Re: Owen's Two-Phase Model of Earth Expansion

From: don findlay (don_at_tower.net.au)
Date: 03/03/05 

Date: 3 Mar 2005 07:49:12 -0800

Stuart wrote:
> don findlay wrote:
> > Stuart wrote:
> > > don findlay wrote:
> > > > Matt wrote:
> >
> >
> > > > It's based on the **ASSUMPTION** (assumption) that an increase
> of
> > > > depth away from the ridge is caused by the thermal contraction
as
> > the
> > > > plate cools on moving away from the ridge axis, and that this
> > > reflects
> > > > the age.
> > >
> > > Not an assumption, but fact.
> >
> > My little PT book (and my big one) says "assumption" :-
> > "The dashed line is the theoretical elevation curve calculated on
the
> > assumption that an increase of depth with age is caused by the
> thermal
> > contraction of the lithosphere as the plate cools on moving away
from
> > the ridge axis."
>
> In other words one can compute an expected topographical profile from
a
> simple themral model.

You can use as many "other words" as you like, but it would be a poor
do if you couldn't, after assuming that the curve of the topography is
thermally induced, and you make your model from it. (Wouldn't you say,
obfuxscator?)

> However, I was referring to the ages themselves. Not any model. Nor
is
> sea-floor spreading predicated on any thermal model.

Aw, Stuart, stick to your spelling errors! You mean convection is not
a thermal model? What then?

> Thats an
> observation.

Oh right, it's an observation, is it? Like the observation at the
other end that it is subduction and not overriding we're looking at,
..this 'energy imbalance'. Come off it.

> Sea-floor spreading does make predictions as to what the
> depth-age relation should be like.

Umm, .."Spreading". You mean 'movement'? or 'Growth'? Or 'accretion'?
  Which verb would you consider most closely approximates this "Thermal
model that sea floor spreading is not predicated on"?
>
> >
> >
> > > What Don talks about however, does also
> > > happen. Google "Propagating Rifts". However ocean basin form by
> > > spreading at ridges, not their propagation.
> >
> > Ridge spreading *IS* ridge propagation. Spreading across and along
> > cannot be divorced one from the other.
>
> Uh, actually they can Don. THose pesky magnetic stripes tell it all.

Yes, ...Tell what all? What are you talking about? Nothing to do with
the structure of the ridges I hope..

> Of
> course its entirely possible that what you mean by propagation has
> nothing to with geophysicists mean by ridge propagation.

Given the mess that your pals have made of this one, this is entirely
possible. In fact it is not just "possible", it's an out-and-out *DEAD
CERT*. And it's time they got a clue, given the length of time my site
has been up on the web for them to pinch it from.

> > (You really do through pronouncements/edicts around like Gurfies
> > ('George's furfies')
>
> LOL.
>
> Don, it may interest you to know, that scientists have actually
drilled
> into the sea-floor to obtain ages.

How else? I do believe this is one purpose of sea-floor drilling. And
the idea of drilling the sea floor is drill to basement (basalt). But
mostly they use the sediment layer that sits just on top of it for
dates because the basalt underneath is mostly not much use when it
comes to radiometric age dating.

> What you posted above concerns
> sediments. I agree that much of the sea-floor is dated by virtue of
its
> magnetic stratigraphy. But direct dates from drilling also exist.

but direct (radiometric) dating is not the way they go about it,
..correct? A very indirect method used, in which the 'thermal cooling
curve' features prominently. Or are you saying that there are no
problems with using the basalts of the ocean floors for dating? Your
statement that "direct dates from drilling also exist" invites a "so
what"? So tell us 'what'. Obfuscator.

> On the other hand thanks for illustrating the use of the magnetic
time
> scale.

(Putting words in my mouth..)
 
> Stu

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