Magnetism is a class of physical phenomena that are mediated by magnetic fields. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments.The Earth's magnetic field is somewhat caused by the composition of the earth's core which is rich in iron minerals. There is a solid inner core that is made of iron which makes up to 2/3 of the moon's size. The charged metal of the iron produces electric currents, consequently resulting to Earth's magnetic field.