Re: Extinction

[@lepomis.psych.upenn.edu:murphy!acmcr!vr@uunet.uu.net (Vicki Rosenzweig)]

I think you're assuming some of what you hope to prove. Is there
any evidence that the Chicxulub impact reached all the way to the
mantle, as you describe? (I raise this because some of the most
dramatic effects you're invoking here seem to require mantle
material as distinct from dust and ash.)

Also, you can't simply say that it's impossible that such an impact
wouldn't lead to massive extinctions until/unless we've established
the connection between a cometary or asteroid impact (at _some_ point
in Earth's history) and extinctions. (I'm inclined to think that there
would be some damage, but how widespread it would be is still in 
question.)

Third, nobody (as far as I know in this discussion) is denying the
connection between the impact and the iridium layer--the question is
how we can be sure that the impact, rather than the Deccan basalt flow
or some other cause, led to the K-T extinctions.

(I should note here that I'm inclined to believe that there is a
connection between the impact and the extinction, but I don't regard
it as proven yet. Provable, perhaps, but not proven.)

Vicki Rosenzweig
vr%acmcr.uucp@murphy.com
New York, NY