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Natural Science Forum / Biology / Paleontology / June 2006Asteroid impacts
The Discovery Channel aired a show about impacts throughout the ages, offering a new hypothesis about how Chixilub could have caused such a global result. The claim is that as the impact debris rained down through the atmosphere it generated sufficient heat to raise the temperature on the surface to several hundred degrees, killing vitually all the land dwelling animals. The show then speculated that the remaining matter, mostly dust, blocked out the sun for about six years, killing plankton and decimating life in the oceans. While this would explain why certain specific species survived, it seems a bit contrived. The problem I had with this hypothesis is that there have been a number of titanic impacts throughout the ages, at least two of them larger than Chixilub based on crater size, but they did not produce comparable results. Still, the elemental makeup of the Chixilub rock might have differred enough to account for this discrepancy. I don't think we can ever really 'know' what happened back then. We do know, for a fact, that the dinos didn't make it through the K-T boundary. Boyle's book Full Circle begins with an ELE pandemic fifty thousand years before the Chixilub event, and while it's only fiction, it explains the results as well as the program on Discovery. Furthermore, it would leave no evidence behind. A giant solar flare is another possibility, but I think we would find evidence of irradiation. Anyway, the big lizards had a helluva long run, but we will probably never be absolutely certain what happened to them. > The Discovery Channel aired a show about impacts throughout the ages, > offering a new hypothesis about how Chixilub could have caused such a global [quoted text clipped - 18 lines] > evidence of irradiation. Anyway, the big lizards had a helluva long run, but > we will probably never be absolutely certain what happened to them. At present the bolide impact theory is the best available. All other speculation fails due to an absolute lack of evidence or for being absurd. Note that not only only all the non avian dinosaurs died at the K-T but so did virtually all species of terrestrial animals weighing more than a few pounds. Also many different groups of marine vertebrates and invertabrates went extinct or suffered a dramatic decline in number of species. Some absurd ideas include the above pandemic "theory." A deadly pathogen may occasionally mutate into a form able to infect and kill another organism but for this too happen the several tens of thousands of times required to eradicate the species at the K-T is simply unbelieveable. Now about the "raining flaming debris" idea presented by the Discovery Channel. This would have been a local phenomena only. Without knowing a great deal more about the impact it is impossible to say whether the area where lethal ejecta fell was outside of the zone of total destruction caused by the impact shockwave but I doubt it was significantly more widespread than that area. All present evidence indicates a nuclear winter phenomena was the bolide impacts prime killing effect. The fern spike and world wide crash of the marine ecosystem strongly imply that most terrestrial plants and marine plankton died and the most likely culprit for such an occurence is a global reduction in sunlight reaching the surface. Ken >> The Discovery Channel aired a show about impacts throughout the ages, >> offering a new hypothesis about how Chixilub could have caused such a [quoted text clipped - 34 lines] > speculation fails due to an absolute lack of evidence or for being > absurd. That's a great-sounding soundbyte. The only problem is that you've not supported your claim. > Note that not only only all the non avian dinosaurs died at the K-T but > so did virtually all species of terrestrial animals weighing more than > a few pounds. Umm, the crocodiles and aligators (all large sub-tropical and tropical species) survived. Amazingly, very fragile species such as frogs and other amphibians survived quite nicely. Similar, many very fragile marine species managed to survive, while hearty ones apparently didn't. > Also many different groups of marine vertebrates and > invertabrates went extinct or suffered a dramatic decline in number of > species. And many survived. It should be pointed out that the marine flora and fauna didn't see quite the same level of extinction that the terrestrial species experienced. > Some absurd ideas include the above pandemic "theory." A deadly > pathogen may occasionally mutate into a form able to infect and kill [quoted text clipped - 16 lines] > > Ken I think there are problems with the dating/timing of the impact relative to the extinction event. It is also known that the Deccan trapps began erupting something like 500,000- 2 million years prior to the impact. It has also been shown that there was a floral/faunal decline prior to the impact, a decline that may conicide with the initiation of the flood basalts. My view is that species go extinct, and the reasons are almost always unknown and/or unknowable. This has been true since life first evolved on the planet. Whatever occurred at the K-T boundary, I believe the dinosaurs and others were already on their way off the scene, and if the impact made any difference at all, it only hastened the inevidable. George > >> The Discovery Channel aired a show about impacts throughout the ages, > >> offering a new hypothesis about how Chixilub could have caused such a [quoted text clipped - 37 lines] > That's a great-sounding soundbyte. The only problem is that you've not > supported your claim. I've been down this road with you before. Last time you denied global dimming was possible. You also tried to claim that blocking most sunlight would cause the Earth to freeze solid. Both claims you couldn't support and refused to back away from. > > Note that not only only all the non avian dinosaurs died at the K-T but > > so did virtually all species of terrestrial animals weighing more than > > a few pounds. > > Umm, the crocodiles and aligators (all large sub-tropical and tropical > species) survived. As was also discussed last time we debated this topic the crocodilians are a very starvation resistant group. Crocodilians being the lone survivor of the large terrestrial vertabrates is a fairly strong argument in favor of widespread starvation being the cause of the extinction. Amazingly, very fragile species such as frogs and other > amphibians survived quite nicely. Similar, many very fragile marine > species managed to survive, while hearty ones apparently didn't. Very little is known about the diversity of species of amphibians that survived the K-T. Some modern species are quite starvation and hostile condition resistant so it is entirely possible that those sorts of species are the ones that made it through the K-T and then diversified. > > Also many different groups of marine vertebrates and > > invertabrates went extinct or suffered a dramatic decline in number of [quoted text clipped - 35 lines] > the dinosaurs and others were already on their way off the scene, and if > the impact made any difference at all, it only hastened the inevidable. Of course you are still basing your claims on refuted studies. More recent studies of late Cretaceous deposits shows no decline in species diversity. See here: Sheehan, P.M., Fastovsky, D.E., Barreto, C., and Hoffmann, R.G., 2000, Dinosaur abundance was not declining in a "3 m gap" at the top of the Hell Creek Formation, Montana and North Dakota. Geology 28:523-526. A single study casting doubt on the date of the impact would be significant if other workers had found the same thing which apparently has not happened. For the Deccan traps to be the cause requires someone to specify what mechanism was involved. To the best of my knowledge all the ones so far put forward take too long or would have left behind chemical indicators which we don't find. Got anything new or novel? Ken >> That's a great-sounding soundbyte. The only problem is that you've not >> supported your claim. [quoted text clipped - 3 lines] > sunlight would cause the Earth to freeze solid. Both claims you > couldn't support and refused to back away from. I vaguely recall that argument. As I recall, I didn't deny the possibility. I suggested that there was little, if any evidence for it. As for blocking most of the sunlight, what result other than freezing would you expect to occur? >> > Note that not only only all the non avian dinosaurs died at the K-T >> > but [quoted text clipped - 9 lines] > argument in favor of widespread starvation being the cause of the > extinction. Crocodilians are also highly susceptible to cold temperatures. If that were not the case, one would expect to find them swimming in the Ohio River and other temperate streams. Since they don't inhabit thsuch rivers, and since they didn't go extinct, I suspect that there is more to this story than simply a change to a colder climate. > Amazingly, very fragile species such as frogs and other >> amphibians survived quite nicely. Similar, many very fragile marine [quoted text clipped - 4 lines] > condition resistant so it is entirely possible that those sorts of > species are the ones that made it through the K-T and then diversified. Yet the fossil record is full of amphibians and other species who would be expected to be starvation and hostile environment-resistant that are just as extinct as the dinosaurs. >> I think there are problems with the dating/timing of the impact relative >> to [quoted text clipped - 21 lines] > significant if other workers had found the same thing which apparently > has not happened. I find that amusing for several reasons: 1) You accuse me of using one study to cast doubt on the impact while using one study (the one cited above) to support it. 2) There is more than one study that casts doubt not only on the date of the impact but on the idea that the extinctions were instantaneous. 3) Researchers have obviously not reached a consensus on this and other related issues. http://www.springerlink.com/(rbwjx4fpmmn2ot55eqbbjq45)/app/home/contribution.asp ?referrer=parent&backto=issue,1,17;journal,12,15;linkingpublicationresults,1:100 419,1 http://pubs.nrc-cnrc.gc.ca/cgi-bin/rp/rp2_abst_f?cjes_e00-048_38_ns_nf_cjes http://links.jstor.org/sici?sici=0022-3360%28199805%2972%3A3%3C556%3ADOFMHA%3E2. 0.CO%3B2-K&size=LARGE http://www.springerlink.com/(depelv55m0okn3550gitv045)/app/home/contribution.asp ?referrer=parent&backto=issue,5,15;journal,4,45;linkingpublicationresults,1:1049 18,1 http://www.bioone.org/perlserv/?request=get-abstract&issn=0094-8373&volume=027&i ssue=01&page=0140 http://links.jstor.org/sici?sici=0026-6493%28199921%2986%3A2%3C230%3A1MYOLV%3E2. 0.CO%3B2-2&size=LARGE http://www.ingentaconnect.com/content/geol/jgs/1998/00000155/00000002/art00015 > For the Deccan traps to be the cause requires someone to specify what > mechanism was involved. To the best of my knowledge all the ones so far > put forward take too long or would have left behind chemical indicators > which we don't find. I didn't suggest that the Deccan Trapps were the only cause, but did suggest that considering the recent findings for the P-T extinction event in relation to the Siberian Trapps, it cannot be so easily dismissed (as some have attempted to do) that the Deccan Trapps eruptions were one of several causes for the K-T event. George <snipping a great deal of previously refuted claims> So, nothing new or novel I guess. buh bye. Ken > <snipping a great deal of previously refuted claims> > So, nothing new or novel I guess. > > buh bye. > > Ken Anything you say, Ken. George >>> The Discovery Channel aired a show about impacts throughout the ages, >>> offering a new hypothesis about how Chixilub could have caused such a [quoted text clipped - 88 lines] > > George Way back, further than I care to say, in grade school, they said that evolving mammals ate dino eggs at a rate high enough to wipe them out. Possible, but maybe just a little mammalian arrogance. GIVE ME A BEAST WITH HAIR... GO TEAM GO!!! Volcanic activity is also possible, as is the pandemic theory mentioned above. If our methods of dating ancient events were 99% accurate (and they are not) we would have a window in time of hundreds of thousands of years during which the dinos said farewell. Let's be real here, we will never be certain what happened unless we find Mr. Peabody's Way Back machine. >>>> The Discovery Channel aired a show about impacts throughout the ages, >>>> offering a new hypothesis about how Chixilub could have caused such a [quoted text clipped - 101 lines] > Let's be real here, we will never be certain what happened unless we find > Mr. Peabody's Way Back machine. I agree to an extend. I give some reservations because there are things we can rule in and others we can out. And there is certainly plenty of evidence to sift through. Whatever was the reason for the K-T event, it wasn't caused by one single event. George >>> The Discovery Channel aired a show about impacts throughout the ages, >>> offering a new hypothesis about how Chixilub could have caused such a [quoted text clipped - 46 lines] > other amphibians survived quite nicely. Similar, many very fragile marine > species managed to survive, while hearty ones apparently didn't. What is fragile and what is robust is often in the mind of the beholder. One thing that seems to have tied most of the things that made it was fairly small size and resitance to starvation. Frogs and toads for example have been known to go years between meals and as individuals they are fairly long lived. If they weren't killed out right they could simply tough it out in some sheltered niche and wait for conditions to get better. Either that or they were small enough that they could get by on very little (mammals). >> Also many different groups of marine vertebrates and >> invertabrates went extinct or suffered a dramatic decline in number of [quoted text clipped - 37 lines] > > George I still like Boyle's explanation, even if it is only fiction. Check it out yourself boys and girls. http://www.amazon.com/gp/product/1591296471/qid=1069538287/sr=1-4/ref=sr_1_4/102 -7711775-0330503?s=books&v=glance&n=283155 >>>> The Discovery Channel aired a show about impacts throughout the ages, >>>> offering a new hypothesis about how Chixilub could have caused such a [quoted text clipped - 99 lines] >> >> George I read it, Bob. Pretty cool, but still fiction. >I still like Boyle's explanation, even if it is only fiction. Check it out >yourself boys and girls. [quoted text clipped - 104 lines] >>> >>> George >I still like Boyle's explanation, even if it is only fiction. Check it out >yourself boys and girls. >http://www.amazon.com/gp/product/1591296471/qid=1069538287/sr=1-4/ref=sr_1_4/102 -7711775-0330503?s=books&v=glance&n=283155 If its viruses you like, I recommend Greg Bear's books "Darwin's Radio" and "Darwin's Children". George |
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