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filthy
SFN Die Hard
USA
14408 Posts |
 Posted - 04/29/2009 : 13:29:35
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Seems there might be a new hypothesis out there as concerns the demise of the dinosaurs, et al: April 27, 2009
The enduringly popular theory that the Chicxulub crater holds the clue to the demise of the dinosaurs, along with some 65 percent of all species 65 million years ago, is challenged in a paper to be published in the Journal of the Geological Society on April 27, 2009.
The crater, discovered in 1978 in northern Yucutan and measuring about 180 kilometers (112 miles) in diameter, records a massive extra-terrestrial impact.
When spherules from the impact were found just below the Cretaceous-Tertiary (K-T) boundary, it was quickly identified as the "smoking gun" responsible for the mass extinction event that took place 65 million years ago.
It was this event which saw the demise of dinosaurs, along with countless other plant and animal species.
However, a number of scientists have since disagreed with this interpretation.
The newest research, led by Gerta Keller of Princeton University in New Jersey, and Thierry Adatte of the University of Lausanne, Switzerland, uses evidence from Mexico to suggest that the Chicxulub impact predates the K-T boundary by as much as 300,000 years.
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It'll be interesting to see where this leads -- I've never been terribly fond of the impact theory either but in the absence of anything better, had to go along with it. It could be that the Chicxulub strike was the trigger that set off the conditions leading to the extinctions. Geologically speaking, 300,000 years isn't all that long.
Heh, but it's still a lot longer than 6,000..... 
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 04/29/2009 : 14:05:07 [Permalink]
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Well, we'll see. I'm sure the asteroid-extinction folks will have a reply. Meanwhile, it's hard for me to believe that the huge Chicxulub impact could happen without causing mass extinctions. I'm just guessing here, but I expect that maybe those 300,000 years will be whittled down to nothing over time.
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“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 04/29/2009 : 14:57:43 [Permalink]
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Originally posted by HalfMooner
Well, we'll see. I'm sure the asteroid-extinction folks will have a reply. Meanwhile, it's hard for me to believe that the huge Chicxulub impact could happen without causing mass extinctions. I'm just guessing here, but I expect that maybe those 300,000 years will be whittled down to nothing over time.
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Indeed, but it has always seemed to me to be a little too localized, tremendous as it was. Conceivably, it might have been the catalyst for a slow (relatively speaking), long-term climate change that killed off creatures long adapted, even to the point of locked-in, to certain conditions.
I dunno. I'll continue to wait on the science and this paper should stir it up to a nicety. Science works best when it is all stirred up....
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"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)
"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres
"The default position of human nature is to punch the other guy in the face and take his stuff." ~~ Dude
Brother Boot Knife of Warm Humanitarianism,
and Crypto-Communist!
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HalfMooner
Dingaling
Philippines
15831 Posts |
Posted - 04/29/2009 : 22:19:59 [Permalink]
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One thing to consider, I think, is that the Chicxulub impact almost certainly would have had global impact. The Chicxulub bolide was enormous, about six miles in diameter, and left a carter 110 miles in diameter. Striking through the ocean and into the seabed, it would have thrown up a plume of superheated steam and vaporized rock. Wiki says:| The impact would have caused some of the largest megatsunamis in Earth's history, reaching thousands of feet high. A cloud of super-heated dust, ash and steam would have spread from the crater, as the impactor burrowed underground in less than a second. Excavated material along with pieces of the impactor, ejected out of the atmosphere by the blast, would have been heated to incandescence upon re-entry, broiling the Earth's surface and possibly igniting global wildfires; meanwhile, enormous shock waves spawned global earthquakes and volcanic eruptions. |
In addition, I would want to suggest that on the opposite side of the earth's surface, focused, converging shock waves would probably have caused a disruption in the earth's crust, much as has happened on the Moon's far side due to impacts on its earth-facing side.
The huge lava flows of the Deccan Traps are in about the right position, but they have been dated to a few million years prior to the Chicxulub impact. If the timing was not off, I could see the Deccan Traps as being caused by a bolide impact on the other side of the globe, but I can't imaging the Deccan Traps as even possibly being the cause of Chicxulub. Is it possible the dates for the Deccan Traps and Chicxulub may someday be revised and converge?
One thing's for sure: Scientific evidence can be very inconvenient for pet hypotheses, including my own.
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“Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive. |
| Edited by - HalfMooner on 04/29/2009 23:32:48 |
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Dr. Mabuse
Septic Fiend
Sweden
9687 Posts |
Posted - 05/01/2009 : 05:05:33 [Permalink]
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| The thing is... the K-T boundary is global, and some the minerals in it are of extra-terrestrial origin. There aren't many alternatives besides a massive asteroid strike. So if we got the wrong crater, then some other crater has to be it. |
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 05/01/2009 : 05:58:42 [Permalink]
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Originally posted by Dr. Mabuse
The thing is... the K-T boundary is global, and some the minerals in it are of extra-terrestrial origin. There aren't many alternatives besides a massive asteroid strike. So if we got the wrong crater, then some other crater has to be it.
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Entirely correct, but was it the direct cause? 300,00o years after the fact is a lot of years -- assuming that Dr.s Keller and Adaette have their facts in order.
I think we'll hear more about it in the bear future.
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"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)
"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres
"The default position of human nature is to punch the other guy in the face and take his stuff." ~~ Dude
Brother Boot Knife of Warm Humanitarianism,
and Crypto-Communist!
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Kil
Evil Skeptic
USA
13476 Posts |
Posted - 05/01/2009 : 07:52:44 [Permalink]
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Originally posted by filthy
Originally posted by Dr. Mabuse
The thing is... the K-T boundary is global, and some the minerals in it are of extra-terrestrial origin. There aren't many alternatives besides a massive asteroid strike. So if we got the wrong crater, then some other crater has to be it.
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Entirely correct, but was it the direct cause? 300,00o years after the fact is a lot of years -- assuming that Dr.s Keller and Adaette have their facts in order.
I think we'll hear more about it in the bear future.
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I get oochy when a single cause is postulated. I have always considered that iridium layer in the KT boundary a smoking gun in terms of a giant global disaster, but I wonder how the small mammals made it though and no dinosaurs other than birds survived. It has been suggested that those small mammals were feasting on dino eggs. Why are these two possibilities, a global disaster by way of an asteroid hit, and yummy eggs seen as mutually exclusive? It's important to note that not all of the dinosaurs were giants. Would smaller dino's, requiring a food sources more similar to the small mammals be anymore vulnerable than the mammals themselves? Perhaps, because dinosaurs laid eggs. A food source for the mammals and dino' as well, who may have helped to take themselves out.
I think sometimes scientists get stuck in an either or fallacy based on their favorite hypothesis. The truth may be, as it often is, a lot more messy. |
Uncertainty may make you uncomfortable. Certainty makes you ridiculous.
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Dave W.
Info Junkie
USA
26020 Posts |
Posted - 05/01/2009 : 10:03:32 [Permalink]
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Originally posted by Kil
I get oochy when a single cause is postulated. I have always considered that iridium layer in the KT boundary a smoking gun in terms of a giant global disaster, but I wonder how the small mammals made it though and no dinosaurs other than birds survived. It has been suggested that those small mammals were feasting on dino eggs. Why are these two possibilities, a global disaster by way of an asteroid hit, and yummy eggs seen as mutually exclusive? It's important to note that not all of the dinosaurs were giants. Would smaller dino's, requiring a food sources more similar to the small mammals be anymore vulnerable than the mammals themselves? Perhaps, because dinosaurs laid eggs. A food source for the mammals and dino' as well, who may have helped to take themselves out. |
The yummy-eggs hypothesis doesn't explain the loss of 57% of plant species in North America and gazillions of marine species worldwide, or the fact that the surviving animals didn't include any "pure" carnivores or "pure" herbivores. What was left on land was pretty much only omnivorous scavengers and/or critters like the crocodile (which can go for months without eating), or animals that could dig shelters or swim. |
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Simon
SFN Regular
USA
1992 Posts |
Posted - 05/01/2009 : 10:27:12 [Permalink]
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I always thought that the Yucatan impact caused a nuclear-like winter resulting to a drop in temperatures as well as a global food shortage.
Omnivorous animals were less affected by the shortage and dinosaurs were not efficient at withstanding the cold... |
Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.
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Kil
Evil Skeptic
USA
13476 Posts |
Posted - 05/01/2009 : 10:45:25 [Permalink]
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Originally posted by Dave W.
The yummy-eggs hypothesis doesn't explain the loss of 57% of plant species in North America and gazillions of marine species worldwide, or the fact that the surviving animals didn't include any "pure" carnivores or "pure" herbivores. What was left on land was pretty much only omnivorous scavengers and/or critters like the crocodile (which can go for months without eating), or animals that could dig shelters or swim.
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Oh sure. Being omnivorous and other adaptive traits would certainly be an advantage. And it could very well be that an impact started the ball rolling that lead to extinction of the dinosaurs. I even I suggested that dino eggs would be seen as a tasty treat for small dinos too, helping the mammals to take them out. My point really is that the mammals probably helped, given the change in the environment. I'm only suggesting the possibility that if those mammals didn't exist, it could be that the food source for the smaller dinosaurs may have been enough to get them through the disaster. I'm suggesting the possibility of a one-two punch. But yeah, it seems likely that a large asteroid strike set the table. |
Uncertainty may make you uncomfortable. Certainty makes you ridiculous.
Why not question something for a change?
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Kil
Evil Skeptic
USA
13476 Posts |
Posted - 05/01/2009 : 10:53:00 [Permalink]
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Originally posted by Simon
I always thought that the Yucatan impact caused a nuclear-like winter resulting to a drop in temperatures as well as a global food shortage.
Omnivorous animals were less affected by the shortage and dinosaurs were not efficient at withstanding the cold...
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As I understand it, it's likely that the theropod's were warm blooded, and in some cases, furry with down like feathers. |
Uncertainty may make you uncomfortable. Certainty makes you ridiculous.
Why not question something for a change?
Genetic Literacy Project |
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Simon
SFN Regular
USA
1992 Posts |
Posted - 05/01/2009 : 11:00:04 [Permalink]
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They were; at least a significant number of them.
But we don't know how warm they were. Also, only a limited number of species had proto-feathers, from what I understand. And many of these species did make it through, evolving into bird. |
Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.
Carl Sagan - 1996 |
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filthy
SFN Die Hard
USA
14408 Posts |
Posted - 05/01/2009 : 12:16:30 [Permalink]
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Birds were already well established by the time the K-T event occured. | Most paleontologists regard birds as the only surviving dinosaurs (see Origin of birds). However, all non-neornithean birds became extinct, including flourishing groups like enantiornithines and hesperornithiforms.[54] Several analyses of bird fossils show divergence of species prior to the K-T boundary, and that duck, chicken and ratite bird relatives coexisted with non-avian dinosaurs.[55] Neornithine birds survived the K-T boundary as a result of their abilities to dive, swim, or seek shelter in water and marshlands. Many species of birds can build burrows, or nest in tree holes or termite nests, all of which provided shelter from the environmental effects at the K-T boundary. Long-term survival past the boundary was assured as a result of filling ecological niches left empty by extinction of dinosaurs. |
And they've had some 65 my to diversify into what we know today.
Fossils of song birds, like those of bats, aren't easy to come by due to their habitate (forest, mainly) and their fine-boned skeletons, but it is easy to conjecture that such existed in considerable numbers, at least somewhat in their present form, in the Upper Cretcaeous. Judging by the species of today, many were omniviorus. Heh, toss an egg into the chicken coop and just watch what happens to it.
Darwin's finches give us a bright window on the process -- hell, one of them is at least a part-time vampire, aren't they lovely? 
As delicate as birds appear, they are tough and hardy, and time at the species level means little to them. There only needs to be barely enough and really, that isn't all that much.
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"What luck for rulers that men do not think." -- Adolf Hitler (1889 - 1945)
"If only we could impeach on the basis of criminal stupidity, 90% of the Rethuglicans and half of the Democrats would be thrown out of office." ~~ P.Z. Myres
"The default position of human nature is to punch the other guy in the face and take his stuff." ~~ Dude
Brother Boot Knife of Warm Humanitarianism,
and Crypto-Communist!
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Chippewa
SFN Regular
USA
1496 Posts |
Posted - 05/01/2009 : 14:29:00 [Permalink]
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Originally posted by Kil
I get oochy when a single cause is postulated. I have always considered that iridium layer in the KT boundary a smoking gun in terms of a giant global disaster, but I wonder how the small mammals made it though and no dinosaurs other than birds survived...
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I get the impression that Paleontologist Robert Bakker is also "oochy" about the asteroid impact as a single cause for extinction. He theorizes the weakening of dinosaur populations from disease as the main cause due to its effect when new species are introduced into environments - (via the land bridges that had formed recently - geologically speaking.) He theorizes the dinosaurs were migrating and populations were mixing, resulting in selective extinctions. Snails and mammals were staying put or moving to new regions slowly for the most part, implying less exposure to plagues. He says the danger of mass extinctions accelerated from many diseases introduced by foreign animals and also sites the fact that the fossil record doesn't reveal thousands of corpses fallen from a single sudden cause.
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Landrew
New Member
44 Posts |
Posted - 05/02/2009 : 08:24:19 [Permalink]
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The K-T line is purported to be a bit blurry in places extinct life forms found above the line in some cases, and it leads to skepticism about the asteroid extinction theory. This is not evidence of disproof, but suggests a less simple version of events.
I believe the asteroid was the main event in that time, but it didn't succeed in wiping out all the now-extinct cretaceous life forms immediately. I believe that the ones that survived the impact were forced to compete in a radically changed ecosystem, dominated by a different organisms occupying niches left vacant. They may have persisted for a few thousand or million years, in pockets here and there, but were eventually wiped out.
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Simon
SFN Regular
USA
1992 Posts |
Posted - 05/02/2009 : 09:56:26 [Permalink]
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| Welcome to the fora Landrew! |
Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.
Carl Sagan - 1996 |
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K-T Extinction?
