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00:00Dinosaurs.
00:15Perhaps some of the most dramatic animals ever to have walked the Earth.
00:23They dominated the world for over 150 million years
00:27until a huge asteroid struck the planet.
00:36But how exactly did they die?
00:40Paleontologists have been searching for the answer for decades.
00:46And now, new evidence is coming to light.
00:51We're out looking for clues.
00:54And each fossil is a clue.
00:58And that tells us something about what the world was like at that time.
01:02Since 2012, a team of paleontologists has been investigating a remarkable site deep in the Badlands of North Dakota.
01:11The team's leader, Robert De Palma, hopes it holds evidence of what happened on the very last day of the dinosaurs.
01:25Could it even contain the remains of an animal that bore witness to that terrible event?
01:29We'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.
01:44The idea that there is a dinosaur fossil potentially that's a direct victim of that, that's very exciting.
01:49Oh, that's skin right there. That's actually scaly skin.
01:54Can they find a dinosaur to die on the day the asteroid hit?
02:02Dinosaur Apocalypse, the last day, right now on NOVA.
02:07Dinosaur Apocalypse, the last day, right now on NOVA.
02:08Dinosaur Apocalypse, the last day, right now on NOVA.
02:09Dinosaur Apocalypse, the last day, right now on NOVA.
02:13For ten years,
02:36paleontologist Robert De Palma and his team
02:39have been digging in a small corner of the Hell Creek Formation,
02:44an area famous for more than a century of major dinosaur discoveries.
02:49They've already found a wealth of fossilized creatures
02:53in a patch of land they call Tannis.
02:55Oh, wow.
02:58What appears to be a piece of fossilized skin from a triceratops.
03:04The unhatched egg and what looks like a pterosaur embryo.
03:07Jawbones of a mammal called a pediomyid.
03:13And teeth and footprints of carnivorous dinosaurs like T-Rex.
03:19There is no other dinosaur that has teeth like this.
03:23Many of these fossils were found in a thick layer of crumbly rock.
03:28The rock here is really not quite rocky,
03:31and it just falls apart in your hands.
03:34Right above the crumbly rock is the KPG boundary,
03:38a layer of iridium-rich debris from the asteroid impact
03:42that hit the Earth 66 million years ago.
03:46It marks the end of the age of dinosaurs.
03:50If you look below this layer, you see fossils of dinosaurs.
03:54If you look above this layer, no dinosaurs.
03:56The four-foot-thick layer of rock at Tannis
04:00is full of ejectospherules.
04:03And beautiful. Look at that.
04:08Tiny glass droplets created in a major asteroid impact.
04:16Robert thinks that this is compelling evidence
04:19that everything in the lair was buried while the spherules fell.
04:23If he's right, and the spherules he's found
04:30can be matched to the asteroid impact,
04:32this dig site could provide a snapshot
04:35of what happened on the very last day of the dinosaurs.
04:39Stories like this are eminently plausible.
04:42Proving them is more challenging.
04:45It opens up that whole debate about
04:47how do we link catastrophic events
04:50to fossil and geologic deposits.
04:54If we can both match spherules to the impact site
04:58geochemically and in terms of radiometric ages,
05:01that's pretty accurate.
05:03That's a smoking gun.
05:05After 10 years of digging,
05:08there is now enough evidence to piece together
05:10much of the story of Tannis
05:13and the creatures which lived here.
05:16But how exactly did they die?
05:29The asteroid that struck the Earth 66 million years ago
05:34created what is today known as the Chicxulub Crater.
05:39To find out if the ejecta spherules
05:42they found in North Dakota can be linked to Chicxulub,
05:46Robert has come to the diamond light source synchrotron in the UK.
05:51Joining him is Phil Manning of the University of Manchester.
05:56They've already run initial tests in America
05:59on over a dozen spherules found in different areas of the crumbly lair.
06:06What have you found out so far?
06:09These little glass spherules,
06:10these globs of molten material from the impact site
06:13have a chemical signal that ties it with where they came from.
06:17Because when an asteroid hits,
06:18it melts the ground that it hits,
06:20but also that glass has a little bit of contamination
06:24from the asteroid itself,
06:25and that gives you a unique geochemical fingerprint.
06:28We can see once we've scanned it
06:30and looking at other sites from around the world,
06:33Haiti, Mexico and North Dakota,
06:36we can get a baseline for what the ejecta should look like
06:40when it's related to the Chicxulub Crater.
06:44You can see each element here and the ratios of those elements.
06:47And when we look at TANIS, it's a match.
06:51I mean, it perfectly overlays.
06:53So I think this is powerful evidence supporting that TANIS and Chicxulub are linked.
07:00Wow.
07:01And what do these findings mean for the rest of the fossils that you're finding in TANIS?
07:06This data is key for the entire site,
07:09because once you have that link and you know what impact affected TANIS,
07:14then you essentially know that every object in that site,
07:17all the animals and the plants and everything buried in those sediments,
07:21are linked to the last day of the Cretaceous.
07:26This is very important because it immediately gives a time stamp for the locality itself.
07:32The TANIS site is like a window into a snapshot of time.
07:39With ejecta spherules found everywhere throughout the four-foot-thick deposit,
07:45Robert and his team seem to be able to link their site to a single day.
07:51And the synchrotron here in the UK reveals something even more remarkable.
07:57So, this is showing a beautiful synchrotron scan of the half of one spherule.
08:05The glass is a good geochemical fingerprint,
08:08but when we look at the entire thing, we see something quite unexpected.
08:13That's your entire spherule.
08:16What's this?
08:17In this, we've got a little bit of a nugget.
08:20There is a little particle right there.
08:21So, we scan it, and that's a lot of iron in there.
08:25Over here, we've got chromium.
08:28A big peak in chromium.
08:29Over here, we've got a big peak in nickel.
08:31And the abundances of iron, nickel, and chromium, all together,
08:36that matches what you expect to see in a meteoric body.
08:39That does not match what you would normally have down here.
08:42So, this is extraterrestrial material.
08:46If you were to sort of grind up and stuff into a spherule,
08:50a piece of meteorite,
08:53that's what it's going to look like.
08:55This could be a piece of the Chichalube asteroid.
08:58The piece of the bullet that killed the dinosaurs.
09:01No.
09:07Robert's team may have found a fragment of the asteroid itself in North Dakota.
09:14Physical evidence linking this site to the Chichalube impact.
09:19But Tannis is almost 2,000 miles away from where the asteroid hit.
09:24So, exactly how did the asteroid cause the death of the animals here?
09:32To answer that question, Robert is searching in something he calls the mass death assemblage.
09:38Right here, we've got this inner tangled mass of fish.
09:44There's one fish here.
09:45Another sturgeon goes this way, underneath the body of a paddlefish.
09:49There's another sturgeon that goes this way, underneath this log, and continues out the other side.
09:54And his head hit that log and has deflected downward at a 90-degree angle.
10:01Robert uncovered a tangled mass of fossilized creatures and logs surrounded by spherules and crushed together in what's known as a log jam.
10:12He has a theory that the creatures were swept to their death in some kind of turbulent surge of water and quickly entombed in sediment, which is why they're so well preserved.
10:25But what could have caused the wave?
10:30One hypothesis, 6,000 feet of water, at least half of that would have left as the rim wave.
10:36So, at least 3,000 feet high at a minimum.
10:40The tsunami raced towards land.
10:42When they reached the coastlines, they were still very high waves of up to 300 feet high, at least, probably as high as 1,000 feet high wave.
10:56That's a very impressive wave.
10:58Imagine the waves that's the size of the building approaching the coastline.
11:04In the late Cretaceous, North America was divided by a narrow sea that's been called the Western Interior Seaway.
11:13The tsunami could have theoretically traveled up this towards Hell Creek.
11:19Tsunamis generally travel at about the speed of a jet plane.
11:23It's not something you could, say, run away from.
11:27It had plenty of energy to get over the coastline.
11:32It could easily still have been tens of meters high by the time it reached well into the seaway.
11:36Could the rapid deposition at Tannis have been caused by a tsunami?
11:46To test the idea, the team needs to look at the timing.
11:50Oh, which fish is that?
11:54It's a new contact.
11:56Yeah.
11:57If a tsunami buried the fish, it would have to have hit while the ejecta spherules were falling because spherules were found everywhere, including in the fish's gills.
12:09So much depends on determining when these spherules were falling at the site.
12:17Modeling the ejecta always has error bars on it.
12:20In that we're not there to measure it.
12:25We've had no equivalent impact like this on Earth since then.
12:30But we can look at the computational models that we do and say, all right, this material is coming from this point.
12:41It's now moving away this fast with about this much mass.
12:46And then we can tell with the sorts of equations that we might use to calculate the trajectory of a cannonball, where it would go.
12:53And we can observe from these simulations how long it takes these ejecta to reach their final destinations, down to the order of a few minutes.
13:05What the calculation shows is surprising.
13:09Robert and his team have found that these ejecta spherules landed at Tannis between 13 minutes and two hours after the impact.
13:19So if a wave buried the fish, it must also have reached the site within two hours.
13:29Data from recent tsunamis show even a powerful wave would take much longer than this to travel almost 2,000 miles from the impact site to North Dakota.
13:39So if it wasn't a tsunami, what could have caused the surge of water at Tannis?
14:03Stein Bondebeck is an expert in tsunamis.
14:09The fjords in Norway are very special.
14:16We have tall mountains surrounding bodies of water.
14:21So the water is usually very pumped.
14:24In 2011, something very strange happened.
14:28The water in the fjord began to move violently.
14:33The height of the water increased by one and a half meter.
14:36Like a maelstrom with the turbulent water, someone said that the fjord was boiling.
14:46News started to roll in.
14:48There'd been an earthquake 5,000 miles away in Japan.
14:52A journalist from the local newspaper called me and he said that people were observing waves here in the fjords.
15:02I got a video clip of the waves.
15:06I saw immediately that they looked like a tsunami wave.
15:10Here you can see that the fjord is perfectly calm.
15:13But at the beach here, you could see that the water is sloshing back and forth.
15:20And no one had ever seen anything like it.
15:24Some people got very upset and afraid.
15:27A magnitude 9 earthquake had devastated the northeast of Japan.
15:38But how did that affect a fjord so far away?
15:44So no one in Norway could feel the earthquake.
15:47But I could see that the times matched the arrival of the waves here in the fjord.
15:59Eventually, Stein and his team realized that this might have something to do with seismic waves.
16:07Shock waves that pass quickly through the earth during an earthquake.
16:11So it took only 12 minutes before the first signal of the earthquake in Japan reached all the way here to western Norway.
16:22So it was the seismic waves that caused the normally calm water in the fjord to slosh turbulently back and forth.
16:31Just thinking of that, scientifically, it's fantastic.
16:41Could something similar have happened in Tannis?
16:47When large weather fronts come through large lakes, they can set up such time.
16:53Geophysicist Mark Richards has been studying the site for several years.
16:58The events in Norway support a hypothesis that he's been working on with Robert's team
17:04about what could have caused the surge of water here.
17:11A tsunami can't get here in less than minimum 12 hours.
17:18But seismic waves traveling from the Yucatan impact site to North Dakota can arrive here fairly quickly.
17:28In the late Cretaceous, the western interior seaway that bisected North America
17:33could have been connected to Tannis through the extensive river system that once flowed here.
17:41If you have a very large body of water, like the western interior seaway,
17:48and you can shake it back and forth, you can generate a large water wave coming up this river at Tannis.
17:57So this is bigger than any tectonic-generated earthquake.
18:00You would have shaking literally everywhere on the planet.
18:06So their hypothesis suggests seismic waves from the impact could have caused surges of water in the Hell Creek river system.
18:16Seismic waves get here quickly enough to cause this wall of water coming up the Tannis river,
18:23inundating this area, arriving at the same time these spherules are still falling out of the air.
18:31If they're right, seismic waves traveling through the Earth could have caused a powerful surge of water at Tannis,
18:38at the same time as spherules fell.
18:48And ultimately dumping it on the Tannis sandbank, burying everything in the churned-up mud.
18:58Debris and fine iridium dust from the asteroid would have gradually covered the deposit, forming the KPG boundary.
19:05Over millions of years, the surge of mud would become the four-foot-deep layer of crumbly rock.
19:14And that's the beauty of Tannis.
19:16What you're seeing is a deposit that is literally recording the last, say, 45 minutes to an hour and a half of the Cretaceous.
19:23The last, say, 45 minutes to an hour and a half of the Cretaceous.
19:28If the extinction of the dinosaurs was a crime, the detective solving it would have plenty of evidence.
19:43They would see that the asteroid was in the right place at the right time.
19:49They would see that no dinosaurs survived after the hit.
19:53They would have a piece of the murder weapon, a fragment of the asteroid.
19:58But they would be missing one very important thing.
20:02A body.
20:03A body.
20:06A lot of the bones that exist from those last Cretaceous days were basically destroyed.
20:12As far as we know, we've never actually found a fossil of a dinosaur individual, a single skeleton, let's say,
20:20that we can unequivocally say was there on the day the asteroid hit.
20:24But before the site was time stamped to the Chicxulub impact, Robert's team did find part of a Triceratops in the crumbly lair at Tannis.
20:38So could that be the body? A dinosaur that died on that day?
20:44Something that would help them would be establishing the cause of death, which can be difficult when you only have a piece of skin and horn to go on.
20:52This is the horn after they'd cleaned it up.
21:00The team was particularly interested in these lines here.
21:05And they found that the fractures go right through the horn.
21:10So rather than dying as a result of the impact, they wondered whether it had been killed in a fight.
21:22But when they looked at the fractures in more detail, they found signs of new bone growth here.
21:28An indication that the bone had started to heal.
21:32So it looked as though the Triceratops survived the event that broke its horn.
21:36Could this Triceratops have survived until the day of the impact?
21:47This drooping in the skin and the disarticulation of some of the bones suggested to the team that there was decay underneath.
21:54That means its body had started to rot before it was entombed and preserved by the surge.
22:02So it seems that this dinosaur didn't die as a result of the asteroid impact.
22:08Given the signs of partial decay, it's likely this Triceratops wouldn't have lived to see the last day of the dinosaurs.
22:21However, the Triceratops fossil does show that dinosaurs were alive shortly before the asteroid hit.
22:35Perhaps even within weeks of the impact.
22:38This is an extraordinary discovery and one that has never been found before.
22:43But 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.
22:58This is like looking down onto the side of a dinosaur that died weeks to months before the impact.
23:04That is such a cool thing.
23:06We've got all these bones in the ground right now.
23:08But the one thing that we would just dream of finding is that one dinosaur that died on the day of the impact.
23:21And the weather isn't helping his search.
23:24Got it.
23:32How?
23:39That theropod print is toasted.
23:42Yeah, it was in a low corner.
23:44It's full of mud and water.
23:47The problem is it's wet. Look, see, if we're not careful, we're going to lose the print.
23:52And that's the biggest theropod print we've got.
23:55I see some areas that could use glue right now, too.
23:58The team is racing to excavate dozens of fossils before the rains wash them away.
24:13We're up against the clock here.
24:15The stuff that could be exposed right now is going to get ruined by the rain.
24:20But then the team comes across something that looks very unusual.
24:24Oh my God.
24:26What is going on right there?
24:28Are we sure this isn't crocodilian?
24:30That's not crocodilian.
24:32No.
24:34I'm going to try this piece right here.
24:36I'll go in from the top and then twist up and it separates on right on that line.
24:41Oh.
24:43That's skin right there.
24:45That's actually scaly skin.
24:47No, no, no, no, no.
24:48Look, look, look.
24:49Look at that pattern right there.
24:51Have you ever seen elongated scales like that before, Dave?
24:52Scutalates and birds.
24:55Just careful.
24:57Oh, it's changing again.
24:59It's changing again.
25:01We've seen it for the first time in 66 million years.
25:05I think we've got ourselves a dinosaur.
25:10A dinosaur fossil in the same mass death assemblage as the fish with the spherules in their gills.
25:17This is the most incredible thing that we could possibly imagine here. 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 thing that we would always want to find at this site. And here we've got it.
25:40This is unreal. I cannot process this in my brain. I am absolutely blown away by this. Just my heart is literally pumping out of my chest wondering what is behind there. Just a couple of centimeters back in the outcrop. What is waiting for us back there?
25:55The team keeps digging.
25:56So this could be a root cage. It could be laying against ribs that are curved. There's something here. That's hard. That's bone right next to the skin. That's an articular surface right there. So this is either a hip or a shoulder element.
26:16After hours of painstaking work.
26:23And we can go from the thigh of the animal. There's the knee. And you've got the little calf muscles of the dinosaur there bulging out. And you go down to the ankle bones. And these are the toes of the feet. We've got nails at the tips of the toes. It's a beautifully preserved look.
26:34All articulated, 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.
26:41I mean, and now 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.
26:48Robert and his team think they've found the body missing from the crime scene. A dinosaur that might itself have witnessed the cataclysmic impact.
26:55I mean, and now it's got skin and tissue. It does look just like a drumstick.
27:00It looks like a Thanksgiving turkey just laid out in the ground.
27:03Robert and his team think they've found the body missing from the crime scene. A dinosaur that might itself have witnessed the cataclysmic impact.
27:17Dinosaur 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.
27:34And this answers that question. Were dinosaurs still there then? Well, yes, they were there weeks to months before the impact. This one likely died in that search.
27:46But such big claims need verification.
27:52Paleontologists, we kind of fight like tyrannosaurs. There are lots of different opinions. There are lots of different hypotheses. And this is all because science is a process. Science isn't a matter of just going out into the rock and we found a new dinosaur.
28:09So I think we always want to be skeptical. But I think we want to be extra skeptical when there are big claims. And it all goes back to that expression that we hear all the time and that's that extraordinary claims require extraordinary evidence.
28:23Robert is in the process of sharing the team's finds with the wider scientific community. As part of this process, he's brought the dinosaur leg to London, England to get a second opinion from paleontologist Paul Barrett, an expert in ornithischian dinosaurs from the Natural History Museum.
28:44So what do you think this might be?
28:47When we look at the leg, it has claws. Like the claws we see in small, agile, bipedal running dinosaurs that are plant eaters.
28:56We can rule out things like triceratops partly just because it's not big and stocky. And the proportions of those legs are also different from some of the other plant eaters we see in that they have this rather long ankle and shin compared with its thigh bone.
29:12So as we narrow those possibilities down, what we're left with probably is an animal called a Thesalosaur.
29:18Thesalosaurus are thought to have lived next to rivers.
29:25They had leaf shaped teeth common amongst herbivores and claws on their short front limbs, which they may have used for digging.
29:40At the front of their mouth, they had specialized pointed teeth that could help them to pull roots out of the ground.
29:50So it's possible they dug for food.
29:55But how did the Thesalosaur that Robert's team found die?
30:04Could it have been killed by another dinosaur?
30:08It's a possibility. This is a relatively agile animal.
30:12And that turn of speed would have been its primary defense against the large predators living alongside it.
30:21Whenever we're excavating a dinosaur, one of the things that we're always keen to know is how did the animal die?
30:27It's not always easy to do that.
30:29So maybe we can find evidence for things like broken bones that didn't heal back up.
30:34Sometimes we can even see things like bone tumors and gout.
30:39There are some wonderful fossils where you can find bite marks on them.
30:43You can even find a predator tooth buried within the bones.
30:49In science, we don't prove things. We just disprove some things.
30:53Generally speaking, unless a cause of death leaves a signature on the skeleton, it's hard to tell.
30:59CT scans Robert and the team have taken of the dinosaur leg allow a closer look at what the animal might have gone through before it died.
31:08It doesn't seem to me like there is any evidence that this animal was predated.
31:13None of the obvious tooth marks or leftover bits of carnivore teeth suggest it's been eaten.
31:19As we can see that the bones look okay.
31:21So this is an animal that was probably living and healthy at the time that this happened to it.
31:26Could this be a dinosaur that was swept up in the surge?
31:30The idea that there is a dinosaur fossil potentially that's a direct victim of that, that's very exciting.
31:36I think ultimately it comes down to a couple of things.
31:39You know, are there injuries on that fossil that show that this dinosaur was bobbing about, heaving about in the water?
31:48So are there things like breaks on the bone or other things that have not healed?
31:52This is actually a shoulder bone.
31:54And this bone in the living animal would actually be way over here.
31:58And similarly, this little bone here would have been from about maybe a third of the way along the tail, maybe halfway down.
32:04So somehow these two bones have been telescoped together.
32:09So maybe this animal has been tumbled around.
32:12Could this be a victim of the meteor strike?
32:17I think it's entirely possible.
32:19We've ruled out a lot of other possible causes of death for this animal.
32:23So it could well be that this is an animal that was there being tumbled around in its death throes in that river as a result of the asteroid impact.
32:31Paleontologists do depend a lot on tragedy.
32:36Every little disaster is the material we need to actually develop our subject.
32:42Tragic for the individual concerned, but we're just really happy that it happened.
32:47After years of work at this site, Robert and his team have uncovered unprecedented detail about the animals living there.
33:05And he thinks that many of them were alive on that fateful day when the asteroid devastated our planet.
33:14But how exactly did they die?
33:17The team's finds give us new clues to answer that question.
33:22One of the most important days in Earth's history probably started much like any other late spring morning.
33:32We think it was late spring because paleobotanists have found key evidence about the season from fossilized flowers.
33:42The Tannis finds are consistent with this, including the fossils of young fish that died at the size they reach at that time of year.
33:51Perhaps this day that would end with so much death began with something different.
34:06A new life.
34:10Robert only found one pterosaur egg, so it's possible that he had a brother or sister that hatched before the impact.
34:17To see the world for one final day.
34:22No one can be certain of the exact timings of the day when the asteroid collided with our planet.
34:37But it's estimated that within just 40 minutes of the impact, the consequences for the creatures of Tannis would have been profound.
34:50Based on the team's finds and the latest evidence from other scientists, this is how the catastrophe might have unfolded.
34:58The asteroid is around seven miles across, bigger than Mount Everest, and traveling at close to 45,000 miles an hour.
35:11The impact causes an explosion with over a billion times the power of the first atomic bomb.
35:26It comes in so fast that it wouldn't even have been visible passing through the atmosphere, right?
35:32It would have just come and hit in a moment.
35:35At Tannis, almost 2,000 miles away, there might have been an initial flash of light, yet it is completely silent.
35:43But at the impact site, the asteroid vaporizes.
35:55More than three trillion tons of rock are ejected into space in a blast of superheated violence.
36:02More than three trillion tons of rock are ejected into space.
36:06Winds higher than 600 miles an hour.
36:11A colossal earthquake.
36:14Followed by a ring of massive tsunamis.
36:17All the while, the creatures at Tannis go about their business.
36:34Just like any other day.
36:36The evidence suggests that baby pterosaurs may have emerged from eggs ready to fend for themselves.
37:01And that includes...
37:07Flying?
37:10Well, almost.
37:18Elsewhere, as the reverberations of the impact race out across North America...
37:23Dinosaurs and creatures of all shapes and sizes are obliterated by the blast.
37:36Incinerated in a firestorm unlike anything seen since.
37:42If I were a dinosaur standing on the coast of North America, I would just see a flash and a fireball coming at me and then I would be fried.
37:49All you feel is an awfully sharp stabbing pain in your ears.
37:54Then you explode.
38:01At Tannis, for a few more precious minutes, life continues.
38:08But the clock is ticking.
38:09The blast from the impact never reaches Tannis, but seismic shockwaves do.
38:29They are far more powerful than any earthquake ever recorded.
38:43If you were standing on the Gulf Coast of Texas, that magnitude 12 earthquake would have been strong enough to actually jam your femurs up into your body cavity.
38:50While the earthquake that wreaked Tannis was likely less destructive, the effects would have been felt by all that lived there.
39:04Seismic waves are now slowly shaking the whole region, causing water to slosh and churn.
39:11At Tannis, these strange currents in the river may be some of the first signs of what is coming.
39:25Next, it begins to rain.
39:38Ejector spherules are falling back to Earth.
39:41As the spherules plummet, friction heats them until they're red hot.
39:56They soon transfer their heat to the atmosphere,
40:08which grows hotter by the second.
40:18As the searing heat builds, the creatures of Tannis are fighting for their lives.
40:26And then, as seismic waves rock the whole region...
40:31...a violent surge wave, 30 feet high, rushes up the Tannis river.
40:35A violent surge wave, 30 feet high, rushes up the Tannis river.
40:40A violent surge wave, 30 feet high, rushes up the Tannis river.
40:45A violent surge wave, 30 feet high, rushes up the Tannis river.
40:49A violent surge wave, 30 feet high, rushes up the Tannis river.
40:52Surviving the turbulence of the surge
41:10is a challenge even for the best swimmers.
41:13Then the slow but powerful rocking of the river system
41:23draws the water back.
41:43A large, robust animal like a T-Rex might have survived the surge.
41:57As might a hard-shelled reptile.
42:00But there is much more to come.
42:03As billions of tons of super-heated spherules continue to fall,
42:08the atmosphere gets even hotter.
42:10Igniting dead leaves and sparking wildfires.
42:24Earthquakes, fire, devastation.
42:33Little would survive for long.
42:36On land.
42:43Or in the air.
42:53The air around the planet was effectively set to broil.
42:57This was something that you couldn't escape if you were out on the surface.
43:11Those that live underground may have had a better chance.
43:15As the slow rocking of the river system continues to move the water to and fro,
43:27another powerful surge hits the river bank.
43:31For most, there is no escaping the destruction.
43:46For many of the creatures here, their stories end underwater.
44:01No one knows if the giant tsunami caused by the impact ever reaches this far north.
44:16But life here has already changed forever.
44:20The mud the two waves leave behind will gradually turn into the thick layer of crumbly rock,
44:29entombing the creatures which died here.
44:32Until 66 million years later, when they are finally unearthed.
44:39We have a general idea of what horrors were unleashed on the landscape by the asteroid impact.
44:49But I think these sites may give us the ability to actually put them in sequence
44:52and understand exactly what these organisms went through.
44:56Even though there is a lot of debate and there is a lot of controversy,
45:00every new thing that we find, every new hypothesis that's put forward,
45:03whether it's accepted or rejected,
45:05gets us a little bit closer to doing that mental time travel
45:09and imagining ourselves back in that cretaceous world.
45:17Robert's finds have helped us understand in remarkable detail
45:21what might have happened at Tannis in the minutes after the asteroid impact.
45:27But what about the rest of the world?
45:33Fires rage, destroying many of the world's forests.
45:40As the horrific day draws to a close,
45:43many of the world's dinosaurs are likely already dead.
45:51Research shows that the angle at which the asteroid hit
45:55and the sulfur-rich rocks at the impact site amplified the devastation.
46:03Without sunlight, most plants died and food became scarce.
46:10As the weeks and months passed,
46:12any dinosaur left alive would have died of hunger.
46:16In the oceans, it was the same.
46:22Nearly all the world's plankton died,
46:25leading to the starvation of most marine creatures.
46:30It's thought that the impact winter that followed
46:33caused a global temperature drop of at least 48 degrees Fahrenheit.
46:39After this huge change in climate,
46:42the fossil record tells us that three-quarters of all species,
46:46including the dinosaurs, were wiped out.
46:52The location of the Chicxulub impact really was a worst-case scenario.
46:56If the asteroid had actually come in, you know, 30 seconds earlier,
46:5930 seconds later,
47:00it would have actually hit the Atlantic Ocean or the Pacific Ocean
47:03and not the sediment-rich, sulfur-rich target of the Yucatan Peninsula.
47:07Forests collapse.
47:10The plant-eaters didn't have any food to eat.
47:12They died.
47:13The meat-eaters didn't have any plant-eaters to eat.
47:15They died.
47:16Ecosystems collapsed like houses of cards.
47:18This unintentional accident that just was set in motion
47:23long before dinosaurs even existed,
47:26and it just happened to be the one case of bad luck,
47:31the one worst day in the history of the planet.
47:33Studies suggest that the planet was in semi-darkness for around a decade
47:42as dust and soot slowly fell to Earth.
47:46But then came something wonderful.
47:49A new beginning.
47:52Once the dust cleared from the atmosphere and the sunlight returned,
47:56plant life was gradually restored,
48:00led by ferns,
48:02the spores of which had lain dormant deep underground.
48:06And the world began to turn green once more.
48:11But what about the animals?
48:13One of the reasons some mammals survived the Great Extinction were burrows.
48:23During the impact winter, a burrow would have provided warmth, protection,
48:29and a place to store food.
48:30Mammals which were able to thrive in the aftermath were resourceful omnivores.
48:44And the insects which survived could have been one source of food.
48:51Their size would have been another advantage.
48:54When catastrophe strikes and food is scarce, the largest tend to die out,
49:05whilst the smallest often survive.
49:08And they weren't alone.
49:10The turtle found at the dig site may have been unlucky, but many others survived.
49:21As did crocodiles, snakes, and many fish species.
49:29Life has found a way and life is now thriving again.
49:33And it is those ecosystems formed in the recovery from the asteroid
49:37that are the foundations of our ecosystems today.
49:42It's kind of amazing that we're able to put our finger on this one line in the rock.
49:46And as much as we miss the dinosaurs, say,
49:49if this hadn't happened, we wouldn't be here.
49:52And as for the dinosaurs, did the impact really kill them all?
49:58Well, this beautiful fossilized feather isn't from a bird,
50:04but from a predatory dinosaur.
50:05So we have to be careful when we say that dinosaurs are extinct.
50:10Because what we call birds originally evolved from the smallest feathered dinosaurs.
50:18So to be correct, we should say all non-avian dinosaurs are extinct.
50:23The finds from Robert and his team have given us a more detailed picture.
50:32About what might have happened on the day that destroyed the largest beasts ever to walk the earth.
50:40Dinosaurs were perhaps some of nature's most extraordinary creatures, dominating the planet for over 150 million years before they became extinct.
50:57But extinction comes in different forms.
51:03And many of the amazing creatures and plants alive today are also threatened.
51:09It's possible that humanity is having as big an impact on the world as the asteroid that ended the age of the dinosaurs.
51:17As human beings, we are unique in our ability to learn from the distant past.
51:25The 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?
51:37The maps are potentially different courses and of the time.
51:38Let them land in our ability to grow our world.
51:39The maps for America of America-
51:57Transcription by CastingWords
52:27CastingWords
52:57CastingWords
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