Indonesia Journeys into the Ring of Fire

In this series, I'm travelling around the Pacific rim,

to visit some of the most volatile places on Earth,

and discover how the rocks beneath our feet

are fundamental to the history of life on our planet.

My journey includes the hostile peaks of the Peruvian Andes,

the geological booby traps of California,

and the magnificent mountains of Japan.

But in this episode, I'm exploring exotic Indonesia.

To a geologist like me,

this is the land of the Holy Grail.

It has the most awesome range of volcanoes anywhere in the world.

For thousands of years,

these volcanoes have had a huge impact on the lives of those who live here,

destroying whole civilisations.

And these fiery peaks have shaped the history of the whole planet.

As a geologist,

I'm fascinated to discover how the volcanoes of Indonesia have transformed civilisations.

Not just locally but all over the world.

Indonesia has more active volcanoes than anywhere else

and is home to many different religions.

It's an archipelago of 17,000 islands,

but my journey starts with one of the lesser known, Sumbawa.

One volcano here had an extraordinary effect on art, literature,

and even technology, 9,000km away in Europe.

I'm gonna show you how this bizarre sequence of events was triggered by the rocks beneath our feet.

It all took place in 1815,

when a volcano called Tambora blew its top in a ferocious surge of power.

It was a largest known eruption of the last millennium.

From the nearest town, I would need to trek for five gruelling days to reach Tambora,

and I'm not one to shirk a hike,

but taking a helicopter was the best way to see the top of this volcano.

The massive eruption left this crater 8km wide,

and over a kilometre deep.

Known as a caldera,

this is what remains when a volcano collapses in on itself.

It's only from up here that you get a hint of Tambora's devastating power,

when it blew nearly two centuries ago.

To get an idea of the impact,

don't just think about the spewing rivers of molten lava - it was much more than that.

The eruption blasted 52 cubic kilometres of rock high into the atmosphere.

Carried by the winds, it began to spread,

with terrible consequences.

There are plenty of clues as to the devastation wrought by that ejected rock and dust.

Beneath my feet, there's this deep layer of ash.

It's characteristically dark and powdery,

and in these parts, over a metre thick.

When it falls, this ash is terrible stuff.

It adheres to the leaves of plants.

Even a thin coating is enough to stop the leaf from photosynthesising,

from turning the sun's rays into useable energy.

It kills the plant.

It meant that in 1815,

after Tambora blew, there was massive crop failure and widespread starvation.

The effect could be felt in Europe and America, thousands of kilometres away.

The debris blowing into the atmosphere included sulphur particles.

This layer was thick enough to reflect the sun's rays back into space.

And it actually caused the planet to cool.

The results were catastrophic.

1860, the year after the blast, was so unusually cold in places,

that it became known as the year without a summer.

The big chill left countries in the northern hemisphere suffering from severe famine.

On farms across Europe and America,

crops failed to germinate.

In all, 200,000 people died worldwide,

making it one of the worst volcanic disasters of history.

The catastrophe had surprising reverberations across European culture.

At around that time, the British artist Turner painted spectacular sunsets.

These fiery skies are believed to have been caused by particles in the atmosphere

from the Tambora eruption.

The freakishly cold winter of 1816, was said to have inspired Mary Shelley in Europe,

to write this book, her classic story of Frankenstein.

The lack of food during the year of without a summer inspired new technology too.

It said to have prompted a German inventor,

to devise a new form of transport that didn't require a horse.

This beast of burden didn't require feeding.

Known as a running machine, it was a predecessor to the modern day bicycle.

Indonesia is situated in what is known as the ring of fire.

This extends northwards from South America,

arching across Alaska, and goes south past Japan.

It's dotted with volcanoes,

but the largest number of active ones can be found here in Indonesia.

Worldwide, two-thirds of deaths caused by eruptions over the last few centuries

have happened on these islands.

With volcanoes so entwined in the destiny of Indonesians,

I want to find out how they've shaped people's fundamental beliefs about their gods.

Indonesia is a melting pot of religions.

It's home to Hindus, Muslims, Buddhists and Christians,

but I've been told there's a local uniqueness to these faiths,

thanks to the perilous geology here.

To discover this relationship between rocks and religion,

I'm heading 150km west of Tambora to Bali,

where I'll be visiting one of the most extraordinary temples in the world.

The Balinese have been Hindu for thousands of years.

But their faith is different from the original Indian Hinduism,

having absorbed many animistic beliefs.

'I'm meeting Gusaji, who will become a Hindu high priest next year.'

-What's this then?

-It's a sarong. It's a Balinese custom.

-It must be worn by someone who want to attend ceremony, who want to come to temple.

-Ah ha.

What's the difference of Hinduism in Bali and Hinduism in India?

Most important difference that we have, in Bali we have volcanoes.

-Volcanoes.

-They give us life and bring us death.

There's no volcanoes in India, that makes a difference to us.

Gusaji and his family live in the shadow of Gunung Agung,

a volcano they and many Balinese hold to be sacred.

-So do you believe that gods live in the volcano?

-Yes, we believe it very much.

Gunung Agung is the home of the garden of the mountain.

They got good gods or bad gods? Do they destroy or protect?

We expect him to protect here in Bali.

Sometimes, he doesn't always protect.

Some time he doesn't protect us.

Yeah, we try to make him happy.

Perched on slopes of Agung is Besakih,

the great mother temple of Bali.

It's here the islanders perform ceremonies to assuage Vishnu

and the other gods of the mountain.

The Balinese believe rituals must be performed absolutely correctly.

Many remember one time when they got it wrong.

An important ceremony held once every hundred years and known as the Eka Dasa Rudra,

was due to get underway at Besakih on March 8th, 1963.

The Indonesian president wanted the delegates of a huge tourism conference

to see the wonders of Balinese culture.

So he demanded that the timing of the ceremony should coincide with the conference.

But ten minutes after the start of the rituals...

..smoke began to pour from Mount Agung.

These pictures show the volcano erupting.

In that time, I was still young, maybe nine years old.

I could see the explosion, the fire,

the ashes cover all of Bali island,

and also small stone also,

come down from the sky.

Many worshippers at the temple of Besakih decided to stay and pray,

rather than flee even though a massive lava flow was heading straight for them.

The lava flow on the south part of the mountain, it destroyed everything but avoided the temple.

-It avoided the temple?

-Yes.

-You think it avoided it deliberately?

-I think so. I think so.

Agung had laid dormant for hundreds of years.

Many Balinese believe the eruption was no coincidence.

Why do you think the eruption happened?

Because the ceremony was on the wrong day,

I think the god of mountain angry at that time.

It's not surprising that today, the Balinese go to great lengths to please their gods.

Today, hundreds of worshippers bring offerings from all over the island.

They're hoping to entice the gods down from their volcanic home.

BELL RINGS

'Today, I'm a special guest at the ceremony.'

The priest arrives and starts to pray with mantras to the gods.

What the priest say in his mantra,

"Oh God, please come down from the mountain.

"We are ready to worship you here. You are the creator, protector.

"We are ready with all kinds of offerings for you.

"Bless us here and then protect us forever."

Once the gods are lured down to the temple,

worshippers will try to keep them here.

The longer they stay, the greater the good fortune bestowed on the assembled company.

Entertainment is laid on to persuade the gods to dally among the mortals.

This is the sacred dance of the virgins.

They're followed by the warriors.

The warrior are ready to welcome him to entertain him as well.

-And they'll protect the god if he comes down?

-Yeah, to save him exactly. To protect him.

The ceremonies last all day,

and when they're over, the gods return to their mountain.

-So do you think it was successful?

-It was very very successful.

-And then we get the gods out, very very happy.

-Good.

-Very successful I think.

-I'm glad they're pleased!

Volcanoes are fundamental to the beliefs of people on this island.

Thanks to geology, Bali has its own brand of Hinduism,

a faith inextricably woven into this volatile landscape.

I'm travelling 600km to Java,

which is the next island west of Bali.

It's one of the most densely populated parts of Indonesia.

If a reliable warning system for eruptions is needed anywhere, it's here.

Thousands of people live here in the shadow of Mount Merapi,

one of the most dangerous volcanoes in Indonesia.

It erupts every year,

and every six years, there's a big one.

These pictures from Merapi show the cause of most human casualties -

pyroclastic flows.

Extremely hot blasts of ash and debris

which hurtle down at speeds of up to 100mph.

In 1994, a deadly pyroclastic flow ripped right through this village.

It measured an incredible 400 degrees centigrade

and the houses were just incinerated.

43 people died.

Scientists are doing their best to predict eruptions here,

but even with the latest technology,

such forecasts can be notoriously vague.

This is the Babadan Observatory on the flanks of Merapi.

I'm meeting Dr Rudi Hadasantano, a fellow geologist,

who like me has me has been studying volcanoes for years.

We have 69 volcanoes monitored throughout Indonesia.

Rudi has invited me to join him in an expedition to the top of the mountain

to collect crucial data for making predictions.

You don't get a chance like this every day.

But it's gonna be a hard slog up the 3,000m high peak.

First, we need to find out whether the mountain is quiet enough for us to make the claim.

What exactly are you monitoring?

We're monitoring the summit of the volcano.

The growth of the dome of Merapi.

By taking the picture, day by day and week by week,

if there is any change, it means that the dome getting bigger.

So the dome is getting steeper because of magma pushing through?

-Yes.

-And what happens if that steepens?

-It can collapse.

-It can fall off?

-Yeah.

And when the dome falls off, that's when deadly pyroclastic flows occur.

I can show you what's happening with Merapi with this bottle of fizzy water.

If I shake it up, the gas that's trapped inside the drink

separates out.

But it can't escape so it builds up pressure.

Under Merapi, gas is released from the molten rock but it can't escape cos it's underground.

Eventually though...

the pressure builds up and it goes,

taking lava, ash and dust with it.

An explosive eruption.

And gassy too.

The scientists here have another more immediate way of collecting data,

on the state of the volcano.

What are we monitoring here?

Here we have seismograph detecting the earthquake of Merapi.

The significance here is that as molten rock breaks its way to the surface,

it creates earthquakes and lots of earthquakes means it might erupt.

-So anything going?

-Yeah, we have a earthquake example yesterday.

This is during the quiet time.

-Not during eruption.

-Right.

-And what happens during an eruption?

It has a different pattern.

Look at this! It's gone crazy!

Really, that's an eruption about to happen.

Wow.

The main thing is for me, is that's it's quiet is it?

It's quiet. You see we have nothing.

You're waiting for that needle to start going...

We like just plain paper.

These readings suggest that it's safe for us to climb Merapi

and collect more data higher up.

The question is how effective are these measurements for making predictions and saving lives?

We'll find out the answer to that tomorrow.

So we have the gas sampling? He's gone to get it.

'After a few fitful hours sleep, I join Rudi's team of porters and technicians,

'who are loading up ready to make the ascent.'

We have a five-hour trek up the volcano to the summit,

with a 20-man team carrying equipment and water.

These lamps are gonna light our way.

The path's a bit muddy because we've had a lot of rain.

It's been blowing a gale overnight so we'll just see what we're gonna get up there.

We need to reach the top by dawn.

THUNDER RUMBLES

RAIN POURS

The climb proves harder than I'd imagined.

2,000m up, the heavy wind and rain prevent me seeing more than a short distance ahead.

RAIN POURS

We're at the halfway point,

and to be honest, at this moment, it's more like western Scotland than Indonesia.

We're all pretty exhausted.

Finally, the night storm moves off,

leaving us with a breathtaking view of the great peak, towering above us.

Four hours gone, and we're within sight of the summit.

I can see the smoke and fumaroles, it stinks. It's fantastic.

I can't believe it, just coming to the summit of Merapi.

Here it is!

Ahead of me,

is the dome-like plug of hardened lava.

If that collapses, we're all in trouble,

but it's here that we need to take our more accurate measurements, and find out the volcano's state.

Swirling around the pinnacle of Merapi are toxic sulphur and carbon dioxide gases,

so we have to put on masks.

On the gas field,

we join Rudi's team as they start work.

First, a thermometer is thrown into one of the fumaroles.

-800 degrees Centigrade?

-Yes.

We go on to measure the mixture of gases coming out of the volcano.

-Tap's opening.

-Yeah! There it goes!

'It's the ratio of these gases which is the key to predicting an eruption.'

The increase of sulphur dioxide gives us information about the increasing magma

from the magma chamber on to the surface.

And that tells us the magma is getting closer and closer to the surface - is that right?

Yes, just right.

Today, the sulphur dioxide is at normal levels,

and temperatures are stable which suggests the volcano is safe -

for now at least.

Have you made an predictions of eruptions here that have saved lives?

Yes. Some time during the increased activity of the recent one.

We asked the local government to ask the people to leave their villages.

How much time for warning can you give people around Merapi of an eruption?

At least two or three days before the eruption.

The good news is that with modern science, us geologists can predict reasonably accurately,

when a volcano's about the blow.

The bad news is that we can only give a day or so's notice.

When it comes to evacuate the thousands of people, that just may not be enough.

Just a few weeks after my visit,

Merapi began spewing out clouds of ash, gas and rock.

Rudi feared she was about to fully erupt,

and over 20,000 locals were evacuated from the immediate area.

Elderly women and children were taken to special shelters.

Things looked perilous as lava poured from the summit.

Molten boulders crashed down the sides.

And once again, pyroclastic flows swept 4km through fields at the base.

In the end, Merapi calmed down and the threat of a serious eruption passed.

But just as locals were breathing a sigh of relief,

the area was struck by another geological disaster, a huge earthquake.

Nearly 6,000 people were killed and up to 200,000 left homeless.

It was a terrible reminder of just how unstable the geology is in this region.

Throughout history, Indonesia's volcanoes have been responsible for some awful catastrophes.

But the story of the volcanoes here isn't all about destruction.

In the west, we've developed a use of volcanic rocks as ingredients in rather exotic products,

like toothpaste and cat litter.

But in the east, they've been considerably more ambitious.

This is Borobudur, one the of the great wonders of the ancient world.

It's the biggest monument in the southern hemisphere.

Build between the eighth and ninth centuries,

as a Buddhist holy place, Borobudur is made entirely of andesite,

a volcanic rock.

The stone from which this astonishing monument was built originally came from Merapi,

and surrounding volcanoes.

Andesite is a result of lava cooling quickly in contact with air,

trapping bubbles which fill with a glassy crystal.

It's that which gives us volcanic rock great advantages as a building stone.

It must have been hard to haul the stone to the site.

But once there, stonemasons found it had great advantages as a building material.

Toni Tack is an art historian was has studied Borobudur for 30 years.

Is this rock easy to carve?

Yes. It's easier than granite.

It has this character about it.

It has crystals inside,

that have a tendency to explode.

I can see that, attacked by them.

-Can I get a little go, do you think?

-I'll ask him.

THEY SPEAK IN LOCAL LANGUAGE

Yeah.

I won't break it. It's not going to snap in two.

-You need goggles.

-You should. My students, I always tell them.

-Slant it a bit more.

-Do that?

-That's right.

-Yeah, it's all soft and sandy, isn't it?

-It's kind of like volcanic beach sand.

-Yeah.

When this was getting built, there wouldn't have been three of these.

-You must've been able to hear the noise for kilometres.

-Hundreds.

-Hundreds of people.

-Thunderous.

-Gosh, you've quite a hand at this.

I like rocks. I do like rocks. I should stop though - our man here is much better.

-Why don't you try?

-You do it.

Ah!

-Thank you.

-Would you like to walk around, have a look around?

-Yes, please.

See where those rocks go.

This artificial mountain is 35 metres high

and covered in 3km of pictures known as "bass reliefs".

So what does this magnificent monument represent?

Amazing, isn't it?

It's of course a Buddhist monument and it represents... tells the life of Buddha in stone,

the bass reliefs on the lower levels,

and the function was that the monks long ago would circumambulate the monument and read the bass reliefs.

-They couldn't read and write at that time.

-Ah.

It's really, you could say, like a 9th century comic strip.

-A giant comic strip.

-Yeah.

-That's one way of looking at it.

The crystals in the andesite help to form a stone which could be easily carved.

This allowed the ancient Buddhist craftsmen to sculpt beautifully detailed pictures.

This is our story about Buddha, but before he was born as a human being, he had many different incarnations.

Here he is as a turtle. You see him swimming through the sea.

-That's the first panel. The second panel you see that he comes across a ship. See the ship?

-Mmm.

There are merchants on the ship and the ship is sinking.

There's a huge storm. See the waves?

And there's a strange shark with his mouth open.

Buddha turtle comes along and says, "Have no fear. I will take you to safety. Climb on my back."

Here he is taking them all to safety. They're all on his back.

And he takes them to land, the last panel, and here you see the merchants are saved,

and they're listening to Buddha turtle, who is preaching to them,

then because there's nothing to eat, he offers his body to them.

-Ah!

-He sacrifices himself to these people.

He gains merit because of this and in his next life, he has a higher incarnation. Isn't that beautiful?

'It's believed to have taken over 100 years to carve all the 1,500 bass reliefs which grace the monument.

'But this extraordinary cultural heritage is under threat.'

Here I'd like to show you one of the sadder aspects of Borobudur.

This is a bass relief of a sick man.

-If you look at this photograph from about 100 years ago, you can see clearly his ribs are visible.

-Yeah.

-You can hardly see any ribs at all.

-No, no.

-This has happened in other places.

-Has it?

-Yes.

It's the volcanic nature of the stone which makes it so vulnerable.

Those glassy crystals in the andesite are being loosened out.

They're just falling out and leaving behind holes, and the weathering just gets in there and opens it up.

I think that's producing pitting all over the surface. Tragic, really.

'The geological make up of the stone means that some carvings are under greater threat than others.

'The difference in rates of weathering is often apparent in adjacent panels.'

What we're seeing here is different weathering rates from different parts of the lava flow.

At the edge of the lava flow, it cools very fast and the crystals are very small.

If you've got small crystals, it's much harder to weather them.

But if it's from the centre of the lava flow, it cools slowly and you get big crystals,

-so where it is in the lava flow determines the way that it weathers.

-Interesting.

Merapi was also at the centre of the decisive event in the monument's history.

In a terrible twist of irony,

the very volcano that had created the materials to build this monument also proved to be its undoing.

1,000 years ago, an angry Merapi spewed out vast quantities of ash

which fell from the skies and partially covered sacred Borobudur.

It was quickly abandoned and, in time, forgotten.

The monument disappeared along with its Buddhist culture.

Borobudur was not rediscovered until the beginning of the 19th century.

It's been a fascinating geological journey for me so far.

The volcanoes of Indonesia seem to impact on everything - religion, culture, art, literature.

This lush landscape of Java is a clue to an even grander claim made on behalf of the country's volcanoes -

that they were the key to the discovery of new worlds.

This place is known as the Garden of Java because of its fertility.

For such productive land, we have the volcanoes to thank.

This red brown earth was once ash that fell from the sky during a volcanic eruption.

As well as iron, which gives it the red colour, it contains a strong natural fertiliser, phosphorous,

which, when combined with plant matter, makes for a rich soil,

perfect for growing cloves and nutmeg.

'Nutmeg is pretty fussy about where it grows, but it does love soil like this.

'500 years ago, when the spice first became popular in Europe,

'it could only be found in Indonesia or a small archipelago called the Spice Islands.

'Nowadays, nutmeg trees are much more widespread.

'The Ngobo Plantation on the slopes of the Ungaran volcano is one of the largest in the country.

'It takes a certain skill to harvest the mature trees.

'Even though often precariously perched up to 15 metres above the ground,

'an experienced worker can pick the crop on one tree in under an hour.'

This is what she's harvesting.

On the outside, it's a white pulp.

In the middle is the nutmeg itself.

This humble nut changed the world in the most profound way.

Between the 16th and 19th centuries, it was the must-have spice of Europe.

Highly valued as a food preservative and for medicinal purposes.

There were curious applications as well.

Popping a nutmeg under your left armpit prior to social events was believed to attract admirers.

A 16th century monk advised young men to carry a vial of nutmeg oil to anoint their genitals for virility.

I'll hang on to this one.

Nutmeg became worth its weight in gold.

Arab traders held a monopoly on its import to Europe, and could charge whatever price they wanted.

Not surprisingly, European buyers decided to take control of this lucrative trade for themselves,

so they launched expeditions to find the root to the spice and bring it back directly.

Christopher Columbus was searching for the root to the Spice Islands when he stumbled upon the New World.

So these nutmeg-friendly volcanic soils played a key role in the discovery of America no less.

'A few years later, Ferdinand Magellan also set off to find a westward route to the Spice Islands.

'He died on the way, but his surviving crew continued west and made it back to Spain.

'They became the first men to circumnavigate the globe.

'Indonesia's volcanoes have been instrumental in shaping the history of the world.

'But so far, I've only looked at human history.

'Volcanoes provide the answer to one of the most intriguing mysteries of the plant and animal kingdoms.

'It's a story centred on these exotic islands.'

The principle character is a brilliant, but forgotten hero of history.

He should be a household name, as well known as Charles Darwin,

but Alfred Russel Wallace somehow got lost in the mist of time.

In the 19th century, he made a discovery which was hugely significant

for our understanding of the world around us.

To show you what I mean, I'm in one of the leading centres for bird conservation.

Here, Ria Saryanthi from Birdlife Indonesia will take me on the trail of Wallace's discovery.

At first, he observed the many birds of Bali,

such as the magpie robin.

It's one of the popular songbirds.

Rich men, they have a house, they have a car, wife, and also that bird, the magpie robin.

-So it's a status symbol?

-Yes.

Wallace catalogued these and thousands of other species.

When it came to mapping where they lived, he came across something that puzzled him.

Generally, Asian birds like these are only found on Bali to its west.

There's fish and things like that.

But to the east of Bali, there were completely different birds.

Instead, they were all Australian species, such as the cockatoo.

This is Anne-Marie.

This is one of the Australian species.

He came from the eastern part of Indonesia.

-It's magnificent.

-It's well known as a mimic bird.

Do you think it'll understand Scottish?

-Hello.

-Och aye the noo!

-Hello. Hello.

-BIRD SQUAWKS

If he's Australian, I have to say "good day" or something, do I?

There you are.

Anne-Marie. Hello.

I keep thinking it's going to bite my nose off.

Aw, look at that. Hello.

'It was a mystery. Why should there be Asian birds on one side and Australian on the other?'

Wallace realised there was some kind of line dividing bird species, and it didn't stop at birds.

It effected other animals too.

Oh! Oh!

Look what I've got. I've got eggs.

Hey, hey, hey!

Greedy!

They're so cheeky. Hiya. He's got two!

You cheeky one.

'From Bali and to the west, Wallace found mammals that were more typical of Asia.

Species like monkeys which carried their unborn offspring in their wombs.

To the east, there were marsupials who carried their young in pouches.

They are more associated with Australia.

Wallace carefully mapped out this division, which became known as the "Wallace Line".

It extended northwards, right through Indonesia.

To the west, Asian species dominated.

To the east of Bali, there were completely different Australian species.

For all his genius, Wallace never completely understood

the mechanisms that made the species on either side so different.

Today, partly thanks to volcanoes, we have the means to find an answer.

This rock, called a loadstone, is like a miniature version of the earth,

because just like the earth, it's magnetic.

If I put these iron filings on top of it, they line up with the magnetic field of the rock.

'Over millions of years, as the surface of the earth was being formed,

'volcanoes spewed out red-hot molten lava.

'That liquid rock contained particles like the iron filings

'which aligned themselves with the earth's magnetic field.'

As the molten volcanic rock cooled and hardened,

their alignment became fixed, like tiny compass needles stuck in time.

These were the key to solving the mystery of the Wallace Line.

The earth's surface consists of giant plates,

which float on a viscous interior.

The original north-south alignment of the stuck compass needles

reveals how these plates have moved through time.

Today, that alignment is out of synch with the earth's magnetic field.

Let me show you with these rocks. This is Asia with Indonesia, and this is Australia.

Today they meet across the Wallace Line.

But if we spool back in time 150 million years, this is what happens.

Australia breaks from Asia and heads south.

Asia, just a little bit northwards.

So these were two completely separate land masses.

The fauna and flora evolved entirely independently of each other.

We discover that Asia and Australia have come together from opposite ends of the world.

That explains why animals on either side of the Wallace Line have evolved to be so profoundly different.

It's volcanoes that have helped solve the mystery.

'Volcanoes have a much more obvious role to play in evolution.

'Every so often, eruptions suddenly obliterate every animal and plant for miles around.

'Quite simply, life has to begin all over again.

'For fauna and flora to recolonise an island laid bare by volcanoes and surrounded by miles of water,

'is an extraordinary feat.

'I want to know how they do this.

'I'm off to look for clues on one of the most famous volcanoes in the world, Krakatoa.'

Krakatoa sits ominously between Java and Sumatra.

Its most notorious eruption was in 1883 when nearly 40,000 people died.

There was a subsequent eruption of Krakatoa in 1930 which is not so well know.

But it has allowed scientists to discover how plants and animals re-establish themselves

following volcanic annihilation.

Hi!

Oh!

'I'm meeting up with Dr Tucaren Partimeharju, a biologist who's spent years studying Krakatoa.

'I'm hoping he'll be able to explain to me the process of natural colonisation.'

-Hi.

-Hello.

-How are you?

-Fine.

Look at the weather! Amazing!

-Krakatoa!

-Welcome to Krakatoa.

-Thank you very much. Fantastic!

'When the first scientist visited the island two months after the eruption, they could find no sign of life.'

Look at the size of that!

-They parachute in?

-That's right.

When they get here, there's nothing, so they die.

'However the pollen of simple plants, such as mosses, lichens and grasses,

'was carried out to the island by the wind.'

'The big breakthrough came with the arrival of larger plants.'

-So when this arrives, it provides the food for the other plants and insects?

-Yes, that's right.

'We are to spend the night in a hut in the shadow of the volcano.

'As dinner is prepared, Tucaren tells me how, seven years ago, he experienced Krakatoa's power.'

What's it like being in the middle of an eruption?

It was that strong?

What was coming down on you? Was it just ash?

'After the 1930 eruption, animals and plants were carried great distances to the island,

'often transported on logs, branches and other, more surprising rafts.'

Pumice like this would have been hurled a great distance by the eruption.

Air holes inside make it light and extremely buoyant.

Large boulders of pumice often get tangled up with other debris to create a seaworthy platform.

They acted like a kind of Noah's Ark carrying small insects, eggs and seeds thousands of miles.

If I want to get washed up onto the shore,

this floating life raft would have introduced new and exotic species.

'From their studies, scientists found that within three years of an eruption,

'insects could survive on the island by eating the simple plants already growing there.

'But bigger creatures had a more difficult time.

'They needed to eat more nourishing food if they were to survive.

'One breakthrough plant allowed them to get established.'

What's this tree?

What sort of animal eats figs?

-Right, so bigger animals now.

-Relatively bigger.

The fig was quickly followed by other fruit trees.

Not long after, higher order land animals made the island their home.

What are the biggest animals on Krakatoa?

Pig?! How did that get here?

Can they? I didn't know that! What about anything dangerous?

That's quite dangerous. How did that get there?

'However, there's not the same mix of species here as on the Indonesian mainland.'

As life returns to islands like Krakatoa, it seems there's a natural filter.

Only species with mechanisms to travel across the ocean can colonise them.

As a result, there's a real uniqueness to their habitat.

'Even when the ecosystem is fully fledged,

'fresh eruptions can render barren swathes of the island all over again.

'There have been dozens on Krakatoa since 1930.

'Each one has left its own trail of destruction.

'Just like Tambora, which I visited at the beginning of my journey,

'Krakatoa erupted so violently in 1883 that it effected world climate.

'But Krakatoa and Tambora are small fry compared with what may lie ahead.'

There could be an unfathomably huge eruption on the horizon,

one which would eclipse anything I've talked about so far,

and there's evidence that it'll happen right here in Indonesia.

One ancient eruption of this monster volcano came close to wiping out the entire human race.

'I'm now travelling to Sumatra on the far west of Indonesia

'on the trail of the world's most ominous volcano.

'Toba is the biggest lake in southeast Asia.

'It's a lovely place, a real tourist attraction with its cool, refreshing waters.

'But don't be fooled by its serenity.

'74,000 years ago, this place couldn't have been more different.'

The proof that something happened here is written into these rocks.

They're called "ignimbrites", and they can only be formed by those hot, pyroclastic flows.

The lake itself, well, that's a pretty big clue too.

It's a volcanic crater filled with water, the biggest in the world.

You can see the edge of it over there.

'As for the other end, that's 100km away.

'When the Toba volcano blew, it must have been ferocious.

'Geologists have found ash from here as far away as India.

'The eruption was probably the biggest in the history of mankind.

'Toba is estimated to have ejected some 7,000 cubic kilometres of magma.

'It was over 3,000 times more powerful than the 1980 Mount St Helens eruption.

'Volcanologists have adopted the term "humungous" to describe Toba's eruption.

'I can't argue with that one.'

The ash and sulphur thrown up by Toba into the atmosphere

caused six to seven years of global volcanic winter.

It may even have kick-started a new ice age.

There's evidence that this dealt a devastating blow to early man,

and even affects the way we are today.

'There are significantly fewer genetic variations in the human race

'than would be expected for a species that has been around for as long as we have.'

One explanation is that the food shortages caused by Toba wiped out 75% of the human population,

meaning that we're all related to a surprisingly small genetic pool of distant ancestors.

'These are the ancient Karo Batak people who have lived with this sleeping giant for millennia.

'They're bringing me to their sacred ceremonial pools.'

THEY CHANT IN THEIR NATIVE LANGUAGE

The Batak are worried.

Recently the area has been shaken by big earthquakes.

So today the villagers pray to their gods and make offerings

before submerging in the steamy water and anointing their hair.

This boiling pool is a sign that the area is geologically unstable.

These bubbles are coming up from a series of fault lines or cracks near the surface caused by earthquakes.

15km below Toba is a massive reservoir of molten rock, known as a magma lake.

It's the only one in this part of the world,

and its meshed into this network of unstable fault lines.

The fear is that the earthquakes could open up the faults

which would act as pathways to allow the magma to burst through and create a super volcano.

It could be as bad as the one that shook the world 74,000 years ago.

The big question is, how would the human race survive should Lake Toba erupt once again

and become a cataclysmic super volcano?

Some scientists predict that if one of these eruptions happens again, we'll have to colonise space.

I think we'd be better off trying to figure out how to cope with such a colossal event back here on Earth.

The people of Indonesia have been living with their fiery peaks for thousands of years.

I just hope that we can do as good a job.