What Caused the Dinosaur Extinction?(theatlantic.com)
theatlantic.com
What Caused the Dinosaur Extinction?
https://www.theatlantic.com/magazine/archive/2018/09/dinosaur-extinction-debate/565769/?single_page=true
46 comments
The evidence for a massive impact precisely at the K/T boundary is ironclad. Any alternate theory in which the impact was not causal has to explain how this incredible coincidence (the largest impact in the past 100 million years occurring in a layer deposited in just thousands of years, right at the boundary) occurred.
This struck me as precisely the type of thing that they were giving out about in the article. So I asked a geologist was there more to it. They said:
The Cretaceous-Paleocene event is dated to 66m years ago [1]. The crater has been dated to 65m years ago [2]. The deccan traps was from 63-69m years ago with the bulk of activity 66m years ago [3].
Obviously both the volcano and the meteor were life-changing events. Of the three events the fossil record analysis is the hardest to analyse. But there are indications that the volcanos main activity may have preceded the meteor and that while the meteor did obviously contribute may not have been the main cause of the extinction. IE the dinosaurs may have been on their way out before it, or it may have been a "combination" of the two.
[1] https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_e...
[2] https://www.ncbi.nlm.nih.gov/pubmed/17789640
[3] https://link.springer.com/article/10.1007%2FBF02981139
The Cretaceous-Paleocene event is dated to 66m years ago [1]. The crater has been dated to 65m years ago [2]. The deccan traps was from 63-69m years ago with the bulk of activity 66m years ago [3].
Obviously both the volcano and the meteor were life-changing events. Of the three events the fossil record analysis is the hardest to analyse. But there are indications that the volcanos main activity may have preceded the meteor and that while the meteor did obviously contribute may not have been the main cause of the extinction. IE the dinosaurs may have been on their way out before it, or it may have been a "combination" of the two.
[1] https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_e...
[2] https://www.ncbi.nlm.nih.gov/pubmed/17789640
[3] https://link.springer.com/article/10.1007%2FBF02981139
If that dating is at all accurate, it seems pretty obvious that both Deccan Traps and the Chicxulub impact contributed. I don't get why it's gotta be either-or.
There is no evidence the dinosaurs were on their way out. The evidence is entirely consistent with abrupt extinction with no precursor decline.
The global mass extinction killed things that can be much more precisely dated than dinosaurs. Forams, for example, go extinct right at the impact boundary, cut off like a knife.
The global mass extinction killed things that can be much more precisely dated than dinosaurs. Forams, for example, go extinct right at the impact boundary, cut off like a knife.
Geologist here: I've studied in 1997-2003, than I've had a PhD in stratigraphy in 2007. I researched on a similar subject trying to identify what caused "dinosaurs" appearence (spoiler: another extinction event). At that time the two hypotheses, at least in Europe, were still presented as equally valid.
How these two phenomena can be equally the cause of the mass extinction at the end of Cretaceous?
Two reasons, at least. The first is the uncertainty about how rapid was the decline of Life. Any geologic date has an error, so it is extremely hard to assess the velocity of geological events. Around the K/T boundary most rock samples cannot be dated with a precision greater than a million year, that means that 2 separate events have the same probability to be coeval or separated by hundreds of thousands years with 95% confidence. In these case the uncertainty cannot allow us to distinguish an abrupt event from a slow one. More precisely, some rocks can actually be dated with an error of ~10000 years, like the iridium anomaly, or like the Deccan's lava but forams does not live inside lava. So you have to correlate events, to find proxy signals like changes in water geochemistry and so on. This increases uncertainties when dealing with fossils, and may be an easy way to denigrate palaeontological studies, but there are still evidences of a progressive decline.
The second reason is that the decline in marine ecosystems was sharp after the iridium anomaly, but we cannot explain why that precise impact killed big reptiles on sea and land whereas hundreds of other asteroids that hit the Earth during mesozoic had not. It was surely not the asteroid impact alone. There are evidences that all the mass extinction events are not instantaneous, but they are all related to a sequence of (misfortunated) events in rapid sequence. The emplacement of igneous provinces has proven to be a common menace for life on Earth. Asteroids too.
What we actually "read" in the rocks is that Deccan's traps paved the way, the Yucatan impact provided a massive stroke, and the closeness of these two events finished the survivors. In my opinion the "war" between scientists was more an US phenomenon related to their need to get access to NSF funds. The cool one got all.
How these two phenomena can be equally the cause of the mass extinction at the end of Cretaceous?
Two reasons, at least. The first is the uncertainty about how rapid was the decline of Life. Any geologic date has an error, so it is extremely hard to assess the velocity of geological events. Around the K/T boundary most rock samples cannot be dated with a precision greater than a million year, that means that 2 separate events have the same probability to be coeval or separated by hundreds of thousands years with 95% confidence. In these case the uncertainty cannot allow us to distinguish an abrupt event from a slow one. More precisely, some rocks can actually be dated with an error of ~10000 years, like the iridium anomaly, or like the Deccan's lava but forams does not live inside lava. So you have to correlate events, to find proxy signals like changes in water geochemistry and so on. This increases uncertainties when dealing with fossils, and may be an easy way to denigrate palaeontological studies, but there are still evidences of a progressive decline.
The second reason is that the decline in marine ecosystems was sharp after the iridium anomaly, but we cannot explain why that precise impact killed big reptiles on sea and land whereas hundreds of other asteroids that hit the Earth during mesozoic had not. It was surely not the asteroid impact alone. There are evidences that all the mass extinction events are not instantaneous, but they are all related to a sequence of (misfortunated) events in rapid sequence. The emplacement of igneous provinces has proven to be a common menace for life on Earth. Asteroids too.
What we actually "read" in the rocks is that Deccan's traps paved the way, the Yucatan impact provided a massive stroke, and the closeness of these two events finished the survivors. In my opinion the "war" between scientists was more an US phenomenon related to their need to get access to NSF funds. The cool one got all.
The article is, roughly, about a geologist who studies exactly forams and disagrees.
Yes, and others who study forams have looked at the same evidence and come to different conclusions. Someone's inferences are not following the same logic as others, and the most parsimonious explanation is that it's this person -- who I understand has become somewhat notorious -- not the rest of the scientific community.
And you know better because...?
The main point of the article is that the issue is far from settled, and that evidence for both sides is lacking. Until the consensus is reached through scientific means (instead of bullying) the matter is not closed.
The main point of the article is that the issue is far from settled, and that evidence for both sides is lacking. Until the consensus is reached through scientific means (instead of bullying) the matter is not closed.
Could you link to some of this purported notoriety?
The article states that some scientists disagree and have evidence to back their claim that life was on it's way out.
Is it possible for a meteor to cause a chain of volcanoes to blow? like all the pressure under the crust gets rattled around?
Maybe.
On Mercury, it seems the impact that created the Caloris basin [1] may also have created a seriously busted-up region at its antipode (opposite on the planet from the impact) [2]. This may have happened due to shock waves propagating through Mercury's interior, focused by reflection at the planet's surface onto an area opposite the impact. There are alternate theories.
A few years ago, I looked into whether the Deccan Traps eruptions might have been either triggered or enhanced by similar antipodal seismic wave energy from the Chicxulub impact. Based on Earth's continental positions about 65M years ago, it seemed possible, maybe plausible. There were some papers discussing the possibility, but I don't have the data at hand.
[1] https://en.wikipedia.org/wiki/Caloris_Planitia [2] https://en.wikipedia.org/wiki/Caloris_Planitia#Antipodal_cha...
On Mercury, it seems the impact that created the Caloris basin [1] may also have created a seriously busted-up region at its antipode (opposite on the planet from the impact) [2]. This may have happened due to shock waves propagating through Mercury's interior, focused by reflection at the planet's surface onto an area opposite the impact. There are alternate theories.
A few years ago, I looked into whether the Deccan Traps eruptions might have been either triggered or enhanced by similar antipodal seismic wave energy from the Chicxulub impact. Based on Earth's continental positions about 65M years ago, it seemed possible, maybe plausible. There were some papers discussing the possibility, but I don't have the data at hand.
[1] https://en.wikipedia.org/wiki/Caloris_Planitia [2] https://en.wikipedia.org/wiki/Caloris_Planitia#Antipodal_cha...
> A few years ago, I looked into whether the Deccan Traps eruptions might have been either triggered or enhanced by similar antipodal seismic wave energy from the Chicxulub impact. Based on Earth's continental positions about 65M years ago, it seemed possible, maybe plausible. There were some papers discussing the possibility, but I don't have the data at hand.
Could it be worked backwards, there a re a number of flood basalts, some as recently as 10mya, is there any evidence of impacts for any others? Or is there some reason the Deccan traps stand out compared to the others?
Could it be worked backwards, there a re a number of flood basalts, some as recently as 10mya, is there any evidence of impacts for any others? Or is there some reason the Deccan traps stand out compared to the others?
Good idea. There may be enough impact and vulcanism events with reasonably good dating to search for the former as a cause of the latter.
I mean, this is definitely my goto theory. Everything tied up in one single package.
But, unfortunately, just because we like something, doesn't mean it really went down that way. And rightfully so, a horde of nerds will come out of the woodwork, to inform us if we were to claim the validity of an event, without true evidence in hand.
Either way, it won't stop me from harboring a deep suspicion that this is exactly what happened.
Mostly, my own belief is founded in similar conceptual origins for the moon.
But, unfortunately, just because we like something, doesn't mean it really went down that way. And rightfully so, a horde of nerds will come out of the woodwork, to inform us if we were to claim the validity of an event, without true evidence in hand.
Either way, it won't stop me from harboring a deep suspicion that this is exactly what happened.
Mostly, my own belief is founded in similar conceptual origins for the moon.
Seems like yes?
https://www.whitecoatinvestor.com/expense-ratios/
https://www.whitecoatinvestor.com/expense-ratios/
Possible yes. ctrl+f "Some scientists have attempted to find a middle ground between the two camps." in OP for more info and links.
Maybe volcanic debris somehow interacted with a passing object (like Messenger-1) and changed its trajectory to pass through Earth?
It's very human to want to connect these events into a cohesive narrative, but there is still the possibility that they were independent events in our universe.
It's very human to want to connect these events into a cohesive narrative, but there is still the possibility that they were independent events in our universe.
Whether that is possible or not, the primary theory for the Deccan Traps is that they were initially formed as India drifted towards Asia and passed over volcanically active area that lies under the present Reunion islands.
This is about the supervolcano hypothesis.
Note that this and the Alvarez asteroid hypothesis aren't mutually-exclusive; a significant impact event could in fact trigger vulcanism on a massive scale.
There's plenty of evidence that the K-T impactor was real and slammed into the Earth. It alone might've caused the massive die-offs, or it might've triggered vulcanism and/or venting of poisonous gas deposits from beneath the seabed.
Note that this and the Alvarez asteroid hypothesis aren't mutually-exclusive; a significant impact event could in fact trigger vulcanism on a massive scale.
There's plenty of evidence that the K-T impactor was real and slammed into the Earth. It alone might've caused the massive die-offs, or it might've triggered vulcanism and/or venting of poisonous gas deposits from beneath the seabed.
According to the article, the vulcanism starts two hundred thousand years before the impact.
Sure, started, but...
http://science.sciencemag.org/content/350/6256/76
> The existing Deccan Traps magmatic system underwent a state shift approximately coincident with the Chicxulub impact and the terminal-Cretaceous mass extinctions, after which ~70% of the Traps' total volume was extruded in more massive and more episodic eruptions. Initiation of this new regime occurred within ~50,000 years of the impact, which is consistent with transient effects of impact-induced seismic energy.
Then there's the possibility of another impactor coincident in time to Chicxulub: https://en.wikipedia.org/wiki/Shiva_crater
http://science.sciencemag.org/content/350/6256/76
> The existing Deccan Traps magmatic system underwent a state shift approximately coincident with the Chicxulub impact and the terminal-Cretaceous mass extinctions, after which ~70% of the Traps' total volume was extruded in more massive and more episodic eruptions. Initiation of this new regime occurred within ~50,000 years of the impact, which is consistent with transient effects of impact-induced seismic energy.
Then there's the possibility of another impactor coincident in time to Chicxulub: https://en.wikipedia.org/wiki/Shiva_crater
This was discussed in TFA.
Excellent article that I thoroughly enjoyed. I had no idea there was any other compelling explanation for the dinosaurs' extinction other than an asteroid but it makes sense. It's definitely convincing enough that it shouldn't be dismissed outright and it sounds like about half of the scientific community is doing just that.
Is the Radiolab account off? That the impact basically fried the surface of the entire planet at > 1000 degrees? Wasn't that also kind of the premise of Seveneves? That a bunch of particulate matter gets into the atmosphere and rains down, on reentry it burns like the space shuttle but with so much of it around the entire planet it basically bakes the entire earth
In the Radiolab episode they claimed the entire planet is covered in the baked layer. That you can dig anywhere on the planet and find it.
https://www.wnycstudios.org/story/dinopocalypse/
at about the 10 minute mark
or visual
https://www.youtube.com/watch?v=ZYoqtBEzuiQ#t=15m
Is that still a valid theory?
In the Radiolab episode they claimed the entire planet is covered in the baked layer. That you can dig anywhere on the planet and find it.
https://www.wnycstudios.org/story/dinopocalypse/
at about the 10 minute mark
or visual
https://www.youtube.com/watch?v=ZYoqtBEzuiQ#t=15m
Is that still a valid theory?
Extremely well written and fascinating story on a competing theory for the mass extinction. still not convinced that the generally accepted Alavarez Asteroid hypothesis is wrong. Worth a read nonetheless.
That's the thing in pop science though. String theory is generally accepted -- so write about the iconoclasts who reject it. Asteroid accepted as the end of dinosaurs? Write about the iconoclasts there.
String theory is not generally accepted. It has not made a single successful prediction, or indeed any predictions at all. It's more correct to say most physicists view it with skepticism mixed with disdain.
This is interesting less for the science and more for the conflicts between different camps of "rationalists" about what "science" means. Especially given that the "rockstar physicist shows up with a model, gets angry when everyone doesn't accept their conclusions" dynamic is hardly unique to paleontology.
Start with a 3 species model. Imagine a shallow, closed sea, in which there is a shark, a plesiosaur, and a bird. We need to explain why the shark and the bird survive, but the plesiosaur goes extinct.
An asteroid hits somewhere, causing environmental change. For the rest of this comment, I'm going to refer to temperature as a short-hand way of referring to any environmental change.
The shallow, closed sea is undergoing temperature change, so the environment for bacteria and viruses is rapidly changing, therefore new species of bacteria and viruses are emerging at a high speed.
The shark is safe because the shark has general purpose macrophages which fights all pathogens with equal efficiency -- the shark does not care whether a pathogen is new or old, because the shark has a disease fighting system which does not rely on the principle of immunity. Sharks are 350 million years old -- they evolved long before immunity existed.
The plesiosaur and the bird are both in danger, because they have a system of disease fighting that does rely on immunity -- they are efficient at fighting off pathogens they've already been exposed to, but they are inefficient at fighting off pathogens that they have never been exposed to.
The birds see half the flock grow sick and die, so some instinctual fear of disease kicks in and the birds fly away from the shallow, closed sea.
The plesiosaur has no escape. Their disease fighting system is inefficient when dealing with new diseases, and they are in a bath of new diseases, from which they can not escape. They go extinct.
Immunity is the best model I've seen so far for explaining which species went extinct and which species survived.
An asteroid hits somewhere, causing environmental change. For the rest of this comment, I'm going to refer to temperature as a short-hand way of referring to any environmental change.
The shallow, closed sea is undergoing temperature change, so the environment for bacteria and viruses is rapidly changing, therefore new species of bacteria and viruses are emerging at a high speed.
The shark is safe because the shark has general purpose macrophages which fights all pathogens with equal efficiency -- the shark does not care whether a pathogen is new or old, because the shark has a disease fighting system which does not rely on the principle of immunity. Sharks are 350 million years old -- they evolved long before immunity existed.
The plesiosaur and the bird are both in danger, because they have a system of disease fighting that does rely on immunity -- they are efficient at fighting off pathogens they've already been exposed to, but they are inefficient at fighting off pathogens that they have never been exposed to.
The birds see half the flock grow sick and die, so some instinctual fear of disease kicks in and the birds fly away from the shallow, closed sea.
The plesiosaur has no escape. Their disease fighting system is inefficient when dealing with new diseases, and they are in a bath of new diseases, from which they can not escape. They go extinct.
Immunity is the best model I've seen so far for explaining which species went extinct and which species survived.
Yeah, no. There was massive extinction of single cell creatures (forams, for example) and also plants, which don't have immune systems.
A good match for the extinction patterns is which species could survive a prolonged interruption of photosynthesis.
A good match for the extinction patterns is which species could survive a prolonged interruption of photosynthesis.
I don't see how you would distinguish this from a guess?
Why prefer this over any other of the millions of possible explanations? Ecosystems are complicated.
Why prefer this over any other of the millions of possible explanations? Ecosystems are complicated.
There is an easier explanation. Because there are refuges for the shark and the bird.
The shark can go to the deep sea, more stable and breath there. The bird can fly away and high over the poisoned cloud. The mammals can go under the soil. The plesiosaur could swim away but needs return to the surface to breath. Their suitable habitat has vanished.
The shark can go to the deep sea, more stable and breath there. The bird can fly away and high over the poisoned cloud. The mammals can go under the soil. The plesiosaur could swim away but needs return to the surface to breath. Their suitable habitat has vanished.
What’s with all the pretentious exposition? You could’ve shared your shower-thought in 140 chars.
Please don't be nasty here.
https://news.ycombinator.com/newsguidelines.html
https://news.ycombinator.com/newsguidelines.html
Great article, but the ending made little sense:
We all chuckled at this prediction—mass extinction, by this point, having become something of a macabre inside joke. Just past the spoil, we reached the end of the road, which was lined with piles of white dirt too tall to see over. Clambering over them in search of outcrops, we were confronted by a strange view on the other side: an enormous field of coal, pockmarked with holes. The black earth had been dug at regular intervals to create thousands of pits, all the size and depth of shallow graves. Each one had its own mound of white earth beside it, as if waiting to be filled. No one could explain what they were.
This has little to do with the rest of the article, raises a whole slew of questions, and the phrase "no one could explain what they were" is uncharactersitically vague.
It feels like I missed the punchline to a joke. I can imagine the kinds of debates about the origins of the pits might resemble the debate about the impact theory, but this indirection seems like an odd way to end an otherwise clearly written article.
What am I missing?
We all chuckled at this prediction—mass extinction, by this point, having become something of a macabre inside joke. Just past the spoil, we reached the end of the road, which was lined with piles of white dirt too tall to see over. Clambering over them in search of outcrops, we were confronted by a strange view on the other side: an enormous field of coal, pockmarked with holes. The black earth had been dug at regular intervals to create thousands of pits, all the size and depth of shallow graves. Each one had its own mound of white earth beside it, as if waiting to be filled. No one could explain what they were.
This has little to do with the rest of the article, raises a whole slew of questions, and the phrase "no one could explain what they were" is uncharactersitically vague.
It feels like I missed the punchline to a joke. I can imagine the kinds of debates about the origins of the pits might resemble the debate about the impact theory, but this indirection seems like an odd way to end an otherwise clearly written article.
What am I missing?
The author seems to be talking about mining fossil fuels. And how they believe that fossil fuels will end humanity.
This articles tone comes across as incredibly snide, sarcastic, and condescending. This is how it describes the impact theory:
‘Mystery solved’. ‘Scientists cheered’. ‘a heartwarming story about the integrity of the scientific method.’
It reads more like a snarky movie review than science journalism.
‘Mystery solved’. ‘Scientists cheered’. ‘a heartwarming story about the integrity of the scientific method.’
It reads more like a snarky movie review than science journalism.
'snide, sarcastic, and condescending' was not just the authors view, but the way involved scientists view theories of each other. So it's unfair to blame the article for that, which is an article about a scientist and not science in general.
From the article:
"In 1997, hoping to reconcile disagreement over the speed of extinction, scientists organized a blind test in which they distributed fossil samples from the same site to six researchers. The researchers came back exactly split."
Oh dear, that is bad.
"In 1997, hoping to reconcile disagreement over the speed of extinction, scientists organized a blind test in which they distributed fossil samples from the same site to six researchers. The researchers came back exactly split."
Oh dear, that is bad.
I’m going to disagree that this was well written. I expected a factual article about dinosaur extinction and had to stop at the navel-gazing comment on a suicide attempt.