Answer:
The movement of seismic waves: p waves and s waves
Step-by-step explanation:
seismic waves are produced by earthquakes as shock waves and can be detected by seismometers.
P waves travel through solid and liquid rock; they are longitudinal.
S waves travel though solid rock only and therefore are slower. They are transverse.
Looking at the speed of these waves with a seismometer.... You can identify which parts of the Earth are liquid or solid.