The primary source of Earth's magnetic field is generated by movements within the outer core, which is composed chiefly of molten iron and nickel. The motion of the electrically conductive fluid in this layer creates electric currents, which in turn produce magnetic fields. This phenomenon is described by the dynamo theory, explaining how the Earth's rotation and convection currents contribute to the generation of the magnetic field over geological timescales. The magnetic field is essential for protecting the planet from solar and cosmic radiation, maintaining a stable environment for life.