0:00:07 > 0:00:09This is what we go on, is it?
0:00:09 > 0:00:13This is one of those boats the locals used...long time back.
0:00:13 > 0:00:14Oh, dear.
0:00:14 > 0:00:16GRUNTS
0:00:17 > 0:00:21On 17th November 1855,
0:00:21 > 0:00:24on the banks of the Zambezi here in southern Africa,
0:00:24 > 0:00:27the Victorian missionary explorer David Livingstone
0:00:27 > 0:00:30stepped into a traditional dugout canoe, like this,
0:00:30 > 0:00:31and set off downstream.
0:00:31 > 0:00:33Right, let's go.
0:00:35 > 0:00:37What Livingstone stumbled upon that day
0:00:37 > 0:00:42would not only help put Africa on the map, it would also explain
0:00:42 > 0:00:45how this huge continent was created in the first place.
0:00:51 > 0:00:52In this series,
0:00:52 > 0:00:55I'm going to do something I've never really done before -
0:00:55 > 0:00:57search out the clues
0:00:57 > 0:01:01that take us back to the key moments in the story of each continent...
0:01:02 > 0:01:04LAUGHS
0:01:06 > 0:01:09..because the continents are constantly on the move...
0:01:12 > 0:01:16..and the traces of their secret past are hidden all around us...
0:01:16 > 0:01:18HISSES
0:01:18 > 0:01:22..in the Earth's rocks, but also in its landscapes...
0:01:22 > 0:01:24That is very spectacular.
0:01:25 > 0:01:27..and even its wildlife.
0:01:27 > 0:01:29It's moving.
0:01:30 > 0:01:34The tiniest detail can reveal the history of a vast continent.
0:01:37 > 0:01:42I'm beginning in Africa, the most ancient continent...
0:01:42 > 0:01:43LAUGHTER
0:01:44 > 0:01:45ROARS
0:01:45 > 0:01:50..and discovering the main turning points that forged this land...
0:01:50 > 0:01:53They're just all around us, aren't they?
0:01:53 > 0:01:56..creating its wealth, fuelling its wars,
0:01:56 > 0:01:59shaping its ancient civilisations...
0:02:01 > 0:02:05..and seeing how events deep in Africa's past
0:02:05 > 0:02:07have influenced the whole planet.
0:02:09 > 0:02:15But Africa now stands on the threshold of a spectacular change,
0:02:15 > 0:02:17as the immense forces that shaped this continent
0:02:17 > 0:02:20now threaten to bring about its destruction.
0:02:46 > 0:02:49The discovery of Africa's deepest origins
0:02:49 > 0:02:54started with Livingstone's fateful expedition 150 years ago.
0:02:54 > 0:02:58As he made his way down the Zambezi river,
0:02:58 > 0:03:01Livingstone found his progress suddenly interrupted
0:03:01 > 0:03:03by a strange sight...
0:03:07 > 0:03:12..a huge curtain of mist rising up from the river ahead...
0:03:14 > 0:03:18..accompanied by a steadily increasing roar.
0:03:20 > 0:03:22Right.
0:03:23 > 0:03:28Leaving his team behind, for fear of putting them in danger,
0:03:28 > 0:03:32the explorer continued his journey on foot...
0:03:35 > 0:03:40..only to find his way blocked by the most impenetrable of all obstacles...
0:03:50 > 0:03:54..known to the locals as Mosi oa Tunya -
0:03:54 > 0:03:57"the smoke that thunders".
0:03:59 > 0:04:02We, of course, know it as the Victoria Falls.
0:04:07 > 0:04:10And the ultimate way to experience the Falls
0:04:10 > 0:04:13involves getting your feet wet.
0:04:19 > 0:04:21Ah!
0:04:22 > 0:04:24Oh, dear!
0:04:31 > 0:04:33LAUGHS
0:04:35 > 0:04:38This is the way to see the Victoria Falls.
0:04:39 > 0:04:41Oh, my God!
0:04:41 > 0:04:43Aah!
0:04:49 > 0:04:51While the water around me
0:04:51 > 0:04:55cascades down more than 100 metres to the river below...
0:04:57 > 0:04:59..this pool forms a hidden sanctuary.
0:05:10 > 0:05:12Livingstone thought the Falls so lovely,
0:05:12 > 0:05:16they must have been gazed upon by angels in their flight.
0:05:19 > 0:05:22Staring down at this precarious drop,
0:05:22 > 0:05:25it's not hard to see how Livingstone was completely bowled over
0:05:25 > 0:05:28by the scale, the grandeur and beauty of the Falls.
0:05:28 > 0:05:30But what he had no way of knowing
0:05:30 > 0:05:36was how this feature has got huge geological significance.
0:05:42 > 0:05:46But to appreciate that significance,
0:05:46 > 0:05:49we need to go back some 200 million years.
0:05:56 > 0:05:58The Earth looked very different.
0:05:59 > 0:06:04All the continents were clumped together into one enormous landmass,
0:06:04 > 0:06:07a supercontinent called Pangaea.
0:06:08 > 0:06:10It was a land of extremes...
0:06:12 > 0:06:16..an enormous mountain range higher and longer than the Himalayas...
0:06:18 > 0:06:20..and an interior covered in a vast desert
0:06:20 > 0:06:23five times the size of the Sahara.
0:06:26 > 0:06:28Victoria Falls can tell us
0:06:28 > 0:06:32how Africa was carved out from the heart of that great supercontinent.
0:06:41 > 0:06:46You can see exactly what happened here 180 million years ago
0:06:46 > 0:06:49by looking in the vast gorge beneath the Falls.
0:06:51 > 0:06:55Because hidden in the rocks is some intriguing evidence
0:06:55 > 0:06:57of a cataclysmic geological event
0:06:57 > 0:07:02that would create Africa as we know it today.
0:07:09 > 0:07:13What a place! It's like a... an amphitheatre of rock.
0:07:13 > 0:07:16The thing is, all these cliffs are carved from the same rock,
0:07:16 > 0:07:17a rock called basalt,
0:07:17 > 0:07:20and it comes to us from deep underground,
0:07:20 > 0:07:22rising up as molten magma.
0:07:22 > 0:07:25To appreciate basalt, to understand what it's trying to tell us,
0:07:25 > 0:07:27you have to get inside it, though.
0:07:30 > 0:07:34In here are the secrets of its formation.
0:07:36 > 0:07:38These crystals...
0:07:38 > 0:07:40cooled really rapidly.
0:07:42 > 0:07:45You see there's a...there's a slight speckled appearance,
0:07:45 > 0:07:48which, if you look with a hand lens,
0:07:48 > 0:07:53you can see is lots and lots of tiny, tiny crystals.
0:07:54 > 0:07:56These crystals were formed as the hot rock cooled,
0:07:56 > 0:08:00and their size tells you how quickly it happened.
0:08:00 > 0:08:01So, what this is telling us, really,
0:08:01 > 0:08:04is that this rock must have cooled really rapidly.
0:08:05 > 0:08:08Sudden cooling of searing-hot magma
0:08:08 > 0:08:10means crystals don't have time to grow,
0:08:10 > 0:08:13which is why they're so small.
0:08:14 > 0:08:16And one way to rapidly cool a rock like basalt
0:08:16 > 0:08:18is to erupt it from the surface,
0:08:18 > 0:08:20expose it to the air,
0:08:20 > 0:08:23and it just solidifies very quickly before the crystals can grow.
0:08:26 > 0:08:28So, all of these rocks here,
0:08:28 > 0:08:30all these basalts were erupted out as lava flows.
0:08:31 > 0:08:36Lava flows that reveal their size in the soaring cliffs.
0:08:38 > 0:08:40What takes your breath away here
0:08:40 > 0:08:42is just the sheer scale of the eruptions.
0:08:42 > 0:08:45I mean, that cliff there is 120 metres high,
0:08:45 > 0:08:48and it's just layer upon layer upon layer of lava flows.
0:08:48 > 0:08:52And the thing is, that continues down underneath for hundreds of metres.
0:08:54 > 0:08:58I mean, across this region, it's thought that over a kilometre of lava
0:08:58 > 0:09:01was erupted out in a million years or so.
0:09:01 > 0:09:05It must have been the most staggering volcanic event.
0:09:20 > 0:09:23These eruptions were the start of an immensely destructive event
0:09:23 > 0:09:26that happens only rarely in the Earth's history.
0:09:27 > 0:09:30They would have stretched for thousands of kilometres,
0:09:30 > 0:09:33burying huge swathes of what was to become Africa
0:09:33 > 0:09:37under millions of cubic kilometres of molten lava.
0:09:49 > 0:09:54The cause of this mayhem was one of the Earth's most powerful forces...
0:09:56 > 0:10:01..huge upwellings of superheated rock called a mantle plume.
0:10:05 > 0:10:07The sheer force of those mantle plumes,
0:10:07 > 0:10:09making their way towards the surface,
0:10:09 > 0:10:13pushed the land up, causing it to thin and crack,
0:10:13 > 0:10:15cracks which eventually got so big
0:10:15 > 0:10:18that the land slowly began to fragment,
0:10:18 > 0:10:20so beginning the break-up
0:10:20 > 0:10:24of the single largest landmass the Earth had ever seen.
0:10:24 > 0:10:25Pangaea.
0:10:28 > 0:10:32As the supercontinent began to split apart,
0:10:32 > 0:10:37one by one, the Earth's continents were torn from its outer edges.
0:10:39 > 0:10:42The eruptions at Victoria Falls
0:10:42 > 0:10:45led to the formation of India and Antarctica.
0:10:45 > 0:10:50Another mantle plume cleaved off North America, then South America,
0:10:50 > 0:10:54leaving behind Africa as we know it today.
0:11:02 > 0:11:06The break-up of Pangaea meant that for the first time in its history,
0:11:06 > 0:11:07Africa stood alone,
0:11:07 > 0:11:10a continent in its own right.
0:11:10 > 0:11:12And for the next hundred million years or so
0:11:12 > 0:11:17that newfound isolation would transform Africa beyond recognition,
0:11:17 > 0:11:21its landscape, its climate, but also its wildlife.
0:11:21 > 0:11:23It forced animals to adapt
0:11:23 > 0:11:26to a myriad of different complex environments.
0:11:26 > 0:11:29And to my mind, the most remarkable of all those adaptations
0:11:29 > 0:11:33didn't happen here on land, but just out to sea.
0:11:45 > 0:11:50The coast of Africa, carved out 180 million years ago,
0:11:50 > 0:11:53is today home to a wealth of life.
0:11:58 > 0:12:02Perhaps most spectacular of all are whales.
0:12:02 > 0:12:04WHALESONG
0:12:09 > 0:12:14Today these ocean giants are undoubtedly the kings of the sea.
0:12:14 > 0:12:16(WHALESONG)
0:12:22 > 0:12:25But look far enough back in time
0:12:25 > 0:12:28and we find the evolution of these giant animals
0:12:28 > 0:12:32is a direct consequence of the cataclysmic events
0:12:32 > 0:12:36that gave birth to the African continent.
0:12:43 > 0:12:45The first piece of evidence
0:12:45 > 0:12:48can be found at another of Africa's most famous sites.
0:13:07 > 0:13:11Welcome to morning rush hour in Cairo, Egypt,
0:13:11 > 0:13:13the biggest city in the African continent.
0:13:13 > 0:13:16This is a place that's been undergoing
0:13:16 > 0:13:19really dramatic political change in recent times.
0:13:19 > 0:13:21Now, geologically, it's long been stable,
0:13:21 > 0:13:23but 100 million years ago,
0:13:23 > 0:13:27it underwent the most colossal geological transformation.
0:13:27 > 0:13:33A change driven by the same event which gave us the Victoria Falls.
0:13:36 > 0:13:39And some tiny remnants of this transformation
0:13:39 > 0:13:40can still be seen today
0:13:40 > 0:13:44amongst the ruins of Egypt's most famous landmark.
0:13:49 > 0:13:51The pyramids of Giza.
0:14:02 > 0:14:05You get little hints there.
0:14:07 > 0:14:09Nothing really good.
0:14:09 > 0:14:12There must be something better than...
0:14:12 > 0:14:15The trouble with this face is it's been dressed by the stonemasons.
0:14:15 > 0:14:18You've got all these chisel marks. You just can't see anything.
0:14:18 > 0:14:19How frustrating!
0:14:24 > 0:14:29Ah, now, this...this is more like it. That's what I'm looking for.
0:14:30 > 0:14:32VOICE ECHOES: Creamy-coloured discs...
0:14:35 > 0:14:37Every whale in the ocean...
0:14:43 > 0:14:48These features have intrigued and confused people for centuries.
0:14:48 > 0:14:50The Greek historian Herodotus reckoned that they were...
0:14:50 > 0:14:53they were the petrified remains of lentils
0:14:53 > 0:14:57that the pharaoh gave the slaves that built this monument.
0:14:57 > 0:15:00But the truth's actually far more bizarre, far more interesting.
0:15:00 > 0:15:02If Herodotus had one of these, a hand lens,
0:15:02 > 0:15:04he might have made a different interpretation,
0:15:04 > 0:15:06because the surface of these,
0:15:06 > 0:15:09they've got these exquisite whirls and swirls.
0:15:11 > 0:15:14They're clearly something that's living.
0:15:14 > 0:15:16These are actually nummulites.
0:15:16 > 0:15:18They're the shells, really,
0:15:18 > 0:15:23of the very largest single-celled marine organism that's ever lived.
0:15:28 > 0:15:32These nummulites can tell us
0:15:32 > 0:15:35what the seas in which they lived would have been like...
0:15:41 > 0:15:43..because from chemical analysis of their shells
0:15:43 > 0:15:46we know that these nummulites shared their homes
0:15:46 > 0:15:50with millions of photosynthesising microbes...
0:15:52 > 0:15:56..creatures requiring an abundant source of sunlight.
0:16:01 > 0:16:06And that means that the seas in which these nummulites once lived...
0:16:07 > 0:16:10..must have been extremely shallow.
0:16:11 > 0:16:13So, why is that important?
0:16:13 > 0:16:17Well, it's because every single block in this entire site
0:16:17 > 0:16:20has been quarried from just a short distance from here.
0:16:20 > 0:16:24In other words, those shallow seas, that the nummulites lived in,
0:16:24 > 0:16:26were right here.
0:16:36 > 0:16:39100 million years ago, something happened,
0:16:39 > 0:16:42something connected with the birth of the African continent,
0:16:42 > 0:16:45to transform much of northern Africa
0:16:45 > 0:16:49into a shallow sea, teeming with life.
0:16:57 > 0:17:01As the great supercontinent of Pangaea broke up...
0:17:04 > 0:17:08..so the rising molten magma beneath its surface
0:17:08 > 0:17:12threw up a chain of underwater volcanic mountains.
0:17:17 > 0:17:22These displaced enormous volumes of water,
0:17:22 > 0:17:27contributing to a staggering 300-metre rise in sea levels
0:17:27 > 0:17:32that not only swamped much of the North African coast,
0:17:32 > 0:17:35it even split the newly formed continent in two.
0:17:42 > 0:17:46And it was this transformation of the landscape
0:17:46 > 0:17:52that was to lead to the evolution of that most spectacular of mammals...
0:17:54 > 0:17:56..the whale.
0:18:04 > 0:18:09To discover how, I've come to Egypt's Western Desert...
0:18:12 > 0:18:14..home to a remote valley
0:18:14 > 0:18:19of sandstone cliffs and wind-carved rocks called Wadi al-Hitan...
0:18:22 > 0:18:23Echo!
0:18:23 > 0:18:25ECHOING
0:18:25 > 0:18:28..that once used to be full of marine life.
0:18:32 > 0:18:34ECHOING VOICE This sculpture underneath rocks...
0:18:34 > 0:18:39'Palaeontologist Charlie Underwood has spent the past four years
0:18:39 > 0:18:42'studying this long-lost seascape.'
0:18:46 > 0:18:48Here's just quite a nice place to show
0:18:48 > 0:18:50what the sea floor was really like at the time.
0:18:50 > 0:18:53- Right.- Really...
0:18:53 > 0:18:54Oh, wow. Yeah.
0:18:54 > 0:18:57- Yeah, you see, if you get up here...- Yeah.
0:18:57 > 0:18:59These are incredible. These tubes are burrows, are they?
0:18:59 > 0:19:03Yeah, so we've got... This is essentially an ancient sea floor,
0:19:03 > 0:19:06and these are the burrows of the various animals
0:19:06 > 0:19:09that were burrowing into this. Shrimps. Small lobsters. Crabs.
0:19:11 > 0:19:17'The closer you look, the more this aquatic landscape comes to life.'
0:19:18 > 0:19:21I can see a snail. There's a little gastropod shell.
0:19:21 > 0:19:22- Just in here.- Yeah.
0:19:22 > 0:19:25There's the small tooth of a lemon shark.
0:19:25 > 0:19:26You've trumped me.
0:19:26 > 0:19:28That's lovely.
0:19:28 > 0:19:30So sharp.
0:19:31 > 0:19:35- There's a small nummulite. - Ah, yes. Saw these in Giza.
0:19:37 > 0:19:41Fairly small ones here, but they really show this is shallow water.
0:19:41 > 0:19:43Yeah.
0:19:43 > 0:19:47Beautiful way they get sculpted by sandblasting.
0:19:47 > 0:19:51'But it's the discovery of some other, much larger marine fossils
0:19:51 > 0:19:54'that has made this valley such a focal point
0:19:54 > 0:19:57'for scientists trying to piece together the story of whales.'
0:19:59 > 0:20:00Look at this.
0:20:00 > 0:20:03- Yeah. Amazing, isn't it? - What a size!
0:20:03 > 0:20:05Yeah, it's impressive, isn't it?
0:20:05 > 0:20:08- What is this, then? - This is a thing called basilosaurus.
0:20:08 > 0:20:11Basilosaurus. What a fantastic name!
0:20:11 > 0:20:12'Since 1983,
0:20:12 > 0:20:17'scientists have uncovered the remains of around 300 skeletons
0:20:17 > 0:20:22'belonging to a very early type of whale, basilosaurus.'
0:20:31 > 0:20:33So, how long were they, then?
0:20:33 > 0:20:37A big one of these could well be something like 15 metres.
0:20:37 > 0:20:40The tail is sort of going off in that direction,
0:20:40 > 0:20:43but the head is sort of going off into the cliff.
0:20:44 > 0:20:47- Do you think the head'll still be here?- It may well be.
0:20:47 > 0:20:49You can just see...
0:20:49 > 0:20:53'And what's so special about basilosaurus are the various features
0:20:53 > 0:20:57'that reveal what these very early whales evolved from.'
0:20:59 > 0:21:02- There we are, look.- What's this?
0:21:02 > 0:21:03There's a tooth starting to come out.
0:21:03 > 0:21:05Oh, that's great.
0:21:05 > 0:21:07That's fantastic.
0:21:07 > 0:21:10- They're very sharp. - This is a tooth for cutting.
0:21:10 > 0:21:12This isn't a tooth just for gripping small fish,
0:21:12 > 0:21:15like those little conical teeth of a dolphin.
0:21:15 > 0:21:18- Yeah.- These are for grabbing a big animal,
0:21:18 > 0:21:21killing it, cutting it up, swallowing the bits.
0:21:21 > 0:21:23Basil was a bit of a fearsome thing.
0:21:23 > 0:21:26In what other ways is this creature different?
0:21:26 > 0:21:29Just in...in many ways. This weird mix of features.
0:21:29 > 0:21:32- Small back legs.- Back legs?- Yeah.
0:21:32 > 0:21:35- These early whales had back legs?- Yeah.
0:21:35 > 0:21:38No use for walking. They're much too small for that.
0:21:38 > 0:21:39But all the bones are there.
0:21:39 > 0:21:42WHALESONG
0:21:42 > 0:21:46Little pores around the jaw that suggest maybe it had whiskers.
0:21:46 > 0:21:48- Whiskers?- Yeah.
0:21:48 > 0:21:51Its nostrils aren't quite in the position of those of a whale,
0:21:51 > 0:21:52with a blowhole.
0:21:55 > 0:21:58A list of features that places basilosaurus
0:21:58 > 0:22:02at almost the midway point, in evolutionary terms,
0:22:02 > 0:22:06between a modern whale and a four-legged land mammal.
0:22:09 > 0:22:13What kind of animal are we talking about for what they came from?
0:22:13 > 0:22:16If this is a transition, what did they come from?
0:22:16 > 0:22:19Well, the closest living relative of whales
0:22:19 > 0:22:21are actually some of the hoofed animals.
0:22:21 > 0:22:25- Right.- Things like pigs, hippos, even antelope.
0:22:25 > 0:22:27But, unlike modern hoofed animals,
0:22:27 > 0:22:28the ancestors of these were carnivorous.
0:22:33 > 0:22:37The shallow seas that formed here would have offered rich pickings
0:22:37 > 0:22:41to tempt the carnivorous animals living along its shores
0:22:41 > 0:22:42into the water...
0:22:45 > 0:22:49..over time losing their connection with the land completely,
0:22:49 > 0:22:52to evolve into whales.
0:22:54 > 0:22:58The fossils here at Wadi al-Hitan are just spectacular.
0:22:58 > 0:23:01And they prove that around 50 million years ago,
0:23:01 > 0:23:04a small group of four-legged mammals made this extraordinary leap,
0:23:04 > 0:23:10going from living on the land to a completely sea-based existence.
0:23:10 > 0:23:13It was an incredible evolutionary U-turn
0:23:13 > 0:23:16that led to every whale in the ocean,
0:23:16 > 0:23:19and it was the direct result of the break-up of Pangaea
0:23:19 > 0:23:22and the birth of the African continent.
0:23:45 > 0:23:50By 30 million years ago, sea levels dropped, the seas dried out,
0:23:50 > 0:23:52and the familiar outline
0:23:52 > 0:23:56of the Africa we know today finally emerged.
0:24:02 > 0:24:04The break-up of Pangaea
0:24:04 > 0:24:08explains how Africa emerged from the wreckage of the supercontinent.
0:24:11 > 0:24:14The next critical moment in Africa's story
0:24:14 > 0:24:17doesn't take us further forward in time,
0:24:17 > 0:24:21it takes us back into an even more distant past...
0:24:24 > 0:24:27..back to an extraordinary sequence of events
0:24:27 > 0:24:29early in the Earth's history.
0:24:31 > 0:24:34These deep origins help explain the formation
0:24:34 > 0:24:38of some of Africa's most iconic landscapes,
0:24:38 > 0:24:42and they also explain one of the great puzzles about the Earth -
0:24:42 > 0:24:45why the continents move at all.
0:24:49 > 0:24:54The clue that solves these mysteries is found in Sierra Leone.
0:24:56 > 0:25:00I've come to the large market town of Kenema...
0:25:02 > 0:25:04- Hello! Hello!- Hello!
0:25:06 > 0:25:08..a busy commercial hub
0:25:08 > 0:25:11of over 100,000 people.
0:25:14 > 0:25:17Everywhere you look, people are selling stuff.
0:25:17 > 0:25:19Like, this is obviously vegetables.
0:25:20 > 0:25:23Hi! What are these called?
0:25:23 > 0:25:25What are these...? Oh, these are okra.
0:25:30 > 0:25:32There's some, er, beauty products here.
0:25:34 > 0:25:38This market is kicking. It's really got a lot of energy to it.
0:25:40 > 0:25:43You know, it's strange, you say Sierra Leone
0:25:43 > 0:25:47and you immediately think of that civil war ten years ago
0:25:47 > 0:25:48and all those horrific pictures
0:25:48 > 0:25:51that you were getting nightly on the television.
0:25:51 > 0:25:55And yet, when you come here, it's just completely different. Hi!
0:26:00 > 0:26:01It's such a great place,
0:26:01 > 0:26:05but there's one commodity that really fuels the economy round here,
0:26:05 > 0:26:07but you won't find it in this market.
0:26:09 > 0:26:10A commodity that can tell us
0:26:10 > 0:26:14what this part of Africa was like billions of year ago,
0:26:14 > 0:26:16long before Pangaea.
0:26:29 > 0:26:32'About 30 kilometres outside Kenema...'
0:26:32 > 0:26:34This is one of the pits.
0:26:34 > 0:26:37'..lies a cluster of steep-sided sandy pits...
0:26:39 > 0:26:41'..called Jah Kingdom.'
0:26:46 > 0:26:48Look at that.
0:27:07 > 0:27:11Three-quarters of working-age men in the area work in pits like these...
0:27:13 > 0:27:17..digging their way through the deep sand of an ancient river bed,
0:27:17 > 0:27:24to uncover a layer of gravel scattered with precious raw diamonds.
0:27:26 > 0:27:28What you don't appreciate till you're actually here
0:27:28 > 0:27:30is the amount of material they have to remove
0:27:30 > 0:27:35just to get at the diamond-bearing gravels which are underneath here.
0:27:35 > 0:27:38- How much time to dig down? - A month. More than a month.
0:27:38 > 0:27:41Just to get through all of the sediments that don't have diamonds
0:27:41 > 0:27:45- to get down to the ones underneath here that do.- Yes, sir.- It's amazing.
0:27:54 > 0:27:56During Sierra Leone's civil war,
0:27:56 > 0:27:59these diamond fields were bitterly fought over.
0:27:59 > 0:28:01Now the war's over,
0:28:01 > 0:28:03but the work of finding diamonds amongst the gravel
0:28:03 > 0:28:08still relies on the same simple technique today as it always has.
0:28:16 > 0:28:19What's happening here is the diamonds are really dense, quite heavy,
0:28:19 > 0:28:22so they...they kind of sink down,
0:28:22 > 0:28:27and you find it glinting in amongst all those dark stones there.
0:28:31 > 0:28:33Nothing. Nothing.
0:28:35 > 0:28:39What happens when someone finds a diamond? Does everyone go shout?
0:28:39 > 0:28:41And...is there lots of noise?
0:28:41 > 0:28:44- You keep cool.- Keep cool?- Yes.
0:28:44 > 0:28:46Say, "I have a diamond, I have a diamond"? No, no, no.
0:28:46 > 0:28:50- Just keep quiet. Cool. - Be discretional. A precious stone.
0:28:56 > 0:28:59For the lucky few, their hard work will pay off,
0:28:59 > 0:29:05as very occasionally a diamond is discovered lying amongst the gravel.
0:29:12 > 0:29:16This is what it's all about, a raw, natural diamond.
0:29:16 > 0:29:18This is what everyone's looking for.
0:29:20 > 0:29:24For the guys around here, this is about a month's salary.
0:29:24 > 0:29:25And for the jeweller that buys it
0:29:25 > 0:29:28and fashions it into something like an engagement ring,
0:29:28 > 0:29:30it's probably several hundred dollars' worth here.
0:29:30 > 0:29:32But for a geologist... I don't know,
0:29:32 > 0:29:35I think it's even more valuable, even more beautiful,
0:29:35 > 0:29:38because it's a window back in time.
0:29:38 > 0:29:42It takes us back right to the birth of the very first continents.
0:29:44 > 0:29:47This diamond contains within it
0:29:47 > 0:29:51the secret of the earliest origins of this part of Africa.
0:29:53 > 0:29:56IAIN'S VOICE ECHOES: Carbon atoms...
0:29:56 > 0:29:58compression and temperature...
0:30:01 > 0:30:03If you could see deep into this diamond,
0:30:03 > 0:30:08what you'd find are carbon atoms that are really tightly bonded together
0:30:08 > 0:30:11and arranged into a kind of pyramid shape, and that arrangement
0:30:11 > 0:30:15is because of the intense pressures that form the diamond,
0:30:15 > 0:30:17something like 50,000 atmospheres.
0:30:18 > 0:30:23The only place we know of where you can find that kind of pressure
0:30:23 > 0:30:26is 150 kilometres below the Earth's surface,
0:30:26 > 0:30:30within an exceptionally hot layer of rock known as the mantle.
0:30:33 > 0:30:36But to form diamonds' distinctive arrangement of carbon atoms
0:30:36 > 0:30:42also requires very specific temperatures, about 1,100 degrees.
0:30:42 > 0:30:45And that's really odd, that, because the Earth's mantle
0:30:45 > 0:30:47has got temperatures that are much higher than that.
0:30:50 > 0:30:52Temperatures over 1,600 degrees.
0:30:55 > 0:30:57So, to explain diamond formation,
0:30:57 > 0:31:01you need to find a place that's over 150 kilometres deep
0:31:01 > 0:31:06to give the right pressure, but not a part of the normal mantle...
0:31:08 > 0:31:11..because this mantle is too hot.
0:31:11 > 0:31:12The only place on the planet
0:31:12 > 0:31:15that's got the right pressure, right temperature,
0:31:15 > 0:31:19is at the base of huge slabs of continental rock
0:31:19 > 0:31:21that extend way down into the mantle.
0:31:22 > 0:31:25Those slabs are called cratons.
0:31:28 > 0:31:31Cratons are incredibly thick pieces of solid rock
0:31:31 > 0:31:34that extend deep beneath the Earth's crust.
0:31:42 > 0:31:44But because of Earth's solidity,
0:31:44 > 0:31:48a craton is much cooler than the surrounding mantle...
0:31:49 > 0:31:52..which means the bottom of a craton
0:31:52 > 0:31:56has the perfect conditions in which to form diamonds.
0:31:59 > 0:32:02The diamonds here found their way to the surface
0:32:02 > 0:32:04in ancient volcanic eruptions,
0:32:04 > 0:32:07and they tell us something remarkable about Africa's past.
0:32:10 > 0:32:14Radio isotope dating of diamonds show that they're billions of years old.
0:32:14 > 0:32:17I mean, this one's probably nearly three billion years old,
0:32:17 > 0:32:20but some of them go back to three and a half.
0:32:20 > 0:32:21What this means,
0:32:21 > 0:32:25what the very existence of this diamond here reveals,
0:32:25 > 0:32:29is that I'm standing on top of an ancient craton,
0:32:29 > 0:32:33a piece of land that formed nearly three billion years ago.
0:32:36 > 0:32:39It's called the West African Craton.
0:32:40 > 0:32:44It's one of the very oldest pieces of land on Earth.
0:32:48 > 0:32:51But it's not the only craton in Africa.
0:32:51 > 0:32:53There are five of these ancient building blocks,
0:32:53 > 0:32:56each forming a distinctive landscape.
0:32:58 > 0:33:01In the south lies the Kalahari Craton,
0:33:01 > 0:33:04that lies beneath most of southern Africa.
0:33:07 > 0:33:11To the east lies the Congo Craton,
0:33:11 > 0:33:14which today forms one of the greatest river basins on Earth.
0:33:17 > 0:33:22Further north beneath the Sahara lies another of these ancient landmasses.
0:33:27 > 0:33:31The cratons were formed at a time when the Earth was in its infancy.
0:33:38 > 0:33:42Three billion years ago, the Earth looked very different to today.
0:33:43 > 0:33:46The only landmasses were the cratons,
0:33:46 > 0:33:49and unlike the continents today, they didn't move.
0:33:49 > 0:33:52They were static islands in one giant ocean.
0:33:54 > 0:33:57Because they're so ancient, the cratons have preserved evidence
0:33:57 > 0:34:01that solves one of the great mysteries about the continents -
0:34:01 > 0:34:04when and why they first began to move.
0:34:06 > 0:34:08Without this momentous event,
0:34:08 > 0:34:11there would have been no Pangaea and no Africa.
0:34:14 > 0:34:18The evidence for why the Earth's crust began to move
0:34:18 > 0:34:20lies hidden inside Africa's diamonds.
0:34:33 > 0:34:36This is the Government Gold And Diamond Office,
0:34:36 > 0:34:39where a team of highly trained valuers
0:34:39 > 0:34:44are examining diamonds from the mines all over Sierra Leone.
0:34:45 > 0:34:48It's a process few outsiders ever get to see.
0:34:54 > 0:34:56So, how do you do the process?
0:34:56 > 0:34:59Say, if you get a pile of diamonds, where do you start?
0:34:59 > 0:35:03Here we look for the shape, the size, the clarity and the colour.
0:35:05 > 0:35:09So, what is...? I see a big one here! What is the size of that one?
0:35:09 > 0:35:12Like, this stone here... is a 20-carat stone.
0:35:12 > 0:35:15So, what would that be worth?
0:35:15 > 0:35:17Well, it depends on the quality.
0:35:17 > 0:35:21Now, I have looked at this stone, and there's no inclusion inside,
0:35:21 > 0:35:24- meaning blemishes inside or outside.- Right.
0:35:24 > 0:35:27Or inclusions that would be inside the stone.
0:35:27 > 0:35:31The shape is not so good. But the colour is excellent.
0:35:31 > 0:35:35So, this kind of stone would normally be about 15,000 a carat.
0:35:35 > 0:35:39- So, multiplied by 20?- Yes.
0:35:39 > 0:35:42- 300,000.- 300,000 stone, yes.
0:35:42 > 0:35:43- In the rough.- That's quite nice.
0:35:43 > 0:35:47So you're looking for ones that are perfect, without any flaws, ideally.
0:35:47 > 0:35:51- Without...ideally, no flaws at all. No flaws.- Right.
0:35:53 > 0:35:56But it's the diamonds with the flaws, or inclusions,
0:35:56 > 0:35:58that I've come here to see.
0:35:59 > 0:36:02IAIN'S VOICE ECHOES: Pyroxene and olivine...
0:36:03 > 0:36:06Diamonds like these, that contain inclusions,
0:36:06 > 0:36:09provide the perfect portal for geologists,
0:36:09 > 0:36:11because hidden in each of these is a clue
0:36:11 > 0:36:15to probably the biggest geological change in the planet's history.
0:36:17 > 0:36:20One that explains how three billion years ago
0:36:20 > 0:36:25the isolated cratons came together to form the first continents.
0:36:26 > 0:36:28Inside every one of these
0:36:28 > 0:36:32is a fragment of the rock that was around the diamond when it formed.
0:36:35 > 0:36:38A fragment from the base of the craton
0:36:38 > 0:36:43150 kilometres beneath the Earth's surface.
0:36:47 > 0:36:53And the key is a change in the sort of rock that's found down there.
0:36:54 > 0:36:57You see, diamonds that are older than 3.2 billion years
0:36:57 > 0:37:03contain minerals like pyroxene and olivine.
0:37:04 > 0:37:08Olivine is typical of the rock normally found underneath cratons.
0:37:10 > 0:37:12But from three billion years onwards,
0:37:12 > 0:37:15there's a strange change in the composition of these inclusions
0:37:15 > 0:37:21to include fragments of a garnet-rich rock called eclogite.
0:37:21 > 0:37:24Eclogite isn't normally found where diamonds are made,
0:37:24 > 0:37:26deep in the base of the cratons.
0:37:27 > 0:37:30It comes from much higher up,
0:37:30 > 0:37:34from the rock that forms the ocean floor, the oceanic crust.
0:37:38 > 0:37:39What's intriguing is,
0:37:39 > 0:37:43why did bits of oceanic crust end up beneath Earth's cratons
0:37:43 > 0:37:46from three billion years onwards?
0:37:46 > 0:37:49The answer turns out to be pretty simple, and that's because
0:37:49 > 0:37:52these tiny differences in the inclusions in the diamonds
0:37:52 > 0:37:57allow scientists to precisely date when rafts of oceanic crust
0:37:57 > 0:38:00first began to be forced underneath continental crust.
0:38:00 > 0:38:04It was a crucial turning point in the mechanics of the Earth.
0:38:04 > 0:38:05RUMBLING
0:38:08 > 0:38:11Three billion years ago, the dense rock of the ocean floor
0:38:11 > 0:38:14began to sink down beneath the cratons...
0:38:16 > 0:38:18..a process called subduction.
0:38:22 > 0:38:25This sinking conveyor belt of rock
0:38:25 > 0:38:28had a dramatic effect on the land above,
0:38:28 > 0:38:31dragging the cratons together.
0:38:38 > 0:38:39It was this process
0:38:39 > 0:38:44that would eventually create the African continent we see today.
0:38:48 > 0:38:51Driven by subduction, the Earth's cratons,
0:38:51 > 0:38:54which up until this point in time had been relatively static,
0:38:54 > 0:38:56began to move.
0:38:56 > 0:38:59So starting an epic geological cycle,
0:38:59 > 0:39:03with cratons coming together and separating,
0:39:03 > 0:39:07to create and destroy a series of long-lost continents...
0:39:10 > 0:39:14..until finally, 550 million years ago,
0:39:14 > 0:39:19subduction brought the five cratons that make up Africa together,
0:39:19 > 0:39:23part of an even bigger continent called Gondwana.
0:39:24 > 0:39:27In the half a billion years since,
0:39:27 > 0:39:30the planet has seen extraordinary change,
0:39:30 > 0:39:32the creation of Pangaea
0:39:32 > 0:39:36and, 100 million years later, its violent destruction.
0:39:39 > 0:39:42But Africa's cratons have stayed together...
0:39:44 > 0:39:46..ancient, stable and solid...
0:39:47 > 0:39:49..until now.
0:39:52 > 0:39:55Because, after half a billion years of stability,
0:39:55 > 0:39:59the long history of this African land is coming to an end.
0:40:01 > 0:40:04Beneath the surface, there's a destructive force
0:40:04 > 0:40:07that now threatens to break up the entire continent.
0:40:10 > 0:40:12A clue to what's happening
0:40:12 > 0:40:17can be seen in how it's shaped life here in the Serengeti.
0:40:17 > 0:40:19For the final chapter in our story of Africa,
0:40:19 > 0:40:22we've come here to the plains of northern Tanzania,
0:40:22 > 0:40:26to see an animal that's synonymous with this part of the continent.
0:40:29 > 0:40:34An animal with one of the most spectacular migrations on the planet.
0:40:50 > 0:40:53This is the largest concentration of grazing animals
0:40:53 > 0:40:55to be found anywhere on Earth.
0:41:03 > 0:41:07A massed gathering of herbivores...
0:41:09 > 0:41:11They're just all around us, aren't they?
0:41:11 > 0:41:14..that owe their very existence
0:41:14 > 0:41:17to a geological struggle going on beneath their feet.
0:41:21 > 0:41:24This is what we've come to see. Wildebeest.
0:41:24 > 0:41:26Some of them will start heading to the north...
0:41:26 > 0:41:29Mm-hm.
0:41:29 > 0:41:31..to an area which is up on our left side here.
0:41:31 > 0:41:35This annual migration of between one and two million wildebeest
0:41:35 > 0:41:38is one of the great animal movements on this planet,
0:41:38 > 0:41:40and here we are right in the middle of it.
0:41:42 > 0:41:44But look closely, though,
0:41:44 > 0:41:47and something rather odd about these animals jumps out at you.
0:41:49 > 0:41:53It's interesting, all the calves are exactly the same size.
0:41:54 > 0:41:56So, how old are they, then?
0:41:56 > 0:41:58They have... They were born in February
0:41:58 > 0:42:02so up till now they have three and a half to four months.
0:42:02 > 0:42:03So, in February,
0:42:03 > 0:42:07that's the time they deliver their babies at once, all of them.
0:42:07 > 0:42:08That must be an incredible period,
0:42:08 > 0:42:11- because just in those few short weeks...- Sure, sure, sure.
0:42:11 > 0:42:15- ..you're getting hundreds of thousands of calves being born.- Yeah.
0:42:16 > 0:42:18Hundreds of thousands of calves,
0:42:18 > 0:42:23born not only at the same time but also in exactly the same place.
0:42:26 > 0:42:29And the reason why they all descend on this same area,
0:42:29 > 0:42:31to have their babies at the same time,
0:42:31 > 0:42:34is the grass that grows on the ground.
0:42:35 > 0:42:37At the start of every rainy season,
0:42:37 > 0:42:40one particular small patch of the Serengeti
0:42:40 > 0:42:45becomes covered with some of the most nutrient-rich grass on Earth...
0:42:45 > 0:42:47THUNDERCLAP
0:42:58 > 0:43:01..containing four times the calcium
0:43:01 > 0:43:04and nine times the amount of phosphorous
0:43:04 > 0:43:07than grasses just a few kilometres away.
0:43:09 > 0:43:13Nutrients that are crucial to healthy calf development.
0:43:20 > 0:43:26It means this one comparatively tiny patch of fortified grass
0:43:26 > 0:43:29can support millions of nursing wildebeest.
0:43:31 > 0:43:35The reason why this grass is so unusual
0:43:35 > 0:43:38can be found looming over the herds.
0:43:41 > 0:43:46Towering almost 3,000 metres above the Serengeti plains
0:43:46 > 0:43:51is one of Africa's strangest and most explosive volcanoes.
0:43:54 > 0:43:58Ol Doinyo Lengai, or "Mountain of God".
0:44:05 > 0:44:11Back in 2007, an eruption lasting almost 12 months threw a giant column
0:44:11 > 0:44:15of steam and ash nearly five kilometres into the air...
0:44:20 > 0:44:23..destroying countless crops...
0:44:25 > 0:44:28..and forcing thousands to flee their homes.
0:44:31 > 0:44:35This ash is unlike any other volcanic ash on the planet...
0:44:41 > 0:44:45..with a chemical make-up so odd, so rich in minerals,
0:44:45 > 0:44:49that the grass around it has become supercharged.
0:44:53 > 0:44:58It's this volcano, and the ash that comes from deep within it,
0:44:58 > 0:45:02that enables the wildebeest to breed in such huge numbers here.
0:45:07 > 0:45:12Without Ol Doinyo Lengai, this wildlife spectacle wouldn't exist,
0:45:12 > 0:45:17and the reason why Ol Doinyo Lengai is so unusual,
0:45:17 > 0:45:19why it's so nutrient-rich,
0:45:19 > 0:45:22is because of what's going on deep beneath it,
0:45:22 > 0:45:26something that threatens not just the future of Tanzania,
0:45:26 > 0:45:29but the entire African continent.
0:45:36 > 0:45:38And we're off.
0:45:41 > 0:45:43It's a journey into the unknown.
0:45:50 > 0:45:53It looks like any normal volcano, really. You get the conical shape.
0:45:53 > 0:45:57You get a few parasitic little cones there that's erupted out.
0:45:57 > 0:46:00There's some evidence of lava flow.
0:46:00 > 0:46:03But actually, that's just one of the strangest volcanoes on the planet.
0:46:12 > 0:46:14We're just coming round to the top now.
0:46:14 > 0:46:17You can start to see the fresher stuff from 2007,
0:46:17 > 0:46:19and that's all the previous eruptions,
0:46:19 > 0:46:23so this just ahead of us here is the crater rim.
0:46:23 > 0:46:26We're coming right up over it.
0:46:26 > 0:46:28Oh, my God. I don't think I've ever approached a volcano
0:46:28 > 0:46:29in quite this way before.
0:46:29 > 0:46:31Look at this!
0:46:40 > 0:46:44Look at that. There's a crater! Staring into the abyss.
0:46:47 > 0:46:49That is just magnificent.
0:46:51 > 0:46:53Very simple.
0:46:53 > 0:46:57It's like your characteristic volcano, and yet it's not.
0:46:57 > 0:47:00It's hiding this great secret.
0:47:01 > 0:47:05The secret of Ol Doinyo Lengai may lie kilometres down,
0:47:05 > 0:47:10but it can be uncovered by looking at some of its very odd lava.
0:47:16 > 0:47:18To get my hands on some of it,
0:47:18 > 0:47:24local Masai guides Rafael and Serengi lead me to a recent flow.
0:47:24 > 0:47:28So, how many times have you been up to the top?
0:47:28 > 0:47:30- Times? 20.- 20 times?
0:47:30 > 0:47:32- The same for you?- Yeah, yeah.
0:47:32 > 0:47:37- So, do you worry it will erupt again?- Yeah, we worry.
0:47:40 > 0:47:43Eventually, we reach a patch of recent lava.
0:47:45 > 0:47:47What a white wonderland! This is from the last eruption?
0:47:49 > 0:47:53Within this flow lies the secret to Africa's future.
0:47:53 > 0:47:57- I want to get a sample.- Really? - Yeah, I got a hammer.
0:47:57 > 0:48:00- OK.- Ta-da.- Yeah!
0:48:00 > 0:48:02I'm going to see if I can...
0:48:02 > 0:48:03OK.
0:48:04 > 0:48:10This lava contains evidence of two huge geological forces at work.
0:48:16 > 0:48:18IAIN'S VOICE ECHOES: Carbon dioxide...
0:48:22 > 0:48:25Releasing its clues involves some basic chemistry.
0:48:28 > 0:48:33So, I want to...I want to show you how special these lavas are.
0:48:33 > 0:48:37I'm just going to... crush them down a little bit.
0:48:37 > 0:48:40Cos I'm going to do something that really only this lava can do.
0:48:40 > 0:48:43For that I need some acid. This is weak...some dilute acid.
0:48:43 > 0:48:47And what I'm going to do is I'm just going to pour it onto the rocks.
0:48:47 > 0:48:50If I poured this on a normal lava, say a basalt,
0:48:50 > 0:48:52then you'd just get no reaction.
0:48:52 > 0:48:57But watch what happens when I put it on this lava.
0:48:58 > 0:49:01Look at that. Isn't that amazing?
0:49:01 > 0:49:03It's just foaming away, effervescing away.
0:49:03 > 0:49:05And...
0:49:09 > 0:49:13What's coming off here is carbon dioxide.
0:49:13 > 0:49:15It's that carbon dioxide that's really important because,
0:49:15 > 0:49:19as well as these lavas being rich in sodium and calcium and phosphorous,
0:49:19 > 0:49:24all of the elements that make the Serengeti grasses so nutrient-rich,
0:49:24 > 0:49:27it's also incredibly rich in carbon.
0:49:28 > 0:49:32And it's an indication that there's something really mysterious
0:49:32 > 0:49:34going on deep beneath this volcano.
0:49:41 > 0:49:44So-called carbonatite lava like this
0:49:44 > 0:49:47only forms when rocks rich in carbon
0:49:47 > 0:49:50are melted at incredibly high pressure.
0:49:54 > 0:49:57And there's only one place in the planet
0:49:57 > 0:50:01where you find carbon-rich rock at high pressure.
0:50:02 > 0:50:05And that's the same place that diamonds are formed...
0:50:08 > 0:50:09..the base of cratons.
0:50:13 > 0:50:16The magma that's feeding that volcano must be punching its way up
0:50:16 > 0:50:20through one of the five deep-seated continental building blocks
0:50:20 > 0:50:21that's formed the African landmass,
0:50:21 > 0:50:27in this case, the incredibly thick and ancient Tanzanian Craton.
0:50:31 > 0:50:35This part of Africa may have been stable for three billion years,
0:50:35 > 0:50:38but now something is melting the rock beneath it.
0:50:43 > 0:50:45The mere fact that magma's rising up
0:50:45 > 0:50:49through the deepest and oldest landmass on the planet
0:50:49 > 0:50:51means that beneath Ol Doinyo Lengai
0:50:51 > 0:50:54there's an even more powerful force at work.
0:51:00 > 0:51:06Deep below this part of Africa lies a giant rising mass of magma...
0:51:07 > 0:51:10..a super-plume,
0:51:10 > 0:51:13and for the last 45 million years,
0:51:13 > 0:51:18this super-plume has been steadily forcing its way upwards.
0:51:19 > 0:51:23It's not only melting the base of the ancient Tanzanian Craton,
0:51:23 > 0:51:28it extends north over 1,000 kilometres across the continent...
0:51:31 > 0:51:33..with spectacular results.
0:51:40 > 0:51:43This super-plume beneath Africa and its surface volcanoes
0:51:43 > 0:51:46have created the very DNA of this landscape.
0:51:46 > 0:51:50Everything you see relates to that.
0:51:50 > 0:51:53But in a way, the real impact of that super-plume has yet to be felt,
0:51:53 > 0:51:58because beneath my feet there's a violent geological struggle going on.
0:52:01 > 0:52:04It's one that began 25 million years ago...
0:52:05 > 0:52:08..when the bulging super-plume beneath Africa
0:52:08 > 0:52:12started to rip and tear the land above...
0:52:15 > 0:52:17..creating a 6,000-kilometre scar
0:52:17 > 0:52:20running half the length of eastern Africa.
0:52:29 > 0:52:31There it is.
0:52:33 > 0:52:35The Great African Rift.
0:52:45 > 0:52:46The Great Rift Valley
0:52:46 > 0:52:50is one of the most complex ecosystems on the planet...
0:52:52 > 0:52:56..home to a staggering array of plant and animal life...
0:53:02 > 0:53:06..as well as being the birthplace, of course, of our own species.
0:53:08 > 0:53:10The Great African Rift Valley is not just
0:53:10 > 0:53:13one of the most spectacular wildlife parks in the world,
0:53:13 > 0:53:17it's also one of the most exciting geological places on the planet,
0:53:17 > 0:53:21a huge crack in the Earth that runs the line of these cliffs
0:53:21 > 0:53:25and is literally a tear in the fabric of this ancient land,
0:53:25 > 0:53:27all of it caused by this super-plume
0:53:27 > 0:53:31of molten rock puncturing its way up through the continent.
0:53:31 > 0:53:36Now, here in Tanzania, we're at the southern tip of that tear,
0:53:36 > 0:53:38but at the northern end of that tear,
0:53:38 > 0:53:41the continent is already being ripped apart.
0:53:50 > 0:53:51At the far end of the Rift,
0:53:51 > 0:53:56Ethiopia's Danakil Depression is in the throes of violent change.
0:54:03 > 0:54:06Great tears are growing in the fabric of the Earth...
0:54:08 > 0:54:09..as the super-plume beneath
0:54:09 > 0:54:12stretches and cracks the surface above...
0:54:13 > 0:54:17..breaking through at volcanoes like Erte Ale.
0:54:20 > 0:54:24The land here is so torn, it's sinking below sea level...
0:54:26 > 0:54:29..leading scientists to predict
0:54:29 > 0:54:34that the neighbouring Red Sea will one day flood this entire plain,
0:54:34 > 0:54:37splitting the region in two.
0:54:42 > 0:54:46So, the big question is, what's going to happen at the other end?
0:54:46 > 0:54:49What we do know is that the split will start here in Ethiopia
0:54:49 > 0:54:53and propagate through Kenya to the edge of the Tanzanian Craton.
0:54:53 > 0:54:56It's here that it gets tricky. Some people argue
0:54:56 > 0:54:59that it will cut right through the craton, splitting it in two,
0:54:59 > 0:55:03but others argue that it will exploit weaknesses
0:55:03 > 0:55:07to go around the edge of it, either this way or round here.
0:55:07 > 0:55:10From there, it's possible that the split will follow
0:55:10 > 0:55:14just the line of the rift, down to the ocean through Mozambique.
0:55:16 > 0:55:19But some people argue that it'll actually swing to the west,
0:55:19 > 0:55:23down in this way, cutting a swathe through southern Africa.
0:55:24 > 0:55:27Whatever course it takes, one thing is virtually certain,
0:55:27 > 0:55:31and that is that Africa, that most ancient of lands,
0:55:31 > 0:55:32will one day break up.
0:55:43 > 0:55:47For over three and half billion years, the African continent
0:55:47 > 0:55:51has borne witness to the upheavals of our restless planet,
0:55:51 > 0:55:56an epic journey that has shaped every aspect of life here today.
0:55:56 > 0:56:02The creation of the very first land on Earth, the ancient cratons...
0:56:03 > 0:56:07..that have left their legacy in the diamond mines of Sierra Leone.
0:56:07 > 0:56:13These cratons, the stable heartlands of Africa...
0:56:16 > 0:56:19..have seen the world around them rip and tear asunder
0:56:19 > 0:56:24through the creation and destruction of the supercontinent Pangaea,
0:56:24 > 0:56:26a series of violent upheavals
0:56:26 > 0:56:31that have left their mark in the spectacular cliff of Victoria Falls.
0:56:31 > 0:56:35They created the ancient seas that shaped our civilisations...
0:56:37 > 0:56:38..and the creatures around us.
0:56:41 > 0:56:44But now Africa's changing in other ways too,
0:56:44 > 0:56:49because, economically, this is a continent on the rise,
0:56:49 > 0:56:52on the cusp of dramatic cultural and social change.
0:56:58 > 0:57:01The transformation that's taking place in African society
0:57:01 > 0:57:04is echoed by an even bigger transformation
0:57:04 > 0:57:08to the very fabric of the continent itself.
0:57:08 > 0:57:11The immense geological forces that are at work beneath my feet
0:57:11 > 0:57:16are preparing to redraw the African map, tearing it in two.
0:57:16 > 0:57:21So, for all Africa's long, long history, this is, in every sense,
0:57:21 > 0:57:26a continent that's in the process of being remoulded and reborn.