What is polar wandering?

Question

I need a good explanation (from one geologist to another) of the different types of polar wander. i.e. what is meant when one talks about polar wander? apparent wander, true wander, magnetic polar wander...

Answer 1

Yeah, you and me both! LOL This guy, Bob Reszka, has a pretty good answer in Expert Answers and a couple of references that are helpful. I've copied it here for you:

“Polar wandering” is kind of a misnomer, well, at least it was until about the year 2000. Let me explain. You know about continental drift. Do you know that magnetic minerals will align with the Earth's magnetic lines when they are floating in a magma? So….we have molten rock with magnetic minerals in it. The magnetic minerals float around freely and respond to the magnetic force of the Earth; think iron filings and a bar magnet. The magma cools and hardens, freezing the magnetic minerals into the position they were pushed into by the magnetic fields. Ok….so now we have rocks with minerals, whose magnetic orientation we can measure. We look at lots of these minerals within the rock and figure out their orientation.
Many times they are not oriented in the same direction as the current magnetic field of the Earth. When the rocks lithified the minerals were aligned with the magnetic field. Now they are not. That can only mean that something has moved. Plate tectonics tells us that the continental plates moved over geologic time. That movement caused a misalignment of the minerals.
So…it's not really that the poles moved it's that the continents did. We can study the orientation of the minerals and infer where the poles were when the rock was lithified. We can then run time back, moving the continents at the same time, and deduce where they were, at least in that location, when the rock hardened.
Saying “polar wandering” is kind of like saying “the sun is rising”. The sun doesn't “rise”, it just looks like it. The more proper term should be “apparent polar wandering”.
This is not an easy concept and the various maps don't make it easy. Some maps have curves that indicate how the continents moved through time. Others show a meridian and a circle that's meant to show the location of the pole in relation to the equator. Neither is intuitive. The best help I can give is to start thinking of the plates as moving, all in relation to each other. Don't try to figure the correct motions yet. Just feel that they are in motion and tie that motion to the north magnetic pole. Not easy I know but it helps me to mentally draw a line from the point in question to the pole and swing it around. Just takes practice.

Ok, there's a problem here though. This was accepted until 2000 when a paper was published in “Science” that showed that about 84 million years ago the pole actually did move. The mechanism is not known, lots of speculation though. This adds a little mud to the not so clear water but most of the maps you will see are drawn to show the movement of tectonic plates in relation to a stationary pole. On the whole they are correct since it appears the poles moved only that one time. We can't ignore that movement but we can assume most “apparent polar wandering” is due to the movement of the continental land masses.
Here are a couple of sites that you might find interesting:

http://www.mala.bc.ca/~earles/polar-wander-jan00.htm

http://www.agu.org/meetings/fm04/fm04-sessions/fm04_U31B.html

Hope this helps! You're not alone in feeling that this is a pretty murky subject! It drove me nuts in grad school because part of my thesis work involved apparent polar wander of some of the terranes attached to California. ;). If I never see another Euler pole I'll be a happy geologist.

Answer 2

Polar Wandering

Answer 3

I don't know what the long answer that was pasted in was about, but he appears to be confusing the magnetic north pole and the rotational north pole. The paper published in 2000 is about the rotational north pole changing 84mya, not the magnetic. This is an oddity, since it was suspected that the Earth has maintained its rotational axis for billions of years. However, the magnetic north pole does wander relative to the currently stationary rotational pole. In fact, geologists measure the northern magnetic pole every year directly by going to the arctic and taking measurements of field orientation. The magnetic pole moves sometimes about 40km a year, and appears to be accelerating towards Siberia.

Ok, so the rotational pole is constant, it does not move geographically, except that one time 84Mya, in which case it was rather sudden. This has nothing to do with the magnetic north.

Magnetic north does wander, and its wander can be measured year to year. However, figuring out where it was before a century ago when there were no direct measurements is difficult. That is where apparent and true wander come into play. Apparent wander is based on the polarization of magnetic minerals in lithifying rock. These minerals aligned in the direction of the magnetic field when they formed from liquid. However, since the continents also moved, the apparent wander seen is not accurate compared to the true wander relative to the rotational axis. To find the true wander, you have to correct for the plate movements of the continents. Once you have removed this movement, one can determine true wander of the magnetic field in the past.

So polar wander DOES EXIST, unlike what the supposed expert said. But one has to correct for the continental plate movements to find the paleomagnetic true wander.

Answer 4

This Site Might Help You.

RE:
What is polar wandering?
I need a good explanation (from one geologist to another) of the different types of polar wander. i.e. what is meant when one talks about polar wander? apparent wander, true wander, magnetic polar wander...

Answer 5

Hi. The 'wander' is the motion of the magnetic pole relative to the rotational axis of the earth. It has moved over 1.100 Km during the last century and effects navigation, primarily, and where the Aurora occurs. http://www.answers.com/main/ntquery?s=polar+wandering&gwp=13