B.4. Interior Of The Earth
Sources to find out the Interior of the Earth:
- Direct source – Mining areas, Projects such as “Deep Ocean Drilling Project”, Volcanic eruption, etc.
- Indirect source – Meteors, gravitation, magnetic field, seismic activities, etc.
[Image: Compositional layers of the Earth]
For instance:
Earthquake – The study of seismic waves provides a complete picture of the layered interior. All natural earthquakes take place in the lithosphere(A portion of depth up to 200 km from the surface of the earth). There are two types of body waves called P waves and S waves. P waves are similar to sound waves and can travel through gaseous, solid, and liquid materials while S waves can travel through only solid states. Hence by the study of these waves, we can understand the interior of Earth.
Hence shadow zones of P and S waves tell us that the interior of the earth has different layers with different densities.