[tt] NS: How Earth's poles went walkabout

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How Earth's poles went walkabout
http://environment.newscientist.com/article.ns?id=mg19826504.800&print=true
8.4.5

STICK a penny to the edge of a spinning top and its axis of rotation
will shift. Now evidence is emerging that something similar may have
happened more than once to the Earth.

The clumping of ancient continents in one hemisphere would have
unbalanced the Earth and caused its axis to slowly migrate, geologists
suggest. This would mean that a land mass formerly at one of the poles,
for instance, would appear to have slipped across the Earth's surface.
Evidence for this "true polar wander" is sparse because it is hard to
distinguish from the normal drift of continents associated with plate
tectonics.

However, Earth's magnetic field would have tracked any changes in the
planet's axis of rotation, so Bernhard Steinberger of the Geological
Survey of Norway in Trondheim and Trond Torsvik at the University of
Oslo, also in Norway, studied the field's "fingerprint" in magnetic
minerals formed over 320 million years.

They found that during several periods, all the continents appeared to
be moving in unison relative to the magnetic field. That's evidence
that the entire Earth was tilting markedly during those intervals, says
Steinberger (Nature, DOI: 10.1038/nature06824).

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Weblinks

Bernhard Steinberger
http://www.geodynamics.no/STEINBERGER/
Trond Torsvik
http://www.forskning.no/personer/1073051030.88

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