CK-12 Foundation
Ck 12: Physical Science: Earth as a Magnet
[Free Registration/Login may be required to access all resource tools.] Explains how Earth is a magnet, its geographic and magnetic poles, and its magnetic field.
CK-12 Foundation
Ck 12: Physical Science: Why Earth Is a Magnet
[Free Registration/Login may be required to access all resource tools.] Why the Earth is a magnet and how its inner structure relates to its magnetic field.