GL102 Lecture Notes - Lecture 9: Mantle Convection, Gravity Anomaly, Outer Core
Document Summary
Earth"s magnetic field: a region of magnetic force - a magnetic field - surrounds earth. These invisible lines of magnetic force surrounding earth deflect magnetized objects, such as compass needles, that are free to move. The field has a north and south magnetic pole, one near the geographic north pole, the other near the geographic south pole. (because it has two prominent poles, earth"s field is called dipolar. ) The strength of the magnetic field is greatest at the magnetic poles, where magnetic lines of force appear to leave and enter. Earth vertically: th positions of the magnetic poles are known to change on decadal time scales, and these variations have been well documented by ship captains navigating the oceans over the last 500 years. Generally, the magnetic poles appear to be moving slowly around the geographic poles. Such a change in the polarity of the magnetic field is a.
