Indeed, but it was intended to be a crude analogy that should still work if
the original idea is true. Try superman swimming through magma if you like,
it doesn't really matter, it's the principle that that counts. Every action
produces an opposite and equal reaction, surely the movement of the material
will always be towards equillibrium.
----- Original Message -----
From: luigi burlini <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, November 05, 1999 8:53 AM
Subject: Re: pressure and depth
> >An analogy would be a man swimming 20 00 leagues beneath the sea is under
> >greater pressure than when not swimming, sorry, it just doesn't seem to
fit.
> >The pressure due to the water above would not alter significantly because
of
> >movement at a particular depth.
> >
>
> Dear Daryl,
>
> If the swimming man do not create an overpressure (even if very very
> small), it will not be able to move at all even in water. For the
> same reason airplanes can fly (overpressure beneath wings)!
> But the Earth is not made of water nor of any material with viscosity
> similar to that of water. Also, it is not so homogeneous, and the
> reason of overpressure is due to viscosity contrasts between rocks
> during deformation. See for instance the differences between the
> Voigt and Reuss bounds for elasticity (or if you want Taylor and
> Sachs approximations in the case of plastic deformation).
>
> Maybe the question is more a preservation problem. What happens to a
> rock and minerals when the differential stresses are released?
>
> Luigi Burlini
> Rock Deformation Lab, ETH ZENTRUM,
> Sonnegstrasse 5, CH-8092 Zürich
> Tel. 0041-1-632.3708 (Office), 3709 (Lab), Fax 632.1080
>
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