Rise Of The Continents (2013) s01e03 Episode Script
The Americas
1 New York City.
Gateway to the new world.
But also a gateway back into the distant past-- not just of New York, but of both North and South America.
I'm going to reach back in time to explore this lost world.
The evidence that unlocks that ancient past is hidden all around us in rocks, landscapes, and even animals.
The tiniest detail can reveal the history of a vast continent.
Those clues reveal the defining moments in the story of The Americas and show how these turning points have transformed evolution It's moving! created incredible economic riches That feels really close.
and changed the human history of these two great continents.
If you really want to understand the modern Americas, you have to understand the remarkable story of how they were born from the wreckage of a lost world.
You can find a clue to the origin of both American continents here at the top of World Trade Center 1.
It's the way that Manhattan skyscrapers are concentrated in just two places-- downtown, where I am, and a couple of miles further north.
And there, you can see the Empire State Building.
That patch is midtown.
New York skyscrapers are concentrated in midtown and downtown for a very good reason-- one that's buried beneath each one of them and that puts New York at the heart of an ancient world.
To find evidence for this ancient world, I need to explore the foundations of the city's skyscrapers.
It's a bit rickety, this thing, isn't it? Before any building goes up high, you got to dig down deep.
And that takes some hard-core tools.
Now, that is the kind of geology hammer I've always wanted to have.
I'm looking for a particular type of rock-- one that dates back at least 300 million years.
Inside it, there's evidence of what this place was like in the long distant past a past that helps explain the mystery of New York's skyline.
Crystal.
High pressures.
This rock face-- it's the foundation stone on which, for me, modern America was built.
If you look at it, you can see there's a whole series of lines.
It's like bands coming through.
And that's because the crystals-- look, you can see them glittering away here-- they're all stacked on top of each other in a series of layers.
You can see that when you look at it closely.
When you zoom in to this rock what you see is a mosaic of crystals that are flattened in this direction and elongated, strung out, in this direction here.
And that transformation, that rearrangement, has been done under really high temperatures-- maybe 700 degrees-- but also really high pressures.
This dense bedrock is known as Manhattan Schist.
The only way that you can generate the heat and pressure that you need to form the dense strength of a rock like this is if you produce it under an enormous weight-- the kind of weight that's far in excess of anything you find around here today.
300 million years ago, New York was at the foothills of a huge mountain range, and this rock-- this rock was buried 13 kilometers beneath those soaring peaks.
Imagine that.
These mountains were the height of the Himalayas, but they weren't just high-- they went on for thousands of miles, and they played a critical role in the story of The Americas, because their formation is what brought North and South America together.
430 million years ago, North and South America were separated by thousands of miles of ocean, but they were on a collision course, a slow-motion crash that raised giant mountains all along the impact zone.
At the same time, it brought all the world's land masses together in one giant supercontinent-- Pangaea.
The two American continents were at the heart of Pangaea on either side of a massive mountain range.
And New York was, in geological terms, at the center of this lost world.
It's funny-- New Yorkers like to think of their city as the center of the world.
300 million years ago, it really was.
Now all that's left here of the enormous supercontinent of Pangaea is the rock beneath the city.
You know, it's staggering to think that, in the last few hundred million years, mountains of Himalayan stature have been eroded down to leave us with a dense bedrock beneath my feet.
And that's left its legacy in this iconic skyline.
Where the bedrock is closest to the surface-- in downtown and midtown-- it makes strong foundations for skyscrapers.
Where it's been eroded away between the two, the foundations are weaker, and the buildings are smaller.
This icon of the modern world, the skyline of this great city, is underpinned by the long-lost world of Pangaea, and it's shaped much more than that.
Pangaea's had a huge influence on the modern-day Americas, from their natural resources to their history.
But Pangaea also left its mark on the whole planet.
It played a critical role in one of the most important evolutionary developments in the story of life on Earth-- nothing less than the invention of sex.
The Grand Canyon.
This is a portal through time, where you can see the history of the planet laid out before you.
You have a strange double vision as a geologist when you come here, because on the one hand, you have this just spectacular, jaw-dropping view, and it's absolutely beautiful.
But as a geologist, you see past that, as well, and you see a kind of deeper significance of what it means.
In this case, it means a huge, huge expanse of time.
The Earth's history being unraveled by the Sun as it exposes the deeper and deeper layers.
The rocks down there are 1.
7 billion years old.
Extraordinary number.
The only life on the planet was single-celled algae.
It was slime.
And then just a little bit higher, the rocks are 500 million, 550 million years old.
That's where complex life starts going.
That's the time when there was great ice sheets across the planet.
So, there's 1 1/2 billion years of time just condensed into that view there.
Absolutely spectacular.
One set of layers that's important for our story of Pangaea is this group of rocks over here.
It's called the Supai Group.
They date from the earliest days of Pangaea, before it was fully formed.
The layers are red because the rocks are packed full of iron.
Sediments are made of silts and sands that have been washed off the land into coastal swamps and deltas.
The rocks show that this early Pangaea was a watery place, and fossils reveal the kind of life that was around at this time amphibians.
Today, amphibians like frogs and salamanders are relatively rare.
But before Pangaea formed, amphibians were the dominant animals on the planet.
And if you imagine frogs and salamanders, you realize how important water is for them, particularly in that early spawning stage and the development of the young, like tadpoles.
And that's something that amphibians have in common past and present, really, is that fundamental attachment to water.
And that wet world of early Pangaea would have been absolutely perfect for these critters to flourish in.
Before Pangaea formed, the world had lots of coastal swamps and wetlands for the amphibians to breed.
But then the world changed.
The evidence is just a short trek down from the canyon rim a layer of yellow rock, called The Coconino, that was formed when The Americas were part of the great supercontinent of Pangaea.
It reveals a landscape that would change the course of life on Earth.
Wind.
Sand.
We know from The Coconino layer that the Grand Canyon had become the western edge of a giant desert.
One huge land mass meant that most of the land was distant from the sea, so rain-carrying winds couldn't reach the center.
250 million years ago, Earth had become a desert planet.
Not good news for the amphibians.
But in the heart of this arid world, one type of animal did flourish.
Although this environment was extreme desert, it wasn't lifeless, and the evidence is right here on the rock, as you can see, these really odd markings.
And what they are are footprints left-- a trackway of an animal that was walking up here, pushing down, kind of displacing the sand.
What it was was a reptile-- a reptile with a tail, because you can see this sinuous track of this reptile that's dragged its tail up.
To adapt to these super arid environments required an evolutionary innovation that would be inherited by all the reptiles, by birds, by mammals, by you and I.
It's mating season at the Colorado Reptile Park and these feisty fellas scrap for the right to breed.
So keeper Jay Young has to tend their wounds.
Helping him treat his injured means I can get up close and personal to an animal whose ancestors roamed The Americas when they were part of Pangaea.
You let me know when you need this thing.
I'm gonna give you the stick.
Wouldn't you need that? Look at this.
He's gonna grab a tail.
Oh, my God.
Whoa, whoa, whoa.
Hissing everywhere.
That's fun.
So, what do I do? Move it-- Ah.
Where should I be, your left or right, when you come out? Either way.
Ready? Okay, now we yank and jump.
Make sure both the hands hit her neck at the same time.
No, you jump.
I'll just stay at this end.
- Ah! - Yeah? Okay, come up here.
- Are you sure? - Yeah.
Jump on her back.
Sit, sit, all your weight.
Put your hands right here on her neck.
- Okay, okay, okay.
- Okay.
You got her? Yeah, I think so.
We'll soon find out, though.
- Okay.
- Hey, there, honey.
- We'll soon find out.
- Anna Ricky, is it? - Yeah.
- Hi, Anna Ricky.
- Pleased to meet you.
- I'm gonna go get lunch.
- I'll be back in a few.
- Hey, hey, hey! I hope that's a joke.
It's moving.
Whoa! Okay, keep your hands on her neck.
I haven't got it.
I'm just letting you get a sense of her power.
It's incredible-- yes, very strong.
She heard that Scots taste like chicken.
Very witty.
This is the closest I'm ever gonna get to a creature from Pangaean times, because alligators share an anatomical connection with ancient reptilian fossils.
It's this, what we call the ankle joint-- it's the crurotarsal joint-- and it's a really distinctive adaptation.
You can get this thing underneath your body.
You can push yourself more upright, and you can really have this really fast gait.
That looks sore, doesn't it? Anna Ricky's ancestors were hugely successful in Pangaea.
The way they moved was part of it.
Back on her, back on her.
I think that's it, though.
But the biggest breakthrough was something that perfectly equipped them to Pangaea's desert world the way they have sex.
Alligator sex is pretty much like human sex, certainly in the style of copulation.
The key is internal fertilization-- delivering the sperm inside the female and directly to the ova.
And that process involved the invention of sex.
Sex is the most efficient, direct way of achieving fertilization.
It's how modern reptiles, birds, and mammals impregnate.
Up until this innovation, fertilization could only occur externally in water.
Amphibians were the first vertebrates to emerge onto land, but because they fertilized externally, they had to return to water to breed.
The newly evolved reptiles did things differently.
They fertilized and developed their eggs inside their females, so by the time the eggs were laid, they had hard, impermeable shells.
These eggs didn't need water to survive.
This is a chicken egg, but surprisingly, it's about the same size as an alligator egg.
But what's important is what's inside 'cause what's inside is the amniotic fluid.
That transparent liquid-- that's the stuff that contains the energy and the life-sustaining waters that amphibians would have found in the rivers and seas.
This object-- the egg-- was the revolution.
Mammals have taken those life-supporting fluids inside ourselves and supplied nutrition through a placenta.
But we're still children of that first amniotic reptile.
The Pangaean deserts were essentially an impenetrable barrier to the amphibians.
But for the reptiles, it was a different story.
The development of internal fertilization and the amniotic egg allowed them to spread into and thrive in those arid environments.
It's a wonderful example of how environmental change can be a catalyst for evolutionary advances.
And those advances would lead eventually to the evolution of us.
It's interesting to think that the way that we have sex and the way that we rear our young have been shaped by these deserts of the distant past.
North and South America spent almost 100 million years nestled together in the heart of Pangaea.
But by 200 million years ago, there were signs that this gigantic land mass was about to break up.
This breakup would have a massive influence on the modern-day Americas.
It would end up creating fortunes, destroying lives, and transforming the landscape.
The evidence for this cataclysmic event is right under the nose of unsuspecting commuters driving in and out of New York every day.
Connecting Manhattan to New Jersey is the George Washington Bridge, anchored on one side by an imposing cliff face-- the Hudson Palisades.
I've come here to find evidence of probably the single most important event in the history of the two American continents-- the moment when they split from Pangaea.
There's a telltale sign here that really shows how these rocks came into being.
Hexing.
Vertical fractures.
You could see it in the shapes of these blocks.
They've got these regular sides to them, and this block, as well-- you can see it beautifully there, and there's six sides.
One, two, three, four, five, six.
These hexagons are the flat top surfaces of columns that go straight the way down.
You can see it as these kind of vertical fractures in the cliffs all the way along here.
And what they're telling you is that this rock started off as a liquid mush-- a molten fluid that must have cooled rapidly-- and as it cooled, as it congealed, it contracted in.
And the most efficient way of doing that is to kind of pull in from all sides and create these-- these wonderful hexagons.
So, this rock, which is a kind of basalt, started off as hot magma.
The magma that erupted out is thought to have been brought up by a current of hot rocks known as a mantle plume.
It's not clear why they form, but rising mantle plumes push the land up, like a heat blister, until it cracks and fractures, triggering immense volcanic eruptions.
These cool and become layers of basalt.
Geologists have found evidence of this humongous volcanic outpouring in places thousands of miles apart.
If we just look at it on a modern map, we find that the equivalent layer of this basalt that we get here in Eastern America has also been found in Eastern Canada.
It's been found in Southern Britain and Portugal and west Africa and in parts of Brazil.
Now, viewed from the perspective of Pangaea, 200 million years ago, it makes perfect sense.
If you wind back time, all these places were joined together, part of a single, huge, volcanic event that spread across Pangaea's heart-- a fiery inferno covering 4 million square miles.
Across this huge area, great sheets and rivers of lava burned for thousands of years.
Volcanic ash and gas played havoc with the planet's climate.
Large numbers of reptiles and half of all plant species were wiped out.
But these were also the death throes of the supercontinent itself.
The eruptions created chasms and rifts that would eventually fill with water.
Pangaea split apart, and out of it emerged a brand-new continent-- North America-- and the beginnings of a brand-new ocean the Atlantic.
So, to think that each year, New York and The Americas get two centimeters further west from Europe and Africa-- the new world driven inexorably away from the old.
It's this separation, with newly formed plates pushing away from each other on one side and jostling for position with their neighbors on the other, that shaped the new world.
By 130 million years ago, North America had fully separated from Pangaea.
Then the action shifted south.
Around 85 million years ago, the remains of Pangaea split again to form another plate.
Moving away west, separate from both Africa and North America, was the newly formed continent of South America.
Its journey was to be anything but smooth.
Today, South America has some of the most spectacular landscapes on Earth.
They're the product of a violent geological past that shaped an equally turbulent human history.
This relationship between geology and history is revealed in the Bolivian town of PotosÃ.
Local miner Pedro Montez Correa is going to take me inside the deadliest mountain in human history-- Cerro Rico.
Before entering the depths, miners fortify themselves with intoxicating coca leaves.
With coca, we are not very thirsty, hungry.
You want, maybe, to sleep.
Yes, we feel that we are stronger with the coca leaves.
So, at what age do you start using coca leaves? When we come to the mine-- we're 10 years old.
- 10 years old? - Yeah, yeah.
- Switch on the light.
- Oh, yeah.
Not only are many of the miners school age, but they're entering a world where tunnels regularly give way and explosives are unregulated.
Watch with the hole.
A hole? - It's deep.
- Yeah.
How far does that go down? It's, like, 80 meters down, more or less.
Yeah, this tunnel is connecting to another mine.
Okay, so the mines are all interconnected.
All the mines.
It's like Swiss cheese full, full of holes.
Every step needs to be taken very carefully.
The miners work by digging and blasting through the rock.
Collapses and fatalities are a fact of life, and you never know what the other miners are doing.
What's happening? - Oh, that was close.
- That's happening.
That was it, was it? Yeah.
Oh.
- That feels really close.
- Yeah.
I can smell the dynamite.
- Yeah.
- Really strong.
Down here is what three centuries of miners have been looking for.
Aha.
So, here we are.
Okay, I see it, yeah.
Look, you see this band coming all the way down here.
Just in amongst it all is a rather dull, gray marrow, and that-- well, that's the silver.
That's what miners like Pedro are after.
And for me, the way this precious silver is laid out reveals a fundamental process that shaped South America and its often bloody history.
Hot fluids.
It's actually concentrated along these really narrow bands.
These are called veins, and you can actually see them all the way up, across there.
Those metals would have been laid down by hot fluids.
And the reason the fluids were hot was because deep beneath my feet at the time was molten magma-- magma that had risen up from the mantle, carrying with it metal elements like zinc and gold and silver.
And as that magma rose higher and higher, it heated up water that was circulating through the crust.
And those waters, at several hundred degrees Celsius, started to pick up those metal elements and carry them higher and higher until they just ditched their cargo, stuffing them into veins like this.
But what's surprising is the source of that water.
Analyzing the steam that emerges from volcanic vents nearby reveals something unexpected.
The steam's chemical signature is similar to that of water found 250 miles to the west the waters of the Pacific Ocean.
So, the most obvious conclusion is that some of the hot waters that have been percolating through these rocks in this region started out in the Pacific.
And that is telling about a process that's going on deep beneath my feet now and is really at the heart of those moving continents, and that process is subduction.
Subduction is the key to understanding how South America was changed as it moved west.
As the South American plate moved apart from Africa, it collided with the Pacific Ocean plate, and the collision is going on right underneath Cerro Rico.
The ocean floor of the Pacific plate is sinking down, dragging a part of the Pacific Ocean deep underneath South America.
This is subduction.
The sinking rock heats up, and minerals and water from the old ocean floor escape into the continental rocks above.
It's this process that has given South America its incredible mineral wealth, from tin, copper, and zinc, to gold and silver.
- Hey.
Fresh air.
- Yeah.
- Hey.
- You did it, my friend.
- Thank you very much.
- Yes.
That's good, then.
As the ocean plate pushes underneath the leading edge of South America, it kind of gets snagged and jarred.
Pressure builds up, and you generate these huge earthquakes, and also open up pathways for magma to rise up to the surface and produce volcanos.
What you get over 60 million years is a gradual uplift and crumpling of this whole region.
The result, almost a byproduct of subduction, is the longest mountain range on any continent-- the Andes.
The Andes stretch for more than 4,000 miles, along almost the entire western coast of the continent.
It's a long, narrow range, because the mountains follow the boundary between the two plates where subduction is taking place.
And in a strange twist of fate, their formation may give Bolivia the chance to gain some measure of compensation for the traumas of the past.
As they've grown, the mountains have lifted one Bolivian lake from its original position, near sea level, to a height of nearly 13,000 feet.
This is the Salar de Uyuni-- the biggest salt flat on Earth.
Hidden in this landscape is a resource worth tens of billions of dollars.
It could have the global impact of the silver of PotosÃ, but without its tarnished history.
The key to understanding this new source of wealth is inside something we nearly all carry in our pockets.
Open up any mobile phone, whether it's a fancy, new touch-screen or one of these old-style handsets, and you'll find the battery.
What all these batteries have got in common is one key element.
The active components inside here are made of lithium carbonate.
As well as being in mobile phones, lithium's in laptops and all electronic devices.
It's used because of one quality above all, and that is lithium is the lightest of all the metals, so it gives more power for its mass.
Now, here's the thing.
Bolivia has as much as 50% of the world's lithium reserves.
Most of it in this extraordinary landscape.
In places, the lithium is only just below the surface.
Where the crust is thin, you can see the brine underneath, and if you really hammer away at it, then you can-- you can actually see the structure of the salt.
Look at that.
It's beautiful.
All these symmetrical crystals.
The white ones are sodium chloride.
That's just ordinary table salt.
But this pink one here-- that's potassium.
And this one, the brown-colored one-- that-- that's lithium.
So today, the lithium is here at the surface in the salt, but it started off way down deep.
Subduction produced magma that rose up and erupted out of volcanoes like that over there.
In fact, there's a whole series of-- all the way around.
So these mountains are rich in lithium.
From the slopes of the Andes, runoff erosion washes the metal-rich sediments down to the lake.
Since it's been uplifted, the lake has become surrounded by mountains, so no river can find a way out to drain the salar.
The result is that the only way water leaves the lake is through evaporation.
Over time, that concentrated minerals, including lithium, in the lake bed.
Subduction and the rise of the Andes has given South America extraordinary mineral wealth, and all that a consequence of that gradual drift of the new world away from the old.
That process has shaped the destiny of South America in another way, though.
I mean, here, it's given us a landscape of jaw-dropping beauty that's completely lifeless.
But elsewhere, it's created some of the richest and most unique habitats on the planet.
One ecosystem above all others owes its existence to the Andes, because as the Andes grew, the rivers of South America went through a series of massive changes.
Before the andes, it's thought the main rivers flowed in the opposite direction to today-- into the Pacific.
When the Andes started to rise, they diverted rivers to the north, where they flowed out into the Caribbean, creating a huge area of wetlands close to the growing mountains.
But then further uplift blocked the route north and forced the rivers to converge towards the Atlantic, forming an enormous drainage basin, and that led to the creation of the Amazon rainforest.
Meanwhile, on its western flanks, the Andes created a rain shadow.
The result is the driest place on the planet-- the Atacama desert.
By 10 million years ago, both South and North America looked similar to today, but there was one critical difference.
They were still separate continents.
The stage was set for the final act in the story of The Americas.
It didn't lead to a dramatic change in the landscape, but it did transform their wildlife.
The llama's ancestors first appear in North America about 40 million years ago.
But they don't appear in South America until 3 million years ago.
The two continents had been edging closer together.
Then, starting around 30 million years ago, volcanic islands began to combine, slowly building a land bridge between the two.
By 3 million years ago, two continents that had been separate since the days of Pangaea were finally joined again.
The New World was born.
Across this narrow link has come a great intermingling of species.
Northern mammals in particular invaded the South.
Deer, foxes, and dogs all crossed over-- and cats that quickly became the prime predators.
The result was to increase South America's biodiversity.
Among the most successful arrivals-- the llama, ironically, now long extinct in the north.
For me, the llama is the perfect symbol of the New World.
Originating in the northern continents and flourishing in the southern, they represent both the isolation and the coming together of The Americas.
Since that momentous joining, the story of The Americas has been of a single land.
When the first humans arrived in North America, they quickly moved into the south.
And when Europeans arrived, both Americas were seen as a single New World.
So, although the single, continuous land mass of Pangaea no longer exists, our modern-day continents are linked in a different way.
Today a great global economy binds all the continents together.
In essence, we've created a new Pangaea.
Pangaea of our own making.
And on this Pangaea just like the one 300 millions years ago, The Americas are right at the heart.
Gateway to the new world.
But also a gateway back into the distant past-- not just of New York, but of both North and South America.
I'm going to reach back in time to explore this lost world.
The evidence that unlocks that ancient past is hidden all around us in rocks, landscapes, and even animals.
The tiniest detail can reveal the history of a vast continent.
Those clues reveal the defining moments in the story of The Americas and show how these turning points have transformed evolution It's moving! created incredible economic riches That feels really close.
and changed the human history of these two great continents.
If you really want to understand the modern Americas, you have to understand the remarkable story of how they were born from the wreckage of a lost world.
You can find a clue to the origin of both American continents here at the top of World Trade Center 1.
It's the way that Manhattan skyscrapers are concentrated in just two places-- downtown, where I am, and a couple of miles further north.
And there, you can see the Empire State Building.
That patch is midtown.
New York skyscrapers are concentrated in midtown and downtown for a very good reason-- one that's buried beneath each one of them and that puts New York at the heart of an ancient world.
To find evidence for this ancient world, I need to explore the foundations of the city's skyscrapers.
It's a bit rickety, this thing, isn't it? Before any building goes up high, you got to dig down deep.
And that takes some hard-core tools.
Now, that is the kind of geology hammer I've always wanted to have.
I'm looking for a particular type of rock-- one that dates back at least 300 million years.
Inside it, there's evidence of what this place was like in the long distant past a past that helps explain the mystery of New York's skyline.
Crystal.
High pressures.
This rock face-- it's the foundation stone on which, for me, modern America was built.
If you look at it, you can see there's a whole series of lines.
It's like bands coming through.
And that's because the crystals-- look, you can see them glittering away here-- they're all stacked on top of each other in a series of layers.
You can see that when you look at it closely.
When you zoom in to this rock what you see is a mosaic of crystals that are flattened in this direction and elongated, strung out, in this direction here.
And that transformation, that rearrangement, has been done under really high temperatures-- maybe 700 degrees-- but also really high pressures.
This dense bedrock is known as Manhattan Schist.
The only way that you can generate the heat and pressure that you need to form the dense strength of a rock like this is if you produce it under an enormous weight-- the kind of weight that's far in excess of anything you find around here today.
300 million years ago, New York was at the foothills of a huge mountain range, and this rock-- this rock was buried 13 kilometers beneath those soaring peaks.
Imagine that.
These mountains were the height of the Himalayas, but they weren't just high-- they went on for thousands of miles, and they played a critical role in the story of The Americas, because their formation is what brought North and South America together.
430 million years ago, North and South America were separated by thousands of miles of ocean, but they were on a collision course, a slow-motion crash that raised giant mountains all along the impact zone.
At the same time, it brought all the world's land masses together in one giant supercontinent-- Pangaea.
The two American continents were at the heart of Pangaea on either side of a massive mountain range.
And New York was, in geological terms, at the center of this lost world.
It's funny-- New Yorkers like to think of their city as the center of the world.
300 million years ago, it really was.
Now all that's left here of the enormous supercontinent of Pangaea is the rock beneath the city.
You know, it's staggering to think that, in the last few hundred million years, mountains of Himalayan stature have been eroded down to leave us with a dense bedrock beneath my feet.
And that's left its legacy in this iconic skyline.
Where the bedrock is closest to the surface-- in downtown and midtown-- it makes strong foundations for skyscrapers.
Where it's been eroded away between the two, the foundations are weaker, and the buildings are smaller.
This icon of the modern world, the skyline of this great city, is underpinned by the long-lost world of Pangaea, and it's shaped much more than that.
Pangaea's had a huge influence on the modern-day Americas, from their natural resources to their history.
But Pangaea also left its mark on the whole planet.
It played a critical role in one of the most important evolutionary developments in the story of life on Earth-- nothing less than the invention of sex.
The Grand Canyon.
This is a portal through time, where you can see the history of the planet laid out before you.
You have a strange double vision as a geologist when you come here, because on the one hand, you have this just spectacular, jaw-dropping view, and it's absolutely beautiful.
But as a geologist, you see past that, as well, and you see a kind of deeper significance of what it means.
In this case, it means a huge, huge expanse of time.
The Earth's history being unraveled by the Sun as it exposes the deeper and deeper layers.
The rocks down there are 1.
7 billion years old.
Extraordinary number.
The only life on the planet was single-celled algae.
It was slime.
And then just a little bit higher, the rocks are 500 million, 550 million years old.
That's where complex life starts going.
That's the time when there was great ice sheets across the planet.
So, there's 1 1/2 billion years of time just condensed into that view there.
Absolutely spectacular.
One set of layers that's important for our story of Pangaea is this group of rocks over here.
It's called the Supai Group.
They date from the earliest days of Pangaea, before it was fully formed.
The layers are red because the rocks are packed full of iron.
Sediments are made of silts and sands that have been washed off the land into coastal swamps and deltas.
The rocks show that this early Pangaea was a watery place, and fossils reveal the kind of life that was around at this time amphibians.
Today, amphibians like frogs and salamanders are relatively rare.
But before Pangaea formed, amphibians were the dominant animals on the planet.
And if you imagine frogs and salamanders, you realize how important water is for them, particularly in that early spawning stage and the development of the young, like tadpoles.
And that's something that amphibians have in common past and present, really, is that fundamental attachment to water.
And that wet world of early Pangaea would have been absolutely perfect for these critters to flourish in.
Before Pangaea formed, the world had lots of coastal swamps and wetlands for the amphibians to breed.
But then the world changed.
The evidence is just a short trek down from the canyon rim a layer of yellow rock, called The Coconino, that was formed when The Americas were part of the great supercontinent of Pangaea.
It reveals a landscape that would change the course of life on Earth.
Wind.
Sand.
We know from The Coconino layer that the Grand Canyon had become the western edge of a giant desert.
One huge land mass meant that most of the land was distant from the sea, so rain-carrying winds couldn't reach the center.
250 million years ago, Earth had become a desert planet.
Not good news for the amphibians.
But in the heart of this arid world, one type of animal did flourish.
Although this environment was extreme desert, it wasn't lifeless, and the evidence is right here on the rock, as you can see, these really odd markings.
And what they are are footprints left-- a trackway of an animal that was walking up here, pushing down, kind of displacing the sand.
What it was was a reptile-- a reptile with a tail, because you can see this sinuous track of this reptile that's dragged its tail up.
To adapt to these super arid environments required an evolutionary innovation that would be inherited by all the reptiles, by birds, by mammals, by you and I.
It's mating season at the Colorado Reptile Park and these feisty fellas scrap for the right to breed.
So keeper Jay Young has to tend their wounds.
Helping him treat his injured means I can get up close and personal to an animal whose ancestors roamed The Americas when they were part of Pangaea.
You let me know when you need this thing.
I'm gonna give you the stick.
Wouldn't you need that? Look at this.
He's gonna grab a tail.
Oh, my God.
Whoa, whoa, whoa.
Hissing everywhere.
That's fun.
So, what do I do? Move it-- Ah.
Where should I be, your left or right, when you come out? Either way.
Ready? Okay, now we yank and jump.
Make sure both the hands hit her neck at the same time.
No, you jump.
I'll just stay at this end.
- Ah! - Yeah? Okay, come up here.
- Are you sure? - Yeah.
Jump on her back.
Sit, sit, all your weight.
Put your hands right here on her neck.
- Okay, okay, okay.
- Okay.
You got her? Yeah, I think so.
We'll soon find out, though.
- Okay.
- Hey, there, honey.
- We'll soon find out.
- Anna Ricky, is it? - Yeah.
- Hi, Anna Ricky.
- Pleased to meet you.
- I'm gonna go get lunch.
- I'll be back in a few.
- Hey, hey, hey! I hope that's a joke.
It's moving.
Whoa! Okay, keep your hands on her neck.
I haven't got it.
I'm just letting you get a sense of her power.
It's incredible-- yes, very strong.
She heard that Scots taste like chicken.
Very witty.
This is the closest I'm ever gonna get to a creature from Pangaean times, because alligators share an anatomical connection with ancient reptilian fossils.
It's this, what we call the ankle joint-- it's the crurotarsal joint-- and it's a really distinctive adaptation.
You can get this thing underneath your body.
You can push yourself more upright, and you can really have this really fast gait.
That looks sore, doesn't it? Anna Ricky's ancestors were hugely successful in Pangaea.
The way they moved was part of it.
Back on her, back on her.
I think that's it, though.
But the biggest breakthrough was something that perfectly equipped them to Pangaea's desert world the way they have sex.
Alligator sex is pretty much like human sex, certainly in the style of copulation.
The key is internal fertilization-- delivering the sperm inside the female and directly to the ova.
And that process involved the invention of sex.
Sex is the most efficient, direct way of achieving fertilization.
It's how modern reptiles, birds, and mammals impregnate.
Up until this innovation, fertilization could only occur externally in water.
Amphibians were the first vertebrates to emerge onto land, but because they fertilized externally, they had to return to water to breed.
The newly evolved reptiles did things differently.
They fertilized and developed their eggs inside their females, so by the time the eggs were laid, they had hard, impermeable shells.
These eggs didn't need water to survive.
This is a chicken egg, but surprisingly, it's about the same size as an alligator egg.
But what's important is what's inside 'cause what's inside is the amniotic fluid.
That transparent liquid-- that's the stuff that contains the energy and the life-sustaining waters that amphibians would have found in the rivers and seas.
This object-- the egg-- was the revolution.
Mammals have taken those life-supporting fluids inside ourselves and supplied nutrition through a placenta.
But we're still children of that first amniotic reptile.
The Pangaean deserts were essentially an impenetrable barrier to the amphibians.
But for the reptiles, it was a different story.
The development of internal fertilization and the amniotic egg allowed them to spread into and thrive in those arid environments.
It's a wonderful example of how environmental change can be a catalyst for evolutionary advances.
And those advances would lead eventually to the evolution of us.
It's interesting to think that the way that we have sex and the way that we rear our young have been shaped by these deserts of the distant past.
North and South America spent almost 100 million years nestled together in the heart of Pangaea.
But by 200 million years ago, there were signs that this gigantic land mass was about to break up.
This breakup would have a massive influence on the modern-day Americas.
It would end up creating fortunes, destroying lives, and transforming the landscape.
The evidence for this cataclysmic event is right under the nose of unsuspecting commuters driving in and out of New York every day.
Connecting Manhattan to New Jersey is the George Washington Bridge, anchored on one side by an imposing cliff face-- the Hudson Palisades.
I've come here to find evidence of probably the single most important event in the history of the two American continents-- the moment when they split from Pangaea.
There's a telltale sign here that really shows how these rocks came into being.
Hexing.
Vertical fractures.
You could see it in the shapes of these blocks.
They've got these regular sides to them, and this block, as well-- you can see it beautifully there, and there's six sides.
One, two, three, four, five, six.
These hexagons are the flat top surfaces of columns that go straight the way down.
You can see it as these kind of vertical fractures in the cliffs all the way along here.
And what they're telling you is that this rock started off as a liquid mush-- a molten fluid that must have cooled rapidly-- and as it cooled, as it congealed, it contracted in.
And the most efficient way of doing that is to kind of pull in from all sides and create these-- these wonderful hexagons.
So, this rock, which is a kind of basalt, started off as hot magma.
The magma that erupted out is thought to have been brought up by a current of hot rocks known as a mantle plume.
It's not clear why they form, but rising mantle plumes push the land up, like a heat blister, until it cracks and fractures, triggering immense volcanic eruptions.
These cool and become layers of basalt.
Geologists have found evidence of this humongous volcanic outpouring in places thousands of miles apart.
If we just look at it on a modern map, we find that the equivalent layer of this basalt that we get here in Eastern America has also been found in Eastern Canada.
It's been found in Southern Britain and Portugal and west Africa and in parts of Brazil.
Now, viewed from the perspective of Pangaea, 200 million years ago, it makes perfect sense.
If you wind back time, all these places were joined together, part of a single, huge, volcanic event that spread across Pangaea's heart-- a fiery inferno covering 4 million square miles.
Across this huge area, great sheets and rivers of lava burned for thousands of years.
Volcanic ash and gas played havoc with the planet's climate.
Large numbers of reptiles and half of all plant species were wiped out.
But these were also the death throes of the supercontinent itself.
The eruptions created chasms and rifts that would eventually fill with water.
Pangaea split apart, and out of it emerged a brand-new continent-- North America-- and the beginnings of a brand-new ocean the Atlantic.
So, to think that each year, New York and The Americas get two centimeters further west from Europe and Africa-- the new world driven inexorably away from the old.
It's this separation, with newly formed plates pushing away from each other on one side and jostling for position with their neighbors on the other, that shaped the new world.
By 130 million years ago, North America had fully separated from Pangaea.
Then the action shifted south.
Around 85 million years ago, the remains of Pangaea split again to form another plate.
Moving away west, separate from both Africa and North America, was the newly formed continent of South America.
Its journey was to be anything but smooth.
Today, South America has some of the most spectacular landscapes on Earth.
They're the product of a violent geological past that shaped an equally turbulent human history.
This relationship between geology and history is revealed in the Bolivian town of PotosÃ.
Local miner Pedro Montez Correa is going to take me inside the deadliest mountain in human history-- Cerro Rico.
Before entering the depths, miners fortify themselves with intoxicating coca leaves.
With coca, we are not very thirsty, hungry.
You want, maybe, to sleep.
Yes, we feel that we are stronger with the coca leaves.
So, at what age do you start using coca leaves? When we come to the mine-- we're 10 years old.
- 10 years old? - Yeah, yeah.
- Switch on the light.
- Oh, yeah.
Not only are many of the miners school age, but they're entering a world where tunnels regularly give way and explosives are unregulated.
Watch with the hole.
A hole? - It's deep.
- Yeah.
How far does that go down? It's, like, 80 meters down, more or less.
Yeah, this tunnel is connecting to another mine.
Okay, so the mines are all interconnected.
All the mines.
It's like Swiss cheese full, full of holes.
Every step needs to be taken very carefully.
The miners work by digging and blasting through the rock.
Collapses and fatalities are a fact of life, and you never know what the other miners are doing.
What's happening? - Oh, that was close.
- That's happening.
That was it, was it? Yeah.
Oh.
- That feels really close.
- Yeah.
I can smell the dynamite.
- Yeah.
- Really strong.
Down here is what three centuries of miners have been looking for.
Aha.
So, here we are.
Okay, I see it, yeah.
Look, you see this band coming all the way down here.
Just in amongst it all is a rather dull, gray marrow, and that-- well, that's the silver.
That's what miners like Pedro are after.
And for me, the way this precious silver is laid out reveals a fundamental process that shaped South America and its often bloody history.
Hot fluids.
It's actually concentrated along these really narrow bands.
These are called veins, and you can actually see them all the way up, across there.
Those metals would have been laid down by hot fluids.
And the reason the fluids were hot was because deep beneath my feet at the time was molten magma-- magma that had risen up from the mantle, carrying with it metal elements like zinc and gold and silver.
And as that magma rose higher and higher, it heated up water that was circulating through the crust.
And those waters, at several hundred degrees Celsius, started to pick up those metal elements and carry them higher and higher until they just ditched their cargo, stuffing them into veins like this.
But what's surprising is the source of that water.
Analyzing the steam that emerges from volcanic vents nearby reveals something unexpected.
The steam's chemical signature is similar to that of water found 250 miles to the west the waters of the Pacific Ocean.
So, the most obvious conclusion is that some of the hot waters that have been percolating through these rocks in this region started out in the Pacific.
And that is telling about a process that's going on deep beneath my feet now and is really at the heart of those moving continents, and that process is subduction.
Subduction is the key to understanding how South America was changed as it moved west.
As the South American plate moved apart from Africa, it collided with the Pacific Ocean plate, and the collision is going on right underneath Cerro Rico.
The ocean floor of the Pacific plate is sinking down, dragging a part of the Pacific Ocean deep underneath South America.
This is subduction.
The sinking rock heats up, and minerals and water from the old ocean floor escape into the continental rocks above.
It's this process that has given South America its incredible mineral wealth, from tin, copper, and zinc, to gold and silver.
- Hey.
Fresh air.
- Yeah.
- Hey.
- You did it, my friend.
- Thank you very much.
- Yes.
That's good, then.
As the ocean plate pushes underneath the leading edge of South America, it kind of gets snagged and jarred.
Pressure builds up, and you generate these huge earthquakes, and also open up pathways for magma to rise up to the surface and produce volcanos.
What you get over 60 million years is a gradual uplift and crumpling of this whole region.
The result, almost a byproduct of subduction, is the longest mountain range on any continent-- the Andes.
The Andes stretch for more than 4,000 miles, along almost the entire western coast of the continent.
It's a long, narrow range, because the mountains follow the boundary between the two plates where subduction is taking place.
And in a strange twist of fate, their formation may give Bolivia the chance to gain some measure of compensation for the traumas of the past.
As they've grown, the mountains have lifted one Bolivian lake from its original position, near sea level, to a height of nearly 13,000 feet.
This is the Salar de Uyuni-- the biggest salt flat on Earth.
Hidden in this landscape is a resource worth tens of billions of dollars.
It could have the global impact of the silver of PotosÃ, but without its tarnished history.
The key to understanding this new source of wealth is inside something we nearly all carry in our pockets.
Open up any mobile phone, whether it's a fancy, new touch-screen or one of these old-style handsets, and you'll find the battery.
What all these batteries have got in common is one key element.
The active components inside here are made of lithium carbonate.
As well as being in mobile phones, lithium's in laptops and all electronic devices.
It's used because of one quality above all, and that is lithium is the lightest of all the metals, so it gives more power for its mass.
Now, here's the thing.
Bolivia has as much as 50% of the world's lithium reserves.
Most of it in this extraordinary landscape.
In places, the lithium is only just below the surface.
Where the crust is thin, you can see the brine underneath, and if you really hammer away at it, then you can-- you can actually see the structure of the salt.
Look at that.
It's beautiful.
All these symmetrical crystals.
The white ones are sodium chloride.
That's just ordinary table salt.
But this pink one here-- that's potassium.
And this one, the brown-colored one-- that-- that's lithium.
So today, the lithium is here at the surface in the salt, but it started off way down deep.
Subduction produced magma that rose up and erupted out of volcanoes like that over there.
In fact, there's a whole series of-- all the way around.
So these mountains are rich in lithium.
From the slopes of the Andes, runoff erosion washes the metal-rich sediments down to the lake.
Since it's been uplifted, the lake has become surrounded by mountains, so no river can find a way out to drain the salar.
The result is that the only way water leaves the lake is through evaporation.
Over time, that concentrated minerals, including lithium, in the lake bed.
Subduction and the rise of the Andes has given South America extraordinary mineral wealth, and all that a consequence of that gradual drift of the new world away from the old.
That process has shaped the destiny of South America in another way, though.
I mean, here, it's given us a landscape of jaw-dropping beauty that's completely lifeless.
But elsewhere, it's created some of the richest and most unique habitats on the planet.
One ecosystem above all others owes its existence to the Andes, because as the Andes grew, the rivers of South America went through a series of massive changes.
Before the andes, it's thought the main rivers flowed in the opposite direction to today-- into the Pacific.
When the Andes started to rise, they diverted rivers to the north, where they flowed out into the Caribbean, creating a huge area of wetlands close to the growing mountains.
But then further uplift blocked the route north and forced the rivers to converge towards the Atlantic, forming an enormous drainage basin, and that led to the creation of the Amazon rainforest.
Meanwhile, on its western flanks, the Andes created a rain shadow.
The result is the driest place on the planet-- the Atacama desert.
By 10 million years ago, both South and North America looked similar to today, but there was one critical difference.
They were still separate continents.
The stage was set for the final act in the story of The Americas.
It didn't lead to a dramatic change in the landscape, but it did transform their wildlife.
The llama's ancestors first appear in North America about 40 million years ago.
But they don't appear in South America until 3 million years ago.
The two continents had been edging closer together.
Then, starting around 30 million years ago, volcanic islands began to combine, slowly building a land bridge between the two.
By 3 million years ago, two continents that had been separate since the days of Pangaea were finally joined again.
The New World was born.
Across this narrow link has come a great intermingling of species.
Northern mammals in particular invaded the South.
Deer, foxes, and dogs all crossed over-- and cats that quickly became the prime predators.
The result was to increase South America's biodiversity.
Among the most successful arrivals-- the llama, ironically, now long extinct in the north.
For me, the llama is the perfect symbol of the New World.
Originating in the northern continents and flourishing in the southern, they represent both the isolation and the coming together of The Americas.
Since that momentous joining, the story of The Americas has been of a single land.
When the first humans arrived in North America, they quickly moved into the south.
And when Europeans arrived, both Americas were seen as a single New World.
So, although the single, continuous land mass of Pangaea no longer exists, our modern-day continents are linked in a different way.
Today a great global economy binds all the continents together.
In essence, we've created a new Pangaea.
Pangaea of our own making.
And on this Pangaea just like the one 300 millions years ago, The Americas are right at the heart.