The question remains, Don...what causes the Earth's manetic pole to periodically reverse itself? And that's an intriguing question.

For instance, an electric motor has polarity with a north and south pole, achieved by rotating a coil around an armature (have I got those technical terms right?). At any rate...the only way you can reverse the polarity on an electric motor is to have it rotate in the opposite direction...or you can rotate it in the opposite direction by a toggle switch which causes a source of electrical power to flow the other way.

Interesting, eh? Perhaps the planet Earth works in a similar fashion. It is said to have an iron core, and the rotation of the planet around that iron core may be exactly what produces the Earth's magnetic field. If so, the direction of rotation would be what determines the polarity of the field, and the magnetic field would collapse to zero if, for instance, the planet stopped rotating...while it would simply drop in amplitude some if the planet were to slow its rotation a bit.

I have no ironclad opinion about any of this, because I don't know. I'm just speculating on what I find an interesting subject.