What are different sources of information about the interior of the earth?

Explanation

Some of the direct sources are:
(i) Mining: It is a process by which commercially variable valuable mineral resources are extracted from Earth.s surface which includes precious stones, rocks and solid fuels.
(ii) Drilling: Scientists world over are working on two major projects such as "Deep Ocean Drilling projects" and "integrated ocean drilling project". The deepest drill at kola, in Arctic Ocean, has so far reached a depth of 12 km.
(iii) Volcanic Eruptions: When molten material is thrown onto the surface of the earth during volcanic eruption it becomes available for analysis. Some of the indirect sources of information: Analysis of properties of matter indirectly provides information about the interior. Knowing the total thickness of the earth, scientists have estimated the values of temperature, pressure and the density of materials at different depths.
(a) Meteors that at times reach the earth: However, it may be noted that the material that becomes available for analysis from meteors, is not from the interior of the earth. The material and the structure observed in the meteors are similar to that of the earth. They are solid bodies developed out of materials same as, or similar to, our planet. Hence, this becomes yet another source of information about the interior of the earth.
(b) Gravitation: The gravitation force (g) is not the same at different latitudes on the surface. It is greater near the poles and less at the equator. This is because of the distance from the centre at the equator being greater than that at the poles. The gravity values also differ according to the mass of material.
(c) Magnetio surveys: Magnetic surveys also provide information about the distribution of magnetic materials in the crustal portion, and thus, provide information about the distribution of materials in this part.