S9 Earth's Dynamic Interior Part 4

Seismic data shows that there are two internal layers: OUTER CORE that is liquid an INNER CORE that is solid. Earth's mass is greater than it would be if Earth were composed of entirely from materials found at Earth's surface. We know this because of Earth's gravitational interaction with the sun.

Scientists infer from this that earth must have a core made of a very dense material, such as iron-nickel alloy.

It makes sense that the core is made of a material such as iron that is a good electrical conductor. You can think of the outer core as working something like an electromagnet. The flow of liquid iron in the outer core generates an electric current that in turn produces a magnetic field.