Re: Extinction

[dbensen <dbensen@gotnet.net>]

Just for kicks, I think I'd like to dip in my oar here.

It's been pretty well demonstrated that there _was_ an impact 65 million years
ago and that dinosaurs went extinct around that time.  Therefor, it is 
reasonable
that the extinction of the dinosaurs was caused by the impact.  However, it has
also been shown that dinosaurian diversity was already dropping before the big
chunk of rock (I don't want to start another argument about what such a chunk 
was
called) hit the Earth.  It is possible that some unrelated crisis was effecting
the dinosaurs and the asteroid finished them off, but that would be a tremendous
coincidence, perhaps too tremendous to be taken seriously.  What about that
theory that Earth passes through a cloud of space junk ever couple of million
years?  Is it possible that our solar system was simply passing through a more
crowded region of space in its orbit around the galactic center 65 million years
ago?  If so, then perhaps the drop in dinosaur diversity toward the end of the
Cretaceous was caused by multiple smaller impacts as the Earth passed through
this cloud, finishing with the last big one that hit the Yucatan.  Such impacts
wouldn't have blanketed the earth in iridium like the big one did (and so
wouldn't show up in the worldwide strata), but would have slowly screwed up
Earth's weather and ecosystems.  Such a long-term bombardment could be proved if
areas of high concentrations of iridium were found in small areas before the KT
boundary.

Dan