Hi,
First of all, as your question implies, the magnetic north and
geographical north aren't at the same place. It isn't even stationary
-- at last report, the magnetic north pole, which is located in the
Canadian Arctic, is moving northwest at about 40 kilometers per year.
It currently is located at a latitude of 82.3 degrees north and a
latitude of 113.4 degrees west.
The pole's location is explained on this page:
North Magnetic Pole
"The Earth's magnetic field is shaped approximately like that of a bar
magnet and, like a magnet, it has two magnetic poles, one in the
Canadian arctic, referred to as the North Magnetic Pole, and one off
the coast of Antarctica, south of Australia, referred to as the South
Magnetic Pole. At the North Magnetic Pole the Earth's magnetic field
is directed vertically downward relative to the Earth's surface.
Consequently, magnetic dip, or inclination is 90° . In addition, the
North Magnetic Pole is the eventual destination for a traveller who
follows his or her compass needle from anywhere on Earth."
http://www.geolab.nrcan.gc.ca/geomag/northpole_e.shtml
The movement of the magnetic pole isn't entirely predictable, as the
following article indicates:
North Magnetic Pole could be leaving Canada
"If the pole follows its present course, it will pass north of Alaska
and arrive in Siberia in a half century, but [geophysicist Larry]
Newitt cautioned that such predictions could prove wrong.
"'Although it has been moving north or northwest for a hundred years,
it is not going to continue in that direction forever. Its speed has
increased considerably during the past 25 years, and it could just as
easily decrease a few years from now,'the geophysicist said.
"The erratic pole can jump around considerably each day, but migrates
on average about 10 kilometers to 40 kilometers each year."
http://www.cnn.com/2002/TECH/space/03/20/north.pole/
As dramatic as that may sound, historically it's not that big of a
deal. In fact, there have been times in the past where the north and
south magnetic poles switched places:
Earth's Inconstant Magnetic Field
"Earth's magnetic field is changing in other ways, too: Compass
needles in Africa, for instance, are drifting about 1 degree per
decade. And globally the magnetic field has weakened 10% since the
19th century. When this was mentioned by researchers at a recent
meeting of the American Geophysical Union, many newspapers carried the
story. A typical headline: 'Is Earth's magnetic field collapsing?'
"Probably not. As remarkable as these changes sound, 'they're mild
compared to what Earth's magnetic field has done in the past,' says
University of California professor Gary Glatzmaier.
"Sometimes the field completely flips. The north and the south poles
swap places. Such reversals, recorded in the magnetism of ancient
rocks, are unpredictable. They come at irregular intervals averaging
about 300,000 years; the last one was 780,000 years ago. Are we
overdue for another? No one knows."
http://science.nasa.gov/headlines/y2003/29dec_magneticfield.htm
The above article also explains where the magnetism comes from; it's
related to the fact that the core of the Earth is made up of molten
iron. Because it's liquid and is rotating slightly faster than the
crust of the earth, it is full of turbulence that leads to shifts in
the magnetism. So there is a connection between the magnetic poles and
the Earth's rotation, although it has more to do with the internal
rotation.
And to answer part of your question, it appears that the magnetic
north can, in theory, end up almost anywhere, at least temporarily.
I believe that if you read the following pages (in addition to those
I've quoted from above) you will find your questions answered further:
Origins of the Earth's Magnetism
http://www.phy6.org/earthmag/dynamos2.htm
The Geodynamo
This article explains the magnetic tensions that exist due to rotation
and other factors.
http://es.ucsc.edu/~glatz/geodynamo.html
The Dynamo Effect
This article points out that the mechanisms behind the magnetism
aren't totally understood. But it seems clear that there is a
connection with rotation. Venus is believed to have a similar core,
but it rotates much more slowly than Earth does and doesn't have a
comparable magnetic field.
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magearth.html
Core Concerns
This article briefly explains the different models for understanding
Earth's magnetism.
http://www.sciencenews.org/pages/sn_arch/10_19_96/bob1.htm
When North Goes South
This article explains the mechanisms behind severe magnetic fluctuations.
http://www.psc.edu/science/glatzmaier.html
Earth's North Magnetic Pole
A bulletin-board discussion on this topic.
http://www.sciforums.com/archive/index.php/t-10275
Earth's Poles Begin Magnetic Reversal
Some scientists believe we're in the beginning stages of seeing a
magnetic reversal.
http://www.antarcticconnection.com/antarctic/news/2002/041802mag_flip.shtml
I hope your curiosity is satisfied by these articles.
Best wishes,
Mvguy-ga
Search strategy: I performed the following Google search and followed
links given in some of the resulting pages:
"magnetic poles" earth "north pole"
://www.google.com/search?q=%22magnetic+poles%22+earth+%22north+pole%22 |
