Re: Magnetic storm on NOVA

"Keith R. Williams" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> In article <[EMAIL PROTECTED]>,
> [EMAIL PROTECTED] says...
> >
> > "Robert Calvert" <[EMAIL PROTECTED]> wrote in message
> > news:[EMAIL PROTECTED]
> > > I thought that this was an interesting show:
> > > http://www.pbs.org/wgbh/nova/magnetic/ I especially liked the part
about
> > the
> > > earth's magnetic field moving 60 degrees in a matter of hours if not
> > minutes
> > > at some time in the distant past. This led me to wonder what effect a
> > change
> > > like this would have on the power grid if it happened today.
> >
> > I saw the show and didn't get that impression.  The scientist mentioned
that
> > the magnetic field of a large mass of lava was in one direction near the
> > outer surface and another direction in the center.  But this mass looked
to
> > be about 1 1/2 to 2 feet thick (as the scientist stood next to it).
> >
> > So the shift had to occur from the time the outer layers cooled to when
the
> > center cooled.  Not hours or minutes, but more like days or weeks.  I
don't
> > think a 2 foot slab of lava cools all that quickly ;-)
>
> ISTR the original hypothesis of the reversal came from under-
> water magnetometer readings, some thirty years ago.  The
> reversals were rather well correlated along the entire mid-
> Atlantic ridge.

The acceptance of reversals is not the issue here.  It has been well
established.  But the evidence found in some solidified lava flows suggest
that the magnetic field has shifted about 60 degrees within a single flow.
This *suggests* that at times the magnetic field of the planet shifted by 60
degrees in a very short (geologically speaking) time, i.e. the time between
when outer layers of the flow cooled and when the inner volume of the same
flow cooled.

The controversy over this evidence is still going on.  How fast did the
inner portion of the lava cool, and did the magnetic field really shift 60
between the time the outer and inner portions cool?  Or did the lava mass
physically rotate?  The jury is still out on this.

daestrom