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Re: Extinction scenarios



    As I have indicated before, the bolide smacking into the earth could and
did do a lot of damage - we've seen about half a dozen effects mentioned
here on this list already.  However, one thing that is unclear is exactly
how much energy was released into the shock wave, how much into ionizing the
ocean, how much into vaporizing the ground, and how much was dissipated
prior to the actual strike.  If the angle was less than 40% (I think that
was the threshold - or something close to that), some ozone layers and other
atmospheric gases would be stripped off.  Also, quite a bit of the energy
and speed that the bolide had would be dissipated by the low angle.  The
slower moving , less energetic bolide would still do tremendous damage, but
not necessarily as much as some people (esp. that guy on sci.bio.evolution)
have indicated.  If the heat and air shock wave went 160 degrees around the
planet (a reasonable assumption), there are plenty of places that would be
relatively untouched (e.g.  the western slopes of the Rocky Mountains'
precursors).  There would be lots of weird local effects even fairly close
to the strike (more than 85 miles from the center of the strike).  I
personally do not think that the freezing temperatures would last more than
a few months, and most of the most recent calculations have tended to
support that.

    Yes, John, there are quite a few killing mechanisms available from the
bolide strike, many of which may have contributed to the various apparently
simultaneous extinctions {NOTE the use of the words 'apparently
simultaneous' - geologically speaking, of course.  :-)  }.  I don't think
that ALL of the mechanisms did anything appreciable, but some of them.......


    Allan Edels

-----Original Message-----
From: John Bois <jbois@umd5.umd.edu>
To: TomHopp@aol.com <TomHopp@aol.com>
Cc: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Sunday, August 16, 1998 10:02 PM
Subject: Re: Extinction scenarios


>
>
>On Sun, 16 Aug 1998 TomHopp@aol.com wrote:
>
>> Regarding a world-sweeping white hot air pressure wave out of Chixulub,
John
>> Bois wrote:
>> <Fortunately, though, there was a deep, steel-reinforced, mammal bunker
>> allowing 100% survival of placentals next to the blast in Montana!>
>>
>> Yes, something like that.  Its denizens probably thought of it as a
burrow.
>
>Touche.  But are you suggesting that 100% of the 100% survivors in
>Montana were burrow dwellers.  I'm not sure where it is from but little
>purgatorius (putative ancestor of primates) was almost certainly not a
>digger and was probably arboreal (at least from memory).  And I'm
>uncertain how a heat/shock wave would work.  Would the white-hotness heat
>up the air for any extended time (minutes? hours?).  What is the killing
>mechanism, burnt flesh, heat stroke--bearing in mind that most extant
>burrows are far more shallow and conductive than the depth of an
>hadrosaurs body core. Could a non-avian find protection in a lake?
>My point here is that it is much easier to invoke killing mechanisms than
>explain how they kill some things and not others.  And are you aware of
>the diversity of killing mechanisms attributed to the boilde?  I am
>arguing with a guy on sci.bio.evolution who is trumpeting the bolide's
>effect of creating more than a decade's worth of near freezing
>temperatures.  I don't know of any tropical mammals that could survive
>this.
>
>I'm not saying you are making such a ludicrous claim.  But how can us
>skeptics tell who is on the money and who is full of hot air when, to tell
>the truth, not much thought seems to have been put into the matter.
>
>
>