What are the two main ways that scientists learn about earth's interior and what do these two things indicate?

The two main ways that scientists learn about Earth's interior is by studying the data collected by  body waves and surface waves. The body waves travel in the interior part of the earth in all direction while the  surface waves travel along the surface of the Earth. Now these body waves can travel through all liquids and solids while the surface waves can travel through only solids. The physical characteristics studied are density and state of material to which these waves respond and studying their seismographic recording would give a description of the composition of the Earth’s interior.

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