For a given star of roughly the same size and composition,there is a
correlation between maximum equatorial speed,differential rotation
rates and deviation from a pshere.
This is another problem . Any star the same size as the earth would
have to be a neutron star. And any other star has far more H and He
than anything else and being gaseous will not be a good analogy to a
terrestrial
planet.
Any change in composition,rotational speed will affect the
differential rotation rates and subsequently the shape of the star.
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Return to the rotation of the flexible/molten interior of the Earth -
What exempts the Earth from the same generalised rotational dynamics
which correlate maximum equatorial speed,interior composition and
spherical deviation.The missing component is differential rotation. I personally , dislike dissmissing , out of hand , differential rotation. However , I need more than shape of a terrestrial planet to accept it. Recent earthquake analysis has found what appears to be subducted plates that have apparently settled to or near the base of the mantle .For those plates to sink ,they must displace mantle material . What was the response of that displaced material ? Perhaps greater resolution will exhibit some bias in favor of DR.
What alternative rotational mechanism can be proposed to differential
rotation of the interior composition to generate the spherical
deviation
centrifugal force , for the crust. Is the core
aspherical ?
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Considering that generalised dynamics do not prohibit differential
rotation in the Earth's interior,it stands to reason that it is a
satisfactory means to explain the 40 km deviation without knowing what
the internal composition and viscosity is. Agreed. unless the density is too great and G is overwhelmed. > In allowing lattitudinal
shear bands which occur where differential rotation occurs in stellar
dynamics,the differential rates automatically qualify as the mechanism
for crustal >motion. Do you then ignore convection ? ( not stationary !) Remember , the mass of the mantle is orders of magnitude greater than the crust. Stars are objects forever on the cusp between gravitational collapse and heat generated expansion. Cool a little and they collapse. Heat up too quickly and they blow up. > It may just be possible to see the slightly
different rotation rates from actual images of the rotating stellar
composition but that is the nub of the agument for a rotational
mechanism -
http://www.youtube.com/watch?v=7dfKoPsA8KQ
If convection didn't exist would you
not expect heavy elements to collect at the base of the mantle?
Differential rotation is not a conclusion,it is a point of departure
along with maximum equatorial speed, and spherical deviation for
determining what the composition and viscosity of the interior is.If
you begin with internal composition,viscosity organised around a
geostationary thermally driven convection cells you will get a
different set of criteria as opposed to a rotational mechanism and
that is the central argument.
Because the mantle is in continuous motion ( tranmitting internal heat
to the surface ) the mineralology is everywhere the same . Plate
Tectonics is just a minor consequence. And, why do you call it
geostationary ?-
There would always come a time when the internal mechanism would begin
to overshadow the outlines of plate tectonics and reduce it to a
'minor consequence' as you would put it in an effort to promote a
geostationary convection cell notion.You csn hide a lot of junk
behind convection cells mainly because they can only be speculated
while rotational dynamics and specifically differential rotation has a
sequential logic to it and can be derived from observing the behavior
of other rotating celestial objects.
Your convection cells notion are geostationary insofar as not only do
they require no reference to axial rotation and planetary shape,they
prohibit differential rotation as a mechanism which binds plametary
shape with crustal motion,For differential rotation to
exist,convection cells have to go and that is about as straight an
answer as I can give.
I think that convection cells is a poor analogy for a heat driven
circulating mantle. I prefer to think of the mantle as a pot of
boiling water with convection as the primary reponse to its internal
energy
( heat )removal.
The geological material is a joy to work with and I never stop
reminding participants that it is not really that important to
establish an internal mechanism,only if it is done,to make sure that
it has the best possible chance of explaining multiple features and
effects rather than a means to an end,something which the ad hoc
ceonvection cell solution would have served.I cannot repeat it often
enough,I am absolutely astonished that the entire community is
prepared to let an observed orbital component to drift by maintaining
variable axial inclination,whatever chance the rotational dynamics
have of emerging,it cannot happen without first handling the observed
motions of the Earth.
It is always easy to point out wrong approaches just for the sake of
it however it is far more difficult to promote a more productive view
of things thereby setting aside older and less productive concepts.-
When you have the force exerted by a circulating , convecting mantle
( in its quest to release heat ) the thin crust has no choice , but
to respond. That response is PT.
