Original subtitles

This is what we go on, is it?

This is one of those boats the locals used...long time back.

Oh, dear.

GRUNTS

On 17th November 1855,

on the banks of the Zambezi here in southern Africa,

the Victorian missionary explorer David Livingstone

stepped into a traditional dugout canoe, like this,

and set off downstream.

Right, let's go.

What Livingstone stumbled upon that day

would not only help put Africa on the map, it would also explain

how this huge continent was created in the first place.

In this series,

I'm going to do something I've never really done before -

search out the clues

that take us back to the key moments in the story of each continent...

LAUGHS

..because the continents are constantly on the move...

..and the traces of their secret past are hidden all around us...

HISSES

..in the Earth's rocks, but also in its landscapes...

That is very spectacular.

..and even its wildlife.

It's moving.

The tiniest detail can reveal the history of a vast continent.

I'm beginning in Africa, the most ancient continent...

LAUGHTER

ROARS

..and discovering the main turning points that forged this land...

They're just all around us, aren't they?

..creating its wealth, fuelling its wars,

shaping its ancient civilisations...

..and seeing how events deep in Africa's past

have influenced the whole planet.

But Africa now stands on the threshold of a spectacular change,

as the immense forces that shaped this continent

now threaten to bring about its destruction.

The discovery of Africa's deepest origins

started with Livingstone's fateful expedition 150 years ago.

As he made his way down the Zambezi river,

Livingstone found his progress suddenly interrupted

by a strange sight...

..a huge curtain of mist rising up from the river ahead...

..accompanied by a steadily increasing roar.

Right.

Leaving his team behind, for fear of putting them in danger,

the explorer continued his journey on foot...

..only to find his way blocked by the most impenetrable of all obstacles...

..known to the locals as Mosi oa Tunya -

"the smoke that thunders".

We, of course, know it as the Victoria Falls.

And the ultimate way to experience the Falls

involves getting your feet wet.

Ah!

Oh, dear!

LAUGHS

This is the way to see the Victoria Falls.

Oh, my God!

Aah!

While the water around me

cascades down more than 100 metres to the river below...

..this pool forms a hidden sanctuary.

Livingstone thought the Falls so lovely,

they must have been gazed upon by angels in their flight.

Staring down at this precarious drop,

it's not hard to see how Livingstone was completely bowled over

by the scale, the grandeur and beauty of the Falls.

But what he had no way of knowing

was how this feature has got huge geological significance.

But to appreciate that significance,

we need to go back some 200 million years.

The Earth looked very different.

All the continents were clumped together into one enormous landmass,

a supercontinent called Pangaea.

It was a land of extremes...

..an enormous mountain range higher and longer than the Himalayas...

..and an interior covered in a vast desert

five times the size of the Sahara.

Victoria Falls can tell us

how Africa was carved out from the heart of that great supercontinent.

You can see exactly what happened here 180 million years ago

by looking in the vast gorge beneath the Falls.

Because hidden in the rocks is some intriguing evidence

of a cataclysmic geological event

that would create Africa as we know it today.

What a place! It's like a... an amphitheatre of rock.

The thing is, all these cliffs are carved from the same rock,

a rock called basalt,

and it comes to us from deep underground,

rising up as molten magma.

To appreciate basalt, to understand what it's trying to tell us,

you have to get inside it, though.

In here are the secrets of its formation.

These crystals...

cooled really rapidly.

You see there's a...there's a slight speckled appearance,

which, if you look with a hand lens,

you can see is lots and lots of tiny, tiny crystals.

These crystals were formed as the hot rock cooled,

and their size tells you how quickly it happened.

So, what this is telling us, really,

is that this rock must have cooled really rapidly.

Sudden cooling of searing-hot magma

means crystals don't have time to grow,

which is why they're so small.

And one way to rapidly cool a rock like basalt

is to erupt it from the surface,

expose it to the air,

and it just solidifies very quickly before the crystals can grow.

So, all of these rocks here,

all these basalts were erupted out as lava flows.

Lava flows that reveal their size in the soaring cliffs.

What takes your breath away here

is just the sheer scale of the eruptions.

I mean, that cliff there is 120 metres high,

and it's just layer upon layer upon layer of lava flows.

And the thing is, that continues down underneath for hundreds of metres.

I mean, across this region, it's thought that over a kilometre of lava

was erupted out in a million years or so.

It must have been the most staggering volcanic event.

These eruptions were the start of an immensely destructive event

that happens only rarely in the Earth's history.

They would have stretched for thousands of kilometres,

burying huge swathes of what was to become Africa

under millions of cubic kilometres of molten lava.

The cause of this mayhem was one of the Earth's most powerful forces...

..huge upwellings of superheated rock called a mantle plume.

The sheer force of those mantle plumes,

making their way towards the surface,

pushed the land up, causing it to thin and crack,

cracks which eventually got so big

that the land slowly began to fragment,

so beginning the break-up

of the single largest landmass the Earth had ever seen.

Pangaea.

As the supercontinent began to split apart,

one by one, the Earth's continents were torn from its outer edges.

The eruptions at Victoria Falls

led to the formation of India and Antarctica.

Another mantle plume cleaved off North America, then South America,

leaving behind Africa as we know it today.

The break-up of Pangaea meant that for the first time in its history,

Africa stood alone,

a continent in its own right.

And for the next hundred million years or so

that newfound isolation would transform Africa beyond recognition,

its landscape, its climate, but also its wildlife.

It forced animals to adapt

to a myriad of different complex environments.

And to my mind, the most remarkable of all those adaptations

didn't happen here on land, but just out to sea.

The coast of Africa, carved out 180 million years ago,

is today home to a wealth of life.

Perhaps most spectacular of all are whales.

WHALESONG

Today these ocean giants are undoubtedly the kings of the sea.

(WHALESONG)

But look far enough back in time

and we find the evolution of these giant animals

is a direct consequence of the cataclysmic events

that gave birth to the African continent.

The first piece of evidence

can be found at another of Africa's most famous sites.

Welcome to morning rush hour in Cairo, Egypt,

the biggest city in the African continent.

This is a place that's been undergoing

really dramatic political change in recent times.

Now, geologically, it's long been stable,

but 100 million years ago,

it underwent the most colossal geological transformation.

A change driven by the same event which gave us the Victoria Falls.

And some tiny remnants of this transformation

can still be seen today

amongst the ruins of Egypt's most famous landmark.

The pyramids of Giza.

You get little hints there.

Nothing really good.

There must be something better than...

The trouble with this face is it's been dressed by the stonemasons.

You've got all these chisel marks. You just can't see anything.

How frustrating!

Ah, now, this...this is more like it. That's what I'm looking for.

VOICE ECHOES: Creamy-coloured discs...

Every whale in the ocean...

These features have intrigued and confused people for centuries.

The Greek historian Herodotus reckoned that they were...

they were the petrified remains of lentils

that the pharaoh gave the slaves that built this monument.

But the truth's actually far more bizarre, far more interesting.

If Herodotus had one of these, a hand lens,

he might have made a different interpretation,

because the surface of these,

they've got these exquisite whirls and swirls.

They're clearly something that's living.

These are actually nummulites.

They're the shells, really,

of the very largest single-celled marine organism that's ever lived.

These nummulites can tell us

what the seas in which they lived would have been like...

..because from chemical analysis of their shells

we know that these nummulites shared their homes

with millions of photosynthesising microbes...

..creatures requiring an abundant source of sunlight.

And that means that the seas in which these nummulites once lived...

..must have been extremely shallow.

So, why is that important?

Well, it's because every single block in this entire site

has been quarried from just a short distance from here.

In other words, those shallow seas, that the nummulites lived in,

were right here.

100 million years ago, something happened,

something connected with the birth of the African continent,

to transform much of northern Africa

into a shallow sea, teeming with life.

As the great supercontinent of Pangaea broke up...

..so the rising molten magma beneath its surface

threw up a chain of underwater volcanic mountains.

These displaced enormous volumes of water,

contributing to a staggering 300-metre rise in sea levels

that not only swamped much of the North African coast,

it even split the newly formed continent in two.

And it was this transformation of the landscape

that was to lead to the evolution of that most spectacular of mammals...

..the whale.

To discover how, I've come to Egypt's Western Desert...

..home to a remote valley

of sandstone cliffs and wind-carved rocks called Wadi al-Hitan...

Echo!

ECHOING

..that once used to be full of marine life.

ECHOING VOICE This sculpture underneath rocks...

'Palaeontologist Charlie Underwood has spent the past four years

'studying this long-lost seascape.'

Here's just quite a nice place to show

what the sea floor was really like at the time.

Right. Really...

Oh, wow. Yeah.

Yeah, you see, if you get up here... Yeah.

These are incredible. These tubes are burrows, are they?

Yeah, so we've got... This is essentially an ancient sea floor,

and these are the burrows of the various animals

that were burrowing into this. Shrimps. Small lobsters. Crabs.

'The closer you look, the more this aquatic landscape comes to life.'

I can see a snail. There's a little gastropod shell.

Just in here. Yeah.

There's the small tooth of a lemon shark.

You've trumped me.

That's lovely.

So sharp.

There's a small nummulite. Ah, yes. Saw these in Giza.

Fairly small ones here, but they really show this is shallow water.

Yeah.

Beautiful way they get sculpted by sandblasting.

'But it's the discovery of some other, much larger marine fossils

'that has made this valley such a focal point

'for scientists trying to piece together the story of whales.'

Look at this.

Yeah. Amazing, isn't it? What a size!

Yeah, it's impressive, isn't it?

What is this, then? This is a thing called basilosaurus.

Basilosaurus. What a fantastic name!

'Since 1983,

'scientists have uncovered the remains of around 300 skeletons

'belonging to a very early type of whale, basilosaurus.'

So, how long were they, then?

A big one of these could well be something like 15 metres.

The tail is sort of going off in that direction,

but the head is sort of going off into the cliff.

Do you think the head'll still be here? It may well be.

You can just see...

'And what's so special about basilosaurus are the various features

'that reveal what these very early whales evolved from.'

There we are, look. What's this?

There's a tooth starting to come out.

Oh, that's great.

That's fantastic.

They're very sharp. This is a tooth for cutting.

This isn't a tooth just for gripping small fish,

like those little conical teeth of a dolphin.

Yeah. These are for grabbing a big animal,

killing it, cutting it up, swallowing the bits.

Basil was a bit of a fearsome thing.

In what other ways is this creature different?

Just in...in many ways. This weird mix of features.

Small back legs. Back legs? Yeah.

These early whales had back legs? Yeah.

No use for walking. They're much too small for that.

But all the bones are there.

WHALESONG

Little pores around the jaw that suggest maybe it had whiskers.

Whiskers? Yeah.

Its nostrils aren't quite in the position of those of a whale,

with a blowhole.

A list of features that places basilosaurus

at almost the midway point, in evolutionary terms,

between a modern whale and a four-legged land mammal.

What kind of animal are we talking about for what they came from?

If this is a transition, what did they come from?

Well, the closest living relative of whales

are actually some of the hoofed animals.

Right. Things like pigs, hippos, even antelope.

But, unlike modern hoofed animals,

the ancestors of these were carnivorous.

The shallow seas that formed here would have offered rich pickings

to tempt the carnivorous animals living along its shores

into the water...

..over time losing their connection with the land completely,

to evolve into whales.

The fossils here at Wadi al-Hitan are just spectacular.

And they prove that around 50 million years ago,

a small group of four-legged mammals made this extraordinary leap,

going from living on the land to a completely sea-based existence.

It was an incredible evolutionary U-turn

that led to every whale in the ocean,

and it was the direct result of the break-up of Pangaea

and the birth of the African continent.

By 30 million years ago, sea levels dropped, the seas dried out,

and the familiar outline

of the Africa we know today finally emerged.

The break-up of Pangaea

explains how Africa emerged from the wreckage of the supercontinent.

The next critical moment in Africa's story

doesn't take us further forward in time,

it takes us back into an even more distant past...

..back to an extraordinary sequence of events

early in the Earth's history.

These deep origins help explain the formation

of some of Africa's most iconic landscapes,

and they also explain one of the great puzzles about the Earth -

why the continents move at all.

The clue that solves these mysteries is found in Sierra Leone.

I've come to the large market town of Kenema...

Hello! Hello! Hello!

..a busy commercial hub

of over 100,000 people.

Everywhere you look, people are selling stuff.

Like, this is obviously vegetables.

Hi! What are these called?

What are these...? Oh, these are okra.

There's some, er, beauty products here.

This market is kicking. It's really got a lot of energy to it.

You know, it's strange, you say Sierra Leone

and you immediately think of that civil war ten years ago

and all those horrific pictures

that you were getting nightly on the television.

And yet, when you come here, it's just completely different. Hi!

It's such a great place,

but there's one commodity that really fuels the economy round here,

but you won't find it in this market.

A commodity that can tell us

what this part of Africa was like billions of year ago,

long before Pangaea.

'About 30 kilometres outside Kenema...'

This is one of the pits.

'..lies a cluster of steep-sided sandy pits...

'..called Jah Kingdom.'

Look at that.

Three-quarters of working-age men in the area work in pits like these...

..digging their way through the deep sand of an ancient river bed,

to uncover a layer of gravel scattered with precious raw diamonds.

What you don't appreciate till you're actually here

is the amount of material they have to remove

just to get at the diamond-bearing gravels which are underneath here.

How much time to dig down? A month. More than a month.

Just to get through all of the sediments that don't have diamonds

to get down to the ones underneath here that do. Yes, sir. It's amazing.

During Sierra Leone's civil war,

these diamond fields were bitterly fought over.

Now the war's over,

but the work of finding diamonds amongst the gravel

still relies on the same simple technique today as it always has.

What's happening here is the diamonds are really dense, quite heavy,

so they...they kind of sink down,

and you find it glinting in amongst all those dark stones there.

Nothing. Nothing.

What happens when someone finds a diamond? Does everyone go shout?

And...is there lots of noise?

You keep cool. Keep cool? Yes.

Say, "I have a diamond, I have a diamond"? No, no, no.

Just keep quiet. Cool. Be discretional. A precious stone.

For the lucky few, their hard work will pay off,

as very occasionally a diamond is discovered lying amongst the gravel.

This is what it's all about, a raw, natural diamond.

This is what everyone's looking for.

For the guys around here, this is about a month's salary.

And for the jeweller that buys it

and fashions it into something like an engagement ring,

it's probably several hundred dollars' worth here.

But for a geologist... I don't know,

I think it's even more valuable, even more beautiful,

because it's a window back in time.

It takes us back right to the birth of the very first continents.

This diamond contains within it

the secret of the earliest origins of this part of Africa.

IAIN'S VOICE ECHOES: Carbon atoms...

compression and temperature...

If you could see deep into this diamond,

what you'd find are carbon atoms that are really tightly bonded together

and arranged into a kind of pyramid shape, and that arrangement

is because of the intense pressures that form the diamond,

something like 50,000 atmospheres.

The only place we know of where you can find that kind of pressure

is 150 kilometres below the Earth's surface,

within an exceptionally hot layer of rock known as the mantle.

But to form diamonds' distinctive arrangement of carbon atoms

also requires very specific temperatures, about 1,100 degrees.

And that's really odd, that, because the Earth's mantle

has got temperatures that are much higher than that.

Temperatures over 1,600 degrees.

So, to explain diamond formation,

you need to find a place that's over 150 kilometres deep

to give the right pressure, but not a part of the normal mantle...

..because this mantle is too hot.

The only place on the planet

that's got the right pressure, right temperature,

is at the base of huge slabs of continental rock

that extend way down into the mantle.

Those slabs are called cratons.

Cratons are incredibly thick pieces of solid rock

that extend deep beneath the Earth's crust.

But because of Earth's solidity,

a craton is much cooler than the surrounding mantle...

..which means the bottom of a craton

has the perfect conditions in which to form diamonds.

The diamonds here found their way to the surface

in ancient volcanic eruptions,

and they tell us something remarkable about Africa's past.

Radio isotope dating of diamonds show that they're billions of years old.

I mean, this one's probably nearly three billion years old,

but some of them go back to three and a half.

What this means,

what the very existence of this diamond here reveals,

is that I'm standing on top of an ancient craton,

a piece of land that formed nearly three billion years ago.

It's called the West African Craton.

It's one of the very oldest pieces of land on Earth.

But it's not the only craton in Africa.

There are five of these ancient building blocks,

each forming a distinctive landscape.

In the south lies the Kalahari Craton,

that lies beneath most of southern Africa.

To the east lies the Congo Craton,

which today forms one of the greatest river basins on Earth.

Further north beneath the Sahara lies another of these ancient landmasses.

The cratons were formed at a time when the Earth was in its infancy.

Three billion years ago, the Earth looked very different to today.

The only landmasses were the cratons,

and unlike the continents today, they didn't move.

They were static islands in one giant ocean.

Because they're so ancient, the cratons have preserved evidence

that solves one of the great mysteries about the continents -

when and why they first began to move.

Without this momentous event,

there would have been no Pangaea and no Africa.

The evidence for why the Earth's crust began to move

lies hidden inside Africa's diamonds.

This is the Government Gold And Diamond Office,

where a team of highly trained valuers

are examining diamonds from the mines all over Sierra Leone.

It's a process few outsiders ever get to see.

So, how do you do the process?

Say, if you get a pile of diamonds, where do you start?

Here we look for the shape, the size, the clarity and the colour.

So, what is...? I see a big one here! What is the size of that one?

Like, this stone here... is a 20-carat stone.

So, what would that be worth?

Well, it depends on the quality.

Now, I have looked at this stone, and there's no inclusion inside,

meaning blemishes inside or outside. Right.

Or inclusions that would be inside the stone.

The shape is not so good. But the colour is excellent.

So, this kind of stone would normally be about $15,000 a carat.

So, multiplied by 20? Yes.

$300,000. $300,000 stone, yes.

In the rough. That's quite nice.

So you're looking for ones that are perfect, without any flaws, ideally.

Without...ideally, no flaws at all. No flaws. Right.

But it's the diamonds with the flaws, or inclusions,

that I've come here to see.

IAIN'S VOICE ECHOES: Pyroxene and olivine...

Diamonds like these, that contain inclusions,

provide the perfect portal for geologists,

because hidden in each of these is a clue

to probably the biggest geological change in the planet's history.

One that explains how three billion years ago

the isolated cratons came together to form the first continents.

Inside every one of these

is a fragment of the rock that was around the diamond when it formed.

A fragment from the base of the craton

150 kilometres beneath the Earth's surface.

And the key is a change in the sort of rock that's found down there.

You see, diamonds that are older than 3.2 billion years

contain minerals like pyroxene and olivine.

Olivine is typical of the rock normally found underneath cratons.

But from three billion years onwards,

there's a strange change in the composition of these inclusions

to include fragments of a garnet-rich rock called eclogite.

Eclogite isn't normally found where diamonds are made,

deep in the base of the cratons.

It comes from much higher up,

from the rock that forms the ocean floor, the oceanic crust.

What's intriguing is,

why did bits of oceanic crust end up beneath Earth's cratons

from three billion years onwards?

The answer turns out to be pretty simple, and that's because

these tiny differences in the inclusions in the diamonds

allow scientists to precisely date when rafts of oceanic crust

first began to be forced underneath continental crust.

It was a crucial turning point in the mechanics of the Earth.

RUMBLING

Three billion years ago, the dense rock of the ocean floor

began to sink down beneath the cratons...

..a process called subduction.

This sinking conveyor belt of rock

had a dramatic effect on the land above,

dragging the cratons together.

It was this process

that would eventually create the African continent we see today.

Driven by subduction, the Earth's cratons,

which up until this point in time had been relatively static,

began to move.

So starting an epic geological cycle,

with cratons coming together and separating,

to create and destroy a series of long-lost continents...

..until finally, 550 million years ago,

subduction brought the five cratons that make up Africa together,

part of an even bigger continent called Gondwana.

In the half a billion years since,

the planet has seen extraordinary change,

the creation of Pangaea

and, 100 million years later, its violent destruction.

But Africa's cratons have stayed together...

..ancient, stable and solid...

..until now.

Because, after half a billion years of stability,

the long history of this African land is coming to an end.

Beneath the surface, there's a destructive force

that now threatens to break up the entire continent.

A clue to what's happening

can be seen in how it's shaped life here in the Serengeti.

For the final chapter in our story of Africa,

we've come here to the plains of northern Tanzania,

to see an animal that's synonymous with this part of the continent.

An animal with one of the most spectacular migrations on the planet.

This is the largest concentration of grazing animals

to be found anywhere on Earth.

A massed gathering of herbivores...

They're just all around us, aren't they?

..that owe their very existence

to a geological struggle going on beneath their feet.

This is what we've come to see. Wildebeest.

Some of them will start heading to the north...

Mm-hm.

..to an area which is up on our left side here.

This annual migration of between one and two million wildebeest

is one of the great animal movements on this planet,

and here we are right in the middle of it.

But look closely, though,

and something rather odd about these animals jumps out at you.

It's interesting, all the calves are exactly the same size.

So, how old are they, then?

They have... They were born in February

so up till now they have three and a half to four months.

So, in February,

that's the time they deliver their babies at once, all of them.

That must be an incredible period,

because just in those few short weeks... Sure, sure, sure.

..you're getting hundreds of thousands of calves being born. Yeah.

Hundreds of thousands of calves,

born not only at the same time but also in exactly the same place.

And the reason why they all descend on this same area,

to have their babies at the same time,

is the grass that grows on the ground.

At the start of every rainy season,

one particular small patch of the Serengeti

becomes covered with some of the most nutrient-rich grass on Earth...

THUNDERCLAP

..containing four times the calcium

and nine times the amount of phosphorous

than grasses just a few kilometres away.

Nutrients that are crucial to healthy calf development.

It means this one comparatively tiny patch of fortified grass

can support millions of nursing wildebeest.

The reason why this grass is so unusual

can be found looming over the herds.

Towering almost 3,000 metres above the Serengeti plains

is one of Africa's strangest and most explosive volcanoes.

Ol Doinyo Lengai, or "Mountain of God".

Back in 2007, an eruption lasting almost 12 months threw a giant column

of steam and ash nearly five kilometres into the air...

..destroying countless crops...

..and forcing thousands to flee their homes.

This ash is unlike any other volcanic ash on the planet...

..with a chemical make-up so odd, so rich in minerals,

that the grass around it has become supercharged.

It's this volcano, and the ash that comes from deep within it,

that enables the wildebeest to breed in such huge numbers here.

Without Ol Doinyo Lengai, this wildlife spectacle wouldn't exist,

and the reason why Ol Doinyo Lengai is so unusual,

why it's so nutrient-rich,

is because of what's going on deep beneath it,

something that threatens not just the future of Tanzania,

but the entire African continent.

And we're off.

It's a journey into the unknown.

It looks like any normal volcano, really. You get the conical shape.

You get a few parasitic little cones there that's erupted out.

There's some evidence of lava flow.

But actually, that's just one of the strangest volcanoes on the planet.

We're just coming round to the top now.

You can start to see the fresher stuff from 2007,

and that's all the previous eruptions,

so this just ahead of us here is the crater rim.

We're coming right up over it.

Oh, my God. I don't think I've ever approached a volcano

in quite this way before.

Look at this!

Look at that. There's a crater! Staring into the abyss.

That is just magnificent.

Very simple.

It's like your characteristic volcano, and yet it's not.

It's hiding this great secret.

The secret of Ol Doinyo Lengai may lie kilometres down,

but it can be uncovered by looking at some of its very odd lava.

To get my hands on some of it,

local Masai guides Rafael and Serengi lead me to a recent flow.

So, how many times have you been up to the top?

Times? 20. 20 times?

The same for you? Yeah, yeah.

So, do you worry it will erupt again? Yeah, we worry.

Eventually, we reach a patch of recent lava.

What a white wonderland! This is from the last eruption?

Within this flow lies the secret to Africa's future.

I want to get a sample. Really? Yeah, I got a hammer.

OK. Ta-da. Yeah!

I'm going to see if I can...

OK.

This lava contains evidence of two huge geological forces at work.

IAIN'S VOICE ECHOES: Carbon dioxide...

Releasing its clues involves some basic chemistry.

So, I want to...I want to show you how special these lavas are.

I'm just going to... crush them down a little bit.

Cos I'm going to do something that really only this lava can do.

For that I need some acid. This is weak...some dilute acid.

And what I'm going to do is I'm just going to pour it onto the rocks.

If I poured this on a normal lava, say a basalt,

then you'd just get no reaction.

But watch what happens when I put it on this lava.

Look at that. Isn't that amazing?

It's just foaming away, effervescing away.

And...

What's coming off here is carbon dioxide.

It's that carbon dioxide that's really important because,

as well as these lavas being rich in sodium and calcium and phosphorous,

all of the elements that make the Serengeti grasses so nutrient-rich,

it's also incredibly rich in carbon.

And it's an indication that there's something really mysterious

going on deep beneath this volcano.

So-called carbonatite lava like this

only forms when rocks rich in carbon

are melted at incredibly high pressure.

And there's only one place in the planet

where you find carbon-rich rock at high pressure.

And that's the same place that diamonds are formed...

..the base of cratons.

The magma that's feeding that volcano must be punching its way up

through one of the five deep-seated continental building blocks

that's formed the African landmass,

in this case, the incredibly thick and ancient Tanzanian Craton.

This part of Africa may have been stable for three billion years,

but now something is melting the rock beneath it.

The mere fact that magma's rising up

through the deepest and oldest landmass on the planet

means that beneath Ol Doinyo Lengai

there's an even more powerful force at work.

Deep below this part of Africa lies a giant rising mass of magma...

..a super-plume,

and for the last 45 million years,

this super-plume has been steadily forcing its way upwards.

It's not only melting the base of the ancient Tanzanian Craton,

it extends north over 1,000 kilometres across the continent...

..with spectacular results.

This super-plume beneath Africa and its surface volcanoes

have created the very DNA of this landscape.

Everything you see relates to that.

But in a way, the real impact of that super-plume has yet to be felt,

because beneath my feet there's a violent geological struggle going on.

It's one that began 25 million years ago...

..when the bulging super-plume beneath Africa

started to rip and tear the land above...

..creating a 6,000-kilometre scar

running half the length of eastern Africa.

There it is.

The Great African Rift.

The Great Rift Valley

is one of the most complex ecosystems on the planet...

..home to a staggering array of plant and animal life...

..as well as being the birthplace, of course, of our own species.

The Great African Rift Valley is not just

one of the most spectacular wildlife parks in the world,

it's also one of the most exciting geological places on the planet,

a huge crack in the Earth that runs the line of these cliffs

and is literally a tear in the fabric of this ancient land,

all of it caused by this super-plume

of molten rock puncturing its way up through the continent.

Now, here in Tanzania, we're at the southern tip of that tear,

but at the northern end of that tear,

the continent is already being ripped apart.

At the far end of the Rift,

Ethiopia's Danakil Depression is in the throes of violent change.

Great tears are growing in the fabric of the Earth...

..as the super-plume beneath

stretches and cracks the surface above...

..breaking through at volcanoes like Erte Ale.

The land here is so torn, it's sinking below sea level...

..leading scientists to predict

that the neighbouring Red Sea will one day flood this entire plain,

splitting the region in two.

So, the big question is, what's going to happen at the other end?

What we do know is that the split will start here in Ethiopia

and propagate through Kenya to the edge of the Tanzanian Craton.

It's here that it gets tricky. Some people argue

that it will cut right through the craton, splitting it in two,

but others argue that it will exploit weaknesses

to go around the edge of it, either this way or round here.

From there, it's possible that the split will follow

just the line of the rift, down to the ocean through Mozambique.

But some people argue that it'll actually swing to the west,

down in this way, cutting a swathe through southern Africa.

Whatever course it takes, one thing is virtually certain,

and that is that Africa, that most ancient of lands,

will one day break up.

For over three and half billion years, the African continent

has borne witness to the upheavals of our restless planet,

an epic journey that has shaped every aspect of life here today.

The creation of the very first land on Earth, the ancient cratons...

..that have left their legacy in the diamond mines of Sierra Leone.

These cratons, the stable heartlands of Africa...

..have seen the world around them rip and tear asunder

through the creation and destruction of the supercontinent Pangaea,

a series of violent upheavals

that have left their mark in the spectacular cliff of Victoria Falls.

They created the ancient seas that shaped our civilisations...

..and the creatures around us.

But now Africa's changing in other ways too,

because, economically, this is a continent on the rise,

on the cusp of dramatic cultural and social change.

The transformation that's taking place in African society

is echoed by an even bigger transformation

to the very fabric of the continent itself.

The immense geological forces that are at work beneath my feet

are preparing to redraw the African map, tearing it in two.

So, for all Africa's long, long history, this is, in every sense,

a continent that's in the process of being remoulded and reborn.