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Thread: The correspondence of Apparent Polar Wandering Paths?

  1. #1 The correspondence of Apparent Polar Wandering Paths? 
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    I am kind of confused with the kind of poles that apparent polar wandering is saying...

    Are the Apparent Polar Wandering Paths saying that the MAGNETIC pole (not the geographic pole) is apparently moving as time goes on? (I understand that the poles weren't really moving, the continents did.) What kind of pole is seemingly moving?
    What and where is the geographic pole and is it always stationary all the time throughout the earth's history?

    I would need some clarification on these to get out of this mess!

    Edit: Please see the 5th reply (figure B) for the correspondence of Apparent Polar Wandering Paths and I am now puzzled with its meanings...


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  3. #2  
    Forum Professor wallaby's Avatar
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    the magnetic poles on the Earth are just like those of a magnet we have a north and a south.

    scientists don't know why but they do know that the magnetic field reverses every so often, between thousands and millions of years, this last occured 780,000 years ago and is believed to have an interval of around 250,000 years.

    the geographic pole is just a place on the map where the lines of longetude meet. we have the north pole which is around the Arctic also the known residence of our friend Santa Clause, and we have the south pole in Antarctica.


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    Universal Mind John Galt's Avatar
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    There are two kinds of polar movement (three if we wish to get really precise and pedantic).
    As you have noted, because the continents (or rather the lithospheric plates the continents are part of) are moving we shall have an apparent polar wandering. Lavas erupted in, say, the Permian in North America will have a magnetic alignment that points towards where the North )or South) Magnetic Pole was at that time. The continent then moves, so when we check its magnetic alignment today we find it pointing in an unexpected direction.
    Secondly, because the magnetic poles are being generated by convection currents in the core, a few thousand miles below the surface, and these convection currents are somewhat chaotic, the precise magnetic pole moves its position. It can move several hundred yards in the course of a day, though it tends to average out around the same point. Over a longer period of time this point also drifts, by scores or hundreds of kilometres. This drift has been increasing of late, which is one the facts cited as evidence that we may be approaching a polar reversal.
    The third kind of polar wandering is a small switch in the position of the geographic pole. Since this is determined by the distribution of angular momentum within the Earth any redistribution of mass, through plate tectonics, mountain building, erosion, etc should produce a change in the precise position of the pole. This will be a very small scale effect: I do not envisage it as being detectable. I mention it only for completeness and to enhance a reputation for pedantry.
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  5. #4  
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    Thank you Ophiolite! I found out from the web that there are 3 types of polar wander: apparent polar wander, magnetic polar wander, true polar wander. And the true polar wander means the migration of the geographic poles.
    Magnetic polar wander is the movement of the magnetic poles with respect to the geographic poles (when the geographic poles are considered stationary)
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  6. #5  
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    "In the past, the geologists examining ancient rocks (paleomagnetism) assumed the continents did not move so the magnetic north pole APPEARED to be moved, hence this is called apparent polar wander.
    When the continents are considered to be moving (RATHER THAN THE POLE), the PATHWAYS correspond."

    When they considered the continents move instead of the pole moving, the pathways correspond, ie Fitting the continents back together results in a single path............but the last sentence in the quote confuses me. It says that scientists consider that the continents are moving instead of the magnetic pole (ie consider the change in position and orientation of the continents), and this gives a perfect match of the apparent polar wander paths for different continents (North America and Europe, for example), but as they consider that the magnetic pole is not moving, why are there still pathways of polar wander? Is this the real MAGNETIC polar wander--the movement of the magnetic pole with respect to the geographic pole, which is considered stationary at most times?)

    Edit: Ha...I have found a nice figure that claries what I mean...the following is the kind of thing I am saying, the paths of the bottom figure, are they the true magnetic polar wander throughout the earth's history?
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