Information that we get about the internal structure of the Earth, has two main types of sources:
1. Direct Sources: Sources from which direct information about the interior structure of the Earth is obtained are called the direct sources. Such as: earth’s rock formation, substances obtained from volcanic eruptions, substances obtained from mining, etc.
2. Indirect Sources: Sources in which information about the interior structure of the Earth is obtained indirectly are called the indirect sources. Such as: temperature, pressure, density, meteorite, gravity, seismic waves and magnetic fields, etc.