What causes the Earth’s magnetic field to change over time?

The Earth’s magnetic field changes over time due to the movement of molten iron and other metals in the outer core. This motion generates electric currents, which, through the dynamo effect, produce the magnetic field. Over time, the field’s strength and orientation can change, leading to phenomena like geomagnetic reversals, where the magnetic poles switch places. This dynamic process is driven by the heat and pressure inside Earth, as well as the planet’s rotation.