ABC - DEF - GHI - JKL - MNO - PQRS - TUV - WXYZ Geomagnetic field
Definition:
The geomagnetic field is the magnetic force field that surrounds the Earth. It is attributed to the combined effects of the planetary rotation and the movement of molten iron in the Earth's' core.
Compasses, instruments that align themselves with the magnetic poles of the Earth, have been used in navigation for centuries. Some birds (particularly migratory species) and other animals seem to rely on the geomagnetic field to orient themselves.
Source & ©: GreenFacts
More:
Source & ©: Graham Bailey, 
Related words: Magnetic field - Magnetism
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