All language subtitles for Volcanic.Odysseys.Series.2.1of5.Indonesia.Islands.of.Fire.1080p.HDTV.x264.AAC.MVGroup.org.eng

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.

♪♪♪

♪♪♪

NARRATOR:
At night, the eruptions
look completely different.

Glowing, incandescent
lava blocks

are thrown from
the craters.

[Explosion]

♪♪♪

♪♪♪

[Explosion]

♪♪♪

♪♪♪

♪♪♪

[Explosion]

♪♪♪

♪♪♪

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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