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Re: Extinction scenarios




TomHopp@aol.com wrote:

>     It seems to me that 65 MYA, the eruption of white hot water vapor (from
> the impacted ocean)

Actually, there wouldn't be water vapor from the immediate impact area.  The
kinetic energy at the impact site is enough to break the bond in the water
molecules, and then strip the outer electrons off the atoms, creating a plasma.
Some water would reform after the plasma cooled sufficiently.

> but no one, to my knowledge, has really run down the possibilities
> for destruction by the shock wave itself.

About 40-45 years ago, there was a really good article on the subject in John W.
Campbell's "Astounding Science Fiction" magazine.  If I remember correctly, the
author even placed his hypothetical 1 mile dia. asteroid impact in the Gulf of
Mexico.  He also pointed out that an ocean impact is more devastating than a 
land
impact. I think he was also the first guy to postulate that the kinetic energy
applied to the resulting plasma might generate gamma radiation intense enough to
kill anything within line of sight even before the shock wave arrived.

> 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.

See above.

>  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.

I don't think it would be quite that great, as the intensity of the pressure 
peak
would diminish roughly with the square of the distance from the impact point.
It's calculable though, and somebody ought to give it a shot.  As an aside, the
the tidal wave from the much smaller Krakatoa explosion was detected in England 
on
each of it's first several passes around the world, and the pressure wave was
directly audible for 3000 miles.

>  This of course, would be
> your closing observation on conditions in the Late Cretaceous.

Well said,Jim