Direct Sources of information about the Earth’s Interior
- Deep earth mining and drilling reveal the nature of rocks deep down the surface.
- But as mining and drilling are not practically possible beyond a certain depth, they don’t reveal much information about the earth’s interior.
- Mponeng gold mine(deepest mine in the world) and TauTona gold mine(second deepest mine in the world) in South Africa are deepest mines reaching to a depth of only 3.9 km.
- And the deepest drilling is only about 12 km deep hole bored by the Soviet Union in the 1970s over the Kola Peninsula.
- Volcanic eruption forms another source of obtaining direct information.
Indirect Sources of information about the Earth’s Interior:
- By analysing the rate of change of temperature and pressurefrom the surface towards the interior.
- Meteors, as they belong to the same type of materials earth is made of.
- Gravitation, which is greater near poles and less at the equator.
- Gravity anomaly, which is the change in gravity value according to the mass of material, gives us information about the materials in the earth’s interior.
- Magnetic sources. 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.
- Seismic Waves: the shadow zones of body waves (Primary and secondary waves) give us information about the state of materials in the interior.