Study: Dinosaurs Died Within Hours After Asteroid Hit

University of Colorado News Center ^ | May 24, 2004

[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.

[FreedomCalls]

FWIW,there's at least one freshwater turtle that can take in oxygen from the water through it's anus.

And I thought only Michael Moore could do that!

[null and void]

T. rex and the Crater of Doom, by Walter Alvarez, Princeton University Press. ISBN 0-691-01630-5

Pages 86-89 give a brief description of the Signor-Lipps effect, and it's implications for determining the abruptness of an extinction event.

Simply, an abrupt die off will be clear if there are abundant specimens on one side of the fossil record, and none on the other, but rare specimens blur the die off date, and make it look gradual.

Foraminifera, very common, sharp discontinuity in the fossil record.

T. rex, known by a few specimens, no clear discontinuity in the record.

[SunkenCiv]

	Asteroids: Deadly Impact National Geographic
	Shoemaker: The Man Who Made An Impact by David H. Levy

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[RightWhale]

I am appreciating Einstein more all the time. He seems to have lent his considerable support to those who think outside the box while staying somewhat near true facts. Einstein himself did that with stupendous success and being thoughtful and reflective apparently knew he did that. He had the confidence that can come with such success to want to encourage others. I still hope we can overcome his Relativity and also improve on his photon.

[null and void]

Me too.

[Free Trapper]

http://www.straightdope.com/columns/011116.html

Sorry I can't link but that should take you to some info on "butt-breathers".Besides the turtle there's a little about dragonfly nymphs and sea cucumbers.

Aracelis,no educated person should be without a firm knowledge of "butt-breathing" turtles,so I pinged you on the slight chance you had missed out in your studies. ;)

[Free Trapper]

Hey Scout,long time-no see. :)

Been in and out of the running for a while cause of meds,etc. but having longer lucid periods all the time.

Sniff out post #166.Glad to see you. :o)

[Aracelis]

However, I fear a misleading impression has been given that all turtles can do so--not true. A few "side-necked" turtles (like the Fitzroy River guy) can, but the vast majority of turtles either don't have cloacal bursae, or have them but can't use them for breathing. I reviewed all available evidence on the topic in a recent paper in the Journal of Experimental Zoology (see: Journal of Experimental Zoology), in which I also proved once and for all that, whatever turtles are doing with their butts, they cannot drink through them. Science marches on. --Chas Peterson, Department of Zoology, Oklahoma State University, Stillwater OK

You're quite correct...my education was incomplete. :)

[ZULU]

I knew this about dragonfly nymphs. I also knew that certain turltes could do this, like the soft-shells (Amyda or Trionyx? They keep changing the genus). That other turtle they mentioned in your article is a new one to me. I never heard of it before. It seems its far better at it than softshells.

Turtles and dragonfly nymphs have a rather sedentary lifestyle. And most turtles use their lungs to breath just like you and me.

I guess Ichthyosaurs and Mosasaurs (which are supposedly closely realyed to modern day monitor lizrds) must have had a far more active lifestyle. At least their body shapes would so indicate.

Interesting stuff.

[Aracelis]

Have you seen the Caloris Basin on Mercury? It is a crater the size of Texas and it fills about one-fourth of an entire hemisphere on Mercury.

Indeed, there are many examples of large impact craters. But as you can see from your images of Caloris Basin, this happened a very long time ago, as evidenced by the number of more recent (and much smaller) craters marring the outline of Caloris Basin.

And here is where I become very hesitant to accept the idea of a large bolide impacting and causing the K/T extinction event: by the time the Sinclair dinosaur lumbered across land, most of the large remnants of solar system formation had been swept up by the still-forming planets.

No, I do not discount the possibility that some rogue chunk of matter was still roaming about, however I think the chances of this happening were very, very small. Until more evidence is presented, I will remain quite puzzled.

[Aracelis]

Of course, I should clarify that I do think we have enough evidence that some sort of bolide impact contributed to the demise of the dinos...but not as the sole cause.

[Free Trapper]

"Butt-breathing turtles"

Hope that worked...my education is continuing. :)

[Aracelis]

Worked great! :) now just make sure you insert the "< /a>" right after the name of the reference, but before your comments. :)

[Free Trapper]

The Australian turtle must get a lot of oxygen in this way.As I understand it,some other types may have more limited abilities.

Our native softshells,spineys in particular,are so active that a little boost to the air supply would be a big plus.

Would be interesting to find out if those giant Asian softshells near extinction have the ability.

[Free Trapper]

Thanks a lot for the help.I caught the deleted code right after posting.It's after 3:00 AM,don't you know. :O)

[VadeRetro]

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.

Yes, and with the reproductive rates of insects and other small animals the main limitation on speed of bounce-back is the recovery of the food plants.

[RadioAstronomer]

RA, you'd have a better grasp of the physics behind this...what do you think? Locally, yes, I can accept this hypothesis, but globally? Musta been one h*lluva bolide, and I'm not convinced that smaller biota would have survived even in well-protected niches...availability of free atmospheric oxygen being a major factor.

Not seeing the thermodynamic models, it is hard to speculate. However, after talking with some of my colleagues yesterday, the jury is still out with me on this one. If there was this world wide thermal event, there should be evidence in the KT layer suggesting such. Is the carbon ratio in the KT layer synonymous with this type of thermal event? I just don't know. However, there is at least some recent data (albeit scaled down by a very large factor) from the Tunguska event of 1908. The best evidence to date is that a meteor exploded during entry into the Earth’s atmosphere. Trees were flattened as far away as 30 kilometers due to this explosion prior to surface impact. And interesting side note: There is an increase of Iridium in the local area, not unlike the Iridium found in the KT layer.

Why did the meteor “explode” prior to impact? It has been proposed that the aerodynamic pressure build up of the atmosphere was greater that the ability of the meteor to remain in one piece. This caused it to explode roughly 10 kilometers above the Earth’s surface with an estimated energy release similar to a 15 Megaton thermonuclear device. This in effect turned the kinetic energy into heat energy. The forest directly under this fireball was immediately ignited.

The 64-dollar question is would it be possible for a meteor with the mass required for the KT event also create enough of a pressure wave to have a similar breakup? Since there is evidence of a crater (Tunguska has none), this suggests the meteor did not succumb to a total atmospheric breakup (kinetic energy to heat energy). With this in mind, would there be enough ejecta during the reentry releasing kinetic energy to heat coupled with the actual impact to create this worldwide heat pulse?

[Bloody Sam Roberts]

I remember what was said but not who said it.

I have no doubt that it was Bob Bakker from your description and from his theories on the "dino-die-off".

He believes that there are plenty of natural, non-asteroid explanations for the demise of the dinosaurs. Posible viruses and land mass shifts and climatic changes being chief among them.

But his statement about the South American frog as related by you only reinforces my opinion of him as something of a noodle head.

[PoorMuttly]

Y'know...so glad that this subject has been raised. Since Muttly was an even littler pup, and found out about this ability in others...he has been jealous.

Consider the possibilities! Eating without having to stop to breathe (a serious Muttly problem), endlessly digging perhaps with a butt snorkel, so for example, Muttly could securely bury his precious secret valuables from other Muttlys, even under and behind this annoyingly flooded flying saucer stuck into this mastodon deep under the birdbath in the back yard....

[null and void]

There was a recent Scientific American article about the near global scale fires started by the ejecta.