Starting subduction in Plate Tectonics - How?

"Hey, ..I got it from a creationist website ..... (But it's not
creationists saying it)"
http://www.newgeology.us/presentation8.html (It's Out of the mouths
of Babes... and not the bellybutton sort either.. ) "Hey, ...you
there, ..Emperor, .. What's that flower you have on? "Can it be a
faded rose from days gone by..?"

*************************************
begin quote
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
STARTING SUBDUCTION IN PLATE TECTONICS - HOW?
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

The theory of plate tectonics is about 40 years old. actually a decade
older (df) http://users.indigo.net.au/don/nonsense/carey.html
Still, "Problems remain unsolved, such as subduction initiation and
asymmetry, temporal evolution of plate geometry, rapid changes in plate
motion, and the Archaean initiation of the plate-tectonic mode of
convection." (emphasis added) (Bercovici p. 107). Here is what a
number of researchers wrote in 2003 and 2004 in professional journals
concerning subduction initiation:

"Pull by the subducting slab as a result of its negative thermal
buoyancy, further enhanced by changes to denser minerals with depth, is
widely accepted as the major driving force for plate motion and plate
tectonics. It follows that there would be no plate tectonics if there
were no subduction zones. Yet how a subduction zone begins remains
poorly understood." (Niu p. 851)

"Subduction zones are really only crudely predicted by simple
convection theory, and there is much to them that is highly atypical of
convection. First, if one were to only consider the strength of cold
super-viscous lithosphere, one would not expect to see subduction zones
at all. Convection with purely temperature-dependent viscosity typical
of the Earth's tends to form a cold, hard, and immobile layer on the
top, and all convective motion occurs beneath it, as if it were a rigid
lid." "Thus, subduction initiation presents a formidable problem to
convection models. Second, in most forms of thermal convection, both
surface boundary layers converging on a sheet-like downwelling will
descend, while this occurs nowhere at any terrestrial subduction zone;
i.e. all subduction is one-sided, with only one plate descending into
the mantle. This asymmetric downwelling is yet another major enigma
not yet well explained in convection theory." (Bercovici pp. 110-111)
http://earth.geology.yale.edu/~dberco/
Hey, ..Stuart...! and George, ..poor 'George-the-consensus', being
led by the nose an' betting dollars with his mouth; I don't think
either of them have read a book since they left school. Or are they
just conducting MASSIVE ACADEMIC FRAUD in the name of science? Both of
you had better pay attention to the numbers in the background there,
because his numbers are bigger than both of yours put together, and
*he* can't make head nor tail of them either, ..but he is prepared to
put his face where his numbers are... Stuart, ..you didn't come to
George's rescue when he bet his money, ..why not?

"The formation of new subduction zones is a fundamental, yet poorly
understood, process in the normal evolution of tectonic plates."
"While events such as the opening and closure of ocean basins suggest
that subduction initiation is common, theoretical models suggest is
should be quite difficult." (Hall pp. 15-16)

"Most theoretical studies have concluded that it is difficult to
initiate a new subduction zone. Although several studies have examined
the initiation of subduction, the dynamics of this process remain
obscure. There remains substantial disagreement and uncertainty about
the significance of different processes influencing subduction
initiation, the material properties of tectonic plates, and even
whether it is possible to initiate a totally new subduction zone in
isolation from an existing one." (Gurnis p. 2)

This is the current situation:

"There are two principal views on the physical mechanism leading to the
initiation of subduction. The first and most common is that as the
oceanic lithosphere ages and cools, its density increases so that an
instability arises and the plate sinks spontaneously in the mantle
under its own weight. According to the other view, externally applied
compressive stresses and moderate convergence are necessary to form a
new subduction zone." (Gurnis
p. 3)

Considering the first view,

Numerical modelling has shown "that it is highly unlikely that the
entire lithosphere at a fracture zone will spontaneously founder."
(Hall p. 20)

Most certainly, "a self-sustaining subduction zone does not form from a
homogeneous plate." (Gurnis p. 1)

"Included in the first view is initiation at a passive continental
margin" such as on the margin of the Atlantic Ocean. One suggestion
was "that with a weaker oceanic lithosphere, such as that occurring
through the addition of water to olivine, that a throughgoing shear
zone could develop directly on the edge of a 10 km thick sedimentary
pile." (Gurnis p. 3) Yet recent modelling found that "no combination of
fault rheology or geometry produced self-sustaining subduction without
applied convergence." (Hall p. 21)

So spontaneous subduction does not work. Considering the second view,

In the past, "the major Pacific and Indian oceanic trench systems were
thought to be more than 200 million years old." (Gurnis p. 25) Now,
however, it is believed that "nearly half of all active subduction
zones initiated during the Cenozoic." (Gurnis p. 1) "Tonga-Kermadec
and Izu-Bonin-Mariana [Trenches] both date to about 45 million years
ago." (Gurnis p. 25) "That such a large proportion of subduction zones
are young indicates that subduction initiation is a continuous process
in which the net resisting force associated with forming a new
subduction zone can be overcome during the normal evolution of plates."
(Gurnis p.1)

"The factor which most strongly dictates where subduction initiation
will occur is the initial tectonic state of the system. [That]
include[s] former spreading centers, fracture zones, transform faults,
passive continental margins, and subduction zones undergoing polarity
reversal." (Gurnis p. 19)

This group believes the Izu-Bonin-Mariana Trench formed on a former
fracture zone or transform fault, and the Tonga-Kermadec Trench formed
on an extinct subduction zone. (Gurnis p. 5) Modelling the compression
option, they "explored the conditions necessary to initiate subduction
within a viscoelastic material with a pre-existing dipping fault
dissecting the lithosphere." (emphasis added) (Gurnis p. 3) "Two
forces must initially be overcome to make a subduction zone: fault
friction (or growth of a lithosphere-cutting shear zone) and plate
bending. Plate bending becomes the principal source of resistance."
(Gurnis p. 24)

The hang-up with the second view is asymmetry: getting only one plate
to sink.

"Models that suggest transform [faults] or fracture zones and spreading
ridges as sites of subduction initiation have difficulties unless a
significant buoyancy contrast exists across these features."
"Materials on both sides of a ridge or transform [fault] should be
broadly similar as they are produced by similar processes in similar
environments. Hence, it is unlikely that compositional buoyancy
contrast across these weak zones would develop throughout their
evolutionary histories." "Therefore, it is physically implausible why
one side of an old ridge, or transform [fault] or fracture zone prefers
to sink while the other side chooses to rise under any deviatoric
stresses." (Niu p. 852)

These researchers instead propose that where there are compositional
differences in the crust, subduction might occur. And so the
investigation continues. At this point,

"Both the initiation of subduction and the asymmetry or one-sidedness
of subduction remain open first-order questions." (Bercovici p. 118)

And how did the very first subduction zones form, before there were
plates and spreading ridges to provide compression? Nobody wants to
touch that one.
/ends quote
***************************

"Touch that one"? Nobody around here wants to touch anything. (
"Leave it alone! Don't rock the boat!") And all in the name of
"Science". Questions in science are like the Plague. The guys writing
above, say it ok though, don't they? ( Dyed-in-the-wool Plate
Tectonicists that they are) (Asps at the heart). These are the
leading edge of Plate Tectonic 'thinking'. Thinking may be not the
right word though, considering the dates of their publications (below),
which are three and four years after this site of mine
http://users.indigo.net.au/don/
went up on the web. (Seems they might be following a trend, ..trying to
stake a claim in it perhaps - I wonder what in??

What they do *not* say though, and what you are intended to read
between the lines, is that the many-headed hydra of paperback-writers
is turning to seriously question the whole thing about subduction,
...all they're doing meantime is pointing out that questions exist; it's
taken a creationist to rubbish it (subduction)..and in the name of
what? I tell you, ..if Plate Tectonics doesn't own its own nonsense in
the classroom (or here) it will be used against it with far more force
than I want to bring to bear on it. You're nuts, you sandbags and
jellybuttons, ..you don't have a political clue, do you? You think
there's strength in numbers, and looking the other way, ..and 'peer
review' .

The next thing you'll have to look at (which nobody has done at all)
(and this is - My Gawd! - six years, which is more than half way to ten
- into the next century), ...is transform faults, and how they form.
Omigod, ..another hundred years coming up, ..of scientists behaving
like scientists,... On the public purse. (And the longer the better,
given the reverberations on that one)
http://users.indigo.net.au/don/re/memory.html

You know, ...don't you, you can get all this (where it's all going to
end up) (in about a thousand years) off my website, rather than listen
to ******s behaving like George, and forking out $100 at a time in
their glad ignorance to do it, to everybody who can cite a mention of
spontaneous subduction in a peer reviewed paper.... (the 'George',
...putting his money where his peer-reviewed protection racket is.)
He's a graphic demonstration of how science *behaves* when it's under
question. Get your head out of your bucket of fools' gold, dope.
You're a laugh mate, ...like I said, a far bigger one than any pyrites
in the Caribbean. (Hey, .. that was a joke..!) (Laugh everybody!)

**********
References

Bercovici, David. 2003. The generation of plate tectonics from mantle
convection. Earth and Planetary Science Letters, Vol. 205, pp. 107-121.

Gurnis, Michael, Chad Hall, Luc Lavier. 10 July 2004. Evolving force
balance during incipient subduction. Geochemistry Geophysics
Geosystems, Volume 5, Number 7, pp. 1-31.

Hall, Chad E., Michael Gurnis, Maria Sdrolias, Luc L. Lavier, R.
Dietmar Müller. 2003. Catastrophic initiation of subduction following
forced convergence across fracture zones. Earth and Planetary Science
Letters, Vol. 212, pp. 15-30.

Niu, Yaoling, Michael J. O'Hara, Julian A. Pearce. May 2003. Initiation
of Subduction Zones as a Consequence of Lateral Compositional Buoyancy
Contrast within the Lithosphe a Petrological Perspective. Journal of
Petrology, Volume 44, Number 5, pp. 851-866.
***********

"Taking 'em to that mansion in the sky..."
And Hey Ho for the Seth Seismic Network and 'research' (into
subduction) ...which does not exist...

("Stirremup, Fanny, ..that's the stuff." )