Skip to comments.Study: Dinosaurs Died Within Hours After Asteroid Hit
Posted on 07/08/2004 12:29:19 AM PDT by LibWhacker
According to new research led by a University of Colorado at Boulder geophysicist, a giant asteroid that hit the coast of Mexico 65 million years ago probably incinerated all the large dinosaurs that were alive at the time in only a few hours, and only those organisms already sheltered in burrows or in water were left alive.
The six-mile-in-diameter asteroid is thought to have hit Chicxulub in the Yucatan, striking with the energy of 100 million megatons of TNT, said chief author and Researcher Doug Robertson of the department of geological sciences and the Cooperative Institute for Research in Environmental Sciences. The "heat pulse" caused by re-entering ejected matter would have reached around the globe, igniting fires and burning up all terrestrial organisms not sheltered in burrows or in water, he said.
A paper on the subject was published by Robertson in the May-June issue of the Bulletin of the Geological Society of America. Co-authors include CU-Boulder Professor Owen Toon, University of Wyoming Professors Malcolm McKenna and Jason Lillegraven and California Academy of Sciences Researcher Sylvia Hope.
"The kinetic energy of the ejected matter would have dissipated as heat in the upper atmosphere during re-entry, enough heat to make the normally blue sky turn red-hot for hours," said Robertson. Scientists have speculated for more than a decade that the entire surface of the Earth below would have been baked by the equivalent of a global oven set on broil.
The evidence of terrestrial ruin is compelling, said Robertson, noting that tiny spheres of melted rock are found in the Cretaceous-Tertiary, or KT, boundary around the globe. The spheres in the clay are remnants of the rocky masses that were vaporized and ejected into sub-orbital trajectories by the impact.
A nearly worldwide clay layer laced with soot and extra-terrestrial iridium also records the impact and global firestorm that followed the impact.
The spheres, the heat pulse and the soot all have been known for some time, but their implications for survival of organisms on land have not been explained well, said Robertson. Many scientists have been curious about how any animal species such as primitive birds, mammals and amphibians managed to survive the global disaster that killed off all the existing dinosaurs.
Robertson and colleagues have provided a new hypothesis for the differential pattern of survival among land vertebrates at the end of the Cretaceous. They have focused on the question of which groups of vertebrates were likely to have been sheltered underground or underwater at the time of the impact.
Their answer closely matches the observed patterns of survival. Pterosaurs and non-avian dinosaurs had no obvious adaptations for burrowing or swimming and became extinct. In contrast, the vertebrates that could burrow in holes or shelter in water -- mammals, birds, crocodilians, snakes, lizards, turtles and amphibians -- for the most part survived.
Terrestrial vertebrates that survived also were exposed to the secondary effects of a radically altered, inhospitable environment. "Future studies of early Paleocene events on land may be illuminated by this new view of the KT catastrophe," said Robertson.
understand that i have tried to be consistent in all this. i am not a velikovsky believer, it is just that i think he deserves a bit more credit for trying something new...
Well, I just hope that if we gen another of these crashes that it happens at night. It's cooler then.
That sounds like a good explanation. Whether or not they were warm-blooded is an interesting question. I'm sure the therapods were, based on what I have read. Leatherback Turtles have been shown to sxhibit some degree of warm-bloodedness.
Ooops, My bad. I guess I'm used to hearing crazy stuff coming from the Dino-Asteroid people I didn't even question it when I read it wrong.
Some owls burrow. Other birds live in caves.
Owls weren't around until the Miocene
But what about Parrots?
Also if the all terriestial birds were wiped out leaving just the cave dwelling birds to later evolve and fill the non-cave niches of modern birds why didn't more bats also diversify into the non-cave niches since they were "Open"?
Did ungulate mammals exist 65 myo? or did they evolve later?
Some birds do burrow, or take over existing burrows.
Plus even if Alligators and Frogs were underwater during the impact wouldn't they die when they came up to breath?
Many species of frog burrow into the mud and estivate during the summer or drought.
No particular reason 'gator eggs wouldn't survive, as you contend some dino eggs did. (KEWL!)
Just a guess - Bottom layer large/or low ejection angle (initial impact) spherules that settled out early. Mid layer turbite marls for the seiches of water sloshing in the Gulf of Mexico basin. Top layer lighter/high ejection angle (carbonate decomposition driven) ejecta.
I see most of the data supporting an impact and impact triggered vulcanism as consistent with the pattern of victims and survivors. I don't see anything that doesn't fit the hypothesis.
We are clearly operating off subtly different data sets, and have reached differing conclusions. It will be fascinating to see where and how we converge on a consistent understanding.
Once again, excellent post. This is why I love FR!
Butterflies don't burrow or swim
How about caterpillers?
How about cocoons? Wouldn't they protect some larva from the effects?
They don't swim or burrow either, Plus they have the most voracious appetites on the planet and in a devastated world where all plant life is gone they would have starved
How about cocoons? Wouldn't they protect some larva from the effects?
Butterflies don't make cocoons (Moths and skippers do) they basically just get hard and become chrysalides so they would be very exposed to the heat/firestorm, Plus even if they did, silk is not exactly fire and heat proof so they would still be toast.
It is a lot easier for small animals (birds, mammals, lizards, etc.) to find themselves in sheltered and protected areas during firestorms and other such than it would be for multi-tonne critters. I can see birds surviving just by being in fortuitous and unexposed areas.
Land animals weighing more a couple Kg were wiped out. Small critters tended to survive, they were more numerous, and widely dispersed. They also tend to be hibernators, that helped. They need less food, etc.
The classic bigger they are, the harder they fall.
On land roots and seeds tend to survive fire and soil tends to buffer acids so vegetation could re-establish fairly quickly.
In the ocean, low pH precipitation, 'nuclear winter' darkness and surface heat kicked the legs out from under the food chain. Plankton doesn't go to seed, or have roots...
Did they blame Bush for this?
Not all Dinos were giants so what about the small Dinosaurs? Couldn't they have hidden also? Many of the mammals that survived them were bigger
Small dinosaurs did survive -- in the form of birds.
Think it rained for 40 days and 40 nights in the middle east after that event?
Prolly. And in keeping with Jewish tradition, it was an acid rain that burned the unjust...
You are wrong. See T. Rex and the Crater of Doom. The clearest evidence of an abrupt extinction is the abrupt and total change in the foramintifera.
Actually the clearest evidence against an abrupt extinction is the little change in plankton
a) Diatoms. The K-T event did not much affect the diatoms. Harwood (1988), based on studies from Seymour Island, eastern Antarctic Peninsula, the first to record siliceous microfossil assemblages across a K-T boundary sequence, notes that diatom survivorship across the K-T boundary was above 90 percent. Resting spores increase from 7 percent below to 35 percent across the K-T boundary.
b) Dinoflagellates. Dinoflagellates also were little affected by the K-T event (Bujak and Williams, 1979). Brinkhuis and Zachariasse (1988) record no accelerated rates of extinction across the K-T boundary in Tunisia. Nor does Hultberg (1986) in Scandinavia. Danish dinoflagellates responded more by appearance of new species than by extinctions (Hansen, 1977), as did Seymour Island assemblages (Askin, 1988).
c) Yes other plankton did suffer massive extinctions but it wasn't because of the Asteroid or K-T event.
Marine calcareous microplankton, the coccolithophorids and planktonic foraminifera, were hit hardest of all by the K-T event. Thierstein (1981) proposes that the coccolithophorids extinctions were the most severe plankton extinction event in geologic history; via a "deconvolution" process, Thierstein (1981, 1982) reduced a Cretaceous-Tertiary "transition," in which Cretaceous assemblages were replaced by "new" Tertiary taxa, to an instantaneous catastrophe. Perch-Nielsen et al. (1982) note that the "catastrophic event"at the K-T boundary did not result in geologically instant extinction of the calcareous nannoplankton, and that most Cretaceous species survived the event. At DSDP Site 524, a sample above the K-T boundary contains 90 percent Cretaceous species. Isotopic analyses indicated that the Cretaceous species were not reworked specimens, but represented survivors of the K-T event that continued to reproduce in the earliest Tertiary oceans. The relict species became extinct some tens of thousands of years after K-T boundary time, probably via environmental stresses.
d) Antia and Cheng's (1970) work on survival times of phytoplankton species in complete darkness indicate that 1 month of complete blackout would produce 13 percent extinction, 3 months 68 percent extinction , and 6 months 81 percent. Thus, the 6 month to 1 year global blackout predicted by Wolbach et al. (1985) would have obliterated diatoms, dinoflagellate, and coccolithophorids precisely at the K-T boundary. A blackout event is not reflected in the algal record. The calcareous coccolithophorids and foraminifera were likely affected by pH change of the marine mixed layer via CO2 mantle degassing by the Deccan Traps volcanism.
So please tell me how did photoplankton who depend on sunlight for their very exsistance not only not die out but actually thrive during a global blackout??
e) And the real kicker is, Microfossils are actually found in the Chicxulub crater itself!!! and even though they are essentially at "Ground Zero" they show no ill effects.
Or it didn't happen as this scientist says it did, which is the most likely slice of Occam's Razor.
It is statements like this that give me pause about Bob Bakker's sanity.
Where in South America, does the atmospheric temperature NOT vary by at least ONE degree? Even at night? Can't happen.
An amphibian moves between water and land. The difference in temperature between the two would vary by at least one degree.
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