Original subtitles

We are entranced by the beauty of our planet.

Just take in this view for a moment.

Lush green meadows, thick forest, jagged mountain peaks -

it's magnificent.

But whilst we appreciate that beauty,

I think sometimes we forget that all of this is so fleeting.

For the last four-and-a-half billion years,

our Earth has been a constantly changing ball of rock,

transforming itself over and over again.

It's more fragile than we like to acknowledge.

It's more indifferent to us than we care to admit.

Now, thanks to pioneering new science,

we can explore our planet's four-and-a-half-billion-year story

like never before.

In this series, we'll witness five pivotal moments

in Earth's history...

..moments of drama...

..of crisis...

..and of rebirth...

..events that shaped the planet we live on.

Wherever you are, you have beneath your feet the most precious object

in the universe -

a living, breathing, life-sustaining world.

And this is its story.

It can feel as if our living world was somehow inevitable...

..that ours is a planet with all the right ingredients

for a rich assortment of life...

..not only to arise, but to flourish and endure.

But, in fact, it's death that is the only true inevitability.

There's an uncomfortable truth about life on Earth.

You see, this great diversity, this weird, wonderful

and beautiful mix of species, of plants, animals and fungi

are all only here because something else has died -

in fact, because an enormous number of other things have died.

If we were to take the sum total of every living thing

on our planet today, it would add up to less than 1% of those

that have ever existed on Earth.

But this colossal loss of life is not a tragedy.

Extinction is a vital part of evolution.

If nothing ever went extinct,

there would be no room for new species to evolve.

Over time, extinction helped create our rich living world.

But our planet walks a tightrope.

If extinction goes unchecked,

the complex web of life crumbles.

Imagine 90% of species suddenly dying -

not just a few endangered plants or animals becoming extinct,

or a handful of ecosystems disappearing,

but nine out of ten living things wiped off the face of the Earth.

Imagine what that Earth would look like in the aftermath -

shattered, broken, bereft of the beautiful complexity

that we take for granted today.

We may think modern climate change is our planet's darkest hour,

or the loss of the dinosaurs,

but the Earth has seen worse.

This is the story of the greatest mass extinction event

in Earth's history.

Something caused our planet's life-support systems to fail,

wiping out most of the species on Earth.

And this is not an apocalyptic vision,

not a doomsday prophesy.

This actually happened.

252 million years ago,

the Earth turned on the life that it had nurtured for so long.

What does it take to destroy almost all life on Earth?

And could it happen again?

Well, the answer lies in Earth's deep history...

..in a time long before humans transformed the planet's surface...

..before the last Ice Age...

..before the asteroid impact wiped out the dinosaurs...

..in fact, back to a time before dinosaurs

even existed at all.

From space, the Earth in the Late Permian is a strange sight.

From one side, a water world,

no land in sight.

But as the planet turns, something else creeps into view...

..all the Earth's major landmasses clustered as one.

This is Pangea...

..a supercontinent rich with life.

Coastal waters teem with weird and wonderful creatures.

At once both alien,

yet eerily familiar.

And in lush forests, a cacophony of animal cries fill the air.

In many ways, the Earth in the Late Permian

was like the Earth we have today -

millions of species of plants and animals, living together

in complex, interconnected webs

which are nurturing and self-sustaining.

But in other ways, it was a very alien world.

This was a time long before mammals or even dinosaurs walked the Earth.

But life was no less remarkable.

Scuttling around in the scrub of the Late Permian,

you might have found one of these.

This is the cast of a beautiful fossil of Nycteroleter.

It's part of an extinct group of reptiles, and fed on things

like proto-cockroaches, dragonflies, millipedes.

It's got quite large eyes,

suggesting that it might have been nocturnal,

and we also know that it had really good hearing -

something quite unique for animals of that time.

But then, look at this chap.

It's Dvinia.

It would've grown to about 50 centimetres.

Looked like a small dog.

Neither a mammal, nor a reptile, it's got forward-facing eyes.

It was perhaps a predator of some kind.

But, look, from the top, you can see it's got really wide cheeks,

and the remains here of perhaps a sagittal crest,

suggesting that it had very powerful muscles, a powerful bite.

In fact, it might have been fishing for shellfish down on the beach

and crunching them up with its powerful jaws.

But last, and perhaps most impressive,

this is a magnificent specimen of a super predator, Inostrancevia.

What an animal.

Just look at those sabre-tooth teeth there.

Now, those are slashing tools.

Those are for wounding prey, waiting for it to bleed to death,

and then catching up with it and swallowing large chunks whole.

This animal would've grown to about 3 metres in length

and very fast-moving

and been terrorising the large herbivores of its time.

What a fantastic beast it must have been.

But by the end of the Permian,

along with nearly every other living thing on Earth,

they would be dead.

We're not certain how it started,

but deep inside the ancient Earth,

superheated rock is rising...

..pushing upwards against the solid outer crust...

..until it can take no more.

The crust fails.

The landscape physically torn apart,

as lava floods onto the surface...

..forming great curtains of fire.

This is just the beginning of the most deadly volcanic event

in Earth's history.

We can get clues to what these ancient eruptions were like

by studying modern volcanoes.

This is Tajogaite Volcano, in the Canary Islands,

and in September of 2021, the ground here split

and tonnes of lava, ash and toxic gases exploded,

shaking the entire island.

Over three months,

170 million cubic metres of lava poured onto the surface.

It was the first eruption on the island in 50 years.

More than 7,000 people had to flee their homes.

This volcano spewed out enough lava to fill around

70,000 Olympic-sized swimming pools,

and that lava covered an area around ten square kilometres -

which sounds pretty impressive,

but it's just a teaspoon compared to those at the end of the Permian.

252 million years ago,

around four million cubic kilometres of lava, ash and toxic gases

erupted in a series of volcanic explosions

that went on for 2 million years.

The Permian eruptions were 1,000 times greater than

any witnessed by humans.

And the ancient lava is still with us.

In Northwestern Siberia,

beneath a landscape of swamps and flood plains,

scientists have discovered a colossal lava field,

dated a little over 250 million years old...

..lava that covers over two-and-a-half million

square kilometres...

..enough to bury the entire continent of Australia

hundreds of metres deep.

252 million years ago, Northern Pangea was hell on Earth.

Fire fountains blast volcanic material over six miles up

into the atmosphere...

..burning millions of square miles of forests.

And clouds bloom high into the atmosphere,

blocking out the sun.

Plants wilt and die...

..ash falls like snow...

..as vast swathes of Northern Pangea lie in ruins.

These eruptions are on a scale almost beyond imagination.

But lava still only covers less than 1% of Pangea's surface.

And elsewhere, something curious is happening.

A strange haze hangs in the air.

Nutrient-rich volcanic ash and sulphur,

transported thousands of miles, reflect the sun's rays...

..pushing global temperatures down...

..and in places, causing a surge of plant life to flourish.

But death is coming.

I've come to an outcrop in Northern Italy,

made of rock that formed at the same time as those ancient eruptions.

It's a fossilised crime scene

with a chilling tale to tell.

Look at this thin, black seam that runs all the way down here.

It looks like coal to me,

which would indicate that at one point...

..it was full of plant life.

Probably full of lots of other life, too.

Coal is little more than ancient organic matter

that's been subjected to extreme temperatures and pressures

over millions of years.

So, where we find coal today,

we know there was once life.

But the rocks above it here tell an altogether different story.

They're grey, dull, look a bit boring,

a bit of a geological mush.

But that's the point -

because, aside from a few fossil microorganisms,

scientists have found very little evidence of life in these rocks.

So, what they are telling us is that 252 million years ago,

the landscape here was almost devoid of life.

In a geological blink of an eye, almost all life here vanished.

You can't help but feel a certain sense of sadness.

Holding this makes it so tangible.

This was death on an unimaginable scale.

But there's no evidence of lava here at all.

When these rocks were laid down in this part of Italy,

they were thousands of miles away from the eruptions in the north -

certainly too far away for any direct impacts.

But what's interesting is that geologists

have found this line of death all over the planet -

China, Australia, South Africa.

And no matter how far away from the lava fields,

there's a deathly silence in the fossil record.

The question is, what could have killed this many creatures?

What could have wiped out almost all life on Earth?

Something more than lava was emerging from the Earth

in Northern Pangea.

Billions of tonnes of gases are injected high into the atmosphere.

Water vapour, sulphur dioxide...

..but primarily a gas we all know too well -

the greenhouse gas carbon dioxide.

We're all becoming depressingly familiar with what happens

when you pump huge quantities of carbon dioxide into the atmosphere.

It's an experiment we've been running ourselves

for more than 100 years.

And the more the CO2, the more the heat is locked in,

and the hotter our Earth becomes.

Global warming isn't a localised effect.

The whole planet feels the burn.

Here we are, yeah, dead ahead.

No creature is safe.

You've got a little feeding party taking place here at the moment.

Oh, look at that!

Oh, yes, yes!

Sorry to be a child, but it's always...

Oh, oh, oh, oh!

Oh, I just saw it catch a fish!

Oh!

There are several species here.

Bottlenose...

..common, rough tooth, spotted.

And dolphins, of course, can live in much warmer waters than these.

So, you might imagine they're not the sorts of creatures

that would be harmed by global warming.

But sadly, I've got to tell you, these dolphins are in trouble.

It's not always the temperature that poses a danger to life.

In fact, for some, the heat is a blessing.

Let's see what I've managed to catch.

Wow, rather a lot.

This mass of detritus here is plankton,

much of it phytoplankton, algae.

Now, most of the organisms wouldn't hurt anything,

but there is one species, Karenia Brevis -

well, that's an algae with a superpower.

You see, when the water warms up here,

it goes into a reproductive frenzy,

producing blooms many hundreds of times greater

than it normally would.

But what's good for the algae, it turns out,

is not so good for the dolphins.

Because recent research has shown that this is extremely toxic.

So, the small fish eat the algae,

the bigger fish eat the small fish,

the dolphins the larger fish.

And this organism has been implicated

in the deaths of dozens of dolphins,

found dead floating in the sea here.

Rising temperatures affect different parts of the food chain

in different ways,

throwing ecosystems out of balance...

..often with deadly results.

You see, when it comes to global warming,

it's not the actual heat that kills those creatures.

It's the increases or decreases in plant or animal populations

which disrupt those long-evolved, stable, beautiful ecosystems.

Death by global warming is not short, sharp, and painless.

It's prolonged and torturous.

As the temperatures rise across Pangea...

..trees begin to die.

Holes appear in the once-thick canopy,

bathing the ground in sunlight.

For some, it's an opportunity.

Weed-like plants flourish,

like spore-bearing lycophytes.

No longer struggling in the shadows,

in times of stress, they thrive.

And foreign species appear.

Woody, seed-bearing cycads that once only grew in the tropics

are now abundant closer to the Poles.

Surprisingly, some areas are now more diverse

than before the warming began.

But this is an ecosystem out of balance.

A few more degrees' warming,

and the living world will crumble.

But then something strange happens.

Red hot rivers of lava...

..turn to solid rock.

Just as quickly as they started,

the eruptions fall silent.

The CO2 released from the Permian lavas

likely dwarfed human emissions to date.

But even that may have been just part of the story.

These eruptions would have produced

an inordinate amount of carbon dioxide -

gigatons of the stuff,

certainly enough to manifest some global warming,

perhaps in the realm of an increase of 5 or 6 degrees Celsius,

something like that.

Now, that's a substantial amount of heating,

but it's not significant enough to account for all of the deaths

that we see in the fossil record.

Yes, there would have been extinctions,

but not 90% of all life on Earth.

The effects of carbon dioxide can be lethal.

But some scientists think there was another killer.

The volcanism hadn't stopped.

It had just entered a terrifying new phase.

Beneath the desolate lava field...

..hot magma still flows,

forming great reservoirs underground...

..and slowly baking the Earth's crust.

The rocks underground were older -

hundreds of millions of years older than the land above.

And amongst them,

there was plenty of this stuff -

coal and other rocks rich in carbon.

Now, what happens when magma meets coal?

Well, the coal burns, releasing yet more dangerous carbon dioxide.

But that was just the half of it.

You see, it wasn't just coal.

There was also lots of salt.

And salt like this can form when ancient lakes and seas dry up.

And when magma comes into contact with salt,

things get really nasty.

The salt begins to bake,

releasing toxic halogen gases rich in bromine and chlorine -

archenemies of the Earth's fragile ozone layer,

that thin layer that protects us from the sun's most harmful rays.

So, what I'm trying to say here is that the magma had found its way

into the worst possible place on the planet.

It had created a time bomb.

That magma begins to heat up the coal and salt

to a temperature of 800 degrees Celsius.

A poisonous cocktail of gases begins to build...

..until the land above can take no more.

More CO2 floods the atmosphere,

pushing global temperatures even higher.

But this time, there were also those toxic halogen gases.

We've seen the Earth's ozone layer damaged in recent history,

when artificial chemicals created a so-called ozone hole.

But in the Permian, the halogens may have eroded

the ozone layer away entirely...

..bathing all life in deadly UV radiation.

Scientists have noticed something strange going on with the pollen

at the end of the Permian.

Take a look at this.

This is a highly-magnified image of a modern pine pollen grain.

And you can see it's got two essential parts to its structure -

the central circular part here, the corpus,

and then these winged sacchi.

These are wind-pollinated pollen species,

and these help it float through the air.

But have a look at this.

This is an image of a fossilised coniferous pollen grain

from the time of those eruptions.

It's got three of these wing structures.

This one has four.

These pollen grains are malformed, misshapen and, in fact,

if you look at this last one,

this appear to have been in the process of dividing,

but somehow it's failed.

These are mutant pollen grains,

and it's thought that the mutation was caused by

the excessive UV radiation -

evidence that those gases had really damaged the Earth's ozone layer.

Now, other theories are available.

Others believe that, in fact, it was acid rain

that caused these mutations, or merely the extreme heat.

But whatever the cause,

what's clear is that at this point, life was on the brink.

At first glance, it seems nothing has changed.

But this already fragile ecosystem

has taken a lethal dose of UV radiation.

Healthy-looking plants are now sterile.

As individuals die, they aren't replaced.

Once-lush forests become ravaged wastelands.

The collapse in the oceans is even more dramatic.

Carbon dioxide reacts with sea water,

which begins to turn to acid.

And oxygen levels plummet -

in some places, dropping to zero.

Algae blooms across the planet.

As it decomposes, it poisons the ocean

with toxic hydrogen sulphide...

..until the seafloor becomes a foetid bed of slime.

Sulphurous tides lap barren shores,

and a smell like rotten eggs hangs in the air.

The Earth's rich complexity has vanished,

seemingly for good.

It's been called many things -

the Great Dying, the mother of all mass extinction events

or, simply, when life nearly died.

The details are still a bit hazy.

Was it a single short, sharp, giant catastrophe,

or a wave of smaller catastrophes?

To what extent did the extinctions occur on land

versus extinctions in the water?

The fossil record is patchy,

so there's plenty of room for academic debate.

But the one thing that almost everyone agrees upon

is that these ancient eruptions caused extinctions

on an unprecedented scale.

Figures frequently cited suggest that 70% of land vertebrates

and 96% of marine life

vanished off the face of the Earth forever.

By the time the eruptions finally stop,

the average global temperature has risen by over 10 degrees Celsius.

Vast areas of the Earth's surface are completely uninhabitable,

and nearly all species are gone.

The End-Permian extinction has a virtually undisputed claim

to being the worst moment in the history of the Earth.

But from the ashes, there was a glimmer of hope,

because life had survived somewhere.

It must have. Otherwise, we wouldn't be here.

In a way, we are all survivors of the Great Dying.

You see, every living organism on the planet has an ancient ancestor,

perhaps millions, perhaps billions of generations back,

that not only survived that mass extinction event

but then went on to prosper in the aftermath

and then to repopulate the Earth.

The Great Dying may have been the end of one world,

but it was also the beginning of a new one.

The Triassic Earth is a shadow of its former self.

Many creatures seek refuge underground...

..sheltering from blistering temperatures

and lethal UV radiation.

Above ground, a single plant species dominates the landscape.

Pleuromeia - a weed-like plant lucky enough to make it

through the apocalypse and find itself with few competitors.

It helps provide sustenance for the cockroaches,

who also made it through unscathed.

But just because the eruptions have stopped

doesn't mean that life's troubles are over.

The Early Triassic was dominated by extreme heat.

The fossil record shows us that ocean temperatures could have been

up to 14 degrees centigrade warmer

than they were prior to the eruptions.

In some places, the water was as warm as it is in a hot tub -

too extreme for most marine organisms.

And on land, things weren't faring much better.

There were probably heatwaves of up to 60 degrees centigrade -

a temperature that would have seriously inhibited photosynthesis.

In fact, for the 10 million years following the mass extinction event,

we see no significant coal reserves laid down anywhere on Earth.

There simply weren't enough trees.

For life to bounce back, the planet needed to cool down.

In normal times, the Earth can cool itself -

over thousands of years, removing carbon dioxide

from the atmosphere, in part through reacting with rainwater.

But vast areas of Pangea are desert.

Little rain falls.

So, it takes millions of years for temperatures to drop.

And even then, recovery is slow.

The living world's struggling to regain the diversity it once knew.

But salvation was coming.

High in the Dolomite Mountains is evidence for a bizarre event,

one that may have helped life rebound.

Look at this.

Absolutely stunning.

And these mountains were formed very shortly after the extinction event,

and they're made up of sedimentary rock -

layers of sediment on top of one another,

each corresponding to a time in the Earth's history.

The oldest rocks are at the bottom,

around 238 million years old.

The youngest at the top,

about 200 million years old.

Now, you might imagine that if we wanted to uncover the secrets

in these rocks, we'd take some, break them open

and look for some details - but not here.

The secrets in these rocks are held in plain view.

The key is the shape of the mountains.

It hints at a planetary intervention that, just a few decades ago,

we had no idea happened.

Look, it starts steep at the bottom, rises sharply,

and then there's a shallow shelf,

and then it rises steeply again to the peak,

currently in the clouds.

But the bit that we're interested in is that shallow slope,

which corresponds to about 2 million years in the Earth's history,

and to a very strange period of time.

This shallow slope is evidence of a softer rock type

that's been eroded over the years.

Here we go.

This is a lump of sandstone.

It's a soft sedimentary rock.

The key is in the name.

It's made up of sediments, like sand, which wash off of the land,

down into the rivers and then down into the sea.

So, what I'm holding here is evidence of rain -

rather a lot of rain,

because in places, this layer is about 80 metres deep.

Sandstone is a common rock,

but scientists have discovered similar layers

right across the planet,

leading some to think this was the result of a global deluge.

Now, we're not precisely sure why it started.

It could have been underwater volcanic activity

disrupting the water cycle.

But at some point in the Triassic,

a time famed for being excruciatingly hot and arid,

it started to rain.

And, boy, did it rain - because that rain

defined the Earth's climate for almost 2 million years.

18 million years after the mass extinction,

the heavens open...

..a sudden increase in rainfall across Pangea.

The rain causes more extinctions...

..but the planet is reborn.

Where arid shrub land once stood...

..lush forests now grow.

It's been called the greening of Triassic Earth,

and it marked the beginning of much of the life we know today.

There were new species of crocodiles...

..amphibians...

..even early ancestors of modern mammals.

But the mammals would have to wait in the wings.

Other creatures were set to inherit this renewed world.

Look at this.

See this impression in the rock here?

Look, there are one, two, three toes.

This is a dinosaur footprint,

and I love the fact that I can put my hand

where a dinosaur once put its foot.

Now, whether dinosaurs existed before the rains, we can't be sure.

If they did, it was only as an obscure group

in the south of Pangea.

But in the millions of years after the rains,

they certainly prospered.

In some places, 90% of the vertebrate fossils are dinosaurs.

Why did they suddenly do so well?

Well, it could be down to the food.

They could use it more efficiently to grow bigger more quickly.

But whatever the reason,

dinosaurs went on to dominate the Earth.

I love this!

By the end of the Triassic,

the stage is set for the reptiles to rule supreme.

This will be their world for the next 140 million years.

The age of the dinosaurs is dawning.

In one way, the End-Permian extinction

exposed the fundamental fragility of life.

Countless species of plants and animals were wiped out

by those volcanic eruptions,

and it took millions of years to recover.

But perhaps the event also taught us another lesson

about the tenacity of life -

because the living world did bounce back, to be just as complex

and just as beautiful, in fact, maybe even more so.

But there's a big unspoken question here.

For over 100 years, we've been pumping carbon dioxide into

the atmosphere and watching as global temperatures creep up.

So, what can the mass extinction 252 million years ago teach us

about our own climate change event?

I think the big lesson we've just learned is that the living world

will ultimately be fine.

Even if we don't address our climate and biodiversity crisis,

if we burn every last lump of coal and drop of oil,

if we leave this place as a complete hellscape,

whilst we might perish, life will bounce back,

and this will all be beautiful again -

which begs the question,

"Should we bother to preserve and protect it?"

Well, that extinction event 252 million years ago

was part of a planetary process.

It was a chance volcanic eruption.

Think of all of that suffering.

Think of all of that wastage.

Do we want those sorts of extinctions on our conscience?

I don't think so.

In this episode, we saw how an Earth-shattering eruption

destroyed almost all life on Earth.

- This is the closest our planet has ever been

to going back to square one.

- To understand the scale of the event,

scientists mapped the Permian lava fields of Russia -

known as the Siberian Traps.

- I have actually been to the Siberian Traps

and flown helicopters.

The helicopter is right, mm...there.

Floated on boats, hiked,

ridden on trains all over Arctic Siberia,

looking for remnants of the Siberian Traps.

And these lava flows go distances that boggle the mind.

The 1 million cubic miles that we have is probably a minimum number,

and it's a minimum because not all of the rocks

are exposed at the surface.

We also sampled the rocks of the Siberian Traps

with sledgehammers and rock hammers

and a lot of hard work.

- The rock samples were key to understanding

why the Earth's climate changed so dramatically.

- When magma comes up from deep within the Earth,

it has gases dissolved in it,

gases like carbon dioxide and sulphur dioxide.

These gases come out into bubbles,

a bit like when you take the lid off a soda bottle and it fizzes.

- But these gases told a contradictory story.

- Sulphur dioxide and carbon dioxide have opposite effects

on the Earth's atmosphere.

Sulphur dioxide reflects sunlight back into outer space,

causing global cooling,

whereas carbon dioxide is a greenhouse gas

and can lead to global warming.

- It turns out that different volcanic gases hang around in our atmosphere

for different amounts of time

because of their different chemical properties.

- Sulphur dioxide tends to stay in the atmosphere

for a shorter period of time,

because it can get rained out.

- But carbon dioxide can stay in the Earth's atmosphere for hundreds,

if not thousands of years.

- Scientists think that heat-trapping carbon dioxide

would have built up in the atmosphere, warming the planet.

And there were other clues in the fossil record.

- So, we can measure what temperatures were like in the past

by the study of fossils,

and particularly fossil bone material.

So, when the bone is formed,

it's partly controlled by the temperature.

And so by studying these bones, we're able to see

what the temperatures were like back in the past.

- Temperature rises of up to 7 degrees brought a deluge of rainfall.

Known as the Carnian Pluvial Episode,

some scientists think these conditions were essential

to the success of the dinosaurs.

- My research suggests that more rain means it's better for the plants.

This era of warm, wet conditions really boosted plant diversity.

More plants equals more insects, more plant-eaters,

and then you get more meat-eaters as well,

and dinosaurs are part of that growth.

So, this is Herrerasaurus.

This is one of the first dinosaurs to appear.

And as you can see by the sharp teeth here,

this was a meat-eater, one of the top predators.

- The evidence for this growth is written in the rock record.

- The success of the dinosaurs after this event is seen in

just an abundance of their fossils, but also in their sort of indirect

records that they leave in the forms of their footprints as well.

- Before the Carnian Pluvial Episode,

dinosaurs and their relatives only made up around 5% of the footprints

at these different fossil sites.

After the Carnian Pluvial Episode, we see a big increase -

it jumps up to 70%.

- The explosion in the population of dinosaurs

is a brand-new area of research.

- We can see that the ecosystems were changing,

but what actually would've affected the dinosaurs,

what would've caused them to be successful,

we don't know yet.

This is why there's so many palaeontologists

doing active research.

- Next time...

..we journey deeper into the past,

to witness one of the strangest moments in history...

..a global deep freeze..

..that transformed the Earth...

..into an ice world.

If the Earth could talk, what would it tell us?

Well, the Open University imagine how it might answer

some of our questions.

To experience this interactive presentation,

go to the website on the screen and follow the links

to The Open University.