You're almost as bad claiming nobody knows something when they do as you are claiming you know something when you don't. When are you going to stop your pretentious proclamations and adopt a standard of ethics?
http://en.wikipedia.org/wiki/Dynamo_theory
Quote:
Dynamo theory describes the process through which motion of a conductive body in the presence of a magnetic field acts to regenerate that magnetic field. This theory is used to explain the presence of anomalously long-lived magnetic fields in astrophysical bodies.
In the case of the Earth, the magnetic field is believed to be caused by the convection of molten iron, within the outer liquid core, along with a Coriolis effect caused by the overall planetary rotation that tends to organize currents in rolls aligned along the north-south polar axis.
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I recently watch a lecture on mass extinction events with a sidenote that a low angular cometary impact could spin the crust/mantle in relation to the core and shear off the convection currents that produce the magnetic field resulting in a period of low field strength and geologic evidence indicate just that scenario once occurred.