what causes the earth magnetic field?

in the earths core a viscous mass containing iron moves around a solid iron core, According to scientists, this flow of iron acts like an electrical coil and is the cause of the earth's magnetic field, like any other magnet the earth has a north pole and a south pole , these poles lie some thousands of kilometres away from the geographical poles..Not only sailors and pilots but also many migratory birds, dolphins, and salmons orient themselves the magnetic field of the earth , small crystals of magnetite in their heads , acting like tiny compass needles, impart them a "magnetic sense".