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Re: impact - LONG



Time for my $2.00 worth about the K-T bolide and mass extinction:   :-)

1)    There was a mass extinction of all the non-avian dinosaurs and several
other families (including several mammal families, ammonites, rudisks,
etc.).

2)    There were a lot of different survivors, including birds, crocs,
mammals, etc.

3)    Pterosaurs had all disappeared prior to the Maastrictian (possible
exception - _Queztacoatlus_).

4)    Icythyosaurs had all disappeared several million years prior to K-T.

5)    Many of the dinosaurs were in a decline (in terms of numbers of genera
and species).  (They may have been approaching another minor extinction
event, which they had recovered from in the past).

6)    All the mega-fauna disappeared.  (i.e. All the large animals
disappeared - including the large crocs).  I believe the largest surviving
land animals were less than 30 Kg.  (Sea-going animals may have been
slightly larger).

7)    The climate changed drastically (geological time) - from very warm and
humid to much cooler and drier.

8)    Foraminifera changed at the K-T, indicating the climate change (They
went from very complex forms, usually indicative of warm water, to very,
very simple forms, usually indicative of cold water).

9)    The Deccan Traps (of India) had been flowing for several million years
prior to K-T, and seem to have continued several thousand years after it.

10)    There was a large bolide impact at the same time we have assigned to
the end of the Cretaceous.  (see Chixulub).

11)    Depending on the angle of entry into the atmosphere, a large bolide
could strip off substantial portions of the atmosphere.  The angle that the
Chixulub crater preserves could strip off a lot of the atmosphere.  (This
bolide impact effect is rarely mentioned).

12)    Possible effects of bolide impact:
    a)    Vaporization at impact site of most organics.
    b)    Shock waves would flatten hundreds of thousands of acres.
    c)    Water strike or partial water strike would create tidal waves.
    d)    Earthquakes and volcanic eruptions could occur, triggered by the
impact.
    e)    Massive firestorms - globally.
    f)    Lots of dust and soot in the atmosphere, causing the 'Nuclear
Winter' effect.  (This would kill a large portion of the global
populations).  [Freeze].
    g)    After sufficient dust settles, the remaining dust in the upper
atmosphere could cause a greenhouse effect.  (The potentially excessive heat
could kill many of the survivors).  [Bake].  Note that this could prevent
proper births of sufficent ratios of males vs. females, as well.
    h)    If the Ozone layer was damaged or removed, increased radiation
reaching the surface would kill many of the remaining survivors, and mutate
many others.

13)    Amber gas inclusions (air bubbles) indicate a variation in oxygen and
carbon dioxide levels.  Both were at their highest levels during the end of
the Cretaceous (last 20 my).
    a)    O2 levels:    Permian  - 15%,  Late Jurassic  -  28%,  Late
Cretaceous (Pre-K-T)  - 35%,
            After K-T  -  28%, Mid-Miocene  -  14%,   Late Eocene - 15%,
Current Levels - 21%.
    b)    There remains some question as to the validity of these levels.
Some other techniques  seem to show the same level as currently (i.e. 21%)
throughout all these eras.

14)    If large firestorms occured, due to a large bolide impact, much of
the atmospheric oxygen would have been coverted into carbon dioxide, with
insufficient vegetation remaining to pump O2 back into the atmosphere
quickly enough.  This would have made it impossible for the larger animals
to survive, because they had evolved to take advantage of the higher O2
content.

15)    Many of the surviving genera either could hibernate, or migrate major
distances quickly.  (This is an assumption by me - not completely known).

*****
    The most likely scenario, IMHO, is that dinosaurs were in one of their
several declines - which they usually bounced back from.  They may or may
not have made it back from this one, but then the bolide (asteroid, comet,
giant meteor, whatever...) hit.  (Probably in the daytime).  It tore off
portions of the Ozone layer, as well as lots of the O2 and CO2 in the
atmosphere.  It caused major firestorms throughout the world, removing more
of the O2 as well as burning and killing many creatures.  Those that were
nocturnal, and were hidden in their nests or dens, MAY have been spared the
initial effects.  If the strike occured during winter or late fall (for some
areas), many genera may have been hibernating, and spared.  The 'Nuclear
Winter' hypothesis may have then created a colder winter for those areas
that normally were approaching winter, and extended or re-introduced winter
to those areas that were leaving winter.  The hibernating animals would have
a survival advantage here.  The larger animals would have had severe
breathing difficulties, and would die.  When the winter finished, the
greenhouse effect might occur briefly, cooking some of the survivors that
ventured out; causing too many (or only) males (or females) to be born  to
some egg-laying genera; and the increased radiation would kill several other
genera, and mutate individuals of other surviving genera, causing a rapid
explosion of new species (with newly advantageous adaptations - those
without advantages would die).

    This would account for almost all the known survivals and extinctions.
Please be aware that this is speculative, but based on some good science.  I
believe that several things were occuring, when the bolide delivered the
'coup de grace' to the long reign of non-avian dinosaurs.

    I am willing to believe other scenarios, but I haven't heard of any
others that come close to accounting for everything.  {Note that NONE of the
current or past scenarios account for the ENTIRE extinction picture}.

        COMMENTS????


        Allan Edels