From: allenroy (allenroy@peoplepc.com)
Date: Mon Oct 06 2003 - 00:21:53 EDT
Glenn Morton wrote:
> Think about it Allen. If the circulation moves with the plate, then the
> hotspot moves with the plate also and doesn't string out a lot of volcanoes.
> Not to mention you have to have 4000 km of differential motion in a few
> years with that kind viscosity. It simply won't happen.
On the other hand, The hotspot may be moving on it's own, independent of the
movement of the athenesphere of the upper mantle.
> >With the athenesphere pushing (dragging) the oceanic crust around,
> >the tensile strength of the crust is not a major factor.
>
> But as I mention, the hotspot will move with it thus not move relative to the
> crust. This theory won't fly.
As I just mentioned, the hotspot may not be related to the movement of the
plates. The one proposed for Yellowstone has apparently moved independent of
the direction of plate movement.
> The gravitational pull due to a sinking slab is too small to pull the crust.
> Many people have calculated this over the years.
Is this at the 10^22 poise coefficient? I'm sure you know that Baumgardner
proposes that the coefficient drops dramatically under special conditions. What
are the calculations for lower coefficients that baumgardner proposes.
> >You, yourself, listed 40 different measurements of chemical changes from
> island to island. It would be impossible to have different computed ages, if
> each island had exactly the same chemical mixture.
>
> But Allen, these are changes due to the decay of radionuclides after they come
> to the surface. it isn't the same as merely a chemical change.
That is your [and other's] interpretation.
> During volcanism, in general the argon escapes leaving potassium to decay to
> argon which then builds up in the volcanic rocks.
This has been shown to be an invalid assumption.
"As with all isotopic dating methods, there are a number of assumptions that
must be fulfilled for a K-Ar age to relate to events in the geological history
of the region being studied. ... [Assumption] 3. The radiogenic argon measured
in a sample was produced by in situ decay of 40K in the interval since the rock
crystallized or was recrystallized. Violations of this assumption are not
uncommon." McDougal, I. and Harrison, T., 1988, Geochronology and
Thermochronology by the 40Ar/39Ar Method. pg. 11
If something is "not uncommon" that means that it is common. So, this
assumption that measured radiogenic argon is the in situ decay of 40K into 40A
is COMMONLY false. That why the now somewhat discredited Ar/Ar was invented to
attempt to decipher when the assumption was false.
> Because most of the argon escapes (no it isn't 100% certain) The chemical
> change is merely the build up of Argon. That isn't the type of chemical change
> you are thinking of, I bet. Why would argon be preferentially trapped 4000 km
> from Kilauea and preferentially released at Kilauea? Makes no sense, Allen.
The different measurements of Argon from the island to island simply reflects
the amount of Argon that was in the original mix as it was extruded from the
source. There was likely more Argon in the mix at first since the first magma
came from the top of whatever magma pool might exist as part of the hotspot.
Later islands originated from magma lower down in the pool having less argon in
the mix.
So we have the earlier islands with greater amounts of Argon in the mix rising
up during the height of the flood and being badly eroded by the cataclysm.
Islands arising during waning stages of the cataclysm would be eroded less and
also contain less Argon. Those possibly arising after the cataclysm would have
even less Argon in the mix. Thus one has a relationship of lower/eroded islands
associated with greater content of Argon in the matrix, grading to higher/less
eroded islands associated with less content of Argon in the matrix.
> The gaseous argon wasn't in the source material. When the lava comes to the
> surface it escapes to the atmosphere.
This is a COMMONLY false assumption, as noted above.
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