50x14 - Ancient Earth: Inferno

[bunniefuu]

♪ ♪

NARRATOR: 252 million years ago,

a catastrophe k*lled
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 k*ll 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.

EMMA DUNNE: It doesn't
contain any mammals,

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 k*ll 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

of habitats, both on
land and in the sea.

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,

covering a huge area
of modern-day Siberia.

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


yards of material.

That's enough to fill...


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.

NARRATOR: But even Krakatau was
minuscule compared to the eruptions...

[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


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 k*ll.

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.

NARRATOR: After


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

left behind whenever
the sea dried up.

In some places, the salt layers

were 650 feet thick.

Now, that's quite a lot of salt.

NARRATOR: When salt
and magma make contact,

the consequences
can be devastating.

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

On its own, salt's a
fairly sort of innocuous,

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 b*mb.

♪ ♪

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.

NARRATOR: We've seen the Earth's
ozone layer temporarily degraded

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 k*ll 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 "m*rder on
the Orient Express."

There's not one
k*ller that can do it all.

SINGH: There's
still a lot of debate

about how all these
K*llers came together

to k*ll 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

all contributed
to the loss of life

we see at the end
of the Permian.

These ocean K*llers
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


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,

the ecosystem
stays relatively intact.

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 c*ck,

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,

is a brand-new
avenue of research.

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...

[expl*si*n 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 ♪

♪ ♪

♪ ♪

♪ ♪

♪ ♪

♪ ♪