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Re: Extinction thing



 From: "Alex W. Hertzog" <ahertzog@ozarks.sgcl.lib.mo.us>
 > A friend of mine, knowing about my interest in dinosaurs, told me about a 
 > radio program she heard which said that there is a theory going around 
 > now about the dinosaurs' extiction involving metorites and sulfer in the 
 > air, and that it's very very likely that this iswhat really happened. 
 > Something like a >90% chance. Anyone else heard this? Anyone know about 
 > this theory's credibilty?

The theory is credible, and is under serious consideration.
I would disagree with the 90% certainty ascribed to it though.
In fact I would put it closer to about 50% certainty.

There is considerable evidence that one (or more) impacts occured
at the time the extinctions happened.  There is good, not entirely
conclusive, evidence that this impact occured near Chicxulub in
the Yucatan.  *If* the location mentioned is correct, there would
have been a great deal of sulfur released by the impact, as the
Chicxulub impact struck sulfur-rich sediment.

There are two major caveats to put on all of this:

1.  There has been one published paper which presented evidence that
the C. impact structure was created *long* before the extinctions.
If this is so, it had nothing to do with the extinctions.


2. There is some suggestive evidence that the extinctions occured
in several steps over a long span of years.  If this is so, then
either a swarm of impacts was involved, or the impact was not the
sole determining cause of the extinctions.  It is worth noting that
the Deccan volcanic episode spans the period of the extinctions,
even if they were episodic.

swf@elsegundoca.attgis.com              sarima@netcom.com

The peace of God be with you.