Why the Dinosaurs Died (cnn.com) 52
"The age of the dinosaurs ended 66 million years ago when a city-size asteroid struck a shallow sea off the coast of what is now Mexico," writes CNN.
"But exactly how the mass extinction of 75% of the species on Earth unfolded in the years that followed the cataclysmic impact has remained unclear." Previous research suggested that sulfur released during the impact, which left the 112-mile-wide (180-kilometer-wide) Chicxulub crater, and soot from wildfires triggered a global winter, and temperatures plunged. However, a new study published Monday in the journal Nature Geoscience suggests that fine dust made from pulverized rock thrown up into Earth's atmosphere in the wake of the impact likely played a greater role. This dust blocked the sun to an extent that plants were unable to photosynthesize, a biological process critical for life, for almost two years afterward.
"Photosynthesis shutting down for almost two years after impact caused severe challenges (for life)," said lead study author and planetary scientist Cem Berk Senel, a postdoctoral researcher at the Royal Observatory of Belgium. "It collapsed the food web, creating a chain reaction of extinctions."
To reach their findings, scientists developed a new computer model to simulate the global climate after the asteroid strike. The model was based on published information on Earth's climate at that point in time, as well as new data from sediment samples taken from the Tanis fossil site in North Dakota that captured a 20-year period during the aftermath of the strike.
"But exactly how the mass extinction of 75% of the species on Earth unfolded in the years that followed the cataclysmic impact has remained unclear." Previous research suggested that sulfur released during the impact, which left the 112-mile-wide (180-kilometer-wide) Chicxulub crater, and soot from wildfires triggered a global winter, and temperatures plunged. However, a new study published Monday in the journal Nature Geoscience suggests that fine dust made from pulverized rock thrown up into Earth's atmosphere in the wake of the impact likely played a greater role. This dust blocked the sun to an extent that plants were unable to photosynthesize, a biological process critical for life, for almost two years afterward.
"Photosynthesis shutting down for almost two years after impact caused severe challenges (for life)," said lead study author and planetary scientist Cem Berk Senel, a postdoctoral researcher at the Royal Observatory of Belgium. "It collapsed the food web, creating a chain reaction of extinctions."
To reach their findings, scientists developed a new computer model to simulate the global climate after the asteroid strike. The model was based on published information on Earth's climate at that point in time, as well as new data from sediment samples taken from the Tanis fossil site in North Dakota that captured a 20-year period during the aftermath of the strike.
Not 0-day (Score:1)
This news is from two months ago.
Obligatory Far Side (Score:4, Funny)
The real reason dinosaurs went extinct [pinimg.com].
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Did you just prove basic income is good for mammals?
One potential problem (Score:5, Informative)
At least with the "Tanis fossil site" supporting data - according to the linked article, almost all of the fossils found there are from fish. They are assuming that die-off was linked to the meteorite impact because of the general time frame, but there is a paleontologist quoted there who basically says "it's great if the assumption is borne out, but it might have been a different, more local, event". It's not like they independently pin down the time frame sufficiently without making some assumptions like that - you're not going to date it that closely with just radiometric techniques.
It's certainly an interesting hypothesis, regardless.
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The gap he suggests does not exist. He is making it up. The original Tanis site paper shows the fish ingested impact debris just before they died. It is tied to the impact directly not too any "million year gap".
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I think I read once that they discovered micro-spheres from the impact in the gills of the fish that would have fallen in the hours and days immediately following the impact event.
Here is the fish paper: During et al. [researchgate.net]
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I think I read once that they discovered micro-spheres from the impact in the gills of the fish that would have fallen in the hours and days immediately following the impact event.
You did indeed read that - it is detailed in the original Tanis site paper. They found the paddlefish had inhaled through its gills impact debris just before they died as the particles were localized there. The site is directly tied to the impact itself.
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But otherwise, you're right.
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At least with the "Tanis fossil site" supporting data - according to the linked article, almost all of the fossils found there are from fish. They are assuming that die-off was linked to the meteorite impact because of the general time frame, but there is a paleontologist quoted there who basically says "it's great if the assumption is borne out, but it might have been a different, more local, event". It's not like they independently pin down the time frame sufficiently without making some assumptions like that - you're not going to date it that closely with just radiometric techniques.
It is too bad that this authoritative sounding post got voted to "5, Informative" because the author is just making stuff up. The claim that they are "assuming that die-off was linked to the meteorite impact because of the general time frame" is simply false. The Tanis site study found [researchgate.net]:
The tomographic data show that impact spherules associated with the paddlefish skeleton are present exclusively in its gill rakers 5 and are absent elsewhere in the preserved specimen. The absence of impact spherules outside the gill rakers demonstrates that spherules were filtered out of the surrounding waters but had not yet proceededinto the oral cavity or further down the digestive tract, and had not impacted the fish carcases during perimortem exposure.
That is, the found the smoking gun with the bullet embedded in the victim.
The poster continues with his made up stuff by saying " there is a paleontologist quoted there who basically says..." but there is nothing like this i
Herbivores? (Score:1)
If photosynthesis shut down for almost 2 years, what did the herbivores eat? I'm wary of extreme depictions of extinction events due to a single cause. While the meteorite definitely had an immediate affect on all forms of life, total cessation of photosynthesis is highly unlikely.
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Would mushrooms still grow?
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Yes, mycelium would have done just fine.
Re:Herbivores? (Score:4)
Photosynthesis didn't have to shut down completely. If it dropped 90% the big herbivores will die (how much does an elephant eat per day?) while the chipmunks can get by on the surviving plants.
It would be interesting to know if the high latitudes faired better than the tropics. The high latitude ecosystems deal with winter already. The tropics might not survive a frost at all.
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Answered my own question,
https://www.npr.org/2022/02/28... [npr.org]
It hit in the northern hemisphere spring. That would be about worst case. The southern hemisphere should have done better. Maybe they did, they got the terror birds and the bigger crocodiles.
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With today's distribution of continents, yes. Not so clear in the terminal Cretaceous with Pangaea still more or less together (The southern South Atlantic was opening, but not the equatorial (today) Atlantic, which was only just getting started on rifting. India and Madagascar were just in the process of moving SE (today's orientation) from the African coast. No, "SE" isn't a typo.)
With effectively only one ocean, the large ocean cur
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Elephants vary, but 100kg per elephant per day is a reasonable number to start from.
(There was an Attenborough on the box yesterday, about an Argentinian titanosaur up in the 100 mt body weight range. Which reminds me to check up on weight-estimating methodologies.
Re: Herbivores? (Score:2)
Why the Dinosaurs Died - jeebus did it as (Score:1)
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There's a larger religion with even more oil than Texas. Wonder why you didn't use them in your attempt at a joke?
What religion is "larger" than Christianity?
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If they're all convinced they're following the one and only god, then perforce they must all be following the same god (though with trivially different practices - wanking turnwise not widdershins over the communion biscuit, that sort of minor detail).
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How'd any plant continue after 2 years? (Score:1)
Curious what they think let any plant continue after 2 years of no photosynthesis. Meaning to start the whole thing over again afterwards...
Was it from hydrothermal vents? Frozen then thawed stuff?
And how can we protect ourselves if the same happens? Can enough truck sized negative ion generators do anything? Or physical filtration with fans? What if the whole human race worked together on something to save some of us...
Re:How'd any plant continue after 2 years? (Score:4, Informative)
It is a miracle called "seeds". We, humans, deal with it now by killing plant life and variety over many years, so that we're pretty sure not enough seeds remain for plant life to recover after us.
We're a better extinction level event than the asteroid.
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"Physical filtration with fans" would have to be deployed into the stratosphere. The dust in the troposphere (approximately ground to 12~15km) would settle out in a few weeks to months.
"We" have no significant technologies other than food storage to cope with an event like this. Which means the impact would
Humans would survive a (Score:3)
The mortality rate might not even be that high. It would depend on how much warning we had. With just a few years of warning, we could waive ALL contruction regulations, build a ton of nuclear plants, and convert major industries over to food production. Oil and coal gets burned in huge quantities. The result would be significant starvation and a worldwide recession that would make the 1920s seem like a cakewalk. But civilization would largely continue. Death toll: 50%. Population and economic recovery: 100 years.
With zero warning, 99% to 99.9% mortality would be my knee-jerk estimate. Which would leave millions alive. Recovery: several centuries, simply due to lack of people.
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Re: Humans would survive a (Score:2)
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Re: Humans would survive a (Score:2)
You might be right, but I donâ(TM)t think itâ(TM)s clear. If we had plans in place it would be much better, but politics might harm our ability to react decisively until it was too late (eg see Covid)
Even now we are not trying very hard with asteroid deflection because âoenukes are badâ.
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(0+% mortality would take several generations, but we've gone from about 1.5 billion to pushing 8 billion in barely more than a century. Not a big problem. A lot of the infrastructure wouldn't have time to physically fall apart before maintenance re-started.
Abortion (Score:1)
My guess is better than your guess! (Score:2)
Let the competition begin!
There's some evidence (Score:2)
That a highly prolonged volcanic eruption elsewhere had massively weakened the ecosystem to the point of being highly vulnerable.
https://www.space.com/dinosaur... [space.com]
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Surprisingly, Indian geologists do a lot of fossil-hunting in the Deccan, but haven't found anything definitive. Yet. Unfortunately, most of the area's rock