EarthRef.org Digital Archive (ERDA) -- Seismic Data for the Earth's Interior

Description
This image contains data for the velocities of P and S waves as they travel through the earth's interior, along with density data for changing densities of the Earth with increasing depth (increasing temperature and pressure). P waves are compressional waves that transmit energy by compressing and dilating the material it moves through. S waves are shear waves that oscillate back and forth at right angles to the direction of the wave. In the mantle, all 3 elements increase in value with increasing depth, with P wave velocity growing at a much higher rate. In the outer core, the shift in density and P wave velocity are evidence for a change in composition. Both have changed due to a large increase in iron concentration present within the core, explaining the large increase in density. Based on lab experiments, the lack of S wave data from this region suggests that the outer core is liquid (allows for the creation of a magnetic field from a convecting iron liquid). The liquid property also affects the p-wave velocity along with composition and depth. The values for the inner core arise due to further increase in depth related values and solidification (s-wave data). Seismic data has been used, along with lab results, to determine composition and physical features of the Earth's interior, accounting for most of the raw data currently known.