molten rock flowing in the asthenosphere convection cells in the lower mantle turbulence in the liquid outer core radioactive decay in the solid inner core
I gave my students this multiple choice question: The magnetic poles of Earth frequently change location. What is the direct cause of this change in magnetic pole location?

Only one answer is correct among these 4 choices:
- molten rock flowing in the asthenosphere
- convection cells in the lower mantle
- turbulence in the liquid outer core
- radioactive decay in the solid inner core

Could you tell me which one is correct?

turbulence in the liquid outer core