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Re: Asteroid impact finally confirmed?



From: Jonathon Woolf <jwoolf@erinet.com>
 > Finally, sediments showing a more normal rate of fossilized animals.

Containing what fauna?  A depauperate Cretaceous fanua?  A low
diversity early Paleogene fauna?  A full diversity fauna of some
sort?  [This is a critical point in arguing that this impact
was the *cause* of the extinctions].

 > I don't think it makes a whole lot of sense.  The
 > general outline hangs together, but one simple question still lacks an
 > answer. Very simply, if this asteroid-induced holocaust swept the
 > world, reached every continent and every corner of the ocean, wiped
 > out dinosaurs, mosasaurs, pterosaurs, ammonites, etc., _everywhere_,
 > with 100% success -- then how did anything survive at all?
 > 
This, actually, is fairly easy to answer.  The answer has two
compnents.

1. Even the largest most devatating explosion will not have uniform
effects over even a single continent, let alone the entire Earth.
Mountains, canyons, isolated seas, undersea ridges, and many other
things will partially protect many areas.  Also there is powerful
evidence that the impact was asymmetrical, with the strongest shock
going northwest towards the American midwest and northwest coast.
Thus many things in may [paces will survive, as small local populations.

2. The full effect was not due just to the initial holocaust,
but also to the persistant climatic effects from the aerial debris.
This phase may well have lasted several years.  Thus the final extinction
of most species will be due to the inability of the small remnant
populations to cope with the changed climate.  The survivors will
be those species that can cope with the change even at small population
sizes.

swf@elsegundoca.ncr.com         sarima@ix.netcom.com

The peace of God be with you.