[meteorite-list] Re: related to tektite origin

From: Darryl S. Futrell <futrelds_at_meteoritecentral.com>
Date: Thu Apr 22 09:37:31 2004
Message-ID: <050001c05e9e$111e0e40$c8e41e3f_at_pavilion>

-----Original Message-----
From: Jarmo Moilanen <jarmom_at_netppl.fi>
To: Meteorite-list <meteorite-list_at_meteoritecentral.com>
Date: Wednesday, November 29, 2000 10:08 AM
Subject: Re: related to tektite origin


I'll quote Mr. Moilanen's points and then try to reply:


">I think that claim that tektites are from moon created by volcanism (or
impacts)
>is impossible. You totally ingnored one of the most important detail about
>tektites: all main tektite fields covers very small fraction of surface of
our
>planet. If those tektites are coming from moon, they should be found in
many
>other locations on Earth too. If they are from moon, then aiming of
volcanic
>ejection from moon has been almost as precise as a laser and for all
tektite
>fields (except K/T boundary material which are smaller)! It's clear that it
is
>statisticaly impossible, since volcanic eruptions are not the same kind of
>events than firing a gun!"


A tektite strewnfield is not found scattered all over the earth, due to the
powerful effect of the earth's gravitional focusing. See page 6332 of :
Chapman, D. R., 1971, Australasian tektite geographic pattern, crater, and
ray of origin, and theory of tektite events. J. of Geophys. Res. 76, #26,
6309-6338.

">Other important detail which is missing in you points is that several
tektite
>fields has an impact structure nearby which has the same age than those
>tektites. Best cases are Ries and Steinheim -> moldavites and Bosumtwi ->
>tektites of Ivory coast. In both cases age of impact and tektites are the
same
>(of cource, there is small differences because tolerance of methods used to
>determinate ages in different kind of materials)."


Such craters are merely "connate" to that particular strewnfield. In other
words, these craters were formed about the same time from large masses
coming from the moon and associated with the tektite producing event, but
such terrestrial craters did NOT produce the tektites. The tektites came in
a separate swarm. See page 6322 of Chapman's 1971 paper for a detailed
explanation of "connate".
For what happens to the tektite swarms that miss the earth, see page 6333 of
Chapman's 1971 paper. There is also eventual "rotational bursting" that's
described in O'Keefe's 1976 book, I believe.


">And how that water got inside the moon? Or do you think that moon has
always be as big as it is now? Well, I won't say that all lunar water has
been delivered
>by comets since astreroids can contain some water too."


The water was already there when the earth "fissioned" to form the moon (the
earth rotated so fast at a certain point that some of the outer layers
peeled off).
My 1977 reference to O'Keefe and Urey is quite old? Yes, but that happens
to be the era when the bulk of the "fission" papers were written. Many of
the people who were convinced of the fission theory are now deceased
(Ringwood, Urey, O'Keefe, etc.). I believe a few might still be around, but
I haven't been able to keep track lately. I can no longer do library
searches like I did.

">I'm sorry, I didn't read that. (My iridium comparison chart). In K/T
boundary of Bottaccione section at Gubbio
>(Alvarez et al. 1980), K/T boundary has 3000 ppt Ir when all other layers
below
>and above it has less than 100 ppt Ir (mainly around 10-20 ppt). That is so
high
>anomaly that it can explain only by impact of an asteroid. It is known that
>iridium does exist inside Earth too. Some pure iridium crystals have even
been
>found on the ground, but they are usually microscopic. Impactites (impact
melts
>mainly) contain very high ration of iridium when compared to usual rocks
and we
>know that only meteorites has iridium enough for that kind of anomaly. When
>studing well impactites of well preserved impact structures anomaly of Ir
has
>been found."


I don't follow what is meant by "ppt". I've only dealt with ppm and ppb.

">You are right, that is only a part of the story! Our moon happens to be a
quiet
>place if we compared it to Io. But can material from those eruptions escape
>gravity of Io? I don't think so. You are claiming that tektites are from
these
>rings? As I said in the begining, we should found tektites from the
planetary
>ring all around the world, maybe they would be in narrow band around the
planet
>but not like they are located today on Earth." (I've already responded to
this last sentence.)


I've read several times in the literature that some volcanic ejecta does
escape Io into space. My reference setup, especially other than tektite
references, is in a terrible mess. Could take days to find any of them. I
put things in stacks and then can't remember which stack, or sometimes even
where the stacks are.

">I haven't heard about those micrometeorite impact pits on microtektites
but it
>sound strange to me too. Maybe those pits were formed due to hypervelocity
>impacts of other ejected particle accelerated by impact.
>So, if those microtektites are from moon, how the hell they manage to get
>through the atmosphere without loosing they surface details?"

Material on a "direct" trajectory from the moon travels much slower (only
about 11 km sec.) than other meteoritic material. Also, tektite
compositions make great heat-shield material.

">You are now talking about very small comets (not reaching the earth's
surface). Big comets (diameter > 1 km which are quite common) will survive
through atmosphere and they do produce impact craters as well as asteroids.
Earth atmosphere can be compare to 4 meter thick layer or rock and what that
can do to big block of ice? Nothing..."


I believe that larger comet nuclei, if dirty ice, will also shatter and
disintergrate before reaching the earth's surface. They would produce
tremendous shock wave wallops but not sure if that would form a shallow
depression.

">The hole in the atmosphere doesn't "snap" back so fast. Comparing a
nuclear
>blast to big impact is as the same as comparing explosion of one dynamite
bar to nuclear blast. Biggest man-made explosion was equivalent of 64 Mt of
TNT when impact, which produce 10 km wide crater (like Bosumtwi), is
equivalent of 11000 Mt of TNT. Impact which can produce so called "blowout"
is equivalent of 150 Mt of TNT and the crater is only about 3 km wide. 3 km
is a small crater. Blowout is name of the event when explosion produced by
impact manage to break a hole into atmosphere. And finaly: in big impacts
the trancient crater is not formed in seconds but in minutes! To move
enormous quantities of bedrock is not an easy task! We also have to
remember, that nobody excatly knows fully what really happens in those huge
impacts. For exsample pressure can be well over 100 GPa in impact point and
that is hard to obtain in laboratories. Shock wave from big impact will be
stong enough to destroy houses hundreds or thousands of kilometers away from
the impact site. It will took some time to atmosphere close the hole in the
impact site when there is lots of rocks and other stuff in the air,
including ejecta curtain produced by the impact."

I simply don't agree. In my opinion, "impact" people often exaggerate
effects of impacts. I feel they came up with "blowouts" in an effort to
help justify their tektite theory. However, if an asteroid is many tens of
km in diameter, then who knows what all the effects would be.

">You really should update your references about impacts (my reference to a
1965 paper by E. Adams)."


Sorry, but from the 1950's through the early 1970's is when most of the
valuable and really important tektite papers were published (with the
exception of O'Keefe, who was at it until 1994). Except for the SILICA 96
paper by O'Keefe and I, and the recent exchange in Meteorite! magazine, all
the other tektite papers in recent years have been written by "impact"
people. I'd rather not get into that here. I've been working on this for
hours now.

">I think it is physically impossible that volcanic event can produce so
high
>speed that material could escape martian gravity. I hope too that we will
see
>some martian volcanic eruption in a near future."

You may be correct. However, lunar volcanic ejection is no problem, if
hydrogen gas is present. Plus several other reasons why it works in
O'Keefe's 1976 book.
You really need to read some of Dean Chapman's papers. If you can look up
his 1971 paper, you'll find references to many of his previous papers. I
need to bail out of this email before there's another local power outage.

Darryl


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Received on Tue 05 Dec 2000 04:30:22 AM PST