How does the motion of the molten iron inside the earth cause magnetic field?

wat i remember about earth sciences back in high school is that the earth's mantle or core is made up of molten iron and other magnetic material and becoz they are rotating around inside the earth, they generate a magnetic field

The theory of the process is very mathematical and intricate, because to produce the currents, you need not only a flow of liquid iron, you also need a magnetic field, and this field is none other, but the one created by the currents themselves!"

regards

toppers expert