[meteorite-list] Largest Crater in the Sahara Desert and LDG

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Sun Mar 5 19:48:37 2006
Message-ID: <005301c640b7$b10b79f0$86e08c46_at_ATARIENGINE>

Hi!

    If we made Norm ("Mr. Tektite") think
because of our babble, then we did a good
job. Does moving out 100,000 tektites mean
that you can move from the pup tent in the
back yard and get back into the house, Norm?

    A few loose ends...

    Doug, the actual language Kroeberl uses
is that the F/B ratio of tektites "should tend
toward 1.0." This is Professional Science
Speak for "too complex to model exactly,
but most of the cows ought to stampede
in this direction..."
    And you're right; he didn't analyze that
many samples. I wish he had more data.
He found one ivorite with a F/B ratio of
0.40 (means more boron than fluorine).
Most results were 0.8 to 1.2, which
indeed is a 'tendency" toward 1.0,
if you think numbers have tendencies.
    Actually taking the trouble to think
about it, I realize that once you get a purely
thermal regime, the slightly lighter boron
will actually escape faster than the more
pudgy fluorine, which would drive the ratio
back the other way, to values higher than
1.0, but by this time you'd be dealing with
temperatures so high, there wouldn't be
any light elements left (my guess).

    Back in the days of the MetList's Great
Tektite War of '01, the question of airbursts
as mega-heating events was bandied about.
Proponents of the mega-airburst pointed to
Muong Nongs as "evidence" of melt-in-place.
At that point I was emailing off-List with the
late Darryl Futrell. He was sending me stuff
and we were kicking the issues back and
forth.
    He made one point about Muong Nongs
that I pointed out was really significant; I don't
think he realized how significant. He had done
a lot of microscopic examination of Muong
Nongs. One thing he noted that distinguished
them from "volcanic" glasses was the nature
of the microscopic voids in the tektite material.
    In a substance that is melted in place (big
heat boils local rock; no flying or maybe just
a flop and plop) is that the multitude of tiny
voids are convex and isolated from each other.
Gases are devolving everywhere from the
melt into little bubbles, but the whole mass
is cooling and they are trapped alone and
still pushing outwards, hence the convexity.
    But in the Muong Nongs, the voids were
concave and highly interconnected. In particular,
they were like "spiny stars." And they were
everywhere, like a sponge's. This "proves" that
the Muong Nongs formed as a rain of tiny
microspheres of molten glass that fell to earth;
at least, it proves it to me.
    To visualize it, take an acrylic clear box
and fill it with marbles or ball bearings and look
at the spaces between the packed spheres.
The voids are 3D stars with spiny concave
points or rays, all interconnected.
    Darryl was thinking of this purely in the
context of stuff flying around next door to the
crater, but I was convinced that it didn't mean
that at all.
    I decided that the conventional view of
Muong Nongs as hardly better than impact
glasses, as molten splash going plop! somewhere
very near the impact site, as only semi-cooked
tektite material that didn't quite get transformed
completely into "true" tektites was nothing but
simple-minded hooey.
    Picture instead a rain of fire, immense volumes
of micrometer scale droplets condensing out of
clouds of rock vapor (that incidentally cover an
area of hundreds of miles across) and falling to
Earth in such quantities that they accumulate
many inches thick in places. (Announcer:
"Tonight's weather: expect a rain of molten
glass vapor with up to a foot of tektites on
the ground by morning...")
    Our term "microtektites" characterize
the ocean sediment layers of degraded glass
spherules from big impacts. Muong Nongs
are the terrestrial microtektite layers. As a
rock, they should be characterized as a
microtektite concretion. They are wet and
dirty as a macro-scale sample because they
were and are contaminated. The small size of
the individual droplets contact welded together
makes them degradable, getting wet and get dirty
just like oceanic microtektites do. A rock (or big
tektite) is a great piece of packaging to preserve
the original composition within. A concretation
of 50 micrometer particles is not.
    They fell (repeatedly) as tiny particles on
dirt, water, plant life, big tropical bugs, perhaps
the occasional hapless hominid, incorporating a
lot of junk. Then, the tiny spheres of the more
porous tektite started soaking up gases, water
vapor, losing silica content, and so forth, a kind
of weathering their more solid cousins are immune
to. Oceanic microtetites decay this way and
are believed to decay to clays eventually.
    Muong Nongs are layered, sub-layered, and
sub-sub-layered, the result of many rains of fire
over some short time scale. Fiery rain, fiery rain,
fiery rain, and after that, fiery rain. So, again the
simple impact scenario -- boom, melt, plop!
-- fails. There's only one impact, hence there
would be only one plop!
    In fact, with this composition, the one thing
everybody seems certain of, that they are found
near the impact site, goes right out the window.
The high speed re-entry of an immense swarm
of glassy rubble (and when I say immense, I mean
many billions of pieces) could produce a rain of
glass vapor cooling to molten microspheres in
the last moment before landing, and then another
swarm, and another. Would that necessarily
happen adjacent to the crater? No.
    There are ocean finds of layered tektites off
the Caribbean coast of South America. That's a
long way from the Chessy Crater. Of course,
they could also be found closer to the crater,
like in Georgia (they are), but they could be
anywhere in the strewn field. That's the point.
    This just takes an already headache level,
very complicated mystery and boosts it way
up the Migraine Scale to what-is-going-on-here?
It produces the paradoxical result that,
while "ordinary" tektites may be superheated
droplets of melt that didn't quite vaporize, the
Muong Nongs may be the product of droplet
condensation from a vapor, a conclusion
that is pretty much completely backwards
from the way most people conceptualize
the formation of tektites. There's that
headache factor again... Why do the layers
"tend" to alternate colors? Shut up; I have
a headache...
    As for Darryl's analysis of the micro-voids
in Muong Nongs, I don't know if he ever
published or even communicated it. We were
talking about it the week he died. Somebody
want to section a Muong Nong and look?
By the way, there are layered tektites from
three of the four major strewn fields, all but
the Ivory Coast. (But, then, ivorites are very
rare, with few examples compared to other
"falls.") So, it's probably a "universal" outcome
of the Tektite Event, whatever that is.

    While I always worried about the asteroid
hit, or the stray comet hit, the "usual" cosmic
catastrophe, a straightforward impact event,
I was so fascinated by tektites that I never
thought to worry that much about the event.
But after envisioning clouds of rock vapor
and repeated fiery rains of molten droplets
over hundreds of miles, I wonder if we ought
to worry more than we do. Or at least,
figure out what they are...


Sterling K. Webb
----------------------------------------------

----- Original Message -----
From: "Norm Lehrman" <nlehrman_at_nvbell.net>
To: "Larry Lebofsky" <lebofsky_at_lpl.arizona.edu>; "Sterling K. Webb"
<sterling_k_webb_at_sbcglobal.net>
Cc: <MexicoDoug_at_aol.com>; <nlehrman@nvbell.net>; <bernd.pauli@paulinet.de>;
<Meteorite-list_at_meteoritecentral.com>
Sent: Sunday, March 05, 2006 9:13 AM
Subject: Re: [meteorite-list] Largest Crater in the Sahara Desert and LDG


> All,
>
> Thanks for the fabulous discussion. I had to take
> time out from the discourse to wash, size-sort, cull,
> and count 10,000 tektites for an order I'm supposed to
> ship tomorrow, and all of this gave me a lot to mull
> over. And it did a lot to reinvigorate the wonderment
> of the puzzle that first drew me to tektites.
>
> For any of you on the list that may be new to the
> subject, this discussion serves as an appetizer for
> the much larger array of puzzles posed by tektites.
>
> On the more immediate topics; Doug, I very much like
> your thought of an aerial thermal event like a
> mega-Tunguska for Muong Nongs and maybe Edieowie also.
> And Sterling, I to find the F/B story intuitively
> comfortable and rational. Larry, your comment
> regarding something like a plasma condensate for true
> tektites as opposed to simple splash glass impactites
> feels good. Pieces are beginning to fall into place
> in new combinations for me.
>
> More after I get the counting finished---
>
> Norm
> http://tektitesource.com
>
> --- Larry Lebofsky <lebofsky_at_lpl.arizona.edu> wrote:
>
>> Sterling:
>>
>> Sounds good to me (though I study big rocks that you
>> can see with a
>> telescope). It sounds like it is time for me to
>> start reading up on tektites
>> too!
>>
>> As a novice, would you basically say that tektites
>> come from volatilized
>> material that has recondensed while an impactite
>> derives from melted material
>> that never got hot enough to vaporize.
>>
>> Obviously, you would have ranges of materials
>> (hotter vapor or hotter and more
>> devolatilized liquid).
>>
>> Larry
>>
>> PS Did you see the comet? Never been clear enough
>> and no access to a telescope
>> where I am.
>>
>>
>> --
>> Dr. Larry A. Lebofsky
>> Senior Research Scientist
>> Co-editor, Meteorite
>>
>>
>
>
Received on Sun 05 Mar 2006 07:48:31 PM PST