Earth's Magnetic North Pole Is On the Move

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The compass,
perhaps the oldest navigational tool of man, does not point to the
geographic north pole with its needle. Instead, it indicates the
magnetic north pole – which, though close to the geographic
north pole, is not at the “top” of the earth’s axis. It
is actually in the Arctic Ocean north of Canada, and moves as the
magnetic fields of the earth change.

The molten
iron core of the spinning earth makes it a giant magnet. However,
that magnetic field is actually moving. Jeffrey
, a research scientist with the U.S. Geological Service’s
Geomagnetism Program, notes: "So that means if you wait five
years, the compass will be off by one degree." During some
periods the drift of the magnetic north pole has been relatively
slight. When it was first identified in 1831, it remained fairly
stable for decades. Then, beginning in 1904, scientists began to
observe a northeastern shift of about nine miles a year. Since 1989,
the drift of the magnetic north pole has accelerated to about 35
miles a year in the direction
of Siberia

The earth’s
magnetic field also seems to be weakening. Scientists believe that
in the last two centuries, the field has decreased by about five
percent per century, after having remained fairly stable for the
previous several centuries. Extensive and reliable information has
been gleaned from centuries of sea travel. Sailors have long used
compasses for navigation, and these sea voyagers have accurately
recorded in their log books extensive and reliable information about
the winds, tides, direction, stars and other variables. The magnetic
orientation of minerals in rocks and pottery shards has also yielded
clues about the planet’s magnetic field at different points
in history.

The earth’s
magnetic field may be in the process of reversing
its polarity
– something which scientists believe has happened
in the distant past of the planet. Although the shift was too far
back for historical records to exist, geologists are able to date
lava flows to periods of planetary history, and this lava (frozen
molten rock) has the same value as pottery shards in fixing the
direction of magnetic fields at certain periods of time. David Gubbins,
an earth scientist at the University of Leeds in Britain, ties this
evidence of the decline in the strength of the planet’s magnetic
field to increases of patches of reverse magnetic fields. He speculates
on when this process began:

It does look
like the patches [of reverse magnetic fields] first formed toward
the end of the Eighteenth Century, when Captain Cook was busy
sorting out navigation and measuring magnetic field all over the

The drift
of the magnetic field and the variation in its intensity appear
to be the consequence of the intense temperatures in the earth's
core and the liquid flow of iron and nickel which make the planet
an electromagnetic dynamo. Scientists have few tools with which
to study the earth’s core. Because of the great depths involved,
the intense subterranean heat, and the complexity of mapping the
molten mass flowing at the earth’s core, scientists must rely on
measurements from the surface to guess the history and the future
of the earth's magnetic field.

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12, 2011

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