAUGHTER

Oh! Jeepers! That's strong.

So clearly, there is something amiss here.

There are a lot of dead birds in the cave.

So that's drawing the gas in and over this tube.

Yeah. And we see we've just gone down to the five,

or just beyond the five, probably about 6%.

Yeah. Which I have to say doesn't sound that high,

but what are sort of normal levels of carbon dioxide?

-It's more than ten times normal levels.

-Wow! OK.

-Yeah.

So tell us what that one says.

It looks much the same. Maybe even a tiny bit higher.

-Oh, yeah.

-Yeah. It's gone quite a bit more.

-It's ten. It's turned to ten.

-That looks like ten. Yeah.

Yeah. Wow!

So I suppose because it's a heavier gas...

It's sunk down. Yeah.

I'm going to have to move.

That's enough to kill you pretty quickly, actually. 10%.

And could that be a precursor to a bigger eruptive event?

Yeah. We would need to measure this constantly

and know whether this gets more or less.

But definitely, this would be a place where regular monitoring,

if there was a big spike in the carbon dioxide output here,

it would be worth definitely warning people.

Presumably, if that much carbon dioxide is being pumped out of here,

standing around here for much longer is not a good idea.

No, I don't think it's a good idea for us to be overnighting here!

LAUGHTER

'The surprisingly high levels of carbon dioxide suggest

'that magma is rising from deep below,

'making the threat of a big eruption more likely.

'It's enough to make me a bit nervous about what we might find

'when we reach the summit in a few days' time.

'Whilst Chris and Shane prepare their kit for the trek up...

'..I'm heading to an annual ritual

'that I've been told I just shouldn't miss.

'The rugged volcanic landscape and old lava flows

'separate the villages here.

'So even on this small island, four different languages are spoken.

'But shared systems of trade and barter bind everyone together.'

-The pigs' food is still here.

-OK.

So she wants to call them in here.

OK. She's going to call them to the house?

-Yeah, to the house.

-Really?

-Yeah.

'And like all over Vanuatu,

'it's based around pigs, which are also used as currency.'

So people live really closely with pigs, almost as if they are part of the family.

Particularly the pigs that start being reared for custom ceremonies.

'On Ambrym, pigs also play a fundamental role

'in the way society works.'

Let's just have a little piggy moment.

Let's just have a little piggy moment.

Look how handsome you are.

'Pigs are used to change social status

'and their value depends on their tusks.'

So pigs are ranked according

to the level by which their tusks are grown.

So the most valuable pig will have the tusk

that's gone round two, sometimes even three times.

So it will go through the cheek,

-into the jaw and come back out again?

-Yes.

This is the kind of pig that you would use if you were taking a rank

in the ceremonial rituals of status alteration

which men go through to gain rank

-in the sort of hierarchy of the village.

-OK.

'Once its tusks have curled sufficiently,

'Janic is hoping to exchange his pig

'either for a bride, or for a new title

'so he can move up a rung in the island's social hierarchy.

'This grade system is called the Maghe.

'In spite of embracing other aspects of the modern world,

'it's a custom that's still preserved.

'Public ceremonies take place once a year.'

TRIBAL SINGING

What we are seeing now is a tamoke dance.

So the tamoke dance is a spirit that dances through the village.

Is that the people that have got the masks?

-With the banana leaves.

-With the banana leaves, yeah.

They use it as an opening for the Magi,

which is the system by which

men will go through a series of different ranks.

And their status will get higher and higher as they do that.

'This is the grade taking ceremony.

'The chief is going to assume one of 15 different grades.

'Each level brings men closer and closer to immortality

'and to the ancestors that reside in the volcano.'

You hear about some men who are so high ranking,

they do mortuary ceremonies for them before they die

because they have almost passed over into the upper realm.

'The chief is pelted with stones

'as a way to display his strength and agility.

'But to get his new title,

'he also has to hand over his most prized tusker pig

'and supply another normal pig for slaughter

'to show he can provide for his community.'

SQUEALING

So they have these big special clubs that you can see there.

They should do it in one blow and then it's painless.

I can't watch that, I'm afraid.

'It's not until the pig is killed that the exchange is complete.

'Ceremonies like this play a crucial role in safeguarding knowledge

'and tradition for future generations.

'And it's shown me a very different side to this island

'and its volcano.'

Marum is central to my whole journey on Ambrym,

but it's really interesting having these two different

approaches to understanding it.

One is the geological, knowing what those forces are that drive it,

knowing and trying to discover what sort of state of activity

it's in now.

But equally important, I'm beginning to realise, is the custom

and tradition that's also wrapped up around this volcano.

It's absolutely fundamental to the identity of this island

and the people who created it.

We've already gathered important evidence from one of the subterranean vents,

but there's still vital data Shane wants to collect before

we set off for the volcano itself and descend into its heart.

Something I'm in two minds about - both excited and frankly terrified.

That cave that we went to,

I'm pretty sure that there will be hundreds of those along the coast.

There must be. There can't be an isolated one.

While the rivers of molten rock that come with major

eruptions are destructive and deadly,

they're not the only danger Marum poses to the islanders.

Its permanently bubbling lava lake brings another equally lethal

threat, in the form of its gas plume,

so large, it's visible from space.

We're on our way to a village on the west of the island.

It's an area plagued by the deadly concoction of gases that pour

out of the volcano.

So, here we are with these beautiful green hills in the foreground, all

the jungles growing there, it's like the Garden of Eden,

and then the hill beyond - there's no vegetation on those upper slopes.

It's not altitude controlled.

It's controlled by the acidic gases, particularly, that are raining

out from that cloud and constantly killing all the vegetation.

So the reason there's no vegetation up there is simply

-because of the gas.

-It's basically because of the gas.

It's killing all the trees.

The people living in and around this area are constantly having to

deal with this acid rain and acid gas situation.

Volcanic ash creates some of the most fertile soil in the world.

But the toxic gases seep into the soil and into the water.

This village happens to be right on the axis of activity.

'We've come to Lolibulo, where in 2005, people were evacuated

'because of the huge amounts

'of toxic gas that was pumping out of Marum.'

When it rained, and the rain then washes through the plume,

and it takes with it sulphur, fluorine...

'Fluorine is good for teeth, in small quantities, but too

'much causes severe tooth decay and debilitating brittle bone disease.

'Shane regularly tests the water here.'

Fill that up.

Stick one of these tablets in each of the...

-One for you, one for me.

-What do these do?

We're going to change the chemistry of the water

and if there's fluorine in here, it will react.

Crush that bottom.

So, have there been, in the past,

very high incidences of children

in this village with evidence of brittle bones and bad teeth?

That kind of thing?

In this village and the villages nearby, there was

a really high incidents of chronic dental fluorosis, which is

a strong indicator that there's bone issues as well.

-Our first result's here.

-OK.

-So, we've got a reading of...

-2.6.

2.6.

The second one...

-2.72.

-2.72.

-So...

-Wow! Almost identical.

-Almost identical.

What would normal levels be in clean or unadulterated rainwater?

-Clean rainwater should have nothing.

-Wow! OK.

-Should have more or less nothing.

-OK. I mean, is this health threatening?

This is... This is, in chronic terms, yes, so it's too high.

It's way too high.

More than twice as much as it should be.

It's shocking to discover how contaminated

the water in this village is.

While the people can reap the benefits of the fertile soil,

the plume of gas they live beneath is more noxious than

the air in any city.

The team on the summit is almost ready for us,

but the weather up there has been wildly fluctuating.

Driving rain and strong winds would at the moment make any

attempt to descend into the crater impossible.

All we can do is hope that things change before we set off.

In the meantime, I want to go in search of some unusual

wildlife that takes advantage of conditions on the island.

The megapode is a rare bird which incubates its eggs in the warm

volcanic soils.

So, with my expert guide George, I'm on the hunt for eggs.

So, what are the signs that we're looking for.

-These birds are quite clever.

-OK.

They usually come up last over the nest.

We can tell if there's lots of leaves and rotting wood

and the ground is soft...

Ah! OK.

'Megapodes are endangered, so to protect them,

'it's taboo to collect their eggs,

'except at certain times of the year.'

It sort of...doesn't feel that warm, actually. I'm surprised.

-It will get warmer.

-It will?

-Yeah.

-Ooh! What's that?

-That's it!

Look at the size of it!

Before we pull it out, let's take a temperature reading,

cos I don't think it feels very warm.

29.9,

which doesn't seem warm enough, but usually across the Pacific,

for them to successfully incubate,

people have found that the temperature is around 33 degrees, so

I would say that's maybe a bit too cool,

but do you sometimes find eggs that won't hatch?

-We find lots of eggs that don't hatch.

-OK.

-And they stink.

-Oh, really?

-Very smelly.

Let me take it out now.

Oh, my goodness!

Look at that!

Look at the extraordinary shape and weight of this egg.

It's really, really heavy.

And if this egg were allowed to go through its full incubation

period of about, of about 60 days,

what would happen is that the chick very well fed on that enormous yolk,

would use its feet to break out of the shell

and then burrow up through the ground... That's right, isn't it?

And then it will emerge fully-feathered

and within 24 hours will be able to be completely independent.

-Do you think there's going to be more?

-I think there should be more.

-God! They go right in, don't they?

-It does!

Maybe it's too far.

George, you know... You're talking to a girl who likes a challenge.

Ha-ha!

OK. So, you might have to drag me out here. Ha-ha!

'The eggs are often buried two metres deep.

'And these birds have done such a good job that our attempts to

'reach them make the entire bank unstable.'

Oh, my God! It's really warm, George!

-Argh!

-Whoa!

-Are you all right?

-Yes. I'm fine!

SHE LAUGHS

I don't know why they don't just go to the

supermarket like everybody else!

Oh, George! Tell you what...

That's one of the difficulties of harvesting the eggs...

-Even though they're delicious...

-Have the soil land on your head!

Even though they're delicious, it's hard to get them.

We'll be lucky...

-Lucky.

-God! I can't see a thing!

'It probably serves me right for disturbing the nest.

'I only hope the eggs are worth it.'

Asbestos fingers.

Also one thing about this egg.

It doesn't peel off nice and clean like a chicken egg.

OK.

So, all in all, you nearly die when you collect them.

When you cook them, they might be rotten.

They might be rotten.

-They don't peel easily.

-No.

I hope they taste really good!

You'll soon find out.

-Just dip in like that?

-Just dip in.

That's delicious, isn't it?

It's incredible to see how these extraordinary birds

have adapted to their environment, and it's another reminder

of how the volcano shapes life on every single part of this island.

The time has finally come to head up to the summit

and to meet Marum face to face.

-OK. Ready to roll?

-Yeah, OK.

-Let's go.

It's early morning

and although the weather is fine down here,

it's no indication of what it might be like at the top.

Is that your water bottle?

Straight up? No?

Off we go.

The first half of the trek takes us through dense jungle.

It's hot and humid, but thanks to our local guides

Robert and Janic, we get some inside knowledge into

the rainforest's weird and wonderful natural resources.

Do you want to try some juice out of a vine?

-Yeah!

-Yeah, yeah.

-Isn't that incredible?

-Yeah.

-Tastes lovely as well, doesn't it?

That sort of slightly fresh, woody taste.

After four strenuous hours,

we've climbed almost 1000 metres above sea level

and the path is getting steeper.

You can see how narrow the ridge is.

It's just like a knife edge, isn't it?

-Yeah, yeah, this is the right one!

-I tell you what,

I'm very pleased it's as vegetated as this

otherwise it would be very scary indeed!

Eventually, we catch our first glimpse of Marum in the distance.

If you look through there, you can see Marum, not very well, but...

-Just that sort of dark patch through the trees?

-Yeah, that's it.

-Wow. OK.

It's a welcome boost for the final leg of our journey.

But there's an important ritual Janic tells us we have to carry out

before we can go any further.

Before we go down to the ash plane

each one of you has to carry their each own bamboo.

-OK.

-So you go down and each one, you throw the bamboo to the ash plane

before all of us go all about the ash plane.

-OK.

-I mean only....

Ah, OK.

-Because you're an old hand you don't need to put one down?

-Yeah, yeah.

-I think you should, though.

-Well, maybe.

HE SPEAKS TO GUIDE IN LOCAL LANGUAGE

If it rains and there's a howling gale, I'll blame you!

-Whoop! Nearly did it!

-Yeah.

-Is this the ash plane?

-Yeah, this is the ash plane.

So before we go down on the ash plane...

Yeah? This is where you have to throw it?

-Just throw the bamboo.

-OK, so from here?

-From here.

Throwing bamboo onto the ash plain is an ancient ritual

to appease the volcano's spirits and keep us safe.

It's a reminder that we have to treat Marum with great respect.

Yeah, it's quite different here now.

After the dense forest, our journey takes us across an epic moonscape

into the volcano's outer crater - its caldera.

From here, we begin our final ascent.

-Lot of smoke coming out of the crater now, we can say.

-Yeah.

-You can just see that line, with the wind.

-Yeah, yeah.

OK, as far as ridges go...

-..how extreme is this one?

-This is the last one.

OK. Damn it, thought you were going to say, "You're doing fine".

You're doing fine!

KATE LAUGHS

You're going to cause a landslide!

Oh, Robert, you and I are going to come up at a sedate

and sensible pace.

Oh, my God, this is quite scary!

KATE LAUGHS

Eventually, after almost eight hours,

it's the moment we've all been waiting for.

-Whoo!

-Yes!

-Oh, my God! Oh!

Oh, my...!

KATE GASPS

Amazing, isn't it?

It's just...

I can't believe what a clear view we're getting of it.

It's just kicking up onto the top of that ledge!

Yeah, yeah, that's amazing.

There's something really kind of inexplicable about

looking at a sight like that, because it's so unfamiliar.

This isn't something that your kind of normal life computes.

It's just this sort of astonishing energy.

This kind of boiling, seething energy that looks like

it just wants to kind of leap up the mountain.

It looks to me, Shane, this is a precursor to it just going, "Woof!"

Oh, yeah.

"Oh, yeah", he says as we stand on the edge!

We're looking so far down. I mean, that's splashing up a long way.

LOW RUMBLING

-This is much, much higher than I've seen it for a long time.

-OK.

This is one of just five lava lakes in the whole world

and Shane is immediately struck by how much bigger

and more vigorous it is than when he was last here three years ago.

To find out why, we need to get much closer.

Shane and Chris want to collect rock and gas samples

from as near to the lake as possible.

It's now all down to the weather.

The weather up here for the last three days

has been spectacularly bad. The team who have been setting up camp

and rigging everything for us have been on the sat phone

and all they could hear was just pounding rain and howling,

howling winds.

So, to get up here in these relatively benign conditions

feels incredibly lucky.

How long it will last, nobody knows.

Hi, welcome to mountain camp.

Here to meet us is intrepid adventurer Geoff Mackley...

You must be Kate.

I am. Are you Geoff?

Welcome to Fire Mountain!

I need to hug you!

..and my long-time friend, climbing expert Tim Fogg.

-Lovely walk.

-It's good, isn't it?

-Isn't it beautiful?

-Spectacular.

Together, they'll help us collect the samples we need.

Hi, Gareth, good to see you.

You've got a dog in camp. That makes me feel I'm going to be able

to cope with almost anything.

We hope this team will be able to keep us safe.

Rusty! What you doing?

If all goes well, tomorrow we'll be descending into this fiery cauldron

with nothing between us and this blistering,

100-metre wide lake of lava.

But with so much to do, Shane wastes no time.

He immediately gets cracking with his thermal imaging camera

to find out how hot and how dynamic the lava is.

It's the most glorious night,

almost no wind, and we're getting

some of the clearest views of the crater that we've had

since we've been up here.

-That's a fantastic image, isn't it?

-It's amazing, isn't it?

Look at the different temperatures across the thing.

-We're measuring 1013, so it's pretty hot down there.

-Wow. It is.

So this temperature jumping around is measuring the highest point

of the lake at this precise moment.

The highest temperature of the lake at this precise moment.

Look at it splashing.

I mean, it does seem particularly furious tonight.

Will this camera also be able to help you to establish the rhythm

and frequency of these pulses of what appears to be new lava

constantly cycling back up to the surface?

I think it's going to be a really good indication of the size

of the reservoir, because if you've got a small pot

that's continually churning

then obviously it will cool down -

but we've got constant temperatures.

Frequently over 1,000, isn't it?

And as you say, at this distance,

to measure radiant heat of that magnitude

is extraordinary and terrifying, really.

It's amazing, isn't it?

It really does look furious tonight.

-It does, it looks like a real hell's cauldron down there.

-Yeah!

FIERCE RUMBLING

The readings reveal an extraordinary 60% increase in the lava lake's

heat and energy since Shane was last here.

And this suggests that more magma is welling up from deep below,

priming Marum to become much more active.

It's a slope of, I'd guess around 50 degrees, that swaps from...

At daybreak, climbing expert Tim gathers us all together

for our first briefing.

And it's not good news.

-The weather's not great.

-No.

The horrible thing about it, is when it rains,

it's not normal rain, it's acid rain

and it's quite surprising how it starts to sting your eyes

and your skin starts to feel a bit funny.

You can't just get off and go inside.

You're stuck, you're in there for hours and hours.

Just staying down there and waiting out the rain,

really, is a pretty horrible option.

The awful weather means it's just not safe to descend today.

It's a huge disappointment, and, with so little time,

all we can do is hope it gets better.

These really fine layers...

But there's still plenty to we can do - so Shane and I

are heading into the densest part of the gas plume to take some measurements.

You need a clear sky above the gas.

Do you think it's looking clear enough?

Well, we're starting to get some good, blue sky.

-The plume is pretty thick but we'll have a go.

-OK.

Shall we use this rock here?

This looks like a good spot to set up.

Just in front of the ash, yeah.

So the last time you were here in 2012,

-presumably you took gas measurements then.

-Yep.

If they're higher than they were then,

what will it tell you about the volcano now?

Yeah, I think, if they're going up, it's telling us that there's perhaps

either more material coming into the deeper magma system

and that gas is bubbling through, or it could mean we're getting

deeper magma that is on its way up

and that would probably herald a new phase of greater activity.

Sort of the little sticks. Just keep going through there.

So we're starting to track some numbers. Yeah, look at that.

It's starting to creep up, basically just as the wind blows across.

We're up to 400 now so I'm thinking we're going to get some

pretty high values once we start to get into the centre of the plume.

The increasing levels of gas show that Marum has become much more active.

If the figures reach as high as they were a decade ago,

the islanders may need to be evacuated once more.

But to get the complete story, we need that good weather

so we can descend into the crater itself.

Later that night

Chris and Shane spot a strange pink glow half a mile from the camp.

-It's incredible, isn't it?

-That is really something.

They suspect it could be a new lava lake.

-Look at it really, really pulsing.

-Yeah.

It's partly obscured by gas

but the thermal camera confirms their suspicions,

revealing an entirely different lava lake,

one that was last active just before the devastating gas plume in 2005.

-That's beautiful, isn't it?

-Yeah!

It's a dramatic turn of events, all adding up to suggest

something momentous is happening deep inside the volcano.

It's our final morning and we all nervously wait

for a break in the weather.

No-one wants to leave without the vital data.

For me now being here, to have this opportunity,

if the weather is kind,

to get down, even part of the way,

down into the crater of an incredibly active volcano

is sort of equally terrifying but absolutely irresistible.

It's irresistible. I have got to get down there.

At last the sun puts in an appearance,

it looks just about safe enough to risk it.

The idea of hanging over a boiling lava lake seems

more than a little crazy, but the rock and gas samples

from deep inside the crater are the final pieces of the puzzle

Shane needs to fully understand what this volcano is doing.

-So are you ready to be a guinea-pig.

-I am.

These are like dip sticks in that they're a glass tube.

-I'm going to break off the end.

-Yes.

And then during your descent and return over that period

the gases you encounter will react with the chemical on the foam in here.

-I'm going to put them facing downwards so we don't get ash in them.

-OK.

When you get back we'll take them off

-and see how much gas you've been breathing.

-Thank you!

Right, where's Tim?

-You want to squeeze that lever.

-Right.

Yeah?

'Once we're clipped in there's no turning back.'

'We plan to abseil down this near vertical drop

'to a ledge above the boiling lake of lava.'

This line pulls one, we're trying to fit two into it.

-Shall I come back down?

-Yeah, come on.

'The tubes on my back should detect, the precise mix of gas coming off the lava lake.'

Oh!

Heart's racing.

OK.

Get it out of that groove.

So, um, it's really hard to describe this feeling

of descending to...well,

certain death, obviously, if anything goes wrong

but the exhilaration of doing something like this,

it makes you feel very connected to the earth and how it works,

if that makes any sort of sense at all.

I have to confess that all I'm looking at, at the moment

is my feet and Tim's feet.

I haven't looked around me, I haven't looked at the view,

I think if I did I would be stuck here forever more.

We've got one of these steps again, one of these vertical bits.

'The heat from the lake is intense.

'and the noxious gases mean we can't spend long here

'so we have to move fast.

'but the crumbling rocks, make it difficult to get a foothold.'

Lean back, feet apart.

Legs straight as you can.

Oh, sorry!

-Oh, Tim, sorry!

-OK, OK, no problem.

I really did bash you. OK.

-You can feel the heat now.

-Yeah.

I don't know whether it's just fear, sweat of fear and fear,

or the heat of the lake itself.

I can hear the sort of lava waves crashing.

It really does feel like you're approaching

some sort of extraordinarily angry sea.

Gas is just one part of our quest.

Shane also wants to collect rock samples from inside the crater.

Just offer that to the next volcano god.

Chris will analyse them to see if any of the newer lava

has a similar composition to the lava from previous major eruptions.

If so, it could mean Marum is heading for another big eruption.

Come on!

-Are we there?

-Yes.

Finally Tim and I reach the ledge we've been aiming for.

The deafening roar of the boiling lava drowns out everything

and the heat coming off the lake is almost overwhelming.

What we'll do is to slowly adjust these knots so you can go forward.

I don't want to go forward. I really don't.

I really don't, I just... Not yet anyway. Let me...

I've got you. I've got you.

I know but I don't want to pull you over the edge, Tim.

It's just so loose, this rock.

'I'm clinging on for what feels like dear life,

'but to get the best samples I have to get even closer to the edge.'

-RADIO:

-'You go back to your left.'

They don't want me right on the edge, do they?

Right on the white rock?

Yes, that way a bit more.

Tim, you've got to be kidding me.

Centimetre by centimetre towards the white rock.

Oh, wow!

OK.

The cloud is cleared, Tim has forced me

to move sideways across this slope,

but it was absolutely worth it.

We are now getting the most astonishing views

of the lava lake.

Furious boiling lake of molten rock.

Now that we're this much closer it really does look like it could

just explode up at any moment.

Oh, that was a huge one.

It really looks like it's barely able to suppress itself.

It's sort of like witnessing the beginning of the Earth...

..but it's the most astonishing feeling really,

to be down the crater of a very active volcano,

and these glass vials on my back

that Shane put there will hopefully give him some sort of clues

as how active this volcano really is at this very moment.

The conditions are intense.

The gas mask keeps out most of the noxious gases,

but I can feel my throat burning

and the heat is becoming unbearable.

It's among the most amazing, terrifying

and exhilarating two hours of my life.

But I have to go while I've got the strength to get back to the top.

Slide yourself up.

Yep. Brilliant!

Whoo!

Wow!

It looked furious, like we shouldn't have been there.

It was like a warning,

and then as we just sat a bit calmly and actually everything around

started to clear, it's so magnificent it kind of takes your breath away.

And the lake sort of calmed, it was almost like, you know,

"Well, OK, you can hang around for a bit,"

and then suddenly it was like this great burst of fury again,

and really chucking lava out, you know, not just over the rim,

but right up into the sky.

And the coming up bit, you think, "Oh, it's going to be really easy.

"I'll just lie back!" But it's not.

I tell you what, my thighs are burning.

But I'm desperate to know what's happened on the back?

Are they still sitting there my little glass...?

They're still there, they're still sitting there.

Yes, and one of them's gone all yellow.

Let's have a look.

-Looks like you've had a bit of noxious gas?

-Yes.

And it's reacted yellow. This is SO2.

-That's sulphur dioxide.

-That's right.

So you would expect a lot of that.

Yes, because we've seen all that brown gas everywhere.

-Do you see that slight pink colour?

-Yes.

-You haven't had much of that.

-What's that?

-That's HF. Ah, well!

-What's HF?

-Yeah, just as well. HF's pretty...

-Oh, it's the really horrible, acidic one.

-It's very, very poisonous.

-Is that the hydrogen fluoride?

-Exactly, yes.

And presumably you're only able to get that reading because

-we were, I was, I should say!

-Because you went down there. Yes.

-I was physically down there, much, much closer to the lake.

-Closer, yeah.

This is really quite spectacular.

It's a huge relief that we're all back on solid ground.

But there's no rest for Shane and Chris

who head off to analyse their results.

They need to compare the evidence we've found this time,

to the data they already have

from the large eruptions in 1989 and 2005.

All I can do is wait to find out if we've uncovered Marum's secrets.

Let's start with those gas results that you and I collected yesterday.

We are getting 2,200 tonnes a day of sulphur dioxide.

Now, in normal kind of conditions,

say you were here in 2012, how did that compare?

Yeah, so normal conditions like the last time for example, about 1,000.

So it's over twice the amount of sulphur dioxide

coming out of it now.

The gas measurements Shane's taken across the island

show the levels are rising towards those in 2005

when toxic gas emissions led to widespread evacuations.

And the rock samples have their own tale to tell.

Certainly the analysis that we did,

suggested that the activity that's occurring today

is similar to the 2005 or the 1989 eruptions.

So, the composition of the lava seems much like it was

during the last two big eruptions.

And then there's the unexpected discovery of the new lava lake.

-I was blown away.

-Yeah, it was an amazing experience.

But surely, surely that,

combined with the data that you've got,

must indicate something, well, quite exciting

with regards to the whole island's volcanic activity, doesn't it?

Something's certainly on the go.

You know, there's definitely, we're definitely double background level,

so we're not just sitting there at normal level. Things are going up.

Volcanoes are very unpredictable.

We haven't had anything a big lava flow like 1989 for a while,

so I would have said, yes, we're overdue for something like that.

The evidence we've collected

suggests something is stirring deep inside the heart of this volcano,

bringing the threat of a big eruption ever closer.

And our discoveries mean that Shane now feels there's enough evidence

to increase Marum's level of risk on the international register.

It's an early warning for the islanders to prepare

should they have to evacuate.

This has been the most astonishing journey

around the volcanoes of Vanuatu.

And to sit here now, looking down at

Marum's magnificent lava lake boiling away,

and to understand just a little bit more about its personality

and to discover that we are potentially on the brink

of a time of really heightened activity

is tremendously exciting.

'It's time to bid farewell to these breathtaking islands

'and their spectacular volcanoes.'

Oh, my goodness!

Oh, it's so beautiful!

'It is without question,

'an experience I'll never forget.'

Oh, my God!

'And it's reassuring to know that the data we've collected

and the knowledge we've gained

will help to keep the people living here safe from harm.