Original subtitles

(dramatic music)

Earth is born out of chaos and catastrophe.

(planets crashing)

Despite such hostile conditions, life emerges on our planet.

But it must withstand deadly disasters, again and again.

(wave crashing)

Planet Earth is a wild world,

shaken by unimaginable impacts,

volcanic eruptions that flood the landscape

and drastic climate changes that lead to ice ages

that freeze the world from pole to pole.

(dramatic music)

Yet each assault creates a path for something new.

Life always finds a way

despite being constantly put to the test.

Without these catastrophes, life as we know it

would not exist on our fateful planet.

(dramatic music)

(birds chirping)

During the Cretaceous period about 66 million years ago,

our closest ancestors are small mammals.

For them, earth is a terrifying place,

one fraught with danger and constant peril

because this is a world ruled by terrifying creatures.

(dinosaurs growling)

The dinosaurs.

(dinosaurs growling)

They dominated earth undisputed

for more than 150 million years

until a catastrophe ended their reign.

A disaster so enormous,

it not only wiped out most of the dinosaurs,

but 75% of all species on our planet.

(fire raging)

Scientists have been investigating the cataclysm for decades

to determine what caused this mass extinction.

There are various theories.

The one states that an asteroid impact is responsible.

(dramatic music)

(asteroid exploding)

Armed with the latest technology,

experts are trying to unravel the mysterious circumstances

behind the fateful event that changed our planet forever.

(dramatic music)

Lance Creek, Wyoming.

(car engine revving)

(dramatic music)

Paleontologist Philipe Havlik, has come here to investigate

how the world of the dinosaurs came to a sudden end.

(dramatic music)

He is visiting an excavation site

filled with fossils of dinosaurs

that lived at the end of the Cretaceous period,

just before the disaster struck.

(footsteps crunching)

[Philipe Voiceover] The Lance Creek area is one of the

most important historic dinosaur areas in the world.

It was, especially at the beginning of 20th century

when there was a lot of dinosaur hunters in this area.

It's a place where you find plenty of dinosaur bones

in one spot.

It's a bone bed, let's say a layer,

which is really kind of built up by dinosaurs.

The rocks here reveal the ancient landscape

that was home to the last dinosaurs.

Observing the geology of the Lance Formation

like this sandstone, like this layering and so on,

we can see it was a big river system.

There was a lot of water about 70 million years ago

in this spot.

So this means it was kind of

the perfect place to live for dinosaurs.

And this is what we have today,

almost at every spot you go,

we will find some isolated bones at least.

It's kind of magic.

This was home to some of earth's

most iconic dinosaurs.

One sports, two massive horns on its huge head

and a third smaller horn on its nose.

Its Greek name triceratops,

means three horn face.

The beast roams the plains feeding on vegetation

and smashing down taller plants by using its horns,

beak and sheer bulk.

But the mighty triceratops has an even larger neighbor,

one that can easily eat the three horn beast for lunch,

the T-Rex.

The king of dinosaurs is on the hunt.

At nearly 42 feet long, this bipedal carnivore

is one of the largest predators to ever live on land.

Boasting the strongest bite of all terrestrial animals,

this apex predator inspires fear.

(dramatic music)

(footsteps thudding)

(dramatic music)

(dinosaurs growling)

This triceratops is lucky.

(dinosaurs growling)

The T-Rex realizes it is too dangerous to try for a meal.

(dinosaurs growling)

(dramatic music)

(footsteps thudding)

In the dust layered rocks. Havlik is searching for clues

about gigantic battles like these fought eons ago.

It's not long before he finds the first interesting fossil.

This is a vertebrae of a dinosaur,

actually of a duck-billed dinosaur of an edmontosaurus.

A pretty small one.

I think it's somewhere from the tate.

Edmontosaurus is a bulky herbivore beast

reaching 42 feet in size.

It has a long flattened tail and became known

as a duck-billed dinosaur because of its unique horny beak,

perfect for smashing tough plants.

Huge herds of edmontosaurus graze on this landscape

and are much safer prey for a hungry T-Rex.

(dramatic music)

(birds chirping)

(dramatic music)

The entire area is rich with fossils

that can reveal the fate of the dinosaurs

at the end of the Cretaceous.

But to uncover the secret behind their demise

and that of 75% of all species on earth,

Havlik's team comes up with an unusual idea.

(dramatic music)

So we wanted to get this absolutely unique bone bed,

which is like that much of bones

over a surface of several square miles.

You should imagine how much this will be in bones, yeah.

We want to take off a piece of about a five to five meters

to uncover it totally to clean the surface,

to fix anything we could find.

We wanted to dig it out

on the highest precision ever possible

and then to take it into pieces with a chain saw

and transporting it about 8,000 kilometers

from Wyoming to Frankfurt, Germany.

Two containers weighing a total of 30 tons

were shipped by boat.

The scientists hope the bone bed will reveal new details

about what life was like

just before the dinosaurs went extinct.

Frankfurt, Germany, the dinosaur bone bed

from the Lance Formation has arrived

in the Senckenberg Museum for Natural History.

Professor Andreas Mulch is the director

of the Senckenberg Research Institute.

He's hoping this bone bed will help him figure out

what the world was like just before the catastrophe struck.

(speaks in foreign language)

In any good detective novel,

the detective looks for the killer

by investigating the crime scene.

We're actually doing the same thing here.

We want to understand what conditions

the edmontosaurus lived in,

what was the climate like, what was the vegetation like?

So to understand how life an

therefore the disappearance of the dinosaurs took place.

At the end of the Cretaceous period.

(speaks in foreign language)

Professor Mulch and his colleagues

recover many fossils from the bone bed,

including teeth from the edmontosaurus.

(speaks in foreign language)

Take a look at this tooth pattern.

They belong together?

Yes, they belong together.

Then the teeth just kept moving forward little by little.

And this is the occlusal surface.

These teeth were all hidden in the jaw.

and then it grows out of the jaw.

Yes, there were just lots of rows

next to each other.

Clues hidden within the tooth enamel

will reveal more about the world

in which the dinosaurs lived.

(machine humming)

(dramatic music)

When we analyze the tooth enamel

of this edmontosaurus we get a snapshot

of the environmental conditions during the Cretaceous period

just before the dinosaurs went extinct.

While the isotope analyses do not allow us

to directly measure temperature and climatic conditions,

they do give us an insight into the conditions

that prevailed at that time.

We get a fingerprint of the climate

and vegetation conditions

and this allows us to reconstruct quite amazing things.

(speaks in foreign language)

By analyzing isotopes preserved

within the dinosaurs tooth enamel,

Mulch discovers what the edmontosaurus ate

66 million years ago.

(speaks in foreign language)

Here we can see from the carbon isotopes

that edmontosaurus fed on plants that grew

in dried up lakes or salt marshes.

So they give us a special insight into the entire ecosystem.

(speaks in foreign language)

This allows the scientists

to reimagine the environment where the edmontosaurus lived

at the end of the Cretaceous.

Along with carbon isotopes, oxygen isotopes

give further insight into the paleo environment.

(speaks in foreign language)

Oxygen isotopes give us information

about the development of precipitation

and temperature at the earth's surface.

From the variation of oxygen isotopes within the teeth,

we can see how the temperature has changed

over the course of the year,

and we can see here that winter temperatures

must have been significantly warmer than they are today.

Everything indicates that we have annual temperatures

that were up to 14 degrees Fahrenheit warmer.

In other words, a whole lot warmer.

(speaks in foreign language)

This happened because of a significant rise

in carbon dioxide.

What we know today from all the data

is that the Cretaceous was basically a time

of high atmospheric CO2 concentration.

The last time CO2 levels soared

was at the end of the Permian period

where unprecedented volcanic eruptions

triggered the largest mass extinction on earth.

Where the changes seen in the Cretaceous atmosphere

also extreme enough to end the reign of the dinosaurs?

(speaks in foreign language)

Unlike the rise in temperature

at the Permian Triassic boundary

or the climate change we are experiencing today,

climate change during the Cretaceous

took place over many millions of years.

So ecosystems and also species had time to adapt.

Long-lasting climate changes are thus much easier

for ecosystems to withstand

and can give rise to entirely new species

and species communities.

The bone bed reveals that many species

benefited from the gradual increase in CO2.

(speaks in foreign language)

That's a really nice little section

of the bone bed with an impressive variety of species on it.

From predatory dinosaurs to edmontosaurus teeth

and pieces of a turtle.

(speaks in foreign language)

We find plant remains, mammals, fish,

everything that lived in and around the river.

It is therefore clear that this great diversity

also brought with it a diverse ecosystem.

The high level of CO2 stimulates evolution

for the majority of species.

Dinosaurs in particular thrive in this new environment

since their metabolism functions much better

in warmer climates.

We can definitely say

that the high temperatures and the high CO2 concentration

at the end of the Cretaceous

were not the killer of the dinosaurs.

66 million years ago, the concentration of CO2

is high and so is the biodiversity.

Life is thriving in a warming tropical world,

but things are about to change.

The rain of the dinosaurs is about to end

along with three quarters of all life on the planet.

Only this time a changing atmosphere won't be to blame.

Something even more deadly and immediate

is just around the corner.

(dramatic music)

South Dakota in the Hell Creek Formation,

one of the world's leading dino hunters

is looking for the remains of the ancient catastrophe.

Peter Larson has discovered many fossils in the area

that date to the extinction of the dinosaurs.

So about 66 million years ago,

this looked a whole lot different than it does today.

(dramatic music)

Our fateful planet is constantly changing

as its tectonic plates reshape the surface.

(dramatic music)

During the Cretaceous, north America is slowly shifting

into the geography we know today.

(dramatic music)

The area around the Hell Creek Formation

was a low-lying floodplain consisting of rivers,

streams, and wetlands.

It's the land of the dinosaurs

where countless species roam freely.

(dramatic music)

So if we were here 66 million years ago,

you'd probably see often the distance,

a giant herd of of duck-billed dinosaurs,

maybe as many as 10 to 20,000 of 'em in one group,

out just basically foraging

and getting as much food as they can.

Maybe you'd see an isolated triceratops

or maybe a family group over in here.

And then somewhere in the taller trees,

maybe there's a T-Rex kinda waiting

for its opportunity to strike.

Larson's picture of the Cretaceous world

is based on decades of work by many paleontologists.

Every new discovery provides another clue

about the creatures that lived here.

This is cool.

It isn't long before the veteran dino hunter

uncovers a new piece of the puzzle.

We've got a couple of ribs,

or maybe the same rib just broken.

And this cervical vertebra of a triceratops.

A bone broken in this way means a larger

and stronger dinosaur was involved,

likely a T-Rex hoping for dinner.

This triceratops was probably killed by a T-Rex.

It's almost positive it was eaten by a T-Rex

and it was actually one of the last dinosaurs to live

These fossils paint a vivid picture

of life here 66 million years ago.

(dinosaur growling)

But then the story ends.

Just somewhere above us, there's a line in the sand

that the dinosaurs never crossed.

To an untrained eye,

this change in the rocks is nearly invisible.

(dramatic music)

But its significance is huge.

(dramatic music)

So this is the line in the sand

that the dinosaurs never crossed.

And it was for a long time people looked at this

because there's no dinosaur bones above it,

but there's dinosaur bones below it,

all the time we find dinosaur bones below it.

This line is known as the K-Pg Boundary.

It represents the end of the Cretaceous period

and the end of the dinosaurs.

This clay layer was deposited literally worldwide

from some event.

And there's, fellas by the name of Walter and Louis Alvarez

who were tracing this clay layer and they found it

in Italy and they found it in Denmark.

And basically wherever we had marine sediment

that preserves that moment in time, they find this clay.

This boundary marks exactly

when one of the greatest mass extinctions

took place on earth.

Radiometric dating reveals that the layer

is 66 million-years-old.

But scientists are still trying to solve the mystery

of how and why it happened.

This discovery of this boundary clay and what it means

is super important to our understanding

of how the dinosaurs died.

It's about two centimeters thick,

it's a layer of clay and it's high in the element iridium.

Iridium is a rare earth element,

which means it's very rarely found on earth,

but it is common in asteroids and meteorites.

Just after our planet formed,

meteorite strikes were common,

but as billions of years passed, most dangerous space debris

was cleared from the solar system.

Still the threat of a major impact remained.

(dramatic music)

And so they came up with a hypothesis

that the this clay layer was formed

by the collision of an asteroid with the earth.

And with the amount of iridium they theorized

that this asteroid would've had to have been

somewhere between,

or somewhere around 10 kilometers in diameter

in order to deposit this much iridium

in that small amount of time.

And so, but there was no crater.

Nobody knew of a crater that was that time or that size.

Because that would mean it was a a 300 kilometer crater

that this 10 kilometer wide asteroid would've created.

(dramatic music)

This killer asteroid theory is popular

in the scientific community,

but the crime scene remains elusive.

Where did it strike?

(dramatic music)

The Barringer Crater in Arizona

is one of the most famous craters on earth.

It was formed by a meteorite

that struck the earth's surface

approximately 50,000 years ago.

The meteorite is estimated

to have been around 160 feet in diameter.

The impactor that may have caused the dinosaurs to vanish

is believed to be far larger.

So the same must be true for the crater it created.

But such a massive crater dating from the late Cretaceous

had not been found anywhere on land.

So scientists turned their search to the sea,

perhaps the crater was hidden beneath the waves.

(dramatic music)

During the 1970s Mexican oil company, Pemex,

was scouting the sea floor in the Gulf of Mexico.

They didn't find oil,

but near the Yucatan town of Chicxulub,

they did discover strange rocks

that hit it at something else.

(dramatic music)

Professor Ulrich Riller, at the University of Hamburg

analyzes maps of the area.

(speaks in foreign language)

The map shows a gigantic ring structure

that is located at a depth of more than half a mile

below the Earth's current surface.

It extends to a depth of 12 miles

with a diameter of about 120 miles.

(speaks in foreign language)

It is a huge pattern

that has all the characteristics of an impact crater.

Could this be the site?

Half of the crater is submerged.

So the scientist searching for the other half on land.

(dramatic music)

Mexico, a series of mysterious sinkholes dot the landscape.

(dramatic music)

These holes known as cenotes appear randomly

across the vast Yucatan Peninsula.

No rivers or lakes exist in this part of the Yucatan.

So villages sprang up around many of the cenotes

that filled with fresh water.

(dramatic music)

Professor Riller believes the fascinating cenotes

may hold clues to what happened here eons ago.

(dramatic music)

(speaks in foreign language)

Since the 1990s, there has been a suggestion

that the cenotes could be related to an asteroid impact.

NASA had mapped the water holes at that time

and found that many of them are circularly arranged.

However, a plausible explanation for this observation

was not offered at the time.

(speaks in foreign language)

(dramatic music)

Thousands of small dots

show where the cenotes are located.

A large part of them lies on a perfect semicircle.

(speaks in foreign language)

NASA experts suspected that this formation

could represent the southern part of the crater ring.

The underwater formation

matches the ring of cenotes perfectly, except for one hitch.

(speaks in foreign language)

But the hypothesis had a problem.

The rock in which the cenotes are located is much younger.

(dramatic music)

Ulrich Riller thinks

the cenotes may have formed because of the impact crater,

but more recently.

To test his theory, he prepares an experiment

with his PhD student, Jan-Oliver Heisman.

They want to simulate how an impact crater

might affect the surrounding sediment

over a long period of time.

The scientists pour a mixture of sand and flour

over a layer of silicon, which simulates the earth's crust.

A rotating blade produces a crater,

then they check how this affects the surface over time.

Time lapse records, any movement.

The crater depression is partially leveled

by the silicon substrate over time.

(speaks in foreign language)

The experiment clearly shows

that the crater floor has risen as an entire platform

and that the area surrounding the crater has sunk.

(speaks in foreign language)

This explains how the cenotes were formed.

Because rock along the crater's rim

moves in opposite directions after the impact,

cracks form in the much younger rock.

This ultimately creates cenotes.

Everything fits

and the crime scene of the killer asteroid

seems to have been found.

But for definitive proof, the scientists

must obtain samples of the rock

from inside the submerged crater.

(waves crashing)

(dramatic music)

In 2016, professor Sean Gulick from the University of Texas

led an international group of scientists on a mission

to drill into the Chicxulub crater.

(dramatic music)

Right now, beneath the the drilling rig

and beneath where we're sitting on this transport vessel

is the peak ring of Chicxulub.

It's buried by 66 million years of limestones.

We've picked this site because it's the place

where the peak ring is closest to the modern sea floor.

(dramatic music)

Woo hoo, here we go.

(dramatic music)

All right.

It has taken years to prepare for the drilling,

but the scientists may finally prove

the crater's significance.

(dramatic music)

It was an opportunity to sort of put to bed

all the questions about,

is it for sure that, that impact crater

is the one that is observed as the global boundary layer?

Is it for sure that that is the impact

that actually caused the mass extinction,

66 million years ago?

(dramatic music)

The water is very shallow at the drilling spot,

so the team must use unconventional equipment

to sample the ancient sediments.

(dramatic music)

We used a land mining rig actually

and hung it off the bow of the vessel

and drilled for two months into the crater.

And then we continued drilling, literally,

until we ran outta money at 1,335 meters down.

(dramatic music)

And so when we were finally on the drilling platform

drilling into the impact crater

and the first cores came up, it was just a heady experience.

Look at the color of the matrix,

it goes from green to red. Red.

That looks like melt.

That does look like melt, doesn't it?

That looks like a giant

cast of melt. Yeah.

We are now fully into impact rocks directly.

It's really easy to see because it's granite.

And so you can see these spotted leopard looking big chunks.

We reached rocks that were clearly not normally laid down

as you see in the ocean sediments, but something else.

And we realized of course, that, that was the impact.

The evidence suggests

that a six mile wide asteroid impacted Earth at this site

completely altering the rock.

(dramatic music)

One of the amazing things was just the, if you will,

the resolution of the record.

'Cause normally, you know, at most a centimeter

might be a thousand years in an ocean core,

in a scientific drill core.

And in this case, we actually had 130 meters,

that because it had a tsunami layer on the top

and had impact melt on the bottom,

we could say was effectively all deposited

within the first day of the Cenozoic.

So you can normally think about drilling

into the ocean sediments that you might get,

you know, a sense about a time.

And because we have 130 meters,

it's like we have an entire novel about a single day

preserved in the rock record.

All of the Chicxulub drill cores

are safely stored in the expeditions repository

at College Station, Texas.

(dramatic music)

This is where Sean Gulick examines them hoping to prove

that Chicxulub was in fact ground zero of the impact.

So it turns out that the peak ring itself

was made of granites, but these granites

are fundamentally altered by having been

in an impact crater.

It is much more porous than it should be.

It's actually weaker.

In fact, you could crush it with your hands.

And in fact, that's proof positive

that this is in an impact crater

that you see these planet affirmation features

and all of these other observations of shock

also say it has to be in an impact crater.

The analysis shows that Chicxulub

is definitely an impact crater.

But can the scientist conclude that this impact

led to the demise of the dinosaurs?

What is viewed as the global boundary layer, right,

what is viewed as the evidence

everywhere outside of the crater,

that there was an impact

is the presence of of iridium, right.

And so one of the interesting questions here is,

do we find it in the crater itself?

Can we directly tie the impact crater

back to this global layer?

And so to check that, we sent samples

to four different laboratories around the world.

And what we discovered is all the laboratories agreed

that right at that location,

right in that singular spot in the core

is where the iridium is found.

All of the evidence suggests

that Chicxulub is ground zero.

By finding the iridium layer in the crater

directly on top of all of the deposits

generated by the impact in the first day,

to weeks, to months, to a few years,

we were able to conclusively say that, you know,

Chicxulub absolutely is the location of the impact.

The drill cores provide indisputable proof

that the Chicxulub crater was formed

by a six mile wide asteroid.

And the impact occurred at the exact time the dinosaurs

and many other life forms vanished from our planet.

To understand if this single event was strong enough

to cause the mass extinction,

the scientists must calculate

the effects an impactor of size would have on the earth.

Freiburg, Germany.

At the Fraunhofer Ernst-Mach-Institut,

Frank Schafer and Professor Thomas Kenkmann

want to see what happens when a six mile diameter asteroid

crashes into a planet at several thousand miles per hour.

For this experiment, they engage

one of the fastest guns ever created.

(speaks in foreign language)

So this is our projectile,

the down-scaled asteroid.

The aim is to achieve as much speed as possible

to simulate the impact on the Chicxulub crater

in the laboratory.

(speaks in foreign language)

The two stage, light gas gun

uses a combination of highly pressurized gases

and rapid expansion

that will accelerate projectiles at super high speeds.

The first stage initiates the acceleration,

while the second stage provides additional propulsion

for even greater velocity.

(speaks in foreign language)

Unlike natural craters,

here we are witnessing the process as it happens.

Chicxulub is a gigantic crater,

but we only see the end result

of a very, very complex process.

Here we can experience all stages of the formation.

The high speed cameras allow us

to follow what is happening at microsecond intervals.

(speaks in foreign language)

The gas gun cannon

can launch projectiles at more than 17,000 miles per hour.

So the team must take extra precautions.

(machine beeping)

(speaks in foreign language)

Three, two, one, fire.

(cannon firing)

(speaks in foreign language)

Nominal trigger points, all right.

I think that was a successful shot.

Yeah, let's take a look at it.

In addition to analyzing

the high speed footage,

the team wants to investigate the crater that was created.

(speaks in foreign language)

The crater is quite deep,

flat at the bottom and full of dust.

There's a lot of dust in the chamber.

You can see steep edges in the limestone and in the center.

This seems to be the deep rock.

(dramatic music)

(speaks in foreign language)

What really surprises me

is the amount of dust and small splinters

that have been produced.

It's very finely fragmented material.

You can see it, you can feel it,

you can hold it in your hand.

It's fine dust.

And this dust was also ejected by Chicxulub.

But this topic is still subject of debate.

(speaks in foreign language)

The impact didn't just make a crater.

(dramatic music)

The incredible force changed the molecular structure

of the once solid rock.

(dramatic music)

(speaks in foreign language)

What we see here is the mineral quartz.

There are strange straight lines.

These lines are exactly what we were looking for.

They are shock indicators that show us

that a shockwave has traveled through the rock.

That's what the experiment shows us.

It's just like the subsurface of the Chicxulub crater.

Professor Kai Wunnermann

must now apply data from the experiment to the proper scale.

He plans to calculate the effects from the asteroid impact,

66 million years ago.

(keyboard keys clacking)

(speaks in foreign language)

Now we can actually simulate

the right dimensions and quantities

such as the right gravity,

and that should tell us something

about how much energy was released.

(speaks in foreign language)

The colossal asteroid was on

an inescapable collision course with earth,

traveling at an astronomical speed.

When the behemoth pierced the atmosphere,

it ignited in the sky.

It hurdled towards earth at nearly 45,000 miles per hour.

Its path of compressed air caused a shockwave

to reverberate across the planet's surface

with a cosmic boom.

Blazing a trail of fire,

the asteroid plummeted towards the ground.

(asteroid crashing)

Then it crashed into the shallow ocean

with apocalyptic force,

the impact released 4.5 billion times the energy

of the Hiroshima atomic bomb.

(speaks in foreign language)

This energy that is released melts the rock,

and it doesn't just melt it,

it actually reaches temperatures

in the region of 36,000 degrees Fahrenheit,

that leads to the rock being vaporized.

(asteroid crashing)

The energy it released was devastating.

After a flash illuminates the sky,

an eerie bright white sphere grows over the impact site.

Bedrock melts into a scalding plasma

that releases a shockwave even greater than the first.

Even deep rocks are so heavily fractured,

they fly like water.

(speaks in foreign language)

It's actually very similar to what you see

when you throw a stone into water,

which also creates a crater.

It usually doesn't last very long, we hardly see it.

But it also collapses

and then it splashes up in the middle

and it forms what we call a central mountain.

So it resembles the splashing up in the middle.

(dramatic music)

The surrounding ocean water is displaced

or instantly evaporates when the asteroid strikes.

Molten crust forms a temporary mountain

taller than any on earth today.

This tower of fiery liquid plasma collapses quickly.

(dramatic music)

(speaks in foreign language)

And at the same time,

the water that was previously displaced

flows back into the crater.

And through the collapse of this temporary mountain,

in interaction with the returning water

waves are generated that are nearly a mile high

and then spread out comparable to tsunami waves.

And this of course, all also devastates coastlines

thousands of miles away from the impact center.

(speaks in foreign language)

The impact destroys everything living

in the immediate vicinity.

First it is burned, then blasted by the shockwave.

Anything left drowns in a miles high tsunami.

But such an apocalyptic wave should have left evidence

in the rock record.

(dramatic music)

800 miles from the impact crater,

Sean Gulick searches for clues in the Brazos River in Texas.

(dramatic music)

This is one of the locations

where the exact time of the impact comes to the surface.

So right where the end of the Cretaceous

and the start of the Paleogene is preserved,

it's preserved in the Brazos River

and it's preserved within little waterfalls

within the creeks nearby.

So it's a great place to search for evidence of the impact.

Gulick wants to build a complete picture

of one of the most terrifying days

in the history of our planet.

Three quarters of life on earth died out

in the same geologic moment.

It's an incredible exposure of the K-Pg boundary.

Basically the shaley stuff at the bottom

predates the impact.

This is the time of the dinosaurs

and the large marine reptiles.

And then this is the boundary.

And the contact is actually, you know,

it's kind of erosional, it's got a lot of energy in it

that carves into what was there before.

And then a series of events are basically recorded

in this, more than a meter of material,

that is the K-Pg boundary.

You see it here, right, these are these cross stratified,

these dipping layers that are present

right here within the rocks

and this high energy looking material above it,

of the finer particles.

All of this probably represents the arrival of the tsunami

here in central Texas,

The tsunami is global

with an estimated force 30,000 times greater

than any in recorded history.

Each piece of evidence gives the scientists a clear snapshot

of how the disaster unfolded at the end of the Cretaceous.

If you were living 66 million years ago,

the effects of the impact would depend

where you were compared to ground zero

in the Yucatan Peninsula.

So we're at about 1300 kilometers away from the site.

Anything within probably 1500 kilometers

would've experienced the direct heat from the impact itself.

In other words, the the impact explosion was so large,

you could see it over the horizon.

You would've been killed

at the speed of light by just the thermal radiation

coming out from the impact.

If you were a little bit further away,

you would've felt the hurricane force winds,

you'd have felt the earthquakes.

The extent of the impact

is impossible to imagine.

Thousands of miles away on both Pacific and Atlantic shores,

enormous tsunamis, wreak havoc,

inundating everything in their paths.

The presence of of a tsunami layer,

especially one as thick as this, you know,

1300 kilometers away from the crater,

is just testament to the incredible energy.

In fact, the energy released by the impact

is billions of times the energy

of a World War II era nuclear bomb.

But despite the epic scale of the event,

Gulick needs more evidence to support

that the impact had global consequences for life.

The thermal radiation, the tsunamis and the hurricanes

were not sufficient to cause

the extinction of 75% of species 66 million years ago.

He must search for additional clues

to uncover what happened to dinosaurs worldwide.

By carefully analyzing the prehistory recorded

in the K-Pg rocks,

he finds a clue that might explain their demise.

Yeah, you can see the spherules,

yeah, that there's little glassy looks,

but you can still see little hints

of the layers of spherules

that are all present inside this rock.

Spherules look like little glass balls.

The largest you might ever find would be maybe a centimeter,

but most of the time they're millimeters

or even sub millimeters in scale.

So they're either referred to as melt

that ejected out of the crater and cooled into a sphere

and traveled and then rained down.

Or they're actually vapor in the plume

that condensed into a glass,

you know, sphere that then rained down.

These innocuous glass balls are key

to the events set in motion after the impact.

The spherules are found

on the K-Pg boundary around the world

and clearly coincide with the impact

at the end of the Cretaceous 66 million years ago.

They are a solid connection to that moment in time.

(asteroid crashing)

When the asteroid slams into the bedrock,

molten and vaporized rock is thrown into the sky,

some even reaches space.

(dramatic music)

Small droplets of rock in the plume,

condense and solidify,

falling back to earth as tiny glass beads.

(dramatic music)

So in any location around the world

that has a well-preserved boundary layer,

you see material that arrived as ejecta

and you see material that was basically a dust

that rained out later.

The ejecta was moving at at high velocities.

And so that is the spherules that we see here

is a big wedge shaped deposit here

underneath the tsunami layer.

And they're little glass balls that,

you know, rained out of the sky.

They traveled here at kilometers per second, speed.

Could the ejecta have contributed

to the extinction of the dinosaurs.

(dramatic music)

Back in Hell Creek, Peter Larson is analyzing

how the Chicxulub effects unfolded across the planet.

So here we have a piece of the boundary clay

and the coal that's just above it.

So if we kind of scrape away the boundary clay a little bit,

and I'm not sure that that's soot,

but sometimes we can find a layer of soot

that's actually right above the very top

of the boundary clay here.

So that is indicative of forest fires.

Remnants of ancient burned forests

are expected at an impact site.

But Larson is in South Dakota,

2000 miles from where the meteorite struck.

(dramatic music)

All of this molten material was flung up

out of the atmosphere and rained down,

that as they came through the atmosphere,

they heated the atmosphere up to the point

where basically all the forests and all the plants

had to burn, the atmosphere was so hot,

as some have estimated is more than 2000 degrees

at the surface of the earth, in some places.

(dramatic music)

(fire raging)

Earth is on fire,

wildfires are reaching globally

with trees and life within the forest turning to ash.

(fire raging)

Earth is scorched in the aftermath and many creatures die.

But was this the definitive mechanism

that led to the mass extinction?

(dinosaur growling)

(dramatic music)

Sean Gulick returns to the lab to reexamine

the Chicxulub crater drill cores.

They might hold a hidden piece that will solve the puzzle.

Sean discovers a strange anomaly he missed before.

It isn't because of what he finds,

but about what he doesn't see.

There is a glaring absence of sulfur bearing minerals

and they should be here.

(dramatic music)

And one of the key clues to understanding,

you know, what ultimately caused the extinction event

turned out to be that even though we knew the original rocks

of the Yucatan Peninsula were 30 to 50% sulfur rich rocks,

we don't find any evidence of the anhydrite or the gypsum

left in the crater.

And so the conclusion that comes from that

is that preferentially, all of these sulfur risk rocks

got put up into the atmosphere.

66 million years ago, life was doomed

when the Chicxulub asteroid impacted a spot

that caused marine rocks to vaporize.

(dramatic music)

Copious amounts of sulfur were released into the sky.

(asteroid crashing)

We would've had an incredible amount of sulfur.

In fact, the estimates are something like 335 gigatons

of sulfur would've been put into the atmosphere.

A chemical reaction

between sulfur from the vaporized rocks and water

expels more than 300 gigatons of sulfur aerosols

into the atmosphere.

The aerosols scatter incoming solar radiation,

which reduces the sun's ability

to warm the surface of the earth.

This leads to rapid planetary cooling.

Even if you use just a hundred gigatons of sulfur

and you run a climate model,

you can drop the global temperatures by 25 degrees Celsius,

just with, you know, a third

of what we think we put into the atmosphere.

(asteroid crashing)

Plunging temperatures on the planet

are just one terrible effect produced by the sulfur.

The ensuing darkness is even deadlier.

(dramatic music)

There's the dust and the sulfur in the atmospheres

that cause darkness or maybe twilight for years.

That meant that all of the things

that eat the sun for their energy,

so phytoplankton in the oceans and plants on land,

that these would've started dying out

and therefore, those that ate the phytoplankton

or ate the plants on land started dying out,

and then the carnivores that ate them started dying out,

and it caused this collapse all the way up the food chain.

(dramatic music)

The impact winter lasts many years.

It freezes and starves most life on our planet.

Darkness in the wake of the Chicxulub impact,

66 million years ago, spells death for plants.

Consequently, most herbivores die,

which leads to the death of carnivores too.

As the food chain collapses,

75% of all life forms on earth become extinct.

Sulfur turns out to be the real killer.

Perhaps the dinosaurs would've survived

if the asteroid hadn't crashed into sulfur rich rocks.

If it had actually hit 30 seconds earlier

and hit the Atlantic ocean

or 30 seconds later and hit the Pacific Ocean,

instead of sulfur rich rocks and limestone dust,

we'd have just had water vapor

and probably not a massive extinction event

like happened 66 million years ago.

(dramatic music)

But how could any living thing

have survived this catastrophe?

The Chicxulub impact triggered the last

of the five mass extinctions in earth's history.

But if there's one lesson we can learn

from the previous cataclysms,

it's that life always finds a way.

It takes around 20 years for the atmosphere

to be cleared of dust and sulfate aerosols.

Once again, the sun pierces through a clean sky.

Plants reappear.

But what about the animals?

(dramatic music)

Paleontologist Philipe Havlik

joins Pete Larson at Hell Creek.

(dramatic music)

They're hunting for clues that might reveal

how life reemerged after the impact.

Near the edge of the K-Pg boundary,

they spot a familiar fossil.

Holy crap.

This is not a rock. That is not a rock,

that's a dinosaur boat.

Oh wow.

Oh, and look at how close we are.

Oh man.

Oh, that's so cool.

It's a tail vertebra from a duck-billed dinosaur.

It's like, holy crap, right here, right here,

half a meter below the boundary.

But it's actually washed down, so it maybe was

really, really close to the boundary.

So this dinosaur might have seen that asteroid

crash into the earth.

I mean, it's possible, it's close enough

that it could have washed down that much.

Oh yeah.

For sure.

Certainly one of the last dinosaurs to live,

no question about that.

You poor unlucky thing.

Soon they find signs

of what they are really searching for.

(dramatic music)

No.

Is it?

I think it's a little,

I think it's a little multituberculate tooth.

Come on, come on.

I think so.

It can't be.

Is that cool?

(both laughing)

Hey, I can see the rootlets. Holy moly.

It is. Ah, ah.

So this is a multituberculate tooth.

Multituberculates lived in Hell Creek,

they lived in the Cretaceous

and they made it all the way through into the paleo scene.

They're a very small mammal.

With over 200 distinct species,

these rodent like mammals range in size

from tiny mice like creatures to the bulk of modern beavers.

They leave diverse lifestyles,

some tunnel underground,

while others navigate canopies like squirrels

or hop across the landscape.

These little guys were able to survive

simply because they were so tiny and so small.

They could hide in little cracks and crevices

into a burrow where a dinosaur couldn't go.

They also didn't need all the food to eat.

So if this animal could survive on dried out,

and maybe even partially burnt plants,

or if it was a carnivore,

it could exist in the carcass of a dinosaur,

there's lots of food there, you know, lots of jerky

that this animal could exist on for a long, long time.

And so it was able to survive that nuclear winter

that was the result of that asteroid

crashing into the earth.

As the impact winter finally fades away.

Small mammals like these find ways to thrive in a world

that had been leveled by catastrophe.

They are the true survivors.

They owe their success to one special characteristic,

being small.

The larger the animal,

the more energy it requires to survive.

When food is scarce, size is a liability

and only the smallest persevere.

When all these dinosaurs died,

not only were there some survivors,

but it left open ecological niches,

which were kinda like job opportunities.

And so little guys like this, little tiny, tiny mammals

grew into things like,

eventually into things like elephants.

Today, mammals are extremely diverse.

From the tiny to the colossal,

mammals span a remarkable range of sizes.

They inhabit wildly different ecosystems

from icy arctic tundras to lush rainforests

and arid deserts.

They enjoy the air, the water and the land.

Surprisingly, dinosaurs didn't become

completely extinct either.

Some of the small avian like dinosaurs survived

and evolved into birds.

Their ancestors thrive today with a vast array of colors,

shapes and behaviors.

The dramatic chain of events

that began with a Chicxulub asteroid impact,

66 million years ago, drastically altered life on earth.

All non avian dinosaurs, including the iconic T-Rex,

could not survive the long-term effects of the impact.

Their demise would pave the way to the rise of mammals

and ultimately to the evolution of humankind.

(dramatic music)