geomagnetism?

Question

What causes earth magnetism?

Answer 1

No one knows the exact cause, but the prevailing theory is the Dynamo Theory
http://en.wikipedia.org/wiki/Dynamo_theory
"When conducting fluid [molten iron in Earth] flows across an existing magnetic field, electric currents are induced, creating another magnetic field. When this magnetic field reinforces the original magnetic field, a dynamo is created which sustains itself."

In order for any world (planet, moon, star) to produce a magnetic field, at least part of its core must be molten (liquid) and metallic, and that world must rotate fast enough (how fast that is varies depending on several factors). Earth's outer core is molten iron, and Earth rotates fast enough, so we have a magnetic field.

Answer 2

I think its the earths Iron core

Answer 3

the spinning of the earths iron core