Original subtitles

# (music)

Dinosaurs.

Perhaps some of the most dramatic animals

ever to have walked the earth.

They dominated the world for over 150 million years,

until a huge asteroid struck the planet.

But how exactly did they die?

Palaeoltologists have been searching for the answer for decades.

And now, new evidence is coming to light.

We're out looking for clues.

Each fossil is a clue and that tells us something about

what the world was like at that time.

Since 2012, a team of palaeontologists has been

investigating a remarkable site deep in the badlands of North Dakota.

The team's leader, Robert De Palma,

hopes it holds evidence of what happened the very last day

of the dinosaurs...

(thunder rolls)

Could it even contain the remains of an animal that bore witness

to that terrible event?

We've got all these bones in the ground right now.

But the one thing that we would just dream

of finding is that one dinosaur

that died on the day of the impact.

The idea that there is a dinosaur fossil potentially who was

a direct victim of that, that's very exciting.

Oh, that's skin right there.

That's actually scaly skin. Oh, my God.

Can they find a dinosaur that died on the day the asteroid hit?

For 10 years, Robert De Palma and his team,

have bene digging in a small corner of the Hell Creek formation.

An area famous for more thna a Century, of major dinosaur discovery.

They've already found a wealth of fossilised creatures in

a patch of land they call Tanis.

What appears to be a piece of fossilised skin from a Triceratops.

The unhatched egg and what looks like pterosaur embryo.

Jawbones of a mammal called a Pediomyid.

And teeth and footprints of carnivorous dinosaurs

like T-rex.

There is no other dinosaur that has teeth like this.

Many of these fossils were found in a thick layer of crumbly rock.

The rock here is really not quite rocky.

It just falls apart in your hands.

Right above the rock, is the KPG boundary,

a layer of iradium-rich debris from the asteroid impact

that hit the earth 66 million years ago.

It marks the end of the age of dinosaurs.

If you look below this layer, you see fossils of dinosaurs.

If you look above this layer, no dinosaurs.

The methaplastic layer of rock at Tanis is full of ejector spherules.

Beautiful. Look at that.

Tiny glass droplets created in a major asteroid impact.

Robert thinks that this is compelling evidence that

everything in the layer was buried while the spherules fell.

If he's right and the spherules can be matched to the asteroid impact,

this dig site could provide a snapshot of what happened

on the very last day of the dinosaurs.

It opens up that whole debate about how do we link catastrophic events

to fossil and geologic deposits?

If we can both match spherules to the impact site geochemically and

in terms of radiometric ages, that's pretty accurate.

The asteroid hit in what is now the Yukutan Peninsula in Mexico.

It's called the Chicxulub Asteroid after the town nearest to

the centre of its crater.

To find out if the spherules the found in North Dakota

can be linked to Chicxulub, Robert has come to the Diamond Light

Synchotron in the UK.

Joining him is Professor Phil Manning of the University of Manchester.

THey've already run initial tests on the spherules in America.

Every piece of ejector from every impact that's ever occurred on earth

has a unique chemical signature.

The Chicxulub impact event is no exception.

When you look at material from different sites, it has a very

diagnostic chemical fingerprint.

That's precisely what the team have been looking for.

By comparing their spherule with spherules from other known

Chicxulub dig sites, the team can see if it's a match.

What the team has done is look at ejector from other sites

and produced an elemental map.

A chemical fingerprint from each site.

Whether they be in Haiti, Mexico or other localities in North Dakota.

You can see they all follow similar concentrations,

and sort of map on top of each other here.

When you look at the material from the Tanis site,

again they perfectly map on top of this chemical fingerprint.

It was unequivocal that Tanis was tied in to the KPG extinction event or the impact event,

that makes this an astoundingly important site.

A site that really brings you down to the last day of the dinosaurs.

This is very important because it immediately gives a time stamp

for the locality itself.

The Tanis site is like a window into a snapshot of time.

With ejector spherules found throughout the deposit,

Robert and his team seem to be able to link their site to a single day.

And the synchotron here in the UK reveals something even more remarkable.

This particular spherule is probably one of the most significant ones

I've ever seen in my life.

This irregular piece of debris which is inside this swirling glass,

is actually a piece of unmelted rock.

That was initially an absolute red flag to us.

Why is there a piece of angular rock inside the spherule?

Then when we look at that chemical map, that's when we really started jumping for joy.

Because we start seeing iron and chromium and nickel

in ratios that we would expect for something that could've been not from earth.

The thought that crosses our mind is this could be a piece of the asteroid.

I've never seen anything like this.

That was immediately of incredible interest to us.

Robert's team may have found a fragment of the asteroid itself,

in North Dakota.

Physical evidence linking this site to the Chicxulub impact.

Tanis is around 3,000 kilometres away from where the asteroid hit.

So exactly how did the asteroid cause the death of the animals here?

To answer that question, Robert is searching in something

he calls the mass death assemblage.

Right here we got this intertangled mass of fish.

There's one fish here. Another goes this way.

Underneath the body of a paddlefish there's another sturgeon that goes this way.

His head hit that log and has deflected downward at a 90 degree angle.

Robert has a theory that the creatures he found surrounded by

spherfules in a logjam, were swept to their death in some

kind of turbulent surge or water and quickly entombed in sediment,

which is why they're so well preserved.

But what could've caused the wave?

One hypothesis is a tsunami.

The asteroid hit at sea.

We talkt about a tsunami of a completely different scale.

Much higher, much larger than we've ever seen before in mondern tsunami.

So if you had 2km of water, at least half of that would've

left as the rim wave.

So at last a kilometre high at a mimimum.

The tsunami raced towards land.

When they reached the coastlines, they were still very high waves

of up to hundreds of metres.

That's a very impressive wave.

Imagine a wave that's the size of a building approaching the coastline.

In the LAte Crutaceous, North America was divided by a narrow sea

that's been called the Western Interior Seaway.

The tsunamin could have theoretically travelled up this towards Hell Creek.

Tsunamis generally travel at the speed of a jet plane.

It's not something you could say run away from.

It had plenty of energy to get over the coastline.

It could easily still have been tens of metres high

by the time it reached well into the Seaway.

Could the rapid deposition at Tanis have been caused by a tsunami?

To test the idea, the team needs to look at the timing.

Which fish is that? That's a new one.

If a tsunami buried he fish, it would have to have hit while

the ejector spherules were falling.

Because spherules were found everywhere,

including in the fish's gills.

So much depends on determining when these spherfules were falling at the site.

Modelling the ejecta always has error bars on it.

In that we're not there to measure it, we've had no equivalent impact like this

on earth since then.

We can look at the computational models that we do and say alright,

this material is coming from this point.

It's now moving away this fast with about this much mass.

Then we can tell with the sorts of equations that we might

use to calculate the trajectory of a canon ball, where it would go.

We can observe from these simulations how long it takes

these ejecta to reach their final destination.

Down to the order of a few minutes.

What the calculation shows is surprising.

Robert and his team have found that these spherules landed at Tanis

between 13 minutes and 2 hours after the impact.

So if a wave buried the fish, it must also have reached the site within 2 hours.

Data from recent tsunamis show even a powerful one would take

much longer than that to travel around the 3,000 km

from the impact site to Tanis.

So if wasn't the tsunami, what could've cause the surge of water at Tanis?

Professor Bondevich is an expert in tsunamis.

The fjords here in Norway are very special.

We have tall mountains surrounding bodies of weater.

So the water is usually very calm.

In 2011, something very strange happened.

The water in the fjord began to move violently.

The height of the water increased by 1.4 metres.

Like a maelstrom with turbulent water.

Someone said that the fjord was boiling.

News started to roll in, there had been an earthquake

8,000 kilometres away in Japan.

A journalist from the local newspaper called me and

said that people were observing waves here in the fjords.

I got a video clip of the waves.

I saw immediately that they looked like a tsunami wave.

Here you can see that he fjord is perfectly calm.

But at the beach here, you can see the water sloshing back and forth.

And no-one had every seen anything like it.

Some people got very upset and afraid.

A magnitude 9 earthquake had devastated the northeast of Japan.

But how that affect a fjord so far away?

So no-one in Norway could feel the earthquake.

But I could see that the times matched the arrival of the waves

here in the fjord.

Eventaully Stein and his team realised that this might have

something to do with seizmic waves, shock waves that pass quickly

through teh earth during an earthquake.

So it took only 12 minutes before the first signal

of the earthquake in Japan reached all the way here to Western Norway.

So it was the seismic waves that caused the normally calm water

in the fjord, to slosh turbulently back and forth.

Just thinking of that...

Scientifically, it's fantastic.

Could something similar have happened in Tanis?

Trying to find out is geophysicist, Professor Mark Richards,

who's been studying the site at Tanis for several years.

He's working with Robert to discover what could've caused a surge of water here.

A tsunami can't get here in less than 12 hours.

But seismic waves travelling from teh Yukatan impact site to

North Dakota, can arrive here fairly quickly.

In the late Crutaceous, the Western Interior Seaway that bisected North America,

could have been connected to Tanis through the extensive river system

that once flowed here.

If you have a very large body of water,

like the Western Interior Seaway,

and you can shake it back and forth, you can generate a large water wave

coming up this river at Tanis.

So this is bigger than any techtonic generated earthquake.

You would have shaking literally everywhere on the planet.

So seismic waves from the impact could have caused surges of water

in the Hell Creek river system.

Seismic waves get here quickly enough to cause this wall of water

coming up the Tanis river, inundating this area,

arriving at the same time these spherules are still falling.

If they're right, those surges could have carried mud and marine creatures

from the Western Interior Seaway.

And dumped on the Tanis sand bank,

burying everything all at the same time, as spherules fell.

Debris and fine iridium dust from the asteroid,

would have gradually covered the deposit, forming the KPG boundary.

Over millions of years the surge of mud would become the deep layer of rock.

That's the beauty of Tanis.

What you're seeing is the deposit that is literally recording

the last say, 45 minutes to 90 minutes of the Crutaceous.

If the extinction of the dinosaurs was a crime,

the detectives solving it would have plenty of evidence.

They would see that the asteroid was in the right place at the right time.

They would see that no dinosaurs survived after the hit.

They would have a piece of the murder weapon,

a fragment of the asteroid,

but they would be missing one very important thing.

A body.

A lot of the bones that exist from those last Crutaceous days

were basically destroyed.

As far as we know, we've never actually found a fossil

of a dinosaur individual.

A signel skeleton, let's say,

that we can unequivocally say was there the day the asteroid hit.

But before the site was time stamped to the Chicxulub impact,

Robert's team did find part of a triceratops in the crumbly layer at Tanis.

So could that be the body? A dinosaur that died on that day?

Something that would help them would be establishig the cause of death.

Which can be difficult when you only have a piece of skin and horn to go on.

This is the horn after they've cleanead it up.

This triceratops horn is probably the most beat up one I've ever seen.

I'm noticing a very big crack right here.

There's another very large one right here.

We have fractures, breakage of the bone that occurred

during the lifetime of the dinosaur.

Triceratops is such a massive animal and a really strong animal.

So it must've taken a tremendous force to cause these cracks

that go all the way through the horn.

Possibly fighting between two triceratopses or

fighting with a predatory dinosaur could've caused this.

A big question that comes into my mind when I see a crack like that is when did it happen?

When I look closely inside that crack,

I see healing bone.

This animal must've survived for some time after the injuries.

So is survived whatever caused it and it started to reheal.

Part of putting the story together of this triceratops

is how it died and when it died.

Was it involved in the impact in some way?

Or was it already dead at that time?

Luckily enough, the animal can tell me its own story.

So I'm looking at the skin here and I see a lot of areas

that have kind of sagged in places.

Where it had already started to rot from the inside.

So before the thing was buried, a lot of decay had already occurred.

So this animal was probably dead and partially devayed shortly before impact.

Given the size of partial decay,

it's likely this triceratops wouldn't have lived to see the last day of the dinosaurs.

However, the triceratops fossil does show that dinosaurs were alive

shortly before the asteroid hit.

Perhaps even within weeks of the impact.

This is an extraordinary discovery and one that

has never been found before.

But if it's true that dinosaurs were here until the final weeks before

the impact, there could be even more still to find in this deposit.

We've got all these bones in the ground right now.

But the thong that we could just dream of finding is that one

dinosaur that died on the day of the impact.

And the weather isn't helping his search.

That print is toasted.

It was in a low corner.

It's full of mud and water.

The problem is it's wet.

If we're not careful, we're gonna lose the print.

That's the biggest print we've got.

I see some areas that could use glue right now too.

The team is racing to excavate the footprints, along with dozens of fish fossils

tangled together in a logjam, before storms wash them away.

We're up against the clock here.

This stuff that could be exposed right now is gonna get ruined by the rain.

But then Robert comes across something that looks very unusual.

What is going on right there?

Are we sure this isn't crocidilian?

That's not crocodilian.

I'll go in from the top and then twist. It separates on that line.

That's skin right there. That's actually scaly skin.

Look, look, look.

Look at that pattern right ther.

Have you ever seen elongated scales like that before, Dave?

Just careful.

It's changing again.

We're seeing it for the first time in 66 million years.

I think we got ourselves a dinosaur.

A dinosaur fossil.

And unlike the triceratops, this is located in the logjam,

the mass death layer,

surrounded by the fish with spherules in their gills.

This is the most incredible thing we could possibly imagine.

The best case scenario.

We're excavating this mass death layer of fish from the surge sent up

by the impact, and we've got dinosaur remains.

The one thinkg that we would always want to find.

And here we've got it.

This is unreal. I cannot process this in my brain.

I am absolutely blown away by this.

My heart is literally pumping out of my chest wondering

what is behind there. Just a couple centimetres back in the outcrop.

What is waiting for us back there?

The team keeps digging.

This could be laying against ribs that are curved.

There's something here.

That's hard. That's bone right next to the skin.

This is either a hip or a shoulder element.

After hours of painstaking work...

And we can go from the thigh of the animal.

There's the knee.

And then you've got the little calf muscles

of the dinosaur, they're bulging out,

and you go down to the anklebones,

and these are the toes of the feet.

We have got nails at the tips of the toes.

It's a beautifully preserved leg,

all articulated, covered with skin.

The complete leg of a dinosaur.

In my wildest dreams,

I never expected to find a dinosaur leg in this deposit.

Yeah. I mean, and then it's got skin and tissue.

It does look just like a drumstick.

It looks like a Thanksgiving turkey,

just laid out in the ground.

Robert thinks he has found the body in question -

a dinosaur that might itself have witnessed

the cataclysmic impact.

Dinosaur fossils are not known

from the last years of the Cretaceous.

And it was unclear whether they were already extinct

or in decline or what was going on.

So they were just sort of absent.

And this answers that question.

Were dinosaurs still there then?

Well, yes - this one likely died in that surge.

For such big claims, Robert needs verification.

He's brought the dinosaur leg to London

to get a second opinion...

...from Professor Paul Barrett,

an expert in ornithischian dinosaurs

from the Natural History Museum.

We thought this was a herbivore similar to a theselosuarus but

not quite certain so hoping to get your opinion.

There are some obvious things we can rule out.

It's clearly not a meat-eating dinosaur.

These are the claws of a small running animal, that's not using

the claws to pin things down.

It's not a heavy, stocky animal. Not a duckbill or a horn dinosaur.

This looks like a more agile runner than one of those.

It limits those possibilities down ot a small bipedal plant-eater.

A thescelosaur sounds like a great way to go with this.

Thescelosaurs lived next to rivers

where there was plenty of rich vegetation to feed on.

They had leaf-shaped teeth,

common amongst herbivores,

and claws on their short front limbs -

excellent for digging.

They probably dug for food.

But how did Robert's thescelosaur die?

I'm trying to think of how this animal might've died.

Could it have been killed by another dinosaur?

It's possibile.

This is one of the more agile dinosaurs.

Its primary defence against the predators is gonna be to run away.

Hopefully giving the advantage over a slower predator.

Whenever we're excavating a dinosaur, we're always keen to know

is how did the animal die.

It's not always easy to do that.

Maybe we can find evidence for things like broken bones

that didn't heal back up.

We can even see things like bone tumours and gout.

There are some wonderful fossils where you can find bite marks.

You can even find a predator tooth buried within the bones.

CT scans allow a closer look at what the animal might've gone through.

I can't see any evidence of predation on this animal.

There are no puncture marks causedby teeth.

There's no obvious scraping or gnawing of the bones.

Then what else could've brought this down?

One thing that does leave marks on bones are some forms of disease.

I can't see any obvious evidence of those kinds of features here.

Could this leg be from a dinosaur that died in the surge?

I think it's certainly compatible with that idea.

Something could've been moved around in a very physical way.

This is actually a shoulder blade,

and this bone in a living animal

would actually be way over my shoulder.

When you have got those big lumps of wood in a rapid flow like

an overflowing river, that would do a lot of damage to anything caught between them.

That's phenomenal. We could be looking at a casualty of the impact.

This could be one of those dinosaurs that saw the fireball coming down.

And was just there on the last day of the Cretaceous, when all the lights went out.

It's unbelievable to think this animal might've witnessed that event.

Paleaontologists do depend a lot on tragedy.

Every little disaster is the material we need to develop our subject.

Tragic for the individual concerned, but we're just really happy that it happened.

After years of investigation,

Robert has found out a great deal

about the creatures which lived at Tanis,

and he knows that many of them were alive on that fateful day

when the asteroid devastated our planet.

But how exactly did they die?

Robert's finds now allow us to tell the story of that day

and finally answer that question.

One of the most important days in Earth's history

probably started much like any other late spring morning.

We know the season because Robert found fossils of young fish that

died at the size they reach at that time of year.

This agrees with evidence already found

by other scientists.

Perhaps this day, that would end with so much death,

began with something different.

A new life.

SQUEAKING

SQUAWKS

No-one can be certain of the exact timings of the day

when the asteroid collided with our planet.

But it's estimated that within just 40 minutes of the impact,

the consequences for the creatures of Tanis

would have been profound.

Based on Robert's finds

and the latest evidence from other scientists,

this is how the catastrophe might have unfolded.

The asteroid is around seven miles across,

bigger than Mount Everest...

...and travelling at close over 70,000km an hour.

The impact causes an explosion

over a billion times the power of the first atomic bomb.

It comes in so fast that it wouldn't even have been visible

passing through the atmosphere.

It would have come and hit in a moment.

At Tanis, almost 2,000 miles away...

...it's completely silent.

But at the impact site...

...the asteroid vaporises.

More than three trillion tonnes of rock

are ejected into space

in a blast of super-heated violence.

Winds of almost 1,000kph.

A colossal earthquake, followed by a ring of massive tsunamis.

RUMBLING

ANIMAL CALLS

All the while, the creatures at Tanis

go about their business...

CACOPHONY OF ANIMAL NOISES

...just like any other day.

COOING

CLICKING

WARBLES

SNEEZES

THUNDER RUMBLES

SQUAWKS

The evidence suggests that baby pterosaurs

emerge from the egg ready to fend for themselves.

And that includes...

...flying?

Well, almost.

Elsewhere, as the devastation spreads out across North America

towards Tanis...

...dinosaurs and creatures of all shapes and sizes

are obliterated by the blast.

If I were a dinosaur standing on the coast of North America,

I would just see a flash and a fireball coming at me

and I would be fried.

All you'd feel is an awfully sharp stabbing pain in your ears,

then you explode.

At Tanis, for a few more precious minutes,

life carries on as usual.

But the clock is ticking.

GRUNTING

DEEP BELLOWING

The blast from the impact never reaches Tanis,

but seismic shock waves do.

RUMBLING

They are far more powerful

than any earthquake ever recorded.

That magnitude 12 earthquake would've been strong enough to actually

jam your femurs up into your body cavity.

While the earthquake that reached Tanis was likely less destructive,

the effects would've been felt by all that lived there.

Seismic waves are now shaking the whole region,

causing water to slosh and churn.

At Tanis, strange currents in the river

give a hint of what is still to come.

THUNDER CRACKS

Next, it begins to rain.

PATTERING

Ejecta spherules are falling back to Earth.

As the spherules begin their fall...

...friction heats them until they're red hot.

Then the heat transfers to the air.

Temperatures rise with every second.

As the heat builds, the creatures of Tanis

are fighting for their lives.

ROARS

And then, as seismic waves

continue to slowly rock the whole region...

...a violent surge wave ten metres high

rushes up the Tanis river.

Surviving the turbulence of the surge

is a challenge even for the best swimmers.

Then, the powerful rocking of the river system

slowly begins to draw the water back the way it came.

A large, robust animal like a T-rex

might have survived the surge.

As might a hard-shelled reptile.

But there is much more to come.

As billions of tonnes of superheated spherules continue to fall,

the atmosphere gets even hotter...

...igniting dead leaves and sparking wildfires.

Earthquakes,

fire...

...devastation.

Little would survive for long,

on land...

ROARS

...or in the air.

SHRIEKS

The air around the planet was effectively set to boil.

This was something that you couldn't escape on the surface.

Those that live deep underground

may have a better chance.

As the slow sloshing of the river system continues...

...another powerful surge hits.

There is no escaping the destruction.

For many of the creatures of Tanis,

their stories end underwater.

In less than two hours, the world has changed forever.

The mud the surge waves leave behind

will gradually turn into the thick layer of crumbly rock

entombing the creatures which died here...

...until 66 million years later,

when they're finally unearthed.

We have a general idea of what horrors were unleashed on the landscape by the asteroid.

I think these sites may give us the ability to put them in sequence

and understand what these organisms went through.

Even though there's a lot of debate,

every new thing that we find, every new hypothesis,

gets us a little bit closer to doing that mental time travel

and imagining ourselves back in the Cretacious world.

Robert's finds have helped us understand in remarkable detail

what happened at Tanis

in the minutes after the asteroid impact.

But what about the rest of the world?

Fires raged, destroying many of the world's forests.

As that horrific day drew to a close,

many of the world's dinosaurs were already dead.

Research shows that the angle at which the asteroid hit

and the sulphur-rich rocks at the impact site

amplified the devastation.

Without light, most plants died, and food became scarce.

As the weeks and months passed,

any dinosaur left alive would've died of hunger.

In the oceans, it was the same.

Nearly all of the world's plankton disappeared,

leading to the starvation of most marine creatures.

It's thought that the nuclear winter that followed

caused a global temperature drop

of at least 25 degrees centigrade.

The fossil record tells us that this huge change in climate

marked the disappearance of three quarters of all species,

including the dinosaurs.

The location of the Chicxulub impact really was a worst case scenario.

If the asteroid had come in 30 seconds earlier,

30 seconds later, it would've hit the Atlanic Ocean or Pacific

and not the sediment-rich, sulphur-rich Yukutan Peninsula.

Forests collapse. The planteaters didn't ahve any food to eat.

They died. The meat-eaters didn't have any plant-eaters to eat. They died.

This unintentional accident was set in motion

long before dinosaurs even existed.

And it just happened to be the one case of bad luck.

The one worst day in the history of the planet.

The planet was in semi-darkness for around a decade,

as dust and soot slowly fell to Earth.

But then came something wonderful.

A new beginning.

Once the dust cleared from the atmosphere

and the sunlight returned...

...plant life was gradually restored,

led by ferns,

the spores of which had lain dormant deep underground,

and the world began to turn green once more.

But what about the animals?

One of the reasons some mammals survived the great extinction, were burrows.

During the nuclear winter,

a burrow would've provided warmth,

protection, and a place to store food.

Mammals that survived were resourceful omnivores,

and insects would've been a plentiful source of food.

Their size woud have been another advantage.

When catastrophe strikes and food is scarce,

the largest tend to die out,

whilst the smallest often survive.

And they weren't alone.

Robert's fossil turtle may have been unlucky,

but many others survived.

As did crocodiles,

snakes,

and many fish species.

Life has found a way and life is now thriving again.

It it those ecosystems that are the foundations of our ecosystems today.

it's kind of amazing that we can put our finger on this line in the rock

and as much as we miss the dinosaurs if this hasn't happened,

we wouldn't be here.

And as for the dinosaurs,

did the impact really kill them all?

Well, this beautiful fossilised feather

isn't from a bird,

but from a predatory dinosaur.

So we have to be careful

when we say that dinosaurs are extinct,

because what we call birds originally evolved

from the smallest feathered dinosaurs.

So to be correct, we should say

all non-avian dinosaurs are extinct.

Robert's finds have given us

a better idea than ever before...

...about what happened on the day that led to the extinction...

...of the largest beasts ever to walk the Earth.

Dinosaurs were perhaps

some of nature's most extraordinary creatures,

dominating the planet for over 150 million years

before they became extinct.

But extinction comes in different forms,

and many of the amazing creatures

and plants alive today are also threatened.

It's possible that humanity is having

as big an impact on the world

as the asteroid that ended the age of the dinosaurs.

As human beings, we are unique in our ability

to learn from the distant past.

The question is will we use that ability wisely and do our very best

to protect the millions of species

for whom, alongside us, this planet is home?

# (music)