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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.
Well, it was 1 hour, forty minutes and thirty-three seconds.
Seriously,
"only those organisms already sheltered in burrows or in water were left alive"
What about Mosasaurs and Ichthyosaurs?
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And, of course, Bush and Halliburton did it.
This explains why the Creationists are still with us.
I'm not a scientist. but I did just finish a museum exhibit on paleontology a few months ago. I would assume that such large animals would have been faced with a new environment in which they had to adapt or die. They either went extinct, or adapted to meet the post extinction event, and evolved into other species.
I had horses on my mind from another thread and thought I'd entered the Twilight Zone for a minute.
After three in the morning you "could" show a little mercy. ;)
You are probably referring to Prof Robert Bakker. He is a vertebrate paleontologist. (Archeologists study historic and pre-historic people and culture.) Bakker is one of the leading researchers who has not jumped on the killer comet/asteroid bandwagon.
(I love Monte Python)
You make a good point. All sorts of species and genera died out with the Cretaceous-Tertiary extinction. Most people only focus on the larger animals, while ignoring the plant kingdom. But there was another natural kingdom to consider - the microfauna. I spent quite a bit of time in my career working with micropaloentological data. These data often provide a better, more complete record of climatological change than do terrestrial fossils. I do not believe the micropaleo records supports a "sudden" extinction.
If this is true, then why did the crocodiles, aligators, birds, and other assorted animals traced to that time period survive?
Isn't the soot the carbon we're looking for?
Also,wouldn't extra heavy,extended rainfall cause much of the carbon to be swept into the oceans and possibly be suspended for quite some time?
Thanks for the ping!
Very interesting.
Thanks for the link.
That is a neat animation of the crater forming.
What is your take on this then? A series of cumulative disasters?
Well, there you go.
I can no more imagine this than I could putting out a charcoal grill with a single ice cube; the deposits of which the author speaks could just as easily been deposited as silt over the course of flux and some several months of time.
That's not good enough, it's like saying you are clever because you're still alive, pure tautology.
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