What Was It Like To Witness The End Of The Dinosaurs
66 million years ago, a massive asteroid hit what we know today as the Yucatán Peninsula of Mexico. Many people have a general idea of what happened next: The age of the dinosaurs was brought to a close, making room for mammals like us to thrive.
But fewer people know what happened in the days, weeks, and years after impact. Increased research on fossils and geological remains from this time period have helped scientists paint a picture of this era. For large, non-avian dinosaurs like Triceratops and Tyrannosaurus rex, extinction was swift following the asteroid impact. But for creatures that were able to stay underwater and underground, their post-impact stories are more complicated.
Joining Ira to discuss her book The Last Days of the Dinosaurs is Riley Black, science writer based in Salt Lake City, Utah. You can read an excerpt of the book here.
The Wave Is A Big Part Of Why Robert And His Teams Fossils Are So Well Preserved Is The Preservation Something That’s Unique About Tanis
Helen: I think it’s because the surge dumped all the mud and debris so quickly, and everything was preserved in an instant, with skin and tissue. It’s about the speed of entombment as it were – a bit like the bodies that were so well preserved in Pompeii.
Sir David: We know quite a lot about skin and tissue of dinosaurs from other deposits. There are some very impressive dinosaur fossils which were found in sand dunes where in fact an animal died and was covered in sand. Some of the first specimens of skin from dinosaurs were found in sandy deposits. And were discovering more and more about the soft tissues of dinosaurs.
David Could You Tell Us What Discovery Or Which Aspects Of The Filming You Found Particularly Fascinating
Sir David: Well, there is one moment when there is one of those electric moments of proof. We didn’t know what the answer was going to be. We had a Professor alongside us and he took a spherule and got the chemical profile of it. And he found that it was exactly the same – from Chicxulub and from Tanis. It was a moment of justification for the whole thing really.
Helen: One of my favourite moments of the filming actually was when we were setting up in what we called the fossil workshop, where we filmed the fossils we brought over from America. And we had a pause in filming to reset and I turned around, and there was David with a brush and a scalpel, and you were examining one of the fish fossils yourself, and it was brilliant, it was as though the filming just didn’t exist and you were investigating the fossil with Robert DePalma and Phil Manning, And it was just such a lovely moment, that you were so invested in the discovery, it was brilliant.
Sir David: It is very romantic. It is escapism in some ways but its very romantic.
The Day The Dinosaurs Died
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If, on a certain evening about sixty-six million years ago, you had stood somewhere in North America and looked up at the sky, you would have soon made out what appeared to be a star. If you watched for an hour or two, the star would have seemed to grow in brightness, although it barely moved. Thats because it was not a star but an asteroid, and it was headed directly for Earth at about forty-five thousand miles an hour. Sixty hours later, the asteroid hit. The air in front was compressed and violently heated, and it blasted a hole through the atmosphere, generating a supersonic shock wave. The asteroid struck a shallow sea where the Yucatán peninsula is today. In that moment, the Cretaceous period ended and the Paleogene period began.
Earth itself became toxic. When the asteroid struck, it vaporized layers of limestone, releasing into the atmosphere a trillion tons of carbon dioxide, ten billion tons of methane, and a billion tons of carbon monoxide all three are powerful greenhouse gases. The impact also vaporized anhydrite rock, which blasted ten trillion tons of sulfur compounds aloft. The sulfur combined with water to form sulfuric acid, which then fell as an acid rain that may have been potent enough to strip the leaves from any surviving plants and to leach the nutrients from the soil.
What Caused Global Mass Extinctions
Around 75% of Earth’s animals, including dinosaurs, suddenly died out at the same point in time. So how was it all caused by a rock hurtling into the coast of Central America?
Paul explains, ‘The asteroid hit at high velocity and effectively vaporised. It made a huge crater, so in the immediate area there was total devastation. A huge blast wave and heatwave went out and it threw vast amounts of material up into the atmosphere.
‘It sent soot travelling all around the world. It didn’t completely block out the Sun, but it reduced the amount of light that reached the Earth’s surface. So it had an impact on plant growth.’
The shockwave from the asteroid’s landing on the YucatÃ¡n Peninsula devastated the immediate area. Image by Donald E Davis courtesy of NASA/JPL-Caltech, via Wikimedia Commons
Like dominos, this trailed up the food chain, causing the ecosystem to collapse. The reduction in plant life had a huge impact on herbivores’ ability to survive, which in turn meant that carnivores would also have suffered from having less food available.
Breeding seasons would have been shorter and conditions harsher. All living things would have been affected in some way, both on land and in the ocean.
‘There is a lot of discussion over the actual kill mechanism and how long that period lasted. There are still a lot of unknowns. But it was a massive event affecting all life on Earth, from microorganisms all the way through to dinosaurs,’ says Paul.
Dinosaurs: The Final Day With David Attenborough Review A Thrilling Slice Of Time
The awe-inspiring broadcaster vividly brings dinosaurs last terrifying minutes to life in this slick, gripping and elegiac feature-length documentary
The last day of the dinosaurs probably began as a morning like any other. On a sandbank bounded by a river and warm wet forests in whats now the dusty North Dakota prairies, triceratops and tyrannosaurs laid eggs, roamed, did their late Cretaceous thing. Thescelosaurs and turtles swam in the river. Pterosaurs flew overhead and furry mammalian creatures burrowed underground. On one of the most important days in Planet Earths history, as only David Attenborough can so portentously pronounce it, life went on in abundance. Until an asteroid bigger than Mount Everest hit what is now Mexicos Yucatan peninsula with an explosion whose force was greater than that of a billion Hiroshima bombs. In less than two hours, the world as we never knew it was for ever changed.
We dont know exactly when the asteroid hit. But within 40 minutes, the consequences 2,000 miles away at Tanis the name given to the Dakotan sandbank by the palaeontologists who have been digging there for a decade were profound. Dinosaurs: The Final Day With David Attenborough recreates those last terrifying minutes as wildfires, earthquakes, tsunamis and seismic waves ravaged the globe and all life at Tanis was swiftly entombed in sediment. For context, this was 60m years before we pitched up. And were seeing in real time how thats panning out.
How Did Robert Depalma Link The Site To The Chicxulub Asteroid Of 66 Million Years Ago
Sir David: The interesting thing about Tanis is that it’s around 2000 miles away from where the meteorite hit, in the sea off Mexico. So how do you know that it was the Chicxulub asteroid that was responsible for killing the creatures in Hell Creek? And the answer is that when a huge meteorite hits and pulverizes the earth the explosion produces an enormous amount of molten rock and some of this turns into tiny glass beads called ejecta spherules.Tthese tiny little fragments are then distributed over a wide area by natural forces.
Helen: Scientists calculated that ejecta spherules from an asteroid that hit off Mexico would have taken between 13 minutes and a couple of hours to fall at Tanis.
Sir David: Robert found spherules in the gills of the fish he was excavating at Tanis. The fish breathe by taking in oxygenated water and putting it through their gills and expelling it and so anything that they take in has just arrived. And they found these spherules in the gills of these fish.
The spherules found at Tanis were first analysed in America. In this country the synchrotron in Oxfordshire is also one of the few places in the world where you can do a detailed analysis of the chemical makeup of spherules. Samples from Chicxulub are identical chemically to spherules that have been discovered in Hell Creek. So you have got the link.
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Fossilized Turtle Impaled By A Stake
Robert and his team used ultra-cold liquid nitrogen to help free the complete fossil of a turtle.
Its a heart-stopping moment but the team manages to get the specimen out in one piece.
Evidence points to the turtle having been impaled by a wooden stake possibly a tree branch as the impact of the asteroid caused a tsunami of destruction that swept across the planet.
Asteroid Evidence At Tanis
There is little doubt that the Tanis site lies close to the end of the Cretaceous Period, because DePalma has identified the iridium layer immediately above the fossil bed, which places it at the K-Pg boundary.
He has also presented some compelling pieces of evidence that the site marks the exact day the asteroid struck.
First, there are the ancient channels in the sedimentary rocks at Tanis these are evidence of the huge standing water waves which engulfed Tanis. At that time North America was divided by a great seaway that passed close to the Tanis site: the seiche waves would have run up the creeks, and out again, several times, mixing fresh and sea waters to create the waves.
The ground-borne shock waves from the asteriod impact which caused the devastating water surges could readily travel through the Earths crust from the impact site to Tanis.
When the asteroid crashed into Earth, tiny ejector spherules, glassy beads about 1mm wide, were formed from melted molten rock and were able to travel up to around 3,200km through the atmosphere because they were so light.
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So Why The Uncertainty
There is no doubt that DePalmas claims have been controversial since they were first presented to the world in 2019 probably because the announcement was in the New Yorker magazine rather than a peer-reviewed journal.
But the findings about seiche waves were then published in an academic paper only a month later, and most geologists were convinced.
It is true that the fossils, which were revealed for the first time in the BBC documentary along with the evidence that the glass spherules at Tanis are linked to the Chicxulub impact have yet to be published in scientific journals, where they would be subject to peer review.
But, experience shows that most of what DePalma has revealed in the past has been backed up subsequently by peer-reviewed papers.
Over the past two years I worked as one of the independent scientific consultants to the BBC, verifying the claims, as they made the documentary. Both I and my colleagues, and many other experts, are satisfied that the Tanis site probably does reveal the very last day of the non-avian dinosaurs.
And of course, as we all know, the impact of the asteriod went far beyond that one day. It led to a freezing dark planet, on a global scale, lasting for days or maybe weeks and, from this mass extinction worldwide, the age of the mammals emerged.
What Do You Hope That People Take Away From Watching This Film
Sir David: I think one thing to take away is how using the right scientific techniques, but also thinking and logic, looking at evidence, quite simple evidence like bits of rocks, you can reconstruct what happened in the past and the importance of it all.
Helen: Yes, and I think that by scientists working hard together, bringing together knowledge, and not being divisive, we can learn faster and that’s what we need to do at the moment.
During the Covid pandemic, everybody worked together and we got the vaccine so quickly, so I like to think that when scientists work together, we can move mountains.
Sir David: Scientists are pretty good at doing this, politicians dont work in the same kind of way.
Main image: Sir David Attenborough is the presenter of Dinosaurs: The Final Day, with David Attenborough
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Dinosaurs: The Final Day
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago, although the exact origin and timing of the evolution of dinosaurs is the subject of active research. They became the dominant terrestrial vertebrates after the TriassicJurassic extinction event 201.3 million years ago their dominance continued throughout the Jurassic and Cretaceous periods.
The fossil record shows that birds are modern feathered dinosaurs, having evolved from earlier theropods during the Late Jurassic epoch, and are the only dinosaur lineage known to have survived the CretaceousPaleogene extinction event approximately 66 million years ago. Dinosaurs can therefore be divided into avian dinosaurs, or birds and the extinct non-avian dinosaurs, which are all dinosaurs other than birds.
Dinosaurs are a varied group of animals from taxonomic, morphological and ecological standpoints. Birds, at over 10,700 living species, are among the most diverse group of vertebrates. Using fossil evidence, paleontologists have identified over 900 distinct genera and more than 1,000 different species of non-avian dinosaurs. Dinosaurs are represented on every continent by both extant species and fossil remains.
One Million Years Post
The second reason the book surpassed my expectations is Blacks reflections on the process of evolution and its role in ecological recovery. This is where her prose sings in places. One thousand years post-impact there is no script for whats about to unfold, no cast of characters that inevitably must be filled , and there is no optimal state that the living world will return to given enough time. Whats being woven now is something entirely new . One million years post-impact a reptilian resurgence seems unlikely, but the rise of the mammals is anything but assured . Mass extinctions do not dictate winners. When a global disaster ends one evolutionary dance, shifting the tempo, another begins, with no certainty as to who will lead . She poignantly notes how the fossil record is not in any way a complete record of life on Earth. It is a record of fortuitous burials . And on the process of evolution, she writes how variation and happenstance provide the raw material for natural selection and other evolutionary forces to shunt down different pathways. Not that there is any intent to this. Its a passive state, a constantly running routine that is merely part of existence itself . This is music to my ears and Blacks writing is one of the highlights of this book.
Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.
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Remarkable New Fossil Finds May Provide A Window Into The Final Day Of The Dinosaur Age
- Christina Zeiders Christina Zeiders is the Communications Specialist at WITF. She helps get the word out about all of WITF’s programs, events and community conversations.
will premiere a new two-part special, Dinosaur Apocalypse, Wednesday, May 11 at 9pm on WITF TV. The special explores how newly discovered fossils from a dig site in North Dakota may provide a glimpse of events on the day an asteroid struck Earth and ended the age of the dinosaurs.
Viewers follow Sir David Attenborough and a team of scientists as they reconstruct a detailed picture of one of the unluckiest days for life on Earth in two back-to-back, one-hour episodes, The New Evidence and The Last Day.
66 million years ago, an asteroid larger than Mount Everest slammed into Earth, killing the giant reptiles that dominated the planet for over 150 million years. There is strong evidence of the impact, but no fossils of a dinosaur killed in the event itself have ever been found.
Now, at a dig site in the Badlands of North Dakota, scientists have uncovered a wealth of fossilized creatures that might be connected to the fateful day that ended the Cretaceous Era.
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People On The Whole Including Yourself Seem Endlessly Fascinated With Dinosaurs Why Do You Think That Is
Sir David: People are fascinated by dinosaurs. And children are fascinated by their names with which they wish to bamboozle their grandparents, do you know grandpa, do you know what this is and the others. I yearn to find a bit of dinosaur myself but they are fairly rare in this country, although of course it was in Britain that they were first discovered.
Well, there were a number that were first found here. They tried to model some of them in Crystal Palace and the early models are still there. The Iguanodon was one of them. In the early 19th century some teeth were found by a doctor who lived on the south coast in Sussex. And it was thought they were very likely the tooth of a lizard that looked like an iguana – and so it was called iguanodon, but its many times bigger than any living iguana. And that was one of the first dinosaurs that was identified. And it was Sir Richard Owen, of course, of the Natural History Mueum who coined the term Dinosauria, he said they were terrible lizards. So this country was the first country to recognise dinosaurs.
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