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Re: Theories on the extinction of dinosaurs
I tend to agree with Jim. The overwhelming factor had to be that huge imact.
The issues of Deccan volcanism and oxygen levels have been invoked more as
alternatives than as co-variables. For the trapps, the fact that they had
been going on for some time before the extinction mitigates against them, but
does not rule them out. As for oxygen, I am deeply skeptical. Having studied
hemoglobin at some length in graduate school, I recall the "Bohr effect" (not
Nils). The hemoglobin molecule can actually ADJUST its oxygen-carrying
capacity based on O2 and CO2 levels, so changes in O2 are not obigatorily
fatal, just a burden.
After having watched Schoemaker-Levy slam into Jupiter, knocking holes in
its atmosphere larger than the diameter of the earth, I'm content that a
comet impact could scald the whole surface of the earth with a giant pressure
wave. This would leave only animals that dwelt under ground or water as
survivors -- cave-and burrow dwelling mammals and birds come to mind. Plenty
of modern examples of those.
So, impact alone could have done it.
- Tom Hopp