Earth's magnetic field
A)is variable,and it has phased to zero some nine times during the past 4 million years.
B)is constant in its intensity.
C)remains a mystery as to its cause.
D)is principally generated in the inner core.
E)has repelled iron from the core to the surface.

Question

Quizplus · Accepted Answer

Earth's magnetic field is not constant and has reversed or phased to zero several times in the past. This phenomenon is known as geomagnetic reversal. It is believed to be caused by the movement of the liquid iron in the outer core, which generates the magnetic field.

Earth's Magnetic Field