Indirect Evidence for the Structure of the Earth

Seismic WavesVibrations from large earthquakes are detetced as seismic waves by seismographs all around the world. Analysis of many earthquakes over the last 100 years has helped geologists build up a detailed picture of the inside of the Earth.P and S waves are seismic waves that travel through the layers of the Earth, so are called body waves. The travel: faster if the rock becomes more rigid and more incompressible slower if the rock becomes more dense If the rock loses its rigidity completely, S waves slow down until they stop. So S waves cannot travel through a liquid.

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