Re: Plate techtonics and asteroid hits

first_name@xxxxxxxxxxxxx (Florian) wrote in
news:1i2lw9u.9ditr3s6z8oiN%first_name@xxxxxxxxxxxxx:

Jim Willemin <jim***willemin@hot***mail.com> wrote:

first_name@xxxxxxxxxxxxx (Florian) wrote in
news:1i2jtrr.1d9yhc319o12yqN%first_name@xxxxxxxxxxxxx:

David Iain Greig <dgreig@xxxxxxxxxxxx> wrote:

One possible answer would be crustal buckling due to expansion,
which could well have pushed oceanic crust upwards.

That is one possibility.

But obduction also occurs if oceanic floor is pushed over
continental crust by a plume. The papuan ultrabasic belt is good
example. See Fig7, Kugler "Subduction and Overthrusting"
http://www.lulu.com/content/421591


Maxlow clais a constant
earth radius to 1.5Bya, but allows some folding may have occurred.

I just posted an issue in another thread - a planet of 1700km
radius has an escape velocity so low it could not retain an
atmosphere. So much for early life...

Except you failed to calculate the correct escape velocity.
So much for ... ;-)


yes but - the moon has an escape velocity of about 2.4 km/sec; a
dwarf planet with a 1700 km radius and mean density of 5.5 has an
escape velocity of 3 km/sec; Mars has an escape velocity of about 5
km/sec. Thus the atmospheric pressure of such a hypothetical dwarf
planet would be much closer to that of the Moon (i.e nil) than Mars
(roughly 1% of earth's atmospheric pressure). While David may have
misplaced a decimal point, the correction makes very little
difference in his argument - a small early Earth ain't gots no
atmosphere, and we KNOW that it in fact did.

Titan has an escape velocity about 2.6 km/s and a dense atmosphere. It
is more complicated than you think.


Further, now that I think about it, said small early Earth must
have
had a spectacularly high heat flow, since it must have been REAL hot.

Why?

I suppose that it depends on the temperature of the mass you create to
make the thing expand, but unless the early, small earth was real, real
hot, it seems to me that it would have cooled to the point where
tectonic and volcanic activity ceased utterly (cf. Mars). Further, this
would have affected the magnetic field of the planet through the
geomagnetic dynamo seizing up. Thus the onset of expansion would also
necessarily represent the onset of renewed heating and the regeneration
of a molten core (and the regeneration of a magnetic field). Now,since
we have measurements of remenant magnetism in rocks well into the
Archean, it seems to me that this implies a continuously molten core
generating an essentially constant magnetic field (yeah, I know it
varies a lot, both reversals and secular variations, but I don't think
that the earth's magnetic field was consistently much stronger or much
weaker in the past, though I could be wrong).



The present radius of the core is something like 3400 km (twice the
radius of the postulated early earth). So for the earth to grow to
its present size, not only do you have to add just bucketloads of
molten iron-nickel (four times the volume of the planet you started
with), you also have to add four times as many bucketloads of
peridotite, and THEN you need to add enough heat to keep the
geomagnetic dynamo running throughout. Not only do you need to add
matter, you need to add hot, glowing matter, some of it in a liquid
state.

You can speculate for a long time. Without data, it won't help much.

What data do you suggest we acquire to address the problem? I was idly
speculating on possible implications of expansion, matters that seem to
me to be germane to the problem, and need to be adequately treated by
those who propose expansion.



And you still need to
explain the geologic and geochemical assymetry of Paleozoic suture
zones... the more I think about it the sillier it gets...

So explain me why the south pacific displays a symetrical age floor
pattern with matching transform faults exactly as expected if it was
closed along the dashed lines 150 millions years ago.

http://nachon.free.fr/southpacific.png


Um, I don't think anyone (except possibly you) denies that Antarctica
and Australia/New Zealand were joined. I don't see why that is a
problem for plate tectonics, nor do I see why that is evidence for earth
expansion, considering the whole raft of active convergent zones along
the eastern boundary of Asia is avaiable to account for subducted
material.



Explain me why the west mediteranean basin is in extension and there
is southward overthrusting in the east mediteranean basin whereas PT
predicts there is a collision between africa and eurasia?


Cite? A quick perusal of earthquake focal mechanisms suggests that the
western Med (west of Sicily anyhow) is in a W to NW trending
right-lateral transpressional regime - perhaps you could point me to the
evidence for extension? See, for example,
http://www.emsc-csem.org/Images/GASPERINI/INFOWU822.Gasperini.jpg which
shows focal mechanisms for earthquakes in the westernmost Mediterranean,
almost all of which are either right-lateral strike slip or thrust or
some combination of the two.

It seems to me that southward compression in the eastern Mediterranian
is perfectly consistent with convergence between Africa and Eurasia or
even Africa and Anatolia, or Africa and Arabia.



PT is flawed, deeply flawed.


Only when you throw out half of it for no particular reason, and distort
the rest.

.

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