S-waves

S-waves are seismic waves that move through rock by shearing it side-to-side, perpendicular to the wave's direction of travel.

Unlike P-waves, which compress and expand material, S-waves cannot pass through liquids or gases—their inability to traverse Earth's outer core helped prove it was molten.

S-waves travel more slowly than P-waves and typically cause more damage during earthquakes.

The S stands for secondary, since they arrive at seismographs after the faster primary waves.