The direction of magnetic poles in iron in Earth’s crust demonstrates that Earth’s magnetic field has reversed itself approximately nine times over the past 3.5 million years. It’s not known how long the reversal lasts and what happens to the field during the reversal. The magnetic poles also wander. The magnetic north pole has moved as much as 800 kilometers toward the geographic north pole since 1831.

The magnetic field of Earth is very important to life on Earth because it helps deflect harmful cosmic rays and solar wind. If we were fully exposed to these charged particles the effects on us could be devastating. Communication systems would be disabled and the particles could cause damage to all living things.