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Re: Dinosaur Extinction (Again)

J. Bois wrote:

> OK.  What killed the dinosaurs?

Meteors, comets, and asteroids fall to earth as naturally as rain.
Periodically, very large bodies strike the earth carrying energies millions
of time more powerful than available from all the world's nuclear arsenal
at its height in the 80's.

These impacts do occur, there is no doubt.

Though our active planet quickly obscures their traces, we need only look
at our moon and other terrestrial planets to gain some idea of their
frequency.  Looking at the moon, it is clear that some of the impacts are
large enough to cause great damage to the earth's life.

So let's say we want to scan the geologic record for evidence of one of
these impacts -- what would we see?  We would see a particulate layer
deposited widely over the earth.  The particulate layer would contain ash
from fires initiated broadly and debris from both the impacter and the
earth.  How could you identify material as possibly coming from the impact
body?  We would look for trace elements that are unusually high in these
bodies -- iridium is just such a key fingerprint element.  Finally, we
would look for indications in the fossil of a widespread, severe ecological
disruption.  Scanning the geologic record, we find at least one, very, very
promising instance and that, of course, is at the KT boundary.

It certainly looks like an impact initiated disaster, but, still, earth's
own activity could cause similar signs.  The only way to be reasonably
certain is to find a very large impact site dated to near that date.

There is at least one large impact site confirmed to date at the KT
boundary, and, as you know, it is at the Yucatan peninsula in Mexico.  The
site is large enough to, at the very least, cause mass extinctions in the
same hemisphere.

Finally, a body large enough to cause the Mexican crater would almost
certainly have been but a piece of a larger body shredded by earth's tidal
forces (similarly to the S-L comet that recently struck Jupiter).  Impact
sites in the Pacific Ocean discovered a few years ago look contemporary to
the Mexican impact and would further the worldwide destruction.

So, we have found an extremely large impact occurrence by merely scanning
for secondary effects in the geological record.

One piece of evidence we searched for was a mass extinction.  By finding
the impact crater by using this piece of evidence can we conclude that the
extinction was caused by the impact?  Almost certainly, yes.  The impact in
Mexico alone would have had extremely dire consequences for all life in the
areas near the impact.  The only indication of such a die-off occurs at the
KT boundary, so we can be sure that is when the impact occurred.  Could it
be that this was just a case of bad timing and that the dinosaurs (and a
huge number other species) would have died out anyway?  Statistically this
is _highly_ unlikely.  Furthermore, all other theories are speculative,
contentious, and contradictory (you may quote sources that cite a gradual,
slow die off, and I can quote those who have found that the dinosaurs'
populations and diversity shows no unusual dip at all).  And yours --
demise by egg eating mammals -- is _absolute_ speculation with no concrete
evidence and, frankly, tries the imagination.

Mr. Bois, the iridium/ash layer is a fact.  The enormous Mexican impact
crater is a fact.  The coincidence with the global mass extinctions is a
fact.  Although I find all other theories to be far too speculative for me
to seriously consider, especially in light of the impact evidence, yours is
devoid of any direct evidence.  If you believe your ideas then find hard,
direct evidence and stop beating us over the heads with vastly
extrapolated, indirect, unsubstantiated reasoning.

Van Smith
Watch _Babylon 5_.  It is the very best of modern television drama/sci fi.