The magnetic poles of the Earth continuously change their position with time i.e., the magnetic North Pole becomes the magnetic South Pole and vice-versa. why does it happens and how ?
The earth’s magnetic field is generated by the electron flow with the rotating liquid-iron core of our planet.
The exact reason of shift of earth’s magnetic field with time is not discovered yet. Some scientists think that convective currents in the core cause the 'polar' magnetic field to shift with time.