All language subtitles for NOVA S50E14 Ancient Earth Inferno 1080p WEB h264-BAE_track3_[eng]

♪ ♪

NARRATOR:
252 million years ago,

a catastrophe killed
nearly all life on Earth.

This is closest our planet
has ever been

to going back to square one.

As many as 90% of species
across the Earth died.

SURESH SINGH:
This extinction was much greater

than the one that ended
the age of the dinosaurs.

NARRATOR:
But an asteroid wasn't to blame.

SONIA TIKOO:
It is not easy to kill
so many species,

so this had to be something
utterly catastrophic.

(rumbling)

NARRATOR:
The culprit was lurking

just beneath the surface.

We're finally able to
piece together

clues from this
ancient crime scene.

Now we finally know
the culprit:

enormous volcanic eruptions.

TIKOO:
It is as if the Earth itself
turned on life.

NARRATOR:
Yet some life stubbornly
hung on.

♪ ♪

And when the threat passed,

thrived again.

PAUL WIGNALL:
Mass extinction events,

although terrible, provide new
opportunities for life.

Death and extinction

shaped the biodiversity
of the living world.

♪ ♪

NARRATOR:
From the ashes of a lost world

comes the story of

"Ancient Earth: Inferno."

Right now, on "NOVA."

♪ ♪

♪ ♪

NARRATOR:
In a time long before

the rise of
human civilization...

♪ ♪

Before the last
glacial period...

♪ ♪

Before an asteroid impact
wiped out the dinosaurs...

♪ ♪

In fact, a time before dinosaurs
even existed at all...

An apocalypse destroyed
nearly all life on Earth,

and it may hold lessons
for our future.

♪ ♪

Over a quarter of a billion
years ago,

the disaster looms.

♪ ♪

("Never Close Enough"
by SIPHO. playing)

♪ Oh, we won't ever hear
the silence ♪

♪ Or ever see the colors ♪

(exploding)

♪ That never lived in
our minds ♪

♪ ♪

♪ Just a moment ♪

♪ Never too far out ♪

♪ Never close enough ♪

♪ ♪

NARRATOR:
253 million years ago.

Earth looks very
different than it does today.

On one side, a water world.

No land in sight.

♪ ♪

But on the other side,

Earth's landmasses are clustered

into a colossal supercontinent.

♪ ♪

This is Pangaea.

♪ ♪

Lush forest ecosystems flourish.

(animals grunting)

♪ ♪

And its waters teem with

weird and wonderful creatures.

♪ ♪

The Permian Earth is
rich, diverse,

and full of life.

♪ ♪

There are no ecosystems
on Earth today

that look exactly like those of
the Permian period,

but some share
a few similarities.

♪ ♪

Life at the end of the Permian
was beautiful.

We had a very diverse ecosystem,

both in the marine realm, but
also on land.

any birds, any flowers,

so completely different.

♪ ♪

JEFFREY BENCA:
But you would recognize

some of the early forerunners

to our modern conifers,
for example.

♪ ♪

So, the rock I'm holding here

has a lot of fossil leaves

from a plant called
Glossopteris--

one of the tree-forming plants

that lived in
the Southern Hemisphere.

It's pretty cool to hold a
fossil from that time period.

It's like going back

in a, in a time machine.

♪ ♪

NARRATOR:
Pangaea is dominated by
animals that lived before

dinosaurs and mammals evolved.

(animals grunting)

Forgotten creatures that
scientists only know about

from the fossil record.

You would have had

these giant armored herbivores

with these crazy, big, bony
sort of processes

on their skulls called
pareiasaurs.

BRANDON PEECOOK:
And the big predators are
called gorgonopsians.

They've got a mouth full of
sharp teeth.

Smaller sharp teeth up in the
front,

and then
these incredible sabers.

This is the first time
that we know of predators

evolving saber teeth
to kill their prey.

On land during the Permian,
we had insects, as well.

We see wings,
some of which span

more than a foot long.

Much larger than
the ones we see today.

♪ ♪

DUNNE:
And we also see the very first
beetles.

The beetles haven't appeared yet
in the fossil record

until about the Permian.

NARRATOR:
There is also great diversity
to be found in the oceans.

The oceans would look

completely different to now,

but with a couple of familiar
characters,

ray-finned fish and sharks.

There were lots of reefs,

but made of very different
types of organisms.

And there would have been
trilobites

scuttling about on the ocean
floor--

more or less seafloor bugs.

By the end of the Permian, life
had become

very rich and diverse in, in a
whole range

SINGH:
I would love to go back

and see all these animals
living together.

It would be
a great prehistoric safari.

♪ ♪

NARRATOR:
But life is about to change
forever.

Deep beneath Northern Pangaea,

superheated liquid rock--
magma-- is rising.

It pushes up against

the Earth's rigid upper layer,
the crust,

until it can take no more.

♪ ♪

The crust splits open.

(erupting)

Within hours,

the local landscape
is torn apart.

Cracks grow,
forming great curtains of fire,

as lava floods onto the surface.

♪ ♪

The insides of Earth spew out.

The eruptions came from
a giant volcanic system

in Northern Pangaea
called the Siberian Traps.

♪ ♪

The remnants, the rock record

of these volcanic eruptions,

still exists in Siberia.

♪ ♪

There's a huge footprint of lava
left behind,

BURGESS:
I've actually been to
the Siberian Traps

and floated down rivers
where both sides of the river

were huge cliffs of
stacked-up lava flows.

♪ ♪

NARRATOR:
These rocks reveal that
the Siberian Traps

erupted on and off
for around two million years...

♪ ♪

...emitting about 700,000
cubic miles of magma and rock.

The eruptions at the end of
the Permian are absolutely huge.

They're, they're vastly greater
in scale

than anything
that we've seen today.

WHITESIDE:
This is a planetary-scale
eruption that would

cover the United States
in lava around 300 yards deep.

♪ ♪

NARRATOR:
We can try to grasp the scale
of these eruptions

by comparing them
to recently active volcanoes.

Witnessing a volcanic eruption

just gives you a sense of how
powerful

the Earth is.

MATHER:
The explosions make
the ground throb,

so you can feel sound traveling
through your whole body.

♪ ♪

And the smell and the fumes
can be really intense.

♪ ♪

NARRATOR:
In 2021,

the volcano Tajogaite erupted
and released around

300 million cubic yards
of material.

That's enough to fill...
80 football stadiums?

NARRATOR:
Other eruptions in
human history,

like the Krakatau Volcano,
were much bigger.

MATHER:
So, when Krakatau erupted
in the 1880s,

it spewed out about
two cubic miles of magma.

YING CUI:
The eruption was so large

that it led to global
temperature decrease

because of the gases emitted.

(eruption roars)

...of the Siberian Traps.

♪ ♪

WHITESIDE:
The Siberian Traps would be like
a Krakatau erupting

every year for 300,000 years.

NARRATOR:
Eruptions on this vast scale

are devastating to life nearby.

♪ ♪

Fire fountains blast
volcanic material

up into the atmosphere.

Untold numbers of creatures
perish in the forest fires

that burn close by.

Sulfur dioxide builds up and
reacts in the atmosphere,

partially blocking out the sun.

Plants wilt and die as
a volcanic winter sets in.

♪ ♪

Ash falls on a dying landscape.

After each eruption,

vast swaths of Northern Pangaea
are scorched.

But is it enough to
cause mass extinction?

♪ ♪

Although these
early eruptions are huge,

Pangaea is big, too.

Most of the supercontinent

remains untouched by
deadly lava.

Elsewhere in Pangaea,
something curious is happening.

♪ ♪

A strange haze hangs in the air.

♪ ♪

Created by nutrient-rich
volcanic ash and sulfur,

blown here from the eruptions

happening
thousands of miles away.

♪ ♪

At first, plant life seems
unaffected,

and may have even benefited
from the nutrients and the ash.

There is no mass extinction.

For now.

But death is coming.

♪ ♪

These rocks,
formed 252 million years ago,

contain evidence
of a massive die-off.

As we go up
in this section,

we are traveling
forward in time.

So, these rocks here are older
than the ones on the top.

♪ ♪

NARRATOR:
These ancient rocks were
formed on the ocean floor,

before being pushed up
to make these mountains.

Rocks not only tell us about

the environment in which
they were formed,

but something
extraordinary about them,

it's that they are
full of fossils.

So, for example, clams,
marine snails,

shelled organisms,
and other fossils,

like this nautilus,

that were living during
that time.

NARRATOR: The diverse fossils in
these rocks show that this

was a vibrant marine ecosystem.

But that was about to change.

So, all the complex ecosystem

that we are seeing here,
full of life,

after

this level, it becomes, like,
super-hard to find fossils.

And the things that we do find
are really tiny,

and we see how all the diversity
that we have below

seems to have just disappeared.

NARRATOR:
Over just a few hundred years--

a geological blink of an eye--

almost all life here vanishes.

This is death
on an astounding scale.

But curiously, these rocks
show no direct evidence

of this volcanic activity.

GÓMEZ CORREA:
So it's actually
really surprising

that here we are,
thousands of miles away

from the eruptions going on
in the north of Pangaea,

and still you see
the consequences going on there.

This event,

it's not only found here,

but also across the planet.

Life just vanished.

You will see this line of that.

You will see how life
seems to just vanish.

♪ ♪

NARRATOR:
How could volcanic eruptions
in the north

wipe out so much life
across the entire planet?

Scientists think that the
Siberian Traps

was erupted in different phases.

Phase one was characterized
by lava flows

for around 300,000 years.

♪ ♪

NARRATOR:
It's not just Earth's surface

that is affected by
the eruptions.

They also eject
billions upon billions

of tons of gas and
tiny particles into the air.

♪ ♪

Water vapor, sulfur dioxide,

toxic heavy metals,
and carbon dioxide,

which begin to disperse
in the atmosphere.

So, what we want to understand
is,

how were these gases affecting
the planet?

♪ ♪

TIKOO:
Sulfur dioxide and carbon
dioxide have opposite effects

on the Earth's atmosphere.

Sulfur dioxide reflects sunlight

back into outer space,

causing global cooling,

whereas carbon dioxide
is a greenhouse gas

and can lead to global warming.

NARRATOR:
The cooling and heating effects
of these gases in the atmosphere

act on different timescales.

Sulfur dioxide tends to stay in
the atmosphere

for a shorter period of time,

because it can get rained out.

TIKOO:
But carbon dioxide can stay
in the Earth's atmosphere

for hundreds,
if not thousands, of years.

(rumbling)

NARRATOR:
After each pulse or surge
of volcanic activity,

any cooling effects from sulfur
dioxide wouldn't last long.

But for heat-trapping
carbon dioxide,

it's a different story.

Carbon dioxide released during
one pulse

of the Siberian Traps volcanism

would have stuck around

for the next pulse.

NARRATOR:
And as carbon dioxide builds up
in the atmosphere,

it affects the entire planet.

BURGESS:
So, the biggest driver of
environmental change

that leads to mass extinction
is not the lavas themselves.

It's the gases that they release
into the atmosphere.

♪ ♪

NARRATOR:
We're witnessing the impacts

of increasing levels
of greenhouse gases today,

but at a much smaller scale.

CUI:
As we are adding

more carbon dioxide to the
atmosphere today,

the global temperature is
rising,

which lead to a series of
environmental changes.

NARRATOR:
Studying our oceans and the
impacts of modern climate change

gives clues as to how life
might have been affected

by the warming
252 million years ago.

We can see right now, in our own
world,

coral reefs affected by climate
change.

The oceans are getting warmer

and they're getting more acidic.

SHUKLA:
This is really stressful
for corals,

and it causes vast swaths
of places

like the Great Barrier Reef
to bleach,

turning corals white.

NARRATOR:
Bleached corals are
more likely to die,

and this can have
devastating consequences.

Coral reefs are a
poster child ecosystem

for one that's complex
and full of life.

If you start taking
away those corals,

it's really easy to see

how ecosystems like that can
collapse.

NARRATOR:
But it's not just coral reefs

that are being
pushed off balance

by present-day climate change.

As temperatures rise
in the ocean,

that allows algae to
reproduce really quickly.

And when it rains,

that pushes nutrients that
we have on land into the ocean,

and the algae
feed on that and grow,

resulting in these
enormous algal blooms.

♪ ♪

NARRATOR:
These vast algal blooms today

have consequences for
life in the oceans.

And in this case,

it's not the rising
temperatures that kill.

As algal blooms occur,

they actually take up the oxygen
in the ocean,

leaving less oxygen behind,

and therefore, organisms
can't live in it.

NARRATOR:
Changes in modern-day ecosystems

show how the process
of extinction can play out.

FORMOSO:
So, these subtle changes

may not seem
so striking at first:

the loss of one species here,

the change in this environment
over there.

But given enough time

and given enough of these
subtle changes,

you can have drastic
negative impacts on ecosystems.

This slow relentless change
is likely what led to

the huge loss of life
at the end of the Permian.

♪ ♪

NARRATOR:
Mass extinction can
take place slowly

over thousands or
even millions of years,

as environmental changes
become too much

for many species to adapt to.

♪ ♪

In Pangaea,
as greenhouse gases build up

over hundreds of thousands
of years,

the temperature rises.

MONARREZ:
During the mass extinction,

it is thought
the ocean warmed up

between 14 and 18 degrees
Fahrenheit,

and on land,
they warmed up even more.

NARRATOR:
On the supercontinent,
trees begin to die.

(trunk cracking slowly)

(creaking)

♪ ♪

Holes appear in the canopy,

bathing the ground in sunlight.

For some life,
it's an opportunity.

Weed-like lycophyte plants

flourish in this new
environment.

And with the
warmer temperatures,

other species migrate.

Woody, seed-bearing plants
called cycads

that are believed to have
once grown in the tropics

now thrive closer to the poles.

♪ ♪

Fossil evidence suggests
that some ecosystems

are now more diverse
than before the warming began.

♪ ♪

But this ecosystem
is still vulnerable.

A few more degrees of warming
and it could crumble.

♪ ♪

But then,
something strange happens.

A silence descends
on the Siberian Traps.

♪ ♪

Greenhouse gas emissions,

including carbon dioxide,
taper off.

After 300,000 years
of lava flows,

the eruptions finally stop.

For now.

♪ ♪

When scientists try
to calculate the amount of

greenhouse gases
released by the eruptions,

and then compare that to
the amount of global warming

implied in the rock record,

something doesn't add up.

When we add up all the carbon

we think we would have got
from the magmas,

making our best guess,

it's not enough to account for
the level of climate devastation

that the geological
record suggests.

♪ ♪

BURGESS:
About half of the
greenhouse gases

needed to drive the
extinction to

the end of the Permian
are missing.

NARRATOR:
So, where do all the extra
greenhouse gases come from?

♪ ♪

One answer
can be found underground.

♪ ♪

It's quiet on the surface.

But beneath
the Siberian lava field...

...reaching
almost eight miles deep...

...hot magma still flows,

forming great
reservoirs underground,

encountering rocks hundreds
of millions of years old

deep below.

The amount of lava that,
over time,

was released from the Siberian
Traps

was so immense

that it caps the Earth's surface
eventually.

building up on Earth's surface,

the path of the magma changes.

The volcanism enters phase two.

BURGESS:
Instead of lavas flowing
on the surface,

magma started
to spread laterally underground.

MATHER:
The Earth's crust is
in some ways

like a layer cake.

So as the magma forced its way
up,

it encountered different layers
of rock.

♪ ♪

NARRATOR:
One such rock was coal.

WHITESIDE:
In this case,
the magma literally

started burning fossil fuels

similar to the way we're burning
them

through our pistons and power
plants.

NARRATOR:
But carbon dioxide
doesn't act alone.

It isn't just coal
in the Earth's crust.

TIKOO:
Beneath the volcanic rocks
released

by the Siberian Traps eruptions

lies an ancient seabed that
contains the salt

In some places, the salt layers

were 650 feet thick.

Now, that's quite a lot of salt.

the consequences
can be devastating.

So, salt is-- I have a piece
with me here.

not very dangerous-looking
rock type, as we know.

We put salt on our food
and so on.

But it can be very dangerous.

So, when the hot magma comes
into contact

with these salt layers,
it, it bakes them,

releasing all
sorts of horrible gases.

TIKOO:
The burning coal

and the heated-up deposits
of salt

that were
triggered by these eruptions

just basically
created a huge time bomb.

♪ ♪

NARRATOR:
The salt and coal underground
are heated

to as much as
1,400 degrees Fahrenheit.

And begin to release
their toxins.

The pressure
beneath the surface increases.

Until the land
above can take no more.

(rock cracking)

♪ ♪

(eruption roars)

Volcanic material
flies miles into the air.

Each eruption releases more
greenhouse gases

from burning coal.

This is thought to be
the missing link that accounts

for the full extent
of global temperature rise.

And the scorching salt
releases deadly chemicals, too.

Toxic gases called halogens,

which can spell trouble
if they reach the ozone layer.

WIGNALL:
It's a layer high in our
atmosphere,

and what it does is,

it protects our planet
from ultraviolet radiation

from the sun, which is
very harmful for all life.

SINGH:
When these halogens react
with the ozone layer,

they weaken it,

and that allows harmful
radiation

from the sun to come through.

in recent history.

In the 1980s,

industrial activity created
a hole in the ozone layer

over Antarctica.

One that is now closing.

But during the extinction event
at the end of the Permian,

the halogens damaged

the ozone layer
on a devastating scale,

bathing life with a massive dose

of harmful
ultraviolet radiation.

The loss of ozone is thought

to have contributed
to the extinctions.

But can scientists
find a way to prove it?

BENCA:
A way we can really understand

the mass extinction is by
looking at

fossilized pollen grains,

microscopic
reproductive structures

plants left behind
in the fossil record.

NARRATOR:
Some tree pollen has remained
relatively unchanged

for hundreds of millions
of years.

So modern-day pollen
should look the same

as that in the fossil record.

So, I have a picture here

of a modern pollen grain
of a pine tree.

It's basically one central body,

and there are these two
structures on the side

that are called sacci.

These help this grain
catch the wind and fly.

And this is very much what
the pollen grains

in the end-Permian trees would
have looked like

under normal conditions.

NARRATOR:
But the fossil pollen from
the extinction event

doesn't look the same.

So, during the mass extinction
at the end of the Permian,

the pollen grains start looking
more like this,

and, boy, they're strange.

This one here has three
sacci when it should have two.

And this one has four sacci.

This here is two grains
that are stuck together.

They come in all sorts

of strange shapes and forms
that really deviate

from what a healthy pollen grain
should look like.

They're malformations.

NARRATOR:
Could increased ultraviolet
radiation be the cause?

To find out,

paleobotanist Jeffrey Benca
grew modern pine trees

under high ultraviolet
radiation in a lab.

BENCA:
We wondered if the plants

would just die on us
under these extreme conditions.

But that's not what we found.

Instead, we found the exact
same types of malformations

in the fossil record were
produced by our modern pines.

NARRATOR:
Although this high
ultraviolet radiation

didn't kill the plants outright,

malformations in the pollen did
have catastrophic consequences.

The results of this experiment
are telling us

that at the end of the Permian,

the forests would
have been sterilized,

unable to reproduce.

NARRATOR:
It is a slow march
to extinction.

♪ ♪

The Permian forests
have been exposed

to extreme
ultraviolet radiation.

Healthy-looking trees
are now sterile.

♪ ♪

As trees die
and are not replaced,

animals lose precious habitat
and food supplies dwindle.

♪ ♪

During the mass extinction,

life on land is
under threat from all sides.

The mass extinction at the end
of the Permian

is like
"Murder on the Orient Express."

There's not one killer
that can do it all.

SINGH:
There's still a lot of debate

about how all these killers came
together

to kill off life on land.

We're talking global warming,
heavy metal poisoning,

acid rain, wild fires,
deadly U.V. radiation.

This was hell on Earth.

♪ ♪

BENCA:
There probably were pulses
of ozone weakening

that were happening throughout
the duration

of the Siberian Traps activity,

but over even longer time spans,

global warming was kicking in

and really driving
ecosystems to full collapse.

NARRATOR:
The collapse
of life in the oceans

is even more dramatic.

The warmer, nutrient-rich waters
contain less oxygen.

Oxygen that marine life
uses to breathe.

And as carbon dioxide reacts
with seawater,

the oceans become more acidic.

Algae and bacteria bloom
across the planet,

poisoning the oceans with the
hydrogen sulfide they release.

Creatures across the oceans die.

Huge stretches of the seafloor
become fetid beds of death.

MONARREZ:
So, in the oceans,

the combination of increases
in temperature,

loss of oxygen, and
acidification

we see at the end of the
Permian.

These ocean killers could have
worked together

to be exceptionally devastating
to ocean life.

NARRATOR:
Exactly how much life
died is debated by scientists,

because the fossil
record is incomplete.

But evidence shows

that the great Glossopteris
forests,

the giant sabertooth predators,

and almost
all marine life disappears.

♪ ♪

By the time
the eruptions finally stop,

the average global
atmospheric temperature

has risen as much
as 22 degrees Fahrenheit.

Countless species have gone.

The rich complexity
of life on Earth has vanished.

The words "mass extinction"
are not

lightly put together by
scientists.

They carry real weight.

And the extinction
at the end of the Permian

was the most
severe of all of these.

It's been called the mother of
mass extinctions,

it's been called the Great
Dying.

It's, it's by far the worst
thing

that's, that life has ever had
to endure.

♪ ♪

NARRATOR:
With so much death
and destruction,

how could any
life hold on at all?

Life on Earth is adapted to
living on Earth.

It has evolved that way.

And if circumstances change,

organisms can adapt
to that change.

(hisses)

And those that cannot adapt
will eventually go extinct.

♪ ♪

NARRATOR:
If species can adapt
to the new conditions,

it gives them
an opportunity to thrive.

Death and extinction shape
the evolution of life.

It's through this act

of creative destruction,
where one species go extinct,

that allows for another species
to actually rise.

Over time, the combination
of these interactions,

of extinction,
adaptation, and evolution,

create resilient ecosystems.

NARRATOR:
But even resilient ecosystems
aren't indestructible.

An ecosystem is a lot like a
Jenga tower,

where each brick is its own
species.

And as you remove one to two
species,

But the more species you lose,

the more unstable
the ecosystem becomes

until it fully collapses.

PEECOOK:
Today, organisms are really
struggling

to adapt to
an ever-changing planet.

SHUKLA:
And it's not
just climate change.

It's also things
like habitat destruction.

Loss of coral reefs,
loss of sea ice.

Deforestation.

Loss of wetlands.

Loss of grasslands and prairies.

NARRATOR:
But even after ecosystems
collapse,

like they did 252 million
years ago,

some life survives.

If it can adapt,
there's a chance to rebuild.

♪ ♪

The Permian apocalypse
isn't just the end of one world.

It's the beginning of a new one.

♪ ♪

Fossil evidence is patchy,

so scientists don't know
exactly where life holds on.

On land, some life likely
survived near the cooler poles.

And many creatures could
have sought refuge underground,

sheltering from
blistering temperatures

and intense solar radiation.

And some life
survives above ground, too.

A single type of plant dominates

much of the post-extinction
landscape.

Pleuromeia.

A hardy plant that makes
it through the apocalypse.

This ecosystem provides

just enough sustenance
for the cockroaches,

who also make it through.

Life endures.

But the searing heat does, too.

The period immediately
after the Permian

is the Triassic period,
and it was very, very hot.

NARRATOR:
Scientists know about these
conditions

from studying fossils

and the chemical composition
of rocks formed at the time.

It's incredible what we can get
from rocks.

They look so unassuming, but
actually,

they hold so many clues

to past environments and past
life.

LOOY:
We, for instance, know that
there were forests growing

on the South Pole,
and to make that happen,

you need a warm planet.

WHITESIDE:
Temperatures on land would be
120 degrees Fahrenheit,

possibly up to 140,
with heat waves on top of that.

LOOY:
And that is so hot that in
several places of the world,

complex life would
not have been possible anymore.

NARRATOR:
It's also hot in the oceans.

Surface ocean temperature may
have reached as high

as 100 degree Fahrenheit,

and that's as hot as a hot tub.

These extreme ocean temperatures
would have been

inhospitable to most ocean life.

MONARREZ:
The mass extinction at the end
of the Permian

was so devastating
to coral reefs

that for about 14 million years
into the Triassic,

we don't see corals
anywhere on the planet.

NARRATOR:
For life to bounce back,
the planet needs to cool down.

♪ ♪

Normally, over vast timescales,

Earth's temperature
naturally resets itself.

Carbon dioxide
is removed from the atmosphere,

in part by
reacting with rainwater.

But vast areas of
Central Pangaea are desert.

Little rain falls.

It takes millions
of years for Earth to cool.

♪ ♪

Much of the supercontinent
remains barren and dry.

But 18 million years
after the mass extinction began,

life is about
to get an enormous boost.

(thunder rumbling)

And traces of what that was
can still be seen today.

♪ ♪

These mountains are largely made
of a hard rock called dolomite.

But hidden within them

are layers of an altogether
different rock.

One that holds clues

to an extraordinary time
in Earth's history.

EVELYN KUSTATSCHER:
This is the rock that formed

during this strange period
of time.

This is a sandstone.

It's a relatively soft stone,
and you can see

all the single grains
of the sand.

And if we take this ones
in here,

this is a softer stone still,

and it easily breaks down
in my fingers,

because it's a mudstone.

These rocks in here are looking
completely different

from the ones below and above
us,

because these are sandstones
and mudstones,

whereas those above and below
are dolomites.

NARRATOR:
The secret of this unusual layer
of rock

is how it was formed.

Sandstones and mudstones
are sediments

that are typically formed

by the erosion of sand and mud
on the continents

which were
washed into the ocean.

NARRATOR:
All over the Dolomites,

there are examples of this

strange layer of softer rocks
made from sand and mud.

KUSTATSCHER:
So now, of course,
we have to ask ourself,

what caused
this dramatic change?

NARRATOR:
The answer came from the sky.

And it was rain, a lot of rain.

This episode
lasted for a long time.

About two million years.

NARRATOR:
A deluge on this scale seems
so unlikely

that when scientists
first discovered the evidence,

some believed
it was just a local event.

KUSTATSCHER:
But later on,
evidence of it popped up

also at China,
Iran, North America.

So nowadays, it is
believed to be a global event.

This period of time is called
the Carnian Pluvial Episode.

(thunder rumbling)

NARRATOR:
18 million years after
the mass extinction began,

the skies become heavy
with moisture...

...until the clouds burst.

(rain falling, thunder rumbling)

Rain falls across Pangaea.

And Earth is changed once more.

♪ ♪

Lush forests grow again.

This two-million-year event
lasted just as long

as the volcanism
that preceded it

and may have marked
the rise of a new life form.

The Carnian Pluvial Episode set
the stage

for the dawn of the age
of dinosaurs.

♪ ♪

SINGH:
My research suggests that this
era of warm,

wet conditions really boosted
plant diversity.

And from the plants, we get

more herbivores,
more carnivores,

and dinosaurs are
part of that growth.

So, this is Herrerasaurus, this
is one of the first dinosaurs

to appear just after
the Carnian Pluvial Episode,

and as you can see by
the sharp teeth here,

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

The Carnian Pluvial Episode,

and what it might have meant
for dinosaurs,

DUNNE:
We see a lot of fossils that we
can't quite

figure out exactly how they fit
into the grand family tree

of ancient life,
and so we are working with

some very difficult fossils,

and putting all this stuff
together

is very, very difficult
for scientists.

(rain falling, thunder rumbling)

PEECOOK:
We can see that the ecosystems
were changing.

We can see
that the climate was changing.

But how those interact,

what actually would have
affected the dinosaurs,

what would have caused them
to be successful,

we don't know yet.

This is why there are
so many paleontologists

doing active research.

NARRATOR:
What scientists do know today

is that the world
of the dinosaurs will persist

for over 160 million years.

♪ ♪

Life on our planet...

(explosion roars)

...has been punctuated by
catastrophes.

And although
the extinction at the end

of the Permian might seem
like a distant nightmare,

it holds lessons
for our own future.

CUI:
Both the end of the Permian
and today,

we are seeing
rising global temperatures,

lower oxygen levels in the sea,
and ocean acidification.

Today, there's no volcano--
it's just us.

TIKOO:
While we're not releasing
as much greenhouse gas

as was released during

the entirety of
the Siberian Traps eruptions,

the fact is, we're releasing
them a lot faster today.

NARRATOR:
And our fast-changing
environment

is affecting life everywhere.

We are driving things
to extinction

at, at an extremely rapid rate.

SHUKLA:
If the loss of life

continues to go unchecked,
we may very well

be in the midst of another
mass extinction on this planet.

NARRATOR:
But even after the worst
catastrophes

in Earth's history,

life recovers.

DUNNE:
The extinction at the end
of the Permian

both shows
us the fragility of life,

but also shows us
how resilient life can be.

FORMOSO:
The most amazing thing
about life

is how it bounces back from
these devastating events.

However,
it comes back differently.

BENCA:
It takes a long time

for life to rebound from
these sorts of events.

MONARREZ:
If we continue on our
current path,

we risk altering
life as we know it.

We also risk our place
as humans on this planet.

NARRATOR:
And yet hope remains.

Human beings are
an ingenious species.

SINGH:
We've gone from hunter-gatherers
to traveling through space.

If we can do all that,

I'm confident we can
sort out our current problems.

NARRATOR:
What does the legacy
of mass extinction

mean for our future?

Whether it's a massive eruption
of lava

or human beings
burning fossil fuels,

the Earth is going to be fine--
it's the species

that are living on the Earth
at the time

that might not make it through.

In the long term,
the Earth will come back

from where we are today.

The question is just
whether we as a species

will be here to see it.

♪ ♪

NARRATOR:
On "NOVA: Ancient Earth"...

AISHA MORRIS: One major event

can have these ripple effects

throughout the rest of history,

and this event is almost
unmatched.

STEVE BRUSATTE:
In the history of life,
it is one unfolding story--

so many new characters coming in

and old characters
going extinct.

ZERAY ALEMSEGED:
What I'm holding is the earliest
child ever discovered.

This species was at the cusp
of being human.

NARRATOR:
"Humans" on "NOVA."

Next time.

SINGER:
♪ Wish I could go back in time ♪

♪ ♪

♪ ♪

♪ ♪

♪ ♪

♪ ♪