Original subtitles

NARRATOR: Volcanologists climb into the inferno

on two of the planet's most active volcanos...

TOM: This is actually a bit worrying.

This is an impact from an explosion.

NARRATOR: Where nature's raw power lay at every turn...

[Explosion]

TOM: It was so fast, I couldn't even get scared.

NARRATOR: And see firsthand the elements that are shaping this earth.

TOM: This volcano is capable of producing

very powerful explosions.

TOM: It's never a safe place to be,

on the rim of an active crater.

NARRATOR: This is the realm of nature's greatest spectacle.

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NARRATOR: Indonesia is called the land of fire.

And for good reason.

It has 147 active volcanos.

Two of them, Dukono and Ibu,

are considered to be among the most active volcanoes

on the planet.

In spite of the intense level of activity,

they're rarely visited or photographed.

That's because of their location:

in a remote part of a country

that is made up of more than 17,000 islands.

NARRATOR: Volcanologist and photographer Tom Pfeiffer

runs a tour company and a news website:

Volcano Discovery.

The website is an important resource on volcanic activity

used by scientists all over the world.

NARRATOR: Dukono and Ibu feature frequently in his reports,

but recently he's noticed a steady upturn

in their behavior.

NARRATOR: Every volcano has a cycle.

There are times when its activity is increasing

and it's still possible to get close enough

to see the eruptions.

If Tom is ever going to see these two volcanoes,

the time is now.

The remote location makes getting there difficult.

Tom has a small group of fellow photographers

who have signed on for the trip.

The furthest they can fly is to the Island of Ternate.

It takes three flights and several days.

From there, Tom charters a boat to get them to the

island of Helmahera where both volcanoes are located.

NARRATOR: They are met by Andi Susanto.

He's Tom's operations manager in Indonesia,

and an expert when it comes to Indonesian volcanoes.

It's arguable that Andi has spent more time

on active volcanos than anyone else in the world.

Andi is one of the few people

who has climbed Dukono and Ibu.

NARRATOR: The boat trip from Ternate to Halmahera takes one hour.

The hope is they'll be able to climb both volcanoes

as they are erupting, but there are no certainties.

Every step of the way will be carefully evaluated for risk.

NARRATOR: Tom and Andi's first step will be to check in

with local authorities to obtain the proper permissions

to climb.

TOM: We are here at the volcano observatory

for Mount Dukono.

Each active volcano in Indonesia has at least one

local observatory.

We hope we can talk to the volcanologists to find out

what the activity has been, what to expect.

Also to let them know that we are climbing.

ANDI: And in here there are three staff who work for

the observatory post.

In every observatory post they have to report

every evening and in the mornings,

to report the seismic activity to the centre of the office

of the Volcanological Survey of Indonesia.

NARRATOR: The volcano is monitored by a series of seismometers.

These machines, up on the volcano,

record every minute earthquake

that indicates magma moving through the system,

or each explosion.

Scientists can tell a lot from these seismic signals.

Here, the near-continuous pattern indicates

the constant venting of ash.

Looking at the read-outs, Tom and Andi can see

that Dukono is now more active than in the proceeding weeks.

ANDI: This is from 7 November; it's yesterday.

Therefore it's really active with the ash plume

and an ash eruption from Dukono

from the main vents.

Two days ago is also the same.

This is 6.

So almost every day with ash explosions,

with ash eruptions.

NARRATOR: Even though it's more active,

the current phase is more predictable and less dangerous.

That's good news.

They get their permission to climb.

First up they hit a local market

to buy everything they will need for the trip.

NARRATOR: At the foot of Dukono is the small village of Tobelo.

About 15,000 people live and work here

and keep a watchful eye on the activity.

ANDI: She said two years ago when Dukono was really active,

she could hear about the rumbling and ash also here

and they were ready to evacuate at the time.

So actually the people here are afraid about Dukono.

NARRATOR: Tom finds a stall selling rocks and minerals.

TOM: A nicely cut piece of black volcanic rock.

I don't... I'm not...

I would guess it's a volcanic rock.

It's dense, glassy, almost like obsidian,

but it's probably something else.

NARRATOR: For locals, trading in rocks and semi-precious stones

is a great way for people to earn money.

In a country prone to earthquakes and eruptions

geology is taught in depth in the local schools.

The subject covers rocks and minerals

as well as the volcanoes around them.

NARRATOR: As the start of the hike is a ways out,

Andi has arranged for transportation

through a local coconut plantation.

TOM: I think the biggest danger right now

will be hit by a branch or something.

I've had similar situations sometimes.

You look at something else

and don't see a branch coming, and bonk!

NARRATOR: You'd think with an active volcano,

people would completely vacate the area.

But Dukono has been active since 1933

and posed little threat to the villages.

People have grown used to living in the shadow

of this volcano.

Here the coconut plantation is still in operation.

However, the roads that extend into the danger zone

are not used and have currently fallen into disrepair

during the rainy seasons.

It makes getting to the volcano's upper slopes

challenging.

[Indistinct chatter]

[Indistinct chatter]

[Indistinct chatter]

NARRATOR: The vehicle will need a good run

at the difficult sections,

so to shed weight, the group walks ahead.

NARRATOR: They are still a ways out.

If the vehicle has to turn back

it will mean that the moderate hike ahead

will turn into a hard full day's journey,

something they won't be able to make before night fall.

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TOM: The truck's made it.

So... time to continue.

Glad it hadn't rained.

When you have a lot of rain you can't pass here.

NARRATOR: All along the way they encounter new obstacles.

The drivers don't give up.

[Indistinct chatter]

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[Indistinct chatter]

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NARRATOR: They've reached the furthest point the cars can go.

TOM: We've made it! Or the car's made it.

Now the last kilometers is on foot.

According to Andi, it's about two to three hours,

easy to moderate.

ANDI: So now we are in the altitude of 350 meters above sea level.

And we have to get packed all the things,

and then we'll proceed to climb.

NARRATOR: They may be climbing an active volcano,

but at this point it's pretty much

like any other ascent.

They plan to stay two days, so a team of porters

brings all the equipment and tents needed.

NARRATOR: Part way up, they run into a surprise.

A university group and their teacher

are also heading up to see the active crater.

These students will be the next generation

of geologists in Indonesia.

Some will go to work on volcanoes around the country.

Here they get first real-world knowledge

of an active volcano.

NARRATOR: As they get closer to the active crater

everything around them is covered in a layer of ash.

NARRATOR: And finally their first reward...

A close up view of Dukono.

They establish a camp at the boundary of the danger zone.

Beyond it, the risk of being hit by falling rocks

during a moderate eruption increases.

Hundreds of trips to volcanoes has led Tom to believe

that if you respect the danger

and pay heed to the warning signs

other elements of the trip will actually pose

a bigger danger than the explosions.

[Crashing]

[Rumbling]

NARRATOR: A lightning strike from a simple rain storm

nearly hits the camp just as the students arrive.

TOM: We just had a lightning strike out of the blue.

It was so fast I couldn't even get scared.

And there was a big bang right that second.

It must've been less than 100 meters.

NARRATOR: After the rain breaks, and the camp is set,

Tom has a look at the volcano he has only read about.

It's a beautiful ash cone

and as the seismographs predicted,

it's constantly emitting ash.

TOM: Right now there is ash fall in the downwind area

of the plume.

Sometimes you can see vertical lines under the ash.

It is a result of light and shadow,

but it's curtains of fine, sandy material

that is falling out of the plume.

NARRATOR: The ash here is washed downstream,

where it builds the lower slopes of the volcano

and provides the nutrient-rich soils

of the village farmland.

TOM: If you go from the top to the bottom,

you go back in history.

You can have an idea of what a volcano has been doing

in the past.

The top black layer would be the phase

of mildly explosive activity,

a bit like what we're seeing now.

NARRATOR: If you go from the top layer to the bottom,

you can have an idea of what a volcano

has been doing in the past.

TOM: Here is also a little pumice layer.

During this activity there must have been

very powerful explosions...

where fresh magma, rich in gases,

came out to erupt and become pumice, especially here.

And I don't know how deep this goes

but typically you find this pumice as an oval-shaped deposit

in the same direction as the wind at the time.

NARRATOR: When they're putting together the history of a volcano,

volcanologists will sample several locations around it.

By determining the ash and pumice thickness

they can plot the total area affected

and calculate the volume of the material deposited.

From this they are able to recreate the volcano's

eruptive history dating back thousands of years.

Information like this can help determine the danger

and understand the far-reaching effects of each volcano.

They can also look for evidence of cataclysmic eruptions

and the phases that preceded them.

TOM: It is important to know

what the volcano has been doing in the past

to have an idea of what it might do in the future.

It might be doing something like this for centuries

but it doesn't mean that it's always like this.

NARRATOR: The group will stay in camp tonight,

for safety's sake.

Before they can do any climbing,

they will take time to watch Dukono,

and make sure that its behavior

is consistent with the seismic data.

It's absolutely necessary to know what the recent

seismic patterns are.

But that's not a safety guarantee.

It is possible that the volcano's activity

will ramp up and become dangerous with no warning.

NARRATOR: For the porters, it is just another day.

TOM: If you choose to go up, it should be based on

a risk-benefit analysis.

Dukono can certainly produce very strong and powerful

explosions that eject bombs and rocks

to the crater rim and beyond.

In which case, if you're there,

you are at risk to be hit and lose your life.

It is not a completely safe thing to do.

But on the other hand, I believe that the risk

if you stayed a couple of hours is lower

than the risk of a car accident,

especially after experiencing how people drive here.

NARRATOR: The group will make their climb to the crater

in the early hours of the morning.

In the meantime, they break for dinner.

And their guide Andi gets to show off

some of his other skills.

ANDI: Now I'm cooking we just call in Indonesia

"Cah Kangkung."

"Kangkung" means "water spinach."

So, the way is easy,

but this is very good flavor,

and then delicious.

[Speaking Indonesian]

NARRATOR: After dinner the group takes time to relax

before their climb.

It will take less than an hour.

NARRATOR: The climb begins at the crack of dawn

and members of Tom's group make it to the rim

before sunrise.

[Rumbling]

NARRATOR: They're standing above the active crater

as it continues to erupt ash in a constant plume.

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NARRATOR: The volcano continues to erupt ash,

as it's been doing for weeks.

Inside you can hear the sounds of the elemental processes

of our earth at work.

ANDI: Now the ash plume looks more active and intense.

[Rumbling]

ANDI: The rumbling comes from ash venting occurring,

and then also with the rock falls down there.

TOM: You can see it's a very active volcano.

It has been in continuous eruptions for decades now.

It almost sounds like hail,

heavy hail during a thunderstorm.

I imagine there's a jet coming out

of gas, ash and small rocks.

We don't see them, but we clearly hear

these little rocks falling back.

And those sounds, these are lightnings, not explosions.

NARRATOR: Scientists don't fully understand why there's

lightning in volcanos.

It's believed to be caused by ash particles

that move against each other, causing a static build up.

As the plume rises, the convection within

pulls apart the two masses with opposite charges.

If the charge is strong enough,

it can create a path of ionized air

that conducts electricity that forms a lightning bolt.

Large ash plumes can generate long bolts of lightning.

Here it happens on a smaller scale

within the denser part of the plume.

Volcanic lightning can be dangerous.

During an eruption of Paricutin Volcano in Mexico,

three people were killed by lightning

that originated from the ash cloud.

NARRATOR: The geology students arrive at the rim

to conduct their classes on active volcanoes.

Here they get a first-hand look at the forces

that are shaping their country.

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TOM: I think we're safe-ish here.

It's not-- of course it's never a safe place to be

on the rim of an active crater,

but I haven't seen any fresh impacts.

In fact, I haven't seen any impacts here in this part.

So the likelihood is very, very little

that something is being ejected here

while we're here.

However, this volcano is capable of producing

very powerful explosions called vulcanian explosions.

Throughout the past years, every now and then

you get reports of very tall ash plumes

rising several kilometers.

That means you have an explosive activity

ten times more powerful than this,

and probably more as an isolated explosion.

When the plug forms at the vent,

which now seems to be more or less open,

but when there is a plug that forms,

it blocks it and pressure can build up

and then release it in a sudden, powerful,

so-called vulcanian type explosion...

then you'd be in trouble here.

NARRATOR: Standing on the rim, the view of Dukono is spectacular.

But looking downhill from the crater

is also an impressive sight.

This cone is mostly built from loose ash deposits.

NARRATOR: When it rains, this material is eroded,

creating an other-worldly landscape.

NARRATOR: This mountain-building process is testament

to Dukono's high activity.

TOM: I would count Dukono as one of the four or five

most active volcanos in Indonesia.

And Indonesia is a heavyweight

when it comes to volcanos.

It is number one when it comes to the number

of active volcanos.

And this is one out of the top four or five of Indonesia.

And on a global scale it's one out of the top 20, I'd say.

NARRATOR: There are many factors that determine

how a volcano erupts.

Three of those are:

the amount of magma in its reserves below the volcano,

the amount of volatile gases contained in the magma,

and the type of magma.

NARRATOR: Some types of magma flow out in gently glowing rivers

that cover the land...

while others explode suddenly with force,

throwing ash and lava blocks into the air.

For the past 80 or more years, Dukono has produced

mostly consistent ash eruptions

mixed with the occasional lava flow.

So, while it is one of the most active volcanoes

on the planet, its activity has had little impact

on the people living around it,

and for the time being is not threatening.

Dukono's neighbor Mount Ibu,

an hour's drive to the west, is a different story.

It is a small volcano with an explosive personality.

NARRATOR: It erupts magma known as andisite,

which is very sticky and collects at the summit

in what's called a lava dome.

Lava domes can build up to the point where they collapse,

causing a burning hot avalanche called a pyroclastic flow.

NARRATOR: Here, the volcano sits above the small town of Talen.

TOM: The first thing we'll do now

is to visit the local observatory

to get informed about the activity.

Also to tell them that we have an intention to climb.

They expect everybody to register so they know

and hopefully give us sort of a permit.

[Speaking Indonesian]

TOM: The observatories are usually at the same time

equipped with a kitchen, bedrooms,

because they are manned 24 hours.

TOM: Up there at the crater you have inside the lava dome,

which has been growing over the past years.

It could easily generate pyroclastic flows

that come down here and threaten this village.

NARRATOR: Tom and Andi want to look at the seismic charts

to see Ibu's most recent eruptive behavior.

ANDI: So he said that since 2012 that actually Ibu volcano

has been erupting, being active.

And also the status now is level 2.

NARRATOR: Level 2 means activity is present

but continuing at a constant level.

If a volcano shows signs of increased activity

that may lead to a larger eruption,

it will be categorized as level 3

and evacuations will begin.

Each mark on the seismograph represents an eruption.

What they can tell from these charts

is this is a very active volcano.

Today alone there have have been more then 50 eruptions.

ANDI: There are explosions and sometimes the pumice

is ejected until 900 meters.

NARRATOR: Where they plan to go will put them right inside

the active crater.

ANDI: Yeah, we'll still climb

but let's see if that is too dangerous.

Yeah, we will see that, so...

NARRATOR: As they're standing,

the seismograph registers an eruption.

TOM: You can see an explosion that occurred right now.

See the ash plume?

Yeah, that's quite an explosion.

If you're close this would be quite something.

That's why the guys are here to observe it

and if the situation changes at some point,

maybe in the future the government

will have to take measures, I guess.

But it could be in 100 years,

it could be next year, it could be in 1,000 years.

But as it is now, life goes on.

NARRATOR: Duono village is a 30-minute drive

from the observatory.

It is the gateway to Ibu.

It is also the place most in danger

if there is a major eruption.

The town sits at the opening of a giant breach

in Ibu's cone.

Any eruptive flow from the volcano

would come straight down to the village.

About two years ago when Ibu woke up

after a short slumber, the village was evacuated.

But as the volcano's activity stabilized,

people have moved back.

But still, outsiders rarely come here.

Duono doesn't even have a hotel.

TOM: I think they haven't seen many visitors here.

It's so remote hardly anybody comes in,

maybe a few Westerners per year,

and that would be a lot, I guess.

NARRATOR: Without any tourism in the area,

Andi is forced to improvise for accommodations.

ANDI: This is actually the house of the Kardesh.

"Kardesh" means the chief of the village.

So that's very important to us.

We're going to stay here for camp tonight.

So we just sleep in the floor.

And then we're going to start climbing Ibu

tomorrow morning then from here.

NARRATOR: With rain continuing into the night,

the group won't be able to see any eruptions.

Tom had hoped to see if the eruptions

were ejecting lava rocks called bombs

as far as the crater rim.

At night these bombs are visible.

NARRATOR: The following morning it's still raining,

and the forecast says rain will continue most of the day.

TOM: We are actually not 100% sure if we can go

all the way to the rim.

It will depend on the activity.

The lava dome has been producing frequent explosions.

We'll have to see if...

and how fresh any impacts are in the upper areas.

If we find too many fresh bombs impacts

obviously it wouldn't be a good idea to go.

NARRATOR: Tom's also worried about the cloud cover.

TOM: If there is no visibility there is no real point

in staying at the crater rim.

It also increases the hazard,

the risk of being caught in an explosion

because you can't see anything.

There is no value of being there.

So we should only go to the rim

if there is also good visibility.

NARRATOR: In spite of the weather,

Tom and Andi decide to go ahead with the climb

in the hope that weather breaks

by the time they reach the crater rim.

NARRATOR: Although the group managed to get the necessary permission,

officials were hesitant to let Andi's group climb

because of Ibu's increase in eruptive activity.

They agreed because of Tom's status and experience.

But the officials require that the group be accompanied

by Arnold who is the spiritual guardian of the volcano.

This is considered a high honor.

One thing Tom's experience has taught him

on volcanoes all over the world

is the importance of having a local guide.

TOM: He's the chief of the volcano.

The most experienced man around who knows Mount Ibu volcano.

I just got the idea a stick would be handy,

and I ask him...

I think this makes it cool. Everybody now will want one.

TOM: It seems this trail hasn't been walked recently,

so Arnold, our head guide, has to use his machete a lot

to clear the path.

NARRATOR: It's likely Andi was the last person to climb the volcano,

six months ago.

He came to check out its potential for guiding.

Tom will rely heavily on his experience,

and Arnold's too.

ANDI: Phew! Challenging!

TOM: Okay, yeah, that's volcanic ash.

Occasionally when the wind is going this way

and there is an explosion

you will have ash fall on this part.

In the dry season the ash will cover the leaves.

With the first rain the forest washes itself.

That happened tonight, but you see remnants.

So I suppose the closer we get to the rim,

the more of this we will see.

NARRATOR: They also have come upon the seismograph station

that relays earthquake info

back to the volcanic observatory.

TOM: So probably right now they'll have some noise

as we're walking by.

Our steps will be recorded by the instrument.

NARRATOR: Now they're entering the high danger zone.

Fragments of rocks thrown from the crater

during large explosions are visible.

TOM: This is actually a bit worrying.

This is an impact from an explosion at the summit.

This is one of the larger fragments.

But they're all around, I guess.

You know, they fall at great speed,

a hundred meters a second.

There's so much energy.

When they fall and the soil is soft

it makes these sort of craters.

GIAN: This one could slice you, man.

TOM: We are one kilometer horizontal distance

from the crater,

so this is entirely within the range

of moderately sized explosions.

Nothing unusual.

So one shouldn't be deceived by the lush vegetation.

We are in a high-risk zone

of an active volcano.

NARRATOR: Arnold their guide tells Tom that impact

was from two years ago.

If it were more recent fresh fragments would be found

on top of the vegetation.

They're thirty minutes from the crater rim,

and should begin to see a lot more of this.

TOM: Here's another bomb, right on the trail.

TOM: Obviously the higher we come,

the closer we get to the dome,

the more of these guys we can expect.

Just hope they're not very recent.

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TOM: It didn't impact right here.

It may be somewhere, but it's difficult to see.

TOM: This could be the same one or another one.

It could be-- likely it's the same.

Maybe it impacted here.

This one sits in the soil.

We're definitely getting close to the crater.

ANDI: According to my experience, my opinion,

even now we are, if we continue to the rim

it's still safe.

From what I saw from the seismograph.

TOM: I've never been on this volcano,

but as a general rule,

you should approach it slowly.

We've been climbing fast,

and to me it looks the rim is in mist at the moment

so we have no added value to be at the rim

but increase our risk.

I'm sorry to talk about risk and these things,

but from here we have much more safety margin.

If we stay here half an hour, relax and maybe listen.

Down there I could hear the weak sound of an explosion.

If we stay here for half an hour,

maybe hear another explosion

and get a better feeling for the mountain,

that it's maybe not too active.

One thing I would hate is we arrive at the rim

and we just hear a very loud explosion

and we don't know what's happening.

NARRATOR: Both the volcano chief and Andi disagree with Tom,

but he overrules them.

The crater rim sits just over a football field away

from the active crater.

There's no room for error on this volcano.

NARRATOR: After 30 minutes and no eruption,

they decide to continue on.

[Explosion]

TOM: There was an explosion, the sound of...

TOM: Uh, no bombs. That's a good sign.

But we are getting close.

I think we are 100, maybe 150 meters

below the crater rim.

So... yeah.

This will be interesting.

NARRATOR: Tom makes it to the volcano rim.

The cloud cover is so thick that they can't see how far

they are from the active vents.

They'll wait for the next eruption and listen

to hear where the bombs are falling.

TOM: This must be the active flow that goes down this way.

I try to go a little bit further there

to see how far it goes.

NARRATOR: The porters begin to set up camp

as the rest of Tom's group makes it onto the rim.

In the mist they hear the sounds of the volcano

violently degassing...

[Hissing]

NARRATOR: ...followed by an eruption.

[Explosion]

NARRATOR: From the sounds they can tell that the bombs

are not flying towards their camp.

That means they're in a good location.

The porters get back to building a shelter

in case the rain starts again.

Tom retrieves a couple of dead trees to use as poles

for a makeshift shelter.

NARRATOR: After a while the clouds begin to break.

They get their first look at the active vents

within the crater.

It's unnervingly close.

This volcano is not for the faint of heart.

TOM: This is Ibu volcano's crater, and the recent lava dome,

this black-greyish mass of lava that occupies

most of the crater.

At its centre, a small cindercone,

which is currently active.

[Explosion]

NARRATOR: It's a small eruption from the furthest crater.

This eruption only produces ash mixed with steam.

It's not from the vent that ejected bombs.

Each vent will erupt differently,

so they will have to see an eruption

from the other two to know if it's safe.

TOM: Right now it seems it is, however,

in a phase of more frequent but smaller eruptions.

That's why I think we're reasonably safe here...

for a limited time, of course.

But you can see all the trees have been stripped

of their smaller branches.

Trees all died as a result of frequent impacts,

leaving just the trunks and the major branches intact.

TOM: These volcanoes in subduction zones

typically produce a kind of lava

that is relatively rich in silica,

so it is rather viscous.

It doesn't flow; it doesn't behave like a lava

on volcanoes like Hawaii, which is fluid

and can form channels and can actually

behave visually like a liquid.

No, the lava that the volcano has been erupting

over the past years accumulates above the vent

to form a broad, cake-like structure called a lava dome.

It's too stiff to actually flow,

so it'd rather accumulates as a huge pile of blocking mass.

These type of eruptions are potentially very dangerous

because the high viscosity of the lava

also traps gases inside,

which can lead to sometimes big explosions.

NARRATOR: This is footage Andi shot on Semeru Volcano

on the Island of Java.

It shows an active lava dome in action.

As the pressure builds up inside

the entire structure lifts and the dome inflates.

If too much pressure builds up,

the dome can suddenly explode.

NARRATOR: Back on Ibu, suddenly the left vent

begins to vigorously de-gas.

[Hissing]

[Hissing]

NARRATOR: The sound is similar to the group heard

when they first arrived on the crater rim,

just before the first explosion.

The gas indicates that this is a small lava dome.

As on Semeru, the gas is trapped under

the crusted-over magma.

When the pressure builds up and the vent explodes

it will likely throw bombs into the air.

[Explosion]

[Rumbling]

NARRATOR: This shoots jets of ash.

[Rumbling]

[Rumbling]

TOM: So I think the vent on our right side is having

so-called phreatomagmatic eruptions,

where ground water interacts with magma

and produces an explosion.

NARRATOR: As it flashes to steam, the instantaneous expansion

of the gas is enough to blast through the rock,

fragmenting it into small pieces.

The pieces fall around the crater,

building up its small cone.

NARRATOR: Now they wait for the third crater to erupt.

[Explosion]

[Explosion]

NARRATOR: We get to see the eruption in detail.

The explosion shatters the dome,

sending chunks of lava away at supersonic speeds.

Thankfully, in a direction away from the group.

The inner crater is bombarded with rock fragments.

It was these types of explosions,

yet on a much larger scale,

that produced the impact site that Tom found

on the way up.

TOM: Volcanoes are always good for surprises.

I didn't expect at all this type of strombolian activity

and the classical, beautiful explosions

where lots of incandescent bombs are thrown up to

maybe 100, 200, meters.

Accompanied by loud bangs that resound

at the crater walls; you have wonderful echoes.

It's an absolutely eerie atmosphere.

TOM: So you see the blueish gas is an indication

of fresh magma underneath.

The same vent is probably feeding a bit the lava flow,

which has a slightly brown color.

[Rumbling]

NARRATOR: As the sun dips behind the horizon,

the faint glow of lava can start to be seen.

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NARRATOR: At night, the eruptions look completely different.

Glowing, incandescent lava blocks

are thrown from the craters.

[Explosion]

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[Explosion]

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[Explosion]

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TOM: So I think we've had a great experience

and we saw another one of the top five

most active volcanoes in all of Indonesia.

Each volcano has its own personality.

It's completely different from what we saw at Dukono,

but it's great as well.

For me this ranks so far number one

in terms of scenery, experience.

Also, the climb here is a relatively long

strenuous climb,

but you are rewarded with a magnificent view.

NARRATOR: It's been another great adventure for Tom,

but getting this close to Ibu's crater

is something very few people will experience.

Its remote location makes it tough to get to,

and the chance that the volcano could suddenly generate

a large eruption keeps people away.

But for Tom,

getting to experience both Ibu and Dukono

and read the geological records they've left

is an important part of his work as a volcanologist.

Both Ibu and Dukono are in the elite,

the top twenty of the most active volcanoes on earth.

They are the surface layer of the elemental forces

that continue to shape and reshape

Indonesia's volcanic islands.

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