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(Time)   Scientists believe there was a second asteroid on the grassy knoll   (time.com) divider line 27
    More: Interesting, dinosaurs, duck-billed dinosaurs, Cretaceous period, number of species, Mexico's Yucatan Peninsula, herbivores, Bruce Chen, asteroids  
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3942 clicks; posted to Geek » on 04 May 2012 at 10:30 AM (2 years ago)   |  Favorite    |   share:  Share on Twitter share via Email Share on Facebook   more»



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2012-05-04 10:45:24 AM
RTFA
 
2012-05-04 10:48:13 AM
If, with some species reaching apex and some declining, a fairly common evolutionary situation was occurring, what does the flourishing species suddenly vanishing along with the struggling ones mean?
 
2012-05-04 10:53:35 AM

DirtyDeadGhostofEbenezerCooke: If, with some species reaching apex and some declining, a fairly common evolutionary situation was occurring, what does the flourishing species suddenly vanishing along with the struggling ones mean?


I don't know, but I love saying "Chixulub".
 
2012-05-04 10:54:55 AM
The bean counters have taken over another area of science. Dammit. Interesting approach actually.
 
2012-05-04 10:57:49 AM
Don't be silly, it wasn't a second asteroid, it was Cthulhu
 
2012-05-04 10:58:41 AM

DirtyDeadGhostofEbenezerCooke: If, with some species reaching apex and some declining, a fairly common evolutionary situation was occurring, what does the flourishing species suddenly vanishing along with the struggling ones mean?


If some of the up and comers die while others survive in similar niches, it means that the impact theory doesn't work and you need to keep adding asteroid hits until it does.

/amphibians, reptiles and dino descended birds survived.
/everything above a certain bodymass is kaput before the iridium layer.
/I'm thinking the culprit came and left long before the boom.
 
2012-05-04 11:04:12 AM
FTA
slammed into the Earth just off the coast of the Yucatan Peninsula


Didn't it actually hit land? I read that if it had hit water (with sufficient depth), it would've probably not killed off the dinos.
 
2012-05-04 11:06:53 AM

machoprogrammer: FTA
slammed into the Earth just off the coast of the Yucatan Peninsula


Didn't it actually hit land? I read that if it had hit water (with sufficient depth), it would've probably not killed off the dinos.


Nevermind, I just wiki'ed it. I read wrong. Apparently it hit some gypsum rock in the ocean.
 
2012-05-04 11:13:40 AM
Small potatoes. Call me when they figure out the Permian Event.
 
2012-05-04 11:14:45 AM

machoprogrammer: machoprogrammer: FTA
slammed into the Earth just off the coast of the Yucatan Peninsula


Didn't it actually hit land? I read that if it had hit water (with sufficient depth), it would've probably not killed off the dinos.

Nevermind, I just wiki'ed it. I read wrong. Apparently it hit some gypsum rock in the ocean.


img208.imageshack.us

At sea one day, you'll hit land where there'll be no land, and on that day the Tyrannosaur will go to his grave, but he'll rise again within the hour. He will rise and beckon. Then all - all save the avian theropods, shall follow.

Mornin', lads... mornin'. May the heavens bless you.
 
2012-05-04 11:23:32 AM

Metaluna Mutant: Small potatoes. Call me when they figure out the Permian Event.


It was a fad. Back in the Seventies, curly hair was "in".
 
2012-05-04 11:25:44 AM

way south: DirtyDeadGhostofEbenezerCooke: If, with some species reaching apex and some declining, a fairly common evolutionary situation was occurring, what does the flourishing species suddenly vanishing along with the struggling ones mean?

If some of the up and comers die while others survive in similar niches, it means that the impact theory doesn't work and you need to keep adding asteroid hits until it does.

/amphibians, reptiles and dino descended birds survived.
/everything above a certain bodymass is kaput before the iridium layer.
/I'm thinking the culprit came and left long before the boom.


F-14 crashes.
 
2012-05-04 11:37:55 AM

Harvey Manfrenjensenjen: way south: DirtyDeadGhostofEbenezerCooke: If, with some species reaching apex and some declining, a fairly common evolutionary situation was occurring, what does the flourishing species suddenly vanishing along with the struggling ones mean?

If some of the up and comers die while others survive in similar niches, it means that the impact theory doesn't work and you need to keep adding asteroid hits until it does.

/amphibians, reptiles and dino descended birds survived.
/everything above a certain bodymass is kaput before the iridium layer.
/I'm thinking the culprit came and left long before the boom.

F-14 crashes.


Maybe it was a comet Shoemaker-Levy 9 type thing. 21 fragments hitting in a string--some large, some small. I'm sure there are plenty of large lakes, bights and other freaky geological thingees strewn over the Earth that might be tied together in time.
 
2012-05-04 11:38:58 AM
I enjoy thinking about "What happens to mammalian evolution if the dinos don't die off?"

Then I go play SimEarth and monolith the early Saurians, and boom! Sentient dinos.

/also fun when you do it with insects
 
2012-05-04 11:54:07 AM

way south: DirtyDeadGhostofEbenezerCooke: If, with some species reaching apex and some declining, a fairly common evolutionary situation was occurring, what does the flourishing species suddenly vanishing along with the struggling ones mean?

If some of the up and comers die while others survive in similar niches, it means that the impact theory doesn't work and you need to keep adding asteroid hits until it does.

/amphibians, reptiles and dino descended birds survived.
/everything above a certain bodymass is kaput before the iridium layer.
/I'm thinking the culprit came and left long before the boom.


So...you're saying an absence of large dinosaurs attracts asteroids? Is this another Pirate/Global Warming thing?

Seriously, there might well be earlier contributive factors, but if you had chronic diabeetus and just got cockpunched, which are you going to say explains why you are doubled over in agony? A smoking BFG in the room has to be conclusively proven to not be involved in a massacre.

This, linked to same article, doesn't help...how close is close enough?
 
2012-05-04 12:01:48 PM
I know that linked tried to make my computer extinct, what a pain....
 
2012-05-04 12:37:28 PM

Metaluna Mutant: Small potatoes. Call me when they figure out the Permian Event.


Definitely not figured out, but there is some potential progress. During the late Permian, most of the land was arranged in a ring around the Paleo-Tethys ocean. This is where the majority of the marine shelf existed, which is where most marine life lives. Other than this, the rest of the world was covered with the Panthallasic ocean. A drop in sea level near the end of the Permian resulted in the exposure of most of the shallow shelf on the exterior margin of Pangaea, and likely reduced circulation between the Paleo-Tethys and the rest of the Panthallasic. This, combined with the emission of massive amounts of CO2 from the Siberian traps would have acidified the ocean, raising the carbonate compensation depth up to the level of the shelves, dooming just about all of the life there. The termination of the exterior shelves would have removed any potential refugia from the picture before the death of the Paleo-Tethys ecosystems, making repopulation extremely difficult. Most of the fossil localities from the end Permian are from the interior ocean, so what we're seeing is limited mostly to this area unfortunately. The fact that all oceanic deposits from the Panthallasic of the end-Permian have long since been subducted makes it difficult to study anything beyond a relatively isolated and geographically restricted area.

This accounts for the marine extinction, but the terrestrial extinction is much more difficult to explain. The lack of any well constrained continuous terrestrial deposits makes analysis spotty at best, and the Karoo Basin is still the best we've got. It's actually entirely possible that the terrestrial extinction is minimal.

That, at least, is my current understanding. Hopefully someone with a bit better knowledge will help elaborate on it, and point out why they think I'm wrong.
 
2012-05-04 12:41:37 PM

DirtyDeadGhostofEbenezerCooke: So...you're saying an absence of large dinosaurs attracts asteroids? Is this another Pirate/Global Warming thing?


Say you have a planet and all these giant dinosaurs growing on it.
That increases gravity and drags the asteroids down out of orbit...

If I recall my expert tutelage on the subject, gained from the history channel (From some guys besides the "It was aliens" guys): The layer that shows dust from the impact is disturbingly devoid of dinosaurs.

If you have a million critters of a declining population, and a rock hits to polish them off, I think you should find at least a few buried in that fallout.
If you don't then maybe the asteroid was a red herring.

Say some future alien dug up human skeletons in the 2100's fossil record, see none of them in the 2200's, and then find asteroid fallout in the 2300's... Yes the asteroid might have gotten a few survivors, but what you'd want to know is what got there before that.
Because whatever it is, it did a number on the planet.
 
2012-05-04 12:43:58 PM
For anyone that wants to read a cool approach to the Permian extinction, check out Hannisdal and Peters, 2011 in Science.
 
2012-05-04 12:46:22 PM

way south: DirtyDeadGhostofEbenezerCooke: So...you're saying an absence of large dinosaurs attracts asteroids? Is this another Pirate/Global Warming thing?

Say you have a planet and all these giant dinosaurs growing on it.
That increases gravity and drags the asteroids down out of orbit...

If I recall my expert tutelage on the subject, gained from the history channel (From some guys besides the "It was aliens" guys): The layer that shows dust from the impact is disturbingly devoid of dinosaurs.

If you have a million critters of a declining population, and a rock hits to polish them off, I think you should find at least a few buried in that fallout.
If you don't then maybe the asteroid was a red herring.

Say some future alien dug up human skeletons in the 2100's fossil record, see none of them in the 2200's, and then find asteroid fallout in the 2300's... Yes the asteroid might have gotten a few survivors, but what you'd want to know is what got there before that.
Because whatever it is, it did a number on the planet.


Check out the Signor-Lipps effect; it helps explain this phenomenon a bit.
 
2012-05-04 12:57:45 PM
This article is in violation of Doctrine.

/hopefully not obscure
 
2012-05-04 01:27:30 PM

Erix: Check out the Signor-Lipps effect; it helps explain this phenomenon a bit.


It might.
...But lack of a fossil immediately before the asteroid hit or after don't prove that the asteroid is the primary cause of extinction. Even if it is the best culprit.

Millions of animals died at once, around the globe, in a hail of fiery ash fallout and mud. There really should be more fossils out there in that layer.

/Maybe, maybe not.
/maybe it was aliens.
 
2012-05-04 03:11:15 PM

way south: DirtyDeadGhostofEbenezerCooke: So...you're saying an absence of large dinosaurs attracts asteroids? Is this another Pirate/Global Warming thing?

Say you have a planet and all these giant dinosaurs growing on it.
That increases gravity and drags the asteroids down out of orbit...

If I recall my expert tutelage on the subject, gained from the history channel (From some guys besides the "It was aliens" guys): The layer that shows dust from the impact is disturbingly devoid of dinosaurs.

If you have a million critters of a declining population, and a rock hits to polish them off, I think you should find at least a few buried in that fallout.
If you don't then maybe the asteroid was a red herring.

Say some future alien dug up human skeletons in the 2100's fossil record, see none of them in the 2200's, and then find asteroid fallout in the 2300's... Yes the asteroid might have gotten a few survivors, but what you'd want to know is what got there before that.
Because whatever it is, it did a number on the planet.


Alvarez' iridium layer was 1 cm thick. Pick any 1 cm stratum anywhere in the world and check it for terrestrial vertebrate fossils.You might have to skin the planet, but I'll wait for your results.
 
2012-05-04 03:28:47 PM

DirtyDeadGhostofEbenezerCooke: Alvarez' iridium layer was 1 cm thick. Pick any 1 cm stratum anywhere in the world and check it for terrestrial vertebrate fossils.You might have to skin the planet, but I'll wait for your results.


*Sigh*
I'll get the shovel.

/Brb.
 
2012-05-04 03:37:41 PM

Erix: This accounts for the marine extinction, but the terrestrial extinction is much more difficult to explain. The lack of any well constrained continuous terrestrial deposits makes analysis spotty at best, and the Karoo Basin is still the best we've got. It's actually entirely possible that the terrestrial extinction is minimal.

That, at least, is my current understanding. Hopefully someone with a bit better knowledge will help elaborate on it, and point out why they think I'm wrong.


Well, consider the timing. We have the dating of the main extinction constrained pretty well, and it's geologically speaking (not compared to the Cretaceous-Paleogene necessarily, but still) pretty rapid. Can you get a rapid drawdown of SL? Sure, but that's going to require a fair bit of ice building up somewhere. And that's a problem, because there's a large warming event just at and through the extinction.

Sure, a shallowing of RSL would have been disastrous for life in the epicontinental waters, but it doesn't explain why extinctions were worse in the open ocean, nor (as you rightly pointed out) does it explain terrestrial extinctions.

You mentioned the Siberian Traps, and IMO they are the closest thing we have to an ultimate rather than proximate driver. There is a very large, very rapid perturbation of the carbon cycle co-incident with the Siberian Traps volcanism, and a huge warming signal. The Siberian Traps alone were once thought to not be sufficiently large enough to cause the magnitude of the perturbation, and that's why methane clathrate release was invoked as a knock on effect and kill mechanism. But there is evidence that the Siberian Traps either baked methane out of, or just straight up intruded into and burned, a large amount of coal as well.

Looking at which marine invertebrates made it through the event points to hypercapnia and ocean acidification, probably exacerbated by anoxia (of course, the Permian seas were already hot and prone to anoxic events before the extinction event really took off).

On land, there's a lot of evidence for wildfires and general warming.

So there's kind of a coherent picture emerging. Carbon pulse from the Siberian Traps resulting in climate change and changes in ocean chemistry. Warming, hypercapnia, ocean acidification, ocean anoxia- maybe even some ozone depletion from volatiles from the eruption, and some outgasing of hydrogen sulfide gas from the ocean for good measure.

Definitive? No. But pretty compelling in its coherence.

The evidence that there was a large SL drop at the very end of the Permian has been questioned for over a decade. There's plenty of evidence for a gradual SL decline through much of the Permian, but at the end Permian, there is evidence for SLR. Which is what you'd expect from a carbon pulse and ensuing warming.

I can get you some references in a second.
 
2012-05-04 03:54:36 PM

Erix:

Jon Snow:
I can get you some references in a second.


Here you go. And obviously the references therein:

For SLR:
Hallam, A., and P. . Wignall (1999), Mass extinctions and sea-level changes, Earth-Science Reviews, 48(4), 217-250, doi:10.1016/S0012-8252(99)00055-0.

For timing:
Shen, S. et al. (2011), Calibrating the End-Permian Mass Extinction, Science, doi:10.1126/science.1213454.

For warming:
Joachimski, M. M., X. Lai, S. Shen, H. Jiang, G. Luo, B. Chen, J. Chen, and Y. Sun (2012), Climate Warming in the Latest Permian and the Permian-Triassic Mass Extinction, Geology, 40(3), 195-198, doi:10.1130/G32707.1.

For coal:
Ogden, D. E., and N. H. Sleep (2012), Explosive Eruption of Coal and Basalt and the End-Permian Mass Extinction, PNAS, 109(1), 59-62, doi:10.1073/pnas.1118675109.
Grasby, S. E., H. Sanei, and B. Beauchamp (2011), Catastrophic dispersion of coal fly ash into oceans during the latest Permian extinction, Nature Geoscience, 4(2), 104-107, doi:10.1038/ngeo1069.


For selective hypercapnia/acidification:
Clapham, M. E., and J. L. Payne (2011), Acidification, anoxia, and extinction: A multiple logistic regression analysis of extinction selectivity during the Middle and Late Permian, Geology, 39(11), 1059 -1062, doi:10.1130/G32230.1.
 
2012-05-04 06:14:05 PM

th0th: This article is in violation of Doctrine.

/hopefully not obscure


One of the few tolerable Voyager episodes.
 
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