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From: marcus@pyuxt.UUCP (M. G. Hand)
Newsgroups: net.physics
Subject: Re: Reversing of Magnetic Poles
Message-ID: <128@pyuxt.UUCP>
Date: Mon, 4-Jun-84 23:02:47 EDT
Article-I.D.: pyuxt.128
Posted: Mon Jun  4 23:02:47 1984
Date-Received: Wed, 6-Jun-84 05:50:12 EDT
References: <1458@seismo.UUCP>
Organization: Bell Communications Research, Piscataway N.J.
Lines: 22

So, geophysics - something at last that I as a geochemist can reply to.
However, on this occasion i would do best to point out that the frequent
reversals in the earths magnetic field have taken place over significant
periods of time even by geological time scales, and then point you to
the Scientific American of September 1983, which ought to become a 1st
year geo-sciences set text book. (Geological time scales tend to be
relatively inaccurate because of the imprecision in measuring a set point
in time. Relative times may be fixed using geologically instantaneous
events - volcanic erruptions, both lava and dust layers, turbidity
currents, then things like ice ages and magnetic reversals which take
place over a significant but short length of geological time, and later
on we get to floral and faunal changes and extinctions, whose duration, as the
age increases becomes less significant as a proportion of absolute age.
Radio active dating still has a number of serious problems resulting from
biological preference for different atomic masses, potential partioning
of atomic masses through statistical thermodynamics of magma differentiation
over geologic time scales, potential isolation and separation of magmas,
contamination with country rocks, .....  this is not to say that they are
no good, but simply that one must be prepared to justify ones assumptions
and that there may be a number of different angles of attack.)

		Marcus Hand	(pyuxt!marcus)