Essay on the Source of information about the internal structure

Our knowledge of earth’s internal characteristics of these concentric layers has been acquired through direct as well as indirect sources.

It is true that most of our knowledge about the interior of the earth is largely based on estimates and inferences.

Since we are unable to drill more than a few kilometers into the earth, our information about various concentric layers have been acquired entirely through indirect evidences.

However, a part of the information is gathered through direct observations and analysis of material. Thus, there have been (i) direct sources, and (ii) indirect sources of our knowledge about the interior of the earth.

Direct Sources:

We get a lot of easily available solid geometries in surface rock or the rocks procured from the mines. But through mining and drilling scientists have gained a very limited knowledge of the earth’s interior.

As we know, the earth has a radius of about 6400 kilometers, but man has succeeded to penetrate and examine directly only its outer skin.

Thus, through mining and drilling we have gained a very scanty knowledge of the earth’s interior. Gold mines in South Africa are as deep as 3-4 km. going beyond this depth is impossible because of very intense heat at this depth.

The rate of increase in temperature with depth which is known as the geothermal gradient has an average value of about 30°C per kilometer.

Besides, oil exploration has penetrated to about 7.2 km by drilling. These explorations could provide knowledge only about the earth’s uppermost layers.

The second direct source though which direct information is obtained has been the volcanic eruption throwing onto the surface of the earth the molten rock material called magma. But it has not been possible to determine the exact depth of its origin.

Indirect Sources

Through the mining activities, it became clear that temperature and pressure increase with increasing depth of the mines. It is also known that there is an increase in the density of the material with depth.

However, the rate of change of these characteristics i.e. temperature, pressure and density can the calculated. Knowing the total thickness of the earth, the values of above characteristics at different depths have been estimated by scientists.

Meteors may be considered as another source of information. However, these materials available for analysis do not come from the earth’s interior.

But there is little doubt that material and the structure observed in the meteors are more or less similar to that of the earth because they are solid bodies developed out of materials similar to our planet. So it may be considered another source of information about the interior of the earth.

Gravitation, magnetic field and seismic activity are other indirect sources of knowledge about the interior of the earth. Gravity anomalies found at different places on the earth’s surface give us information regarding the unequal distribution of mass of material in the crust of the earth.

In the same way, magnetic surveys also give information about the distribution of magnetic materials in the earth’s crust. Seismic activity is undoubtedly the most valuable source of information about the interior of the earth.