What are the two main types of seismic waves and how do they travel through the Earth?

What are the two main types of seismic waves and how do they travel through the Earth?

The two main types of seismic waves are P-waves (primary waves) and S-waves (secondary waves). P-waves are compressional waves that travel through solids, liquids, and gases. They cause particles to move in the same direction as the wave is traveling. S-waves are shear waves that only travel through solids. They cause particles to move perpendicular to the direction of the wave.