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Re: Theories on the extinction of dinosaurs

Seosamh wrote:

> I'm trying to assemble some meaningful description of the interactions
> among these observed (in the fossil record) events. Crudely, the
> body strikes the Yucatan, a concussion travels through the Earth and
> half a globe away the Deccan eruptions begin. The combined effects
> of these two on the atmosphere change its chemistry to something
> higher in oxygen.

Er ah, the following is from memory, so may not be correct in all of its
reconstructed details.  I'll fish out my sources over the weekend if you wish.

Your scenario may have a couple of problems with timing and direction of rate of
change.  The Deccan traps appear to have been several million years older than 
impact (reminds me of Dr. Asimov's thiotimoline), and the amber studies appear 
indicate that at the end of the Cretaceous, the oxygen content of the somewhat
more dense atmosphere was about 25%, which is about 25% higher than now, that it
was already falling toward the present level, and had been doing so for some
time.  At the end of the Carboniferous (sp?), the oxygen content had been about
33% (which is about the level at which the biomass could be expected to
spontaneously combust), which then declined precipitously to a low of about 15%
before climbing back up to the high 20's again.  Also, if estimates of the mass
and velocity of the impactor are correct, then the amount of energy it placed 
the earth, oceans, and atmosphere can be visualized by taking the largest 
bomb ever exploded (Russian, if I recall), strapping them together in clusters 
seven, and then simultaneously exploding those clusters world&ocean-wide, at a
cluster spacing of slightly less than five miles.  Rather than saying that it is
accepted that this alone is not enough to fully  account for the complete
extinction of all the life that was extinguished at the end of the Cretaceous, 
say it was a miracle that anything survived.

I personally doubt that the impactor was quite 10km in diameter, or that it was
going quite that fast (the energies quoted imply a velocity of about 30 
about dead in the middle of the probable 11-50 mile/second range, and I also 
the accuracy of the amber measurements, but the trends they appear to show are 
the opposite direction of your scenario.

Best wishes,