Earth's magnetic field

This makes the usable for navigation. The cause of the field can be explained by  A field extends infinitely, though it weakens with distance from its source. The Earth's magnetic field, also called the geomagnetic field, which effectively extends several tens of thousands of kilometres into  forms the Earth's magnetosphere. A paleomagnetic study of Australian red dacite and pillow basalt has estimated the magnetic field to be at least 3.5 billion years old.

 

Earth's magnetic field (and the surface magnetic field) is approximately a   with the  Snear the 's geographic see  and the other magnetic field N pole near the Earth's geographic .