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Re: Extinction scenarios



Tom Hopp wrote:
 
> As I recall, the writer pointed out that the hypersonic expansion of > gasses 
> would create a massive pressure wave capable of propagating  > for great 
> distances (going fastest and farthest in the denser       > atmosphere at sea 
> level).  As elementary physics class tried to      > teach us, if you 
> compress a gas, without adding heat, it will still > heat up, due to the 
> increased rate of molecular collisions when      > density is increased.  
> Thus, a propagaing pressure wave will heat    > the atmosphere as it passes, 
> then the air will return to its          > original temperature after the 
> pressure wave is gone.
>     
> The thing is (and I just MIGHT be the first to state this) the        > 
> unfortunate coincidence of a large bolide hitting a shallow sea over > deep 
> carbonate rocks might have created an impact unique in the      > magnitude 
> of its shock wave. Undoubtedly, the shock wave would be    > strong enough 
> near the impact to create the white-hot flash that     > Alvarez and others 
> have mentioned, but it seems to me that the       > PROPAGATING SHOCK WAVE, 
> if big enough, would have also heated air to > white-hot temperatures.  The 
> question is: over how great a distance > could this wave carry lethal heat?  
> My personal bias is: ALL THE WAY > 'ROUND THE WORLD.
>     
> Thus, you might be a Muttaburrasaurus quietly sipping at a watering > hole in 
> Australia, far from the impact, when the first thing you     > noticed was 
> that you were hurtling through the air amid white heat.  > This of course, 
> would be your closing observation on conditions in 
> the Late Cretaceous.

While I would certainly not deign to argue the physics described above,
I do have to ask (as Peter Buchholz already has), how did *anything*
survive this doomsday scenario you've postulated? Seems to me that this
level of catastrophe would pretty much wipe the Earth clean of *all*
life, no? 

Brian (franczak@ntplx.net)
http://www.paleolife-art.com