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RE: Hell Creek [VERY LONG]

The following contains edited portions of a series of posts I made back
in August of 1998.  Note that most of the information being discussed
now was known (to some extent) back then.

    Facts are:

    1)    A large object (size of Manhattan Island) DID hit the earth on
what is now the Yucatan Peninsula of Mexico, near the modern town of
Chixulub.  Based on geologic studies of the site, it came in at an angle
(of 20-30 deg.). This usually means more debris would be ejected from
the crater than a straight hit.
    2)    The object hit the earth around 65 mya.
    3)    Lots of things changed on earth around 65 mya - climate, land
vs. sea ratios, etc.
    4)    Lots of creatures died, and lots of genera went extinct around
    5)    There is current no known other method that could destroy so
many genera, and yet leave survivors (in the pattern that we know

    To me, it seems likely that a large object would cause all sorts of
changes throughout the world, yet not ALL of the changes, by themselves,
would be devastating.  However, to many individuals, and to many genera
the sum total effects *were* devastating.

    I, for one, think that the damage done by the impact was
*sufficient* to start a chain of events that led to the extinction as we
see it today.  It did not need to cause the end of all life, or even the
end of all vertebrate life - which we know it did not do.
1)    There was a mass extinction of all the non-avian dinosaurs and
other families (including several mammal families, ammonites, rudists,

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

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

4)    Ichthyosaurs had all disappeared several million years prior to

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).  [Note
that this is for an angle between 10 and 20 degrees].

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
population).  [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 sufficient ratios of males vs. females, as
    h)    If the Ozone layer was damaged or removed, increased radiation
reaching the surface would kill many of the remaining survivors, and

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%.
LEVELS.  Some other techniques seem to show the same level as currently
(i.e. 21%) throughout all these eras.

14)    If large firestorms occurred, due to a large bolide impact, much
of the atmospheric oxygen would have been converted 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

    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 occurred
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 

I don't think that the effects of dust in the atmosphere lasted all that
long - maybe 3-4 months, so that within a year the sky would be nearly
back to normal.  (Except, as I said, the Oxygen levels *may* have been
reduced from 35% to 29%.  This leads me to suggest that the non-avian
dinosaurs may have evolutionarily changed their lungs to expect the
higher O2 percentage, so that, if the baby dinos survived the initial
effects, they would have two problems facing them - Lack of parental
protections and help, and as they matured, their lungs wouldn't work
correctly, causing them to die as they grew older).

    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 occurring, when
the bolide delivered the 'coup de grace' to the long reign of non-avian

    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

NOTE ALSO: The Signor-Lipps effect. The effect is analogous to the
Heisenberg Uncertainty Principle - the closer you get to examining your
subject, the more likely you are to introducing errors, or not noticing
important info.  The time frame of the actual extinction may be measured
in days or weeks, or just as likely, in hundreds of thousands of years.
[From 2002]:  This may affect how we interpret data, such as that from
Hell Creek.

I think that without a time machine and video and other recorders placed
all over the world, that could save data over a 5 million year period
(EACH!), that we could then recover and do a proper data analysis on
that 5 my period - without these fanciful devices, we will never be
certain of any of these extinction scenarios.

Allan Edels