Magnetic fields are generated by moving electric fields. If a planet has a magnetic field, it must have a moving electric field inside of it. Seismic Waves Seismic waves are generated by releases of energy in a planet. We can look at how these two waves travel through a planet and get information about what areas are liquid and which are solid. There is one more type of seismic wave, the surface wave.
Surface waves travel along the surface and are the slowest wave.
Surface features Expressions of internal heat and activity.