[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Theories on the extinction of dinosaurs




On Mon, 15 Nov 1999 TomHopp@aol.com wrote:

> In a message dated 11/15/99 5:33:53 AM, Larry Febo wrote:
> 
> << also,...not a closed system,...V would have expanded to relieve much of the
> 
> pressure......gee!....it`s all coming back now! >>
> 
> My thinking on pressure increase = temperature increase is illuminated by 
> having watched a few old A-bomb films since this thought arose. If you look 
> carefully (and VERY quickly), immediately following the flash, you will see 
> the pressure wave rip outward in a smooth arc. If you see billows arising 
> (smoke or steam) you're too late! The pressure wave seems to my eye, to be 
> contained by the atmosphere above it, going out along the ground/ocean at an 
> incredible rate. Blink and you'll miss it. So the closed system I'm thinking 
> of only exists momentarily at each new increment of expansion, but at the 
> shock front, PV=nRT still seems to operate momentarily. Long enough to heat 
> wood to kindling temperature or water to . . . . well, ouchy hot.
> 
> I may have to surrender to those who suggest that the ground-hugging shock 
> wave couldn't go much farther than one hemisphere. So get ready, undaunted I 
> propose: As in the Schoemaker-Levy impact, suppose that a string of impactors 
> came in (didn't somebody mention another crater in India a few posts back?). 
> In the Jupiter example, the planet turned under the string, and received a 
> globe-encircling series of hits AT THE SAME LATITUDE. Now, Chixulub is 
> relatively close to the equator, so the chain of hits in that case should 
> have been near-equatorial. Voila, earth is swept by a series of 
> hemisphere-obliterating events, all on the same day. Ouch.

        I seem to recall from Dark Sun: The Making of The Hydrogen Bomb
that there is an upper limit to the effective size of an H-bomb because
past a certain point, it just blows a hole in the atmosphere and sends the
blast out that way. So it's not like you're bombing the whole planet. This
hole would probably be a lot smaller than the ones in Jupiter, considering
that our atmosphere is held more loosely. And although doubtless heat,
molten debris, tidal waves and the like are going to be nasty, it's that
layer of iridium clay- suspended in the atmosphere- which is supposed to
have been the real killer, and that would explain why you lose planktonic
organisms (photosynthetic food chain).
        Regarding multiple impacts, it's my impression that the dust layer
gets thicker as you go closer to Yucatan, as opposed to being more evenly
distributed. Still, I suppose you could have much smaller impacts away
from it, and maybe get the same effect.
        Not that I have any authority but my gut feeling is that if you
manage to wipe out every single species of dinosaur, enantiornithine,
ammonite, pterosaur, mosasaur, etc. down below a level from which they can
recover, you're dealing with something massive, simultaneous, and
devastatating, and I would expect that neornithines and mammals, far from
being unscathed, were hit and hit hard. But as Darwin shows with his
example of a couple elephants breeding enough pachyderms to overrun Africa
in 500 years, there is an infinitely huge difference between being 100%
annihilated and only 99.999% annihilated. So the mammals got away? I
imagine if you could go back and talk to one of the little Mesozoic
furballs, with it's frost-covered, singed fur, starving in a perpetual
twilight broken only by cold, starless nights, it would squeak at you:
"Scot free? We got away scot free? Oh, I wish I shared the fate of the
dinosaurs!" 
         But the subsequent recovery and diversification would be
incredibly rapid- nature responds quickly in the wake of disturbance, as
you can see from the recolonization of Krakatau, or the way that many
species bounce back from the brink when you let them.
 I wonder if even 10,000 years after a bolide impact you wouldn't see an
incredibly lush world, and if it was somewhat poor in species, it would
probably be rich in incipient species.
        As to dinosaurs being on the way out, as is frequently pointed
out, that is an impression taken from what we've known of the Hell Creek,
and there are other places that don't show the same thing- this years SVP
had a talk on the "Sandy Site" which includes things like
pachycephalosaurs and oviraptorids in addition to other dinosaurs, and
shows that the Triceratops-Edmontosaurus-Tyrannosaurus fauna was not
typical of everywhere in the latest Cretaceous. I think that North
American alvarezsaur is also from the Hell Creek; Anton Wroblewski also
did a study a few years ago looking just at teeth and didn't find any
change in the number of families running around as you neared the
boundary. 

        -N