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Re: Theories on the extinction of dinosaurs




TomHopp@aol.com wrote:

> 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.

Hmm...why does there have to be one distinct cause of extinction?  I think the
extensive (not sure that's quite the right adjective to use =) volcanism at the
Traps would have brought on enough of a climactic change to cause definite
problems.  Acid rain, ash, all sorts of fun stuff.  If I remember correctly, the
Deccan Traps was one of the most violent periods of volcanism within the last
half-billion years...Interestingly, the worst case of volcanism in this time was
the Siberian Traps, which was at the Paleozoic-Mesozoic boundary--another mass
extinction.  There was most certainly an impact in the Yucatan, but it could 
have
just been the final insult, so to speak.


>     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.

One thing came to mind as I read this:  what about all the large aquatic 
reptiles
that died out at the end of the Cretaceous?  If the asteroid/meteor/large 
falling
rock from space was the cause of their extinction, why didn't it kill off the
sharks and sea turtles and crocodilians?   I could see where their
cold-bloodedness could be an asset, where they wouldn't have to eat as much, but
would this imply the mosasaurs and plesiosaurs were warm-blooded?  Or just too
darn big?

On another note, I tried to get a group of friends together to go see the stuff
at Nat.Geo. this weekend, but no one wanted to go. =(  but..but...dinosaurs are
neat, darnit!!

Going back into list-lurk mode,
Andrea Kirk
Undergraduate, Computer Science
University of Maryland