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Re:Dinosaur extinction



At 05:23 PM 2/24/98 -0600, Seth Ellestad wrote:
>
>Hmmm--and the Permo-Triassic was an even greater extinction.  Any 
>evidence of an even larger bolide impact (or impacts) associated 
>with that one?

Not that I know of.  In fact there is really no substantial evidence of an
impact at that time at all.  If there *was* one, it was almost certainly
*smaller*.

>  I
>tend to think, based purely on educated guesses, that we'll find 
>out that extinctions occur when a combination of changes puts 
>stress on certain types of organisms, the actual extinctions then 
>probably being triggered by catastrophic events that happen to
> occur at those times.

Yep. More or less what many paleontologists who reject the simple impact
hypothesis believe.

Please note here, I never said the impact was not *involved* in the
extinctions, just that *by* *itself* it was not sufficient.

>>The closest we have today are the Iceland volcanics.  (And it is
>>interesting to note, the Late Pliestocene/Holocene has been a time of
>>moderate extinctions).
>
>"Holocene".  That seems to be a false division to me, one based on 
>culture rather than significant changes in the turnover of life on 
>Earth.

Yep, I agree.  If it were up to me, I would make the Holocene, at most, a
substage within the Pliestocene.

But then, the current round of mass extinctions aren't over yet.  When they
are, they may start to rival the K-T extinctions.

--------------
May the peace of God be with you.         sarima@ix.netcom.com
                                          sfriesen@netlock.com