DEEP IMPACT: Evidence from around the globe seems to point to a massive asteroid impact as the cause of the major extinction event on earth 65.5 million years ago. That rock was likely about 10 kilometers across and created a crater more than 100 kilometers wide.
Image: DON DAVIS/NASA
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Although any T. Rex–enthralled kid will tell you that a gigantic asteroid wiped the dinosaurs off the planet, scientists have always regarded this impact theory as a hypothesis subject to revision based on further evidence gathered from around the globe. Other possible causes, such as volcanism and smaller, multiple asteroid strikes, never actually went away, and over the years researchers raised important points that did not fully jibe with a history-changing celestial impact near the Yucatan peninsula one awful day some 65.5 million years ago.
A group of 41 researchers have pored over the evidence and decided that—in accordance with the original postulate put forth 30 years ago by a team led by father and son researchers Luis and Walter Alvarez—it was, indeed, a massive asteroid that slammed into Earth, creating Chicxulub Crater on Mexico's Gulf Coast, that killed off many of the species on the planet, including the non-avian dinosaurs.
The review, published online March 4 in Science, evaluated the whole picture, according to Kirk Johnson of the Research and Collections Division at the Denver Museum of Nature and Science and co-author of the paper. And that meant assessing the other theories that have been put forth about what spelled death for the dinosaurs.
Fiery failures
The researchers dismiss the theory that the volcanism that produced the great Deccan Trap formation in western India at the end of the Cretaceous period might have produced enough sulfur and carbon dioxide to initiate a massive shift in climate. They note that pinpointing the times when the heavy volcanism occurred is sketchy, and it likely kicked off some 400,000 years before the extinction event. In fact, as Johnson noted in a March 3 conference call with reporters, the emissions from these volcanoes likely warmed the planet slightly, actually making life easier for many animals and encouraging diversification and dispersion over wider geographical areas.
Some scientists have pointed to multiple layers of impact residue as evidence that there was more than one asteroid involved in generating the extinction. This theory did not seem to measure up, either. Johnson says they see "no evidence for multiple impacts," and sites that had turned up these various layers were so close to Chicxulub itself that the chaotic event likely churned the layers into different locations in the sediment.
An assertion that the impact occurred hundreds of thousands of years before the extinctions also failed to hold water with the researchers. Evidence of Cretaceous period shells on top of the impact crater are likely not a sign that the animals persisted after the impact, but rather that they got "washed into the hole," Johnson noted.
Global ground zero
The researchers assessed reports from some 350 sites all over the globe that had evidence of the impact—whether it was a dusting of iridium (an element much more common in extraterrestrial objects) or bits of shocked quartz—and could be traced back to the Chicxulub location. In some areas near the crater, the layer was 80 meters thick, pointing to one single devastating day for life on the planet.
"That's the single best explanation for the extinction of so many groups," says Neil Landman, a curator at the American Museum of Natural History in New York City and was not involved in the review, about the single impact theory.
"We've examined sites around the world," he notes of his study of ammonoids, which are shelled cephalopods that went extinct after the Cretaceous. And from the work he and his colleagues have done, he says, the evidence for the Chicxulub asteroid impact is the most consistent. "I'm very comfortable with this explanation."
A massive blow
Based on the size of material from rocky shrapnel and the crater diameter, researchers have estimated the dino-demolishing object to be some 10 kilometers across. And when it struck—at about 20 kilometers per second—it created an instant crater about 100 kilometers wide and 25 to 30 kilometers deep "almost piercing the crust of the Earth," Johnson noted. The final crater that formed after the initial impact was about 180 kilometers across and two kilometers deep, which is still close to the depth of the Grand Canyon, Johnson pointed out.
The impact spewed rock so high, some of it likely was shot into orbit, whereas other pieces entered the upper atmosphere, reheating as they fell back to the ground. The jolt would have spurred massive earthquakes—some surpassing magnitude 11—tsunamis and landslides. While examining ammonoid fossils in southeastern Missouri, Landman says, he found a shallow water site that was "just immediately covered over by a jumble of stuff," he says. "I think what we're seeing is a tsunami," which might have reached as far from the Yucatan impact site as southern Illinois.
Perhaps most devastating, however, the crash would have caused acid rain and darkness, as particulate matter blocked sunlight, prohibiting photosynthesis in both land and water ecosystems, effectively shutting down large swaths of the food chain. Directly after the extinction event, ferns (which reproduce from spores) proliferated and species that depended on detritus seemed to survive.
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Reply | Report Abuse | Link to thisThe article says:
Reply | Report Abuse | Link to thisAnd when it struckat about 20 kilometers per secondit created an instant crater about 100 kilometers wide and 25 to 30 kilometers deep "almost piercing the crust of the Earth," Johnson noted. The final crater that formed after the initial impact was about 180 kilometers across and two kilometers deep, which is still close to the depth of the Grand Canyon, Johnson pointed out.
My question is how do we go from an initial impact crater of 25-30 km to a final crater of 2 km? Is it just that the asteroid itself rested in the crater, filling up that 25-30km?
The article says:
Reply | Report Abuse | Link to thisAnd when it struck—at about 20 kilometers per second—it created an instant crater about 100 kilometers wide and 25 to 30 kilometers deep "almost piercing the crust of the Earth," Johnson noted. The final crater that formed after the initial impact was about 180 kilometers across and two kilometers deep, which is still close to the depth of the Grand Canyon, Johnson pointed out.
My question is how do we go from an initial impact crater of 25-30 km to a final crater of 2 km? Is it just that the asteroid itself rested in the crater, filling up that 25-30km?
The article says:
Reply | Report Abuse | Link to thisAnd when it struck—at about 20 kilometers per second—it created an instant crater about 100 kilometers wide and 25 to 30 kilometers deep "almost piercing the crust of the Earth," Johnson noted. The final crater that formed after the initial impact was about 180 kilometers across and two kilometers deep, which is still close to the depth of the Grand Canyon, Johnson pointed out.
My question is how do we go from an initial impact crater of 25-30 km to a final crater of 2 km? Is it just that the asteroid itself rested in the crater, filling up that 25-30km?
Wow, I totally apologize for the duplication of my comment. I registered with SA after posting the comment and the comment field was empty, so I backtracked to the original page and posted it from there.
Reply | Report Abuse | Link to thisThey need a better verification system stating that the comment has been submitted for newly-registered members.
I'm guessing that the initial impact transmitted so much energy that the "solid" layers of earth that were impacted were either liquefied or suspended enough to act like a fluid for a short time, and that a wave of earth traveled and persisted for a measurable amount of time -- thus an initial crater with a final crater of different size and shape.
Reply | Report Abuse | Link to thisThe article referenced by the 'this impact theory' link stated: "Although a single impactor is the most commonly quoted cause of the K-T mass extinction in the popular press, some scientists still argue that intense volcanism in the Deccan Traps of present-day India was the true killer."
Reply | Report Abuse | Link to thisI've also heard of a hypothesis that states that a large impact to a sphere transfers forces to the polar opposite location. I don't have a globe handy, but if Decca, India is in the location opposite the Yucatan, that theory might also apply. The Deccan Traps was an enormous volcanic event that released huge quantities of toxic and otherwise harmful gases.
A quick check on Google Earth shows that the Decca, India is on the opposite pole of Yucatan. The Theory indeed may be feasible
Reply | Report Abuse | Link to thisA quick check using Google Earth shows that Decca, India is on the opposite pole of Yucatan. The Theory does have some credibility.
Reply | Report Abuse | Link to thisinfosys - Thanks. This panel accepted findings that the Decca eruptions occurred 400,000 before the extinction event. For the polar transference hypothesis to be correct, revision of the current date estimates for Decca would be necessary.
Reply | Report Abuse | Link to thisNot impossible, but the current results do not support it. It does seem unlikely that such an impact could occur without being transferred throughout the mantle, just as earthquakes are.
Actually, the spherical rebound hypothesis would specify that the Yucatan crater and Deccan Traps were in opposing locations at the moment of impact, 65M years ago. I don't know the dates & locations, but I understand generally the the Indian plate has been most recently moving northward, colliding with the western Asia plate to reach its current position. I'd expect that it was somewhat further South at the moment of impact, which may have been closer to opposing Yucatan.
Reply | Report Abuse | Link to thisThis theory still does not make much sense. With heat that great, wouldn't it vaporize or liquefy water, sand, and small rocks? Have they ever found pools of glass anywhere around the craters...you know, liquids run down hill? And if all the vegitation was wiped out from the cloud of dust and debree that formed dark clouds in the atmostphere and lasted years, what did the smaller animals eat and drink when they came out of the holes, caves, or nests they were hiding in? Wouldn't it be too difficult for them to survive until the vegatition grew back or it rained to create more pools of water for them to drink? It seems that a meator with that much power would wipe all life off the earth, and if that happened, how did life restart? Those metors are not smart enough to select what life forms they want to wipe out are they? It seems it would be wiser to hang around with that evolution theory for a while longer.
Reply | Report Abuse | Link to thisSupposedly the earth's magnetic field has flipped orientation before. Is it possible that during a transition of the earth's polarity from one direction to the other 65 million years ago there was an extended period on earth whereby it lost its normal magnetosphere. The additional radiation and solar nuclear particles reaching the earth's surface could have reeked havoc on non-furry, non-feathered, non-marine critters - say like dinosaurs.
Reply | Report Abuse | Link to thisJamesDavis
Reply | Report Abuse | Link to thisI find that when making sweeping statements it is useful to look at boundary conditions. At one end it is certain that such a cataclysmic event would have wiped out higher lifeforms, but how about bacteria? Once you believe that some life could have survived it's only a case of arguing over where the boundary lies. It was stated that ferns proliferated. It's likely that fungi also proliferated. It's probable that these at least would have been a viable food source for some higher lifeforms .
JamesDavis - The panel did state that rock was thrown into the upper atmosphere and even into orbit and that it reheated as it reentered the atmosphere.
Reply | Report Abuse | Link to thisI have heard mention of scenarios in which the atmosphere was heated to such a degree that there was global incineration. I've also heard mention of scenarios where the reheated rock falling to the ground globally caused widespread forest fires, etc.
Some kind of global burning likely took place since the K-T boundary globally contains a thin (ash-like) carbonaceous material that may represent incinerated organic material. But I don't know to what extent or degree global incineration has been definitively established.
The article mentions the regional layer of shocked quartz that increases in depth nearer the Chicxulub crater. It did not mention glass from melted sand or vaporization of water, etc., although it seems reasonable that any or all of those things may have occurred to some extent nearer the impact.
As far as I know it has not been established that any subterranean burning took place. I presume that smaller creatures that avoided the initial affects of the impact continued to eat any remaining or recovering surface vegetation, tubers, insects, each other, etc.
I'm not specifically aware of any species of insects that were wiped out by the affects of the impact, much less microbes, although there may have been some that were.
In wintertime under heavy snow conditions food is very difficult for animals to find food, but they seem to do so or hibernate. Creatures will do pretty much anything to survive when things get tough. Those species that didn't find anything to eat didn't make it - those that did, did.
Eventually successful life accepts the new reality, adapts and survives.
I think the most interesting thing about this article is that proposes alternate hypotheses too to an event that has been "accepted" by most of the scientific community to the extent that it has been taught in schools for at least 20 years.
Reply | Report Abuse | Link to thisI'm not pro- or anti-global warming, but it does seem to me that this a much more recent hypothesis and, from my understanding, not as accepted. Especially the man-made part.
My question is this: Why are there no alternate theories to GW (or AGW) published in SA?
They're not afraid to go against the grain with some issues, as this article shows. But almost completely silent with others.
Just a question.
Its pretty clear that this is without doubt exactly what happened. Its certainly logical.
Reply | Report Abuse | Link to thisJess
www.fbi-logging.at.tc
Although it seems that the asteroid hypothesis explains many aspects of the KT extinction event, many questions remain. Why did some sea creatures within similar niches die, while others survived (e.g. sharks vs the plesiosaurs). Similarly, why did the crocodilians survive, but not those dinosaurs that occupied a similar ecological niche? Perhaps the disappearance of the large dinosaurs can be explained by the loss of large food sources, but if small mammals and reptiles could survive the event, why couldn't small dinosaurs? In other words, it wasn't just that almost everything died but that something seemed to preferentially kill off the dinosaurs and some other species (e.g. pterosaurs), while allowing many other species to come back. At present we can only speculate, but perhaps there was something fundamental that changed in the Earth's environment (atmosphere? climate? solar radiation?) that made it impossible for dinosaur physiology to adapt.
Reply | Report Abuse | Link to thisScience Geek - Excellent points. I'd speculate that many small dinosaurs may have survived, evolving into birds. Also, while it's not often mentioned, larger creatures most often have the longest reproduction cycles, generally making their rapid adaptation to new conditions more difficult.
Reply | Report Abuse | Link to thisDespite the cute title, "Theory Set in Stone", I think this panel's findings should be viewed as an acknowledgment of consensus recognition of the extraterrestrial impact theory of the Cretaceous-Paleogene extinction as the best explanation, certainly not to preclude further refinement and revision.
Reply | Report Abuse | Link to thisHmm, this article generates a few questions in my mind.
Reply | Report Abuse | Link to thisFirst of all, the article never really explains exactly how this impact eradicated non-avian dinosaur life on Earth. How did this "dino-demolishing object" directly achieve the destruction of dinosaurs? The article mentions that it likely generated large amounts of particulate matter which would cause acid rain and darkness, but was this particle cloud global? Did it wipe out vegetative ecosystems worldwide? If so, how? And how did this select against the dinosaurs but not other vegetarians and omnivores? And also, why weren't avian dinos affected?
The whole "asteroid-eradicated the dinosaurs" view just doesn't seem to hold water to me. And speaking of water, the article mentions that the asteroid impact likely generated tsunamis and earthquakes which resulted in an area "immediately covered over by a jumble of stuff." This sounds like the aftereffects of a Genesis flood type event. Bottom line: I think there's still a bit more explaining to do about the extinction of dinosaurs on Earth.
Why does science not mention the other, FAR LARGER impact that occurred around the same time as the Chixulub impact. The dinos got a 1-2 punch, and there are several other craters at the same time. Indeed there are SEVERAL other impacts that occurred at the K-T boundary. Why science doesnt popularize the information is beyond me.
Reply | Report Abuse | Link to thisEveryone that goes on and on about the Deccan Traps fails to come up with a cause of the eruptions: The Shiva Impact. So a way bigger asteroid, part of the same one that busted up and another chunk of which hit at chixulub, crashed into India, moltenized a huge area which continued to erupt, and India's northern drift combined with the mass outpouring of magma, all but erased the crater.
http://en.wikipedia.org/wiki/Shiva_crater
http://www.spacedaily.com/images/deepimpact-india-shiva-site-bg.jpg
why would the small dinosaurs have evolved into birds? Did they just decide to change their genetic makeup and pass it on to their progeny? Hmm, seems a likely scenario
Reply | Report Abuse | Link to thisHogwash. The bible don't say nothing about no asteroid. And it don't say Noah excluded any creatures from his Ark. And since God also didn't command Noah to bring two of every animal and seven of every bird, "because you need to feed the dinosaurs for a year", the only reasonable conclusion is that Dinosaurs were created and then destroyed in a single day, some time when it didn't matter enough for God to write in the bible.
Reply | Report Abuse | Link to thisWhy do Bible beaters come to SCIENTIFIC American?
Reply | Report Abuse | Link to thisThe dark ages are OVER. Please retreat to your cave and stop trying to infect people with your propaganda.
ar5skier - That I clearly stated that I was speculating implies that I have no specific explanation. However, can you explain how, when small dinosaurs existed turkeys did not?
Reply | Report Abuse | Link to thisNot to further bore you with inconsistencies, but the point is that if the small dinosaurs did survive they evolved into something other than small dinosaurs. They needed no reason to do so, since it was not a deliberate choice on their part, but if it happened it allowed most of their genes to continue to survive by adapting to changing conditions.
The outstanding fossil beds discovered not long ago in China indicate that someday soon further evidence may be discovered.
This comment is for "hotblack" If you are going to comment here at least go back to your English teacher and learn the correct use of the English language. You are showing your ignorance.
Reply | Report Abuse | Link to thisI don't think you are capable of coming up with "a reasonable conclusion" in my opinion............
Reply | Report Abuse | Link to thisYou're right...it was apparently similar to the Shoemaker-Levy comet/s strike of Jupiter with multiple collisions, not just the one. That comparison really helps create a fascinating visual imagery.
Reply | Report Abuse | Link to thisIf you're going to refer to the Bible, why sound like such an ignorant hick? You must be intentionally trying to give believers a bad name. Please refrain.
Reply | Report Abuse | Link to thisI have seen the detailed geologic analysis of the region from the oil industry. It wasn't an impact at all in fact no impact occurred at the site. The limestone deposition in the area conflicts as well. The KT irridium line visible at milepost 282 I-65 in Alabama, is capped quite well with sandstones and limestones. This indicates a transition from above sea to below sea event. Sorry guys but this theory on extinction doesn't hold water. The irridium line is probably just a chromatographic boundary anyway. Alabama in this location at the time would have been part of the site of the immediate effects of the impact as portrayed. No impact debris is here. MP 282 (I-65) would have been at the geologic time about 4oo miles from center of impact. This is just one of about 7 innundation events that are clearly shown in Alabama rocks. What happens is pretty simple. Methane builds up in the rocks and the continent rises. Then the whole thing breaks down and the continent sinks. Of course that causes some serious disruptions of life in the area. The existence of Limestones above the boundary is not consistent with the "Geologic" timelines supposed for the event as are the Limestones in the Yuccatan where the ring of pits is found. Had the event happened as supposed the limestone would have been blown clear of the area entirely and the pits would not be there. The Yuccatan site including faults is clearly an old volcanic site. The appearance of sandstones and the like in the area at the time indicates massive volcanic eruptions over a repeated and long period of time. Otherwise you have to ask where the erosion happened to cause the limestones and the capping sandstones. There are no sites to account for these as erosion products. I love these conclusions of groups of "scientists" just like our recent batch of liars from East Anglia U.
Reply | Report Abuse | Link to thisI don't mind in the past, I belive in present, I accept in future,Do my best to carry on my poor life.That all for all. NIRVANA.....
Reply | Report Abuse | Link to thisSirBoss - You seem to have a great deal of practical experience investigating geology in Alabama. I have no idea what a chromatographic boundary is, but it seems you may be referring to a settling of dissolved particles. Please bear with me as I'm trying to understand...
Reply | Report Abuse | Link to thisThe presence of an iridium layer at the same time around much the world should indicate a sudden global event, correct? Doesn't the presence of sandstone and limestone indicate a marine environment? Couldn't capping sandstone and limestone have been deposited after an impact event? Thanks.
Yes the astoroid would reach 20-30km deep creating the initial 100km wide crator... the earth took a 10km wide bullet. What created the second creator is the kinetic energy whose resulting megga megga tonne explotion that launched debrie globally and into orbit. It displaced at least 180km by 2km deep of materials resulting in the visible crator. The heat shock wave would follow as it expands searching for air... 1000kms would vaporise and beyond would ignite as the intense heatwave dissapates. Smoke and dust would block out photosythesis to much of the planet. Could it have killed the dinosaurs... very plausible.
Reply | Report Abuse | Link to this@Cymbaline, the article does mention the multiple impact hypothesis, and rejected it.
Reply | Report Abuse | Link to this@jtdwyer, birds likely began their split from non-avian dinosaurs during the Jurassic.
The animals that survived tended to be small but there was some variability. Think of it like dominoes. If the impact killed off your food source, or your food source's food source you would topple with them, otherwise you may be able to hang on. Many reptiles such as crocodiles and snakes are cold blooded and scavengers so they can go for long periods with little to no food. One captive snake was known to have gone two years without eating. Birds are highly mobile and small, thus able to quickly move to areas where there is food.
I don't think the earth would have been a desert after the impact. The killer would have been the abrupt climate change. Many organisms live within very tight budgets so a sudden change would have been enough to wipe them out. The mistake is to think that just because it was one event that triggered the K-T extinction that all plants and animals that went extinct, did so for the same reason. For some, it could have been loss of sunlight, others it could have been loss of prey species and still others, changes in ocean chemistry. The important thing to note is that the asteroid didn't cause the mass extinction by flattening everything, it did so by triggering global climate change.
@SirBoss, get a grip. Publish a paper if you think you've got evidence but don't B.S. us by claiming that you and you alone have it figured out and all the geologists, palaeontologists, etc. have clearly missed the obvious. That just makes you sound like a nut.
Reply | Report Abuse | Link to thisrobert schmidt - I think that some significant initial burning was involved, as evidenced by the high carbon content of the generally compact K-T boundary. Undoubtedly the extended climate change also had a significant impact.
Reply | Report Abuse | Link to thisinfosys - you got the right longitude, but the wrong latitude... Yucatan is northern hemisphere, so it's antipodal opposite can't be in the same hemisphere...
Reply | Report Abuse | Link to this...unless of course the Indian subcontinent was down there 65 million years ago. Did it move up that fast? I doubt it.
Quentin Rowe - Thanks - I was afraid of that. Thanks, infosys, for the quick-check.
Reply | Report Abuse | Link to thisAgain, the real question (aside from the dating discrepancy) is whether the two sites were antipodal (thanks) 65 million years ago. Aside from the motion of the Indian plate there may have been other relative motions aligning the two sites at that time, but it seems a stretch. The last possibility is that, while not completely aligned to receive the maximum antipodal forces, the Deccan Traps were the nearest site ready to blow.
I know this hypothesis has little support, but their proximally antipodal locations and near coincidence, plus the implausibility that such a force delivered to the Earth could be internally absorbed when earthquakes' forces are not, all make it extremely interesting.
In response to the question of why didn't the dinosaurs survive the impact while other species did, one should think about the various species ability to survive the radical environmental change. Some species likely had specialized diets and environments, without their food source or special biome, they simply perish. Any remaining dinosaurs would have had to compete with other, perhaps, more adapted species for remaining habitable spaces and available food sources. Those species which exhibited specific traits so as to give them an advantage would have survived, likely undergoing radical evolutionary change under the conditions of such a highly competitive and pressured environment.
Reply | Report Abuse | Link to thisFellOnEarth - Good points. Again, I also think that a critical factor in the adaptation equation is simply the periodicity of reproduction. Larger creatures often have reproductive cycles as high as, perhaps 24 months, while small ones may take just a few months. This factor, combined with the number of offspring produced per cycle, puts a constraint on the rate at which a species may produce genetic adaptations. This generally allows smaller creatures to adapt to changing conditions more quickly than larger ones, and is often overlooked in megafauna extinctions.
Reply | Report Abuse | Link to thisAnother factor that could support the antipodal impact hypothesis (that the Yucatan impact created the Deccan Trap eruptions) is that force waves propagating through the Earth's interior are sufficiently deflected by the solid core to produce not a focal point of antipodal impact but a 'ring of rebound'. In this case the Deccan trap would have been located (at the moment of impact) on the antipodal ring that received the peak internally transmitted force of impact.
Reply | Report Abuse | Link to thisI suspect this core deflection scenario is quite likely: if so it should already be recognized in the signal processing of global earthquake detectors.
jtdwyer - Well, does the absence of turkeys and the presence of small dinos at a certain time period necessarily mean that turkeys are evolved dinos? Is that a conclusion we can reasonably draw or are you simply speculating? Couldn't turkeys have developed from a similar more bird-like species?
Reply | Report Abuse | Link to this@ar5skier, "Well, does the absence of turkeys and the presence of small dinos at a certain time period necessarily mean that turkeys are evolved dinos?" that is an idiotic statement. You clearly have no idea of what you are talking about. Is it too much to ask that before you criticize something that you at least take a moment to understand it? That information is easily available so one has to conclude that you have no interest in actually understanding anything, rather you are here to push your own world view. Just another vector carrying the religion virus.
Reply | Report Abuse | Link to thisar5skier - No, but it infers the evolution of turkeys.
Reply | Report Abuse | Link to thisI dont know, the amount of energy that it would take to cause that kind of volcanism would be tremendous. The force needed to move the earth's tectonic plates and create fissures to let the gas and other volcanic material escape would cause massive earthquakes around the globe. If we find some sort of evidence supporting the fact that these earthquakes did occur, then it might be possible.
Reply | Report Abuse | Link to thismario1 - I'm not geologist or scholar, so I can't refer you to specific facts, I'm simply recalling a program presenting this hypothesis, originally developed from a medical study of antipodal brain injuries. If I recall there has been some modeling done to simulate the same effect as a result of extraterrestrial impacts. I'll try to explain what I understand of the proposed phenomena.
Reply | Report Abuse | Link to thisThe basic idea is that an impact produces waves of energy that pass through the Earth as seismic waves. Keep in mind that even the worst earthquakes are essentially a sudden release of pressure, typically directed laterally in relation to the Earth's surface. In the case of this huge mass impacting the Earth at tremendous velocity, its momentum is transferred more vertically to the Earth's surface.
The force is transferred to the Earth's crust, mantle and outer core as extremely high amplitude seismic waves. Like the much lower amplitude seismic waves produced by earthquakes, they are expected to follow a reflective path through the Earth's interior. Eventually a significant percentage of the original force is delivered to the opposing location on the Earth's surface, just like a blow to the head causes brain injury in the opposing location. Unlike the human head, the Earth has a solid iron core that I expect would alter the reflection pattern.
I presume the Deccan trap eruption is well documented: it was referenced in this article as a competing theory to the impact theory as the cause of the mass extinction 65M years ago. I only recall that it laid down a layer of basalt (lava) maybe 50-100 ft. thick over a huge area in Northern India, about 440,000 years before the estimated impact date 65M years ago (a nice round number). For the two events to be coincidental, one of those estimates would have to be in error by a factor of less than 0.7%.
Of course, this hypothesis could only be confirmed by an actual impact of a (not too) large meteorite that could be detected by seismologists around the world.
Reply | Report Abuse | Link to thisHow can the ignore the fact that so many creatures surivived what they say is the aftereffect that lasted years?
Reply | Report Abuse | Link to thisWhat made Birds so special (especially since they were far more dinosaur like back then)?
Why mammals could survive such a period of darkness, amphibions, reptiles.
Yet Dinos the most successful land life in the history of the planet disappeared?
It may make sense to these researchers, but only because they want it to make sense.
The notion that an asteriod impact could have such a selective, specific impact on life is idiotic.
How can the ignore the fact that so many creatures surivived what they say is the aftereffect that lasted years?
Reply | Report Abuse | Link to thisWhat made Birds so special (especially since they were far more dinosaur like back then)?
Why mammals could survive such a period of darkness, amphibions, reptiles.
Yet Dinos the most successful land life in the history of the planet disappeared?
It may make sense to these researchers, but only because they want it to make sense.
The notion that an asteriod impact could have such a selective, specific impact on life is idiotic.
Furthermore, Dinosaurs were extremely varied in form and needs.
Reply | Report Abuse | Link to thisIn fact at that time, they had more variety in terms of lifestyle and diet and environmental needs than any other large land life form.
Yet they disappear, and other lineages with much less diversity on those points survive?
Considering the superior nature of the dinosaurs during this era (in terms of variety of adaptations to avail habitats Etc.) Dinosaurs would be the LEAST likely to disappear from an asteroid impact.
Some whre extremely small like chickens, also able to hide from the blast, underground.
Every conceivable idea as to why other animals survived can also be applied to at least a few dinos, yet none survived.
This is a feelgood theory for scientists who enjoy drama that sounds scientific, but is anything but, because there is simply no way to prove it. It is as the article said "an agreement" but far from fact, and shouldn't be spoken about as such.
At 65.5 millions years ago, the Indian subcontinent was south of the equator and the geography in the region of the Yucatan was very different.
Reply | Report Abuse | Link to thisLets be clear here:
Reply | Report Abuse | Link to this(1) Limestone deposits date well before the proposed impact date
(2) The limestone deposits have not been ejected out or deformed from the "hole"
(3) The State of Alabama where the KT Boundary is evident at Milepost 282 US I-65 would have been covered heavily in ejecta from the event. (not here!) South Alabama was by current geologic time lines essentially adjacent to the impact site at the time. Leaving MP 282 about 400 miles from the site.
(4) The site at MP 282 is clearly topped with sea bed deposits after having land animal deposits below the KT boundary.
--Therefore Alabama sank below the sea and deposited 50 to 100 feet of sediment over the KT boundary.
-- For the question about Chromatography boundaries: The site is probably a site where migrating solutions of water containing minute concentrations of iridium were deposited creating the concentration of metal ions at the site. This is a typical geologic process similar to the transport of Methane upwards until hitting shale. This is how we get coal field gas collections. This is a typical oil deposit event as well. The sands/glass content at that location is typical of a material used to purify water. This process is a standard industrial and chemical technology event.
The presence of limestone and sandstone in Mexico at the site and not ejected or deformed indicates no impact happened.
The site is a deposit consistent of a massive volcanic event such as Yellowstone and having seen the geologic scans of the region I know that no impact happened there. It is an old volcanic structure and all of the deposits are consistent with it. I have seen such deposits at Mt. Pinatubo (Phils early 1990's). These form very suddenly (Literally over night)
I know this pretty well screws up most accepted geology mythology of today but it locks solidly with the facts.
SirBoss - Thanks - you do seem to be very knowledgeable about the specific geological conditions of South Alabama, which are certainly relevant to the geologic discussion. I'm certainly not capable of assessing your observations.
Reply | Report Abuse | Link to thisHowever, unless the similar deposits of iridium found around the Earth all apparently confirmed to represent a process that occurred 65M years ago can be discounted, they seem to be very strong indicators of a global event, or process unique to that time period. Also, the reports of shocked quartz deposits, indicating a high massive velocity impact, increasingly dense nearer the Yucatan seem to confirm the location of an impact event. Do you not find shocked quartz at your site? Thanks.
@jonathanseer, yet another idiot coming here to criticize something they know nothing about. There are numerous hypotheses for why certain animals died out and others survived. Your statement, "Some whre extremely small like chickens, also able to hide from the blast, underground," shows that not only do you not understand what happened during the K-T extinction event, but that you didn't even read the article. The only people ignoring the facts are contrarians such as yourself. You just don't seem to get it. When you come here and make statements that are clearly false, you only show yourself in a bad light. "The notion that an asteriod impact could have such a selective, specific impact on life is idiotic.", actually the notion that someone who knows nothing about a subject should be able to make authoritative pronouncements about it is idiotic. Instead of sharing your ignorance with the world, why don't you take that time to understand it?
Reply | Report Abuse | Link to thisPerhaps the point to discuss is not if certains species could have been more at risk from a direct asteroid impact, giving the impression of selective extinction, as it seems the case with the Dinos, but what attributes did the species that survived had, that gave them a clear advantage to overcome the extreme difficulties of the aftermath. We must depart from a fact: the dinos were killed off along with a very large percentage of fauna and flora. we should not look for what failures the Dinos possesed in dealing with the threat, but what advantages the rest of the species had which brought us to this point today
Reply | Report Abuse | Link to thisjtdwyer- thanks for your simple answer to my simple question
Reply | Report Abuse | Link to thisMr. Schmidt- My "idiotic statement" that you quoted was actually a question, not a statement at all. I was asking a general question. But that's ok, I realize that this is not a grammar discussion forum.
And you are right, Mr. Schmidt, that I am terribly ignorant on the subject of turkey evolution. Hence I asked a few questions. I'm sorry for pushing my world view on everyone reading these comments, but I will not apologize for my beliefs.
@Rixk, you're right, the species that went extinct weren't necessarily less adapted to the environments they were in, i.e. they weren't "primed" for extinction, they just weren't able to adapt to the abrupt changes. There is some controversy that dinosaurs were in decline at the time, but then again individual dinosaur species were in decline during the T-J and J-K boundaries as well, yet the group as a whole continued. Ultimately, dinosaurs did survive the K-T extinction, just in the form of modern birds. One of the major factors in determining what survived the K-T extinction, at least in terrestrial vertebrates, seems to be size. Also, animals that had varied diets, that were able to move to more favourable environments, or that were able to shelter themselves from the extreme environmental changes survived. You pretty much need to look at it on a species by species basis. There is no one-size-fits-all answer here.
Reply | Report Abuse | Link to thisMass, speed and vector can probably be estimated--
Reply | Report Abuse | Link to thiscould we do so and keep an eye in that direction,
perhaps pre-positioning a rocket we could use to intercept, strap on and steer it elsewhere?
@ar5skier, nice attempt at a deflection. Your comment was a "straw man" rephrase of jtdwyer's earlier comment. And as with your earlier sarcastic comment, "Hmm, seems a likely scenario" there was no attempt here to engage in dialog, just an attempt to cast doubt, but instead of arguing the facts you attack a ridiculous oversimplification of your own making. That is how a "straw man" is employed. So don't give me, "it was just a question". If I were to ask, "Are you an idiot?" Would you assume that it was only an innocent question?
Reply | Report Abuse | Link to thisPlease realize, this is a science news site, not a peer reviewed journal. The information provided here is not the complete science any more than the information in a CNN article reflects the complete story of the news item. For those that are interested in these things, this may just serve to keep them up to date with what is going on. If they need more depth they can read Nature or go directly to the source. Most of the people interested in this stuff already have a great deal of understanding about the basic underlying science. We don't need them to explain fossilization, radiometric dating, evolution, etc, every time they write these articles. For someone who doesn't have basic science literacy, articles here would appear to be making a large number of assumptions. I assure you; the assumptions concern the intended audience's expected knowledge and do not reflect a lack of thorough science. It is easy to find fault with oversimplifications. To me, it is a given that, I am not going to get all the answers here.
As I’ve stated, what gets me is the people, such as yourself, that come here and very confidently cast doubt on the quality of science and make sarcastic and acerbic comments about the articles when they clearly have absolutely no clue what they are talking about. I agree that no one should apologize for their beliefs but they should apologize for their actions when they are malicious. The actions of creationist who post here are not directed at engaging in meaningful dialog, which is the intent of the site, only in making unfounded accusations and misrepresentations and ultimately preaching their message. That takes a lack of integrity and they should apologize for that.
robert Schmidt, Rixk – Nice discussion of species’ survival/extinction selection factors.
Reply | Report Abuse | Link to thisNot to beat a dead dinosaur but just in case you missed my earlier post, I’d interject that the duration of the reproductive cycle, along with ‘liter’ size, may be the critical factors in determining a species ability to adapt to radically new environmental conditions. Each new individual produced is a new opportunity for adaptation. Those that produce the most new individuals in the shorted time have the best chance of adapting quickly. Generally, the duration of the reproductive cycle and the size of liters is an inverse function of individual size. This may best explain, both for the dinosaurs and the more recent megafauna extinction at the end of the last ice age, why larger creatures are least likely to survive radically changed conditions.
robert schmidt- I'm sorry, my actions had no malicious intent at all. My comment about birds evolving from dinosaurs was sarcastic but not malicious. I don't believe I've displayed any lack of integrity though. Thanks for the feedback
Reply | Report Abuse | Link to thisHenry S - Thanks. Its be most informative to understand exactly how near precisely antipodal the two sites were at the moment of impact.
Reply | Report Abuse | Link to thisar5skier - You're welcome - I hope it helped.
Reply | Report Abuse | Link to thisMoreover, Id suggest a study ranking the reproductive rate (individuals produced/time) of species living at the moment of impact. I expect that those ranking highly would significantly correlate to those that survived the impact's affects, at least in some form. It might be a good thesis for someone capable...
Reply | Report Abuse | Link to thisCorrection: 'litter' not 'liter'. No wonder nobody understands me (joke, I hope).
Reply | Report Abuse | Link to this@jtdwyer, It's an interesting idea, that smaller animals adapt faster because they have a shorter reproductive cycle. The only problem I see is that the changes happened very quickly, in terms of days, months and years, so it would be unlikely that even the smallest animals would be able to adapt, from an evolutionary perspective, fast enough for it to aid them in surviving the event. It seems more likely that they already possessed the tools needed to cope with the changes. Although, over the millions of years that followed the event, a faster rate of evolution may have helped them rapidly expand into the niches left vacant by the dinosaurs.
Reply | Report Abuse | Link to this"In fact, as Johnson noted in a March 3 conference call with reporters, the emissions from these volcanoes likely warmed the planet slightly, actually making life easier for many animals and encouraging diversification and dispersion over wider geographical areas."
Reply | Report Abuse | Link to thisMy question is, If this is so, why wouldn't a present day slight global warming, benefit the earths current occupants?
@Moredecai, first, Johnson's statement is an unproven hypothesis. Second, he said it may benefit many animals, not all. Some animals may benefit from global climate change but they don't tend to be the ones we "want", e.g. pests like mosquitoes may do very well but the Polar Bear may not make it. Third, the issue today is not only that human activity is changing the climate, but it is doing so at an extremely rapid rate, one that is very difficult for organisms to adapt to. There is no indication in his comment about the rate of warming. Finally, you need to consider that organisms today are already under extreme stress as a result of widespread habitat loss and over exploitation. It is very difficult now for organisms to mitigate some of the stress by moving to new environments as in many cases ecosystems have been fragmented by development.
Reply | Report Abuse | Link to thisOne must be cautious when trying to extrapolate from a comment, especially when dealing with complex phenomenon. The devil is in the details.
robert schmidt – Excellent counter point, thanks. Perhaps my enthusiasm is unjustified. Certainly an ability to eat surviving insects and rotting plant and animal material would be a distinct and immediate advantage.
Reply | Report Abuse | Link to thisHowever, if one considers especially the creatures that did survive, I think at least today’s small mammals are each capable, with adequate nutrition, of producing dozens if not hundreds of offspring per year, each with a unique combination of genes. While few of these offspring might survive, in a few months this would provide a distinct advantage in the probability of producing beneficial adaptations. Larger creatures, in the period of a year would likely each produce less than one offspring.
I agree that reproduction rate is a critical factor in producing adaptations, but probably not the deciding survival factor. Thanks.
Crocs are cold blooded - they need less energy. Dinosaurs were warm blooded. They needed more food. Crocs can go months without tucker and they can hibernate. Dinosaurs - especially big ones would not have had access to the required food. The extinction is not a matter of everything dying in a year or so - there is 10 years of yucky skys, dying plants, acid rain etc ... then things start to recover (albeit very different climate). There may simply not have been sufficient biodiversity for dinosaurs (other than birds) to survive - disease, lack of biodiversity, and displacement by my successful survivors would finish them off over a few tens of thousands of years.
Reply | Report Abuse | Link to thisCatbiscuit - The article states that the panel concluded that rocks were spewed up so high that some entered orbit while others were reheated as they reentered the upper atmosphere.
Reply | Report Abuse | Link to thisSome scenarios envision that the rock thrown into the upper atmosphere and especially those entering unstable orbits were reheated, causing conflagrations around the world. Some even envision that the atmosphere itself was extensively reheated by this activity, producing spontaneous combustion of surface material.
While the long term environmental impact almost certainly killed many plants and animals, I suspect that a significant number of creatures were killed very soon after impact. Some species may have even become extinct in the first 24 hours. Conditions were probably best described as hell on Earth. At least, that how I envision the event.
Reply | Report Abuse | Link to thisI have always asked myself..."why is the moon there and where did it come from"?
We might want to re-examine the clues on the denise of Dino the Dinosaur...
Frozen water crystals on the lunar surface. I'm betting that the water there came from what is now the Pacific Ocean. It struck Earth as part of a multiple impact....just off center, pushing the Earth back...out of it's orbit. The Moon stayed with us and all the other planetary objects richocheted off into space. The lunar impact created the "Ring of Fire" and a 3-4,000 foot psunami. The similar impacts in other oceans of the world created similar consequences. These psunamis rushed across all the Earth's continental land masses at unbelievable speeds...destroying forests and killing off the world's titans...all the dinosaurs and all the larger mammals that lived in the lower elevations. Only the smaller creatures survived. They already lived up high to keep from being eaten ...or could climb onto floating debris until the surge receded. The water rushed in fast and departed the same way.
The dinosaurs became extinct within twenty-four hours and were deposited in their final resting places within thirty-six.
Some clues....
Fossil beds...dinosaurs that ate or were eaten by others of their species died at the same time in the same spot....odd.
Fossil fuel deposits...if they had stayed in the water for very long, they would have floated and would have been scavenged by the fish in the sea. They were washed out to sea or into low spots and covered by silt from the backflow.
Look at where the oil is found....also at where it is ....probably...but undiscovered as yet.
Look at the flow patterns....consider that those things we have thought created by erosion over hundreds of thousands of years...may have come into being in about a week...The Grand Canyon, The Columbia River Gorge, The Snake River Canyon, Zion NP, Canyonlands NP. The Great Salt Lake (might want to check the bottom), Death Valley, The Salton Sea, all the Salt Domes and Salt Caverns across the middle of this country....just to name a few that I've wondered about.
Anyway...something to think about.
Something else. Right after (almost during) these catastrophic events, the "Ice Age" began. Again, it happened fast. As the Earth moved quickly out of its orbit and away from the sun (picture a childs paddleball toy)...everthing just froze. It froze fast and then for the most part, thawed fast... as the Earth reached the farthest point and then started back....at first very quickly and then...slower .
Will human beings experience the same as the dinosaurs did, I'm afraid.
Reply | Report Abuse | Link to thisTo Fang...
Reply | Report Abuse | Link to thisHumans will not experience the same fate. The dinsaurs were brought to their end by water.
As the earth warms by a natural process and totally uninfluenced by mankind... and as the permafrost in the polar regions fails to re-freeze... methane gas may escape and form an atmospheric layer around the earth, which at some point in the future may ignite and ....who knows Fang.....
I stopped following the K-T cause debate years ago, when I realized it had turned into something like a gang war, same as "where did the water on Earth come from?".
Reply | Report Abuse | Link to thisIMO a crucial factor to be discovered is: what was the position (one big impact/many impacts/volcanic) of each of the 41 members of the team BEFORE the study began.
infosys,
Reply | Report Abuse | Link to this65.5 million years is long enough for the continents to have moved from some where else to where they are now.
It is clear that the size of the crater was about 10km across that created an initial impact zone about 100km across. The crater also travelled at a great speed.
Reply | Report Abuse | Link to thisMy question is, having hit an area near the Yucatan Peninsula, were it the tsunamis and the subsequent rising of temperatures over the next tens of years that finally caused the slow death of the dinosaurs across the world? What numbers of Dinosaurs would have been wiped out instantly by this catastrophic phenomenon? Where were the highest population of Dinosaurs when the crater struck?
If the impact was at an angle would the shock wave (surface or transmitted through the planed still have resulted in directly antipodal location?
Reply | Report Abuse | Link to thisEven if they could not adapt quickly a large litter size means a greater chance that some would survive.
Reply | Report Abuse | Link to thisTo SirBoss is a site of www.mammoths.narod.ru - broadly speaking reproduces events which happened on continents for last 600- 700 thousand years, hypotheses about what that asteroids is very primitive explanation of events of the past, for persuasiveness taken arbitrary amount of millions of years - naturally, that the Static model of globe - demonstrates the total consequences of changes on continents in the past, chronology of events of the past this model can not ground never
Reply | Report Abuse | Link to thisCerebral*Origami - I can only guess that any force that reaches the highly viscous mantle produces a similar pattern of waves reflecting through it to the at least near antipodal location. The transmission of force would likely be reflected to at least some extent by the outer and inner core, which may disperse its eventual impact location. I'd guess that the primary affect of impact angle would be the percentage of force transmitted to the mantle.
Reply | Report Abuse | Link to thisWikipedia mentions the antipodal impact hypothesis in its entry on geologic hotspots:
http://en.wikipedia.org/wiki/Hotspot_%28geology%29
Here's a paper "Antipodal hotspots and bipolar catastrophes: Were oceanic large-body impacts the cause?" by Jonathan T. Hagstrum of the U.S. Geological Survey, 2005
http://www.mantleplumes.org/WebDocuments/Antip_hot.pdf
Here is a paper investigating antipodal impact affects in creating magnetic anomalies on the moon:
http://www.agu.org/pubs/crossref/1991/91JB00308.shtml
is there any evidence to show that all the dinosaurs died at the same time.lf this meteorite theory did happen then they would have all died within a year of each other wouldnt you think?
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Reply | Report Abuse | Link to thisBecause actual legitimate scientists with degrees in the relevant field proposed different hypotheses than Chixculub. There really isn't a legitimate minority view to AGW, just politically motivated anti-AGW propaganda.
Reply | Report Abuse | Link to thison a site www.mammoths.50megs.com
Reply | Report Abuse | Link to thisattempt is undertaken to reconstruct event of the past on continents - now is possible to prove particularly: as the flora and fauna varied,
in what degree homo sapiens took into account changes during following stages I - IV
Hey guys! Its been interesting reading the various points / theories raiesd, and I've come across another that is very interesting. It suggests that earth was hit by an asteroid-like object which penetrated straight through earth and 'burst out the other side'. The theory explains that the fallout from the impact created the landmasses of north and south America and Australia. It also suggests that the section of the impactor which exited the other side of earth also generated massive amounts of fallout and when this was combined with the displacement of the existing oceans it 'laid down' most of the landmasses of the northern hemisphere. The evidence provided within the theory includes most of the syrface area of earth. This is really interesting because when I look at the surface of earth from in the context of an impact AND an exit ...I have begun to think that this guy is on the right track... I found the theory at www.theimpactandexitevent.com
Reply | Report Abuse | Link to thisHey guys! Its been interesting reading the various points / theories raiesd, and I've come across another that is very interesting. It suggests that earth was hit by an asteroid-like object which penetrated straight through earth and 'burst out the other side'. The theory explains that the fallout from the impact created the landmasses of north and south America and Australia. It also suggests that the section of the impactor which exited the other side of earth also generated massive amounts of fallout and when this was combined with the displacement of the existing oceans it 'laid down' most of the landmasses of the northern hemisphere. The evidence provided within the theory includes most of the syrface area of earth. This is really interesting because when I look at the surface of earth from in the context of an impact AND an exit ...I have begun to think that this guy is on the right track... I found the theory at www.theimpactandexitevent.com
Reply | Report Abuse | Link to this..I should add that another element of the 'impact and exit event' suggests that "...huge amounts of earth's internal magma were ejected from earth when the exit event took place, and when the corresponding 'magma columnreached its zenith before collapsing back to earth the furthermost tip seperated and remained in space. This molten globule of superheated magma then cooled rapidly in the void of space and settled into orbit aound earth as the newly created moon."
Reply | Report Abuse | Link to thisI have looked into these claims and remarkably, the questions about the unusual angle of rotation of the Moon around earth do seem to be answered when comparing the Moon's angle of rotation with the angle of impact that the theory suggests.
It may be interesting for those who are students of tectonics and continental drift to note the location of the impact. The Chicxulub area was not in the location opposite the Decca India eruptions at the time of impact. The continents were different in location 65 million years ago.
Reply | Report Abuse | Link to thisErn_Malleyscrub Re: 'The Impact And Exit Event' : I'm of the opinion that I'd rather rely on what is suggested in this theory, which is visible and traceable today than supposition on what might have occurred some 65 million years ago. That's much too loooong a timescale for my brain to accept as a reliable source!!
Reply | Report Abuse | Link to thisWhile the large dinosaurs are extinct, descendants of the smaller ones are still around, as the birds.
Reply | Report Abuse | Link to thisThe Emperor Penguin is a "dinosaur" that has adapted to the most extreme conditions on the planet. No mammal could survive where they live.
Birds are far more intelligent than we used to think they were. Who knows in what direction they may evolve if human interference doesn't cause their extinction?
Excellent point, and the one I would have made if you hadn't :)
Reply | Report Abuse | Link to thisI still wonder why researchers don't explore the Grand Canyon as the smoking gun for the impact theory. The Chicxulub crater just doesn't seem deep enough. Have scientists really thoroughly investigated the rock layers in depth to completely rule our the Grand Canyon? How much iridium is found in the region of the Grand Canyon, for example? Would the asteroid that is theorized to have collided with the earth remained on the earth's surface or bumped away (like a billiard ball), taking into consideration its massive size? If so, where are its remnants? The Grand Canyon presents a vertical drop of 5,000 feet and spans 277-miles long within the Arizona desert. Its width is anywhere from 4-18 miles. Scientists are looking for a nice round baseball scar on the earth's surface. Think about the impact of an automobile accident. The area of impact would be the deepest. Suppose the asteroid that impacted the earth was on an angle, causing an irregular piercing of the earth's surface. The initial impact of such a large object would cause water/ocean and rock displacement. This would, in turn cause changes to the surrounding region, such as the creation of a desert and the unique rock formations located in the entire region of the southwest United States. Also take into consideration the effects of time and erosion. To create such a massive change, such as that in the Grand Canyon, and the deeply carved rock layers(up to 2 mile in depth), it only makes sense to explore a catastrophic theory related to its creation. It seems like an obvious choice, but yet, the most ignored.
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