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End of the "Lone Asteroid" Theory?
hussar writes "This BBC article reports on research that suggests the dinosaurs were not killed off by the Chicxulub asteroid's immediate effects but ultimately fell to evironmental stresses caused by a second asteroid that hit about 300,000 years later. The second impact may have been in the Indian Ocean."
Gerta Keller's conclusions are being strongly refuted by Jan Smits, one of the researchers that got funding for the core samples used in the study. He said in this NPR clip that he is really upset that Keller's research passed peer review without catching the obvious mistakes.
Remember... ZG9uJ3QgZm9yZ2V0IHRvIGRyaW5rIHlvdXIgb3ZhbHRpbmU=
Back when I took astronomy the standard theories were carted out before us for our own inspection and consideration.
I've not been convinced climatic change did them in as most theories seemed predisposed to a direct impact on the dinosaurse themselves. i.e. the earth passed through the tail of a comet and the atmosphere cooled and they died off. I'm more inclined to some environmental change which impacted the low end of the food chain, plants in particular, but it still doesn't explain why aquatic dinos went, too.
I'm looking for a theory that says the earth was a warmer place with most of that fossil fuel carbon still on the surface (where we're presently putting it again, one study observed plants are taking up the extra carbondioxide in the air, what's the long term impact of that?) As the carbon became buried (ever think about how much green stuff it took to make pertroleum deposits or coal seams?) the food changed and those at the bottom of the chain adapted or perished. Perhaps dinosaurs were really hugely inefficient creatures and require large amounts of energy, whereas mammals and birds are quite efficient.
Anyway, that's my two cents. Anyone who can point me toward some theories which follow that logic, as opposed to the big-exciting-asteroid-or-comet theories much appreciated. I think in extinction theories, the ones involving some violent cataclysm get too much press, probably due to the sensational value.
A feeling of having made the same mistake before: Deja Foobar
It may just be scientist ruffling their feathers at a new theory, or there may very well be serious problems with the evidence. It's certainly not a final answer yet.
The obviousness of this question makes me suspect it is a dumb one to ask but maybe someone can clarify for me. Why is it so strongly believed that some kind of environmental change wiped out dinos and not some kind of disease/virus?
... is that practically all dinosaurs that lived after the first impact were dead before the second hit earth ;)
The article doesn't seem to make any clear connection between the climatic stress - warming - supposedly caused by the eruptions that created the Deccan Traps and any meteorite. The accompanying graphs show a steady climatic cooling trend in the late Cretaceous and that curve doesn't appear to be affected by the iridium yeilding event. The biological diversity however correlates pretty muc exactly in geological time. So, where are the linking data that make sense of this article?
Remember, Jesus taught us to love all of God's children. Those pesky Asians couldn't possibly be God's children if the Old Testament is an accurate account of history. Noah's flood must have wiped out all of those destable foreigners, except that the Chinese had a society at the time with written history that has no details of an unusual flood.
Even more eye-opening is the fact that literal interpretations of the Bible are extremely new. Such intellectual hobbling wasn't popular until the 19th or 20th century - for almost 2000 years Christians realized what the purpose of the Bible was, only recently did some of them shut off their God given faculties and prescribe to a system of belief founded on utter and incredible ignorance.
To the idiot who moderated this as a troll.
1. The phrase "'Lone Asteroid'" in the title of the story is a reference to the JFK "lone gunman" theory.
2. The grand parent is an acknowledgment of same.
3. My post above is a quote from the film "J.F.K." (with some topical modifications).
I respectfully request that if you simply don't understand a post in the future that you not assume that it is a troll. This sort of idiotic moderation is exactly what a large faction of slashdot trolls use as an excuse for their behavior.
Be part of the solution, not part of the fucking problem.
-Peter
Been decades, wasn't the worldwide commonality of stories of an unusual flood one of Velikovsky's data points?
First my compliments to the author of the previous post. Obviously a person interested in a learned discussion. Secondly I would like to throw in a few more observations.
At Mile 282 on US I-65 in Alabama the KT Boundary is exposed in a Road Cut about 1/2 way up the cut. It is exposed frequently across Alabama. The following facts are observable by anyone looking at these sites.
[1] The site has contigious deposition of strata from well below to well above the KT Boundary
[2] The site has a crumbly rock/clay consistancy for some 20 feet below the KT Boundary
[3] The Rock is Sandstone for about 20 feet above and then is Limestone for about 60 feet.
[4] Above that mapping contigious strata are layers of coal, shale, and again limestone
All of these layers represent a contiguious geologic layering as they are essentially like pages in a book and of fairly consistent thickness over great distances. The presence of Limestone which has sea bed fossils brings into question exactly what we are seeing at the site. The reasons for this are multiple including the geologic age of the Limestone (Very Old) and the means of deposition of it (Sea Bed activity). I believe it would be quite fair to question very nearly any theory regards the KT Boundary. It is clear that the area was under the Ocean for a substantial period after the KT Boundary and it would appear that the KT deposition was fairly consistent with that event and possibly just one of many depositions layered this way. The fossil and other data from the KT Boundary area is inconsistent with any existing theory. The Limestone for example dates from early life times per Geologic Estimates about 600 Million Years. Yet it is above the KT Boundary.
These inconsistencies with existing theories need investigation as the area is one with a very substantial amount of data and has a very stable history geologically allowing the story to be read in order of events.
It can be safely said that the presence of the rocks above the KT Boundary are consistent with the continent being sunk below the ocean. Many rocks below this level hold the same data. The strata being so stable in deposition process showing large fairly even deposition layers calls into question exactly what happened to deposit the soft material and the KT Boundary. The sandstones above are similar to volcanic ash depositions.
Never Politically Correct ~ I prefer the facts If you don't like what I say, get a life, or comment yourself.
actually, it was 75,000 years ago, and only ~10,000 humans survived it. This is why there is so little genetic diversity among humans.
What has bothered me for a long time about the Chicxulub theory is that nobody ever provides evidence linking the impact to the extinction. Every time new evidence appears indicating that there was an impact, it's reported as being new evidence that the dinosaurs were wiped out by it. Actually, all it shows is that there was an impact of some sort.
Years ago I read Robert Bakker's book, 'The Dinosaur Heresies". In it he claims that the fossil evidence shows that the dinosaurs were in decline long before the KT boundary and the appearance of its famed iridium layer. Furthermore, many species survived the extinction, and some of those species (such as amphibians) were ones that you might expect to be particularly susceptible. So although the impact might have contributed to the mass extinction, it's not likely to have been the root cause.
Lost: one sig, witty, 120 chars, sentimental value. Reward offered.
When I was an undergrad geology student 20 years ago, the prevailing theory of how dinosaurs went extinct involved an asteroid hitting the Earth on the Atlantic Ridge system. The target location would be the present-day island of Iceland. The evidence used to support the conclusion included iridium-soaked sediments ringing Iceland dated right at the Mesozoic/Cenozoic (K/T) break, the high concentration of ultramafics at the surface, etc. etc.
The problem for this theory was (is!) the chain of events that would have led to a mass extinction. The theory assumed that the explosive force of the impact would have kicked up large amounts of dust and moisture, which would reduced solar activity and stunted or halted sufficient production of vegetative matter. That would have led to the die-off of herbivores, which in turn would have led to carnivore die-off. The hitch? Insufficient evidence of mass flora extinction at the K/T boundary.
Some years later, the location of the impact changed to Mexico, but the mechanics stayed the same. But there is still a huge lack of vegetative data to support a mass extinction.
So now there are several asteroids hitting the Earth. Did that change the fundamental assumptions?
Nope.
I'm glad the debate is still alive. Nothing bothers me more than a theory that attempts to tie everything together in a neat package.
"Rocky Rococo, at your cervix!"
Turtles and crocodiles seem to have survived the mass extinction(s) of the dinosaur age quite well. Both are ectotherms, neither migrates especially far. The general "coldbloodedness = vulnerability to the extinction" correlation just plain isn't there. The major case we're talking about, the dinos, is an open question to start with -- cold-blooded? Endotherms? Somewhere in between? Varying by species?
Something on the scale of the impact we're talking about would have all sorts of indirect effects. Mass extinctions, too, are going to be complex events, which is one big reason to be skeptical of any single-impact idea. For my money, what we have is a correlation -- not a causal link we can describe in concrete ways.
The model I always think of is Krakatoa's eruption in 535 AD. Global climate change kicked in just after that -- years without any harvest in Europe, extreme volatility. There are people who think that eruption changed human history: ushered in the "dark ages," partly caused or influenced the rise of Islam, destabilized governments, and so on. Maybe so -- but this is an event well within recorded human history, and it's still pretty doubtful trying to connect all the causes with their effects. That's if we accept the volcano -> weather changes link to start with.
Simple biological example: take ammonites and nautiloids. Similar chambered-shell mollusc floaters, right? Why did ammonites die out after the crateceous event, while at least a few nautiloids didn't? Ammonites were by far the more dominant critters before the extinction. Were there differences in their reproductive strategies, so that Nautiloids could "wait out" a bad phase better? What? It just ain't that simple.
(As far as mammals eating sleeping dinos at night, there were early mammals for a long time during the age of the dinosaurs. The jurassic, at least.)
"Fundamentalism" isn't about divine morality. It's about human authority.
This isn't such a stretch if they had been in similar orbits. For instance, they might have been part of the same asteroid at one time, which had been split up by some other collision at some point in time. There may have been other, smaller fragments of the same original asteroid which hit the earth or moon. Second, the assumption that the ones who survived the first one would have the best odds against the second just isn't true. If dinosaur populations never really rebounded after the first episode, they'd clearly be at risk for the second.
Too bad that many major scientists think that this conclusion is totally wrong given the evidence presented. (At least according to some NPR program I listened to).
Based on studies of fossil plants, spores, and pollens, Kirk R. Johnson of the Denver Museum of Nature and Science and his colleagues concluded that 51 percent of angiosperm species, 36 percent of gymnosperms, and 25 percent of ferns and fern allies were extinguished in North America. The fossil pollen suggests that deciduous trees survived better than evergreen trees, perhaps because they could lie dormant.
The article also mentions why: forest fires. The initial impact itself would have been bright enough to ignite fires in any vegetation within visible range, but the real kicker was the debris that was launched from the impact, much of which entered space, some comoing down quickly in a trail pointing westward (due to eastward rotation of the Earth under the debris trail), but some of which made half orbits to the antipodal (opposite) side of the Earth and reentered. It was the heat from the reentring debris which first dried and then ignited vegetation over vast swaths of ground in both hemispheres, especially North America and India.