Re: Extinction

["Marcel F. Williams" <hydra9@flash.net>]

> 
> King, Norm R wrote:
> >
> > I always have had a problem with climatic extinctions of major taxonomic
> > groups.  Like dinosaurs.  I know they couldn't migrate very successfully,
> > for reasons Joe Daniel brought up.
> >
> > Say it gets a lot colder, fast.  What about the dinosaurs (or whatever) that
> > already live close to the equator?  I am always impressed by the daily high
> > temperature readings in Freetown, San Salvador, Quito, Nairobi, etc. during
> > the middle of the winter, when it might be zero degrees here in Indiana.  If
> > our temperature regime were to suffer a further decline, I'll bet just about
> > everything already living in equatorial zones would survive there.  However,
> > the tropical climatological zone would surely shrink latitudinally.  But
> > some dinos or whatever (e.g., banana trees, etc.) would hardly be affected,
> > if at all.
> >
> > So, during climatic changes, some species or genera should survive.  Later
> > on, those could repopulate areas (probably very slowly) that may indeed have
> > been vacated due to the climatic downturn.  The fossil record would likely
> > show a diversity decrease that slowly recovered.  But total extinction of
> > every member of the group, everywhere?  I wonder.
> 
 MW: There was obviously no nuclear winter as the result of the asteroid
> impact. And if it was an ocean impact then it is likely that it produced
> a super 'greenhouse' effect, IMO. Water absorbs titanic amounts of gases
> from the atmosphere-- and a disproportionate amount of carbon dioxide
> relative to oxygen. And the colder the water-- the more carbon dioxide
> is absorbed. However, the heat from an ocean impact from a huge asteroid
> would have not only heated up the oceans (reducing CO2 absorption) but
> the increased evaporation of sea water would have put even more CO2 into
> the atmosphere. This could have created a global  super greenhouse
> effect that would have raised global temperatures and  increased
> rainfall and the tropicalization of the planet. Birds, small mammals,
> crocodiles, amphibians, turtles and other small reptiles  love these
> kinds of hot humid and wet conditions. But large herbivorous dinosaurs
> disliked swampy environments but would have gradually lost their dryer
> open country niches and gone into extinction as greenhouse conditions
> gradually increased-- and their large carnivorous dinosaur predators
> would have followed.
> 
Marcel F. Williams
 3/30/00