Q. Which among the following is/are the indirect source of information about the interiors of Earth?
1. Seismic Activities
2. Volcanic Eruption
3. Meteors
Select the correct answer using the codes given below:

[A] 1 and 2 only

[B] 2 and 3 only

[C] 1 and 3 only

[D] 1, 2 and 3

Answer: C

The earth’s radius is 6,370 km. No one can reach the centre of the earth and make observations or collect samples of the material.  

  • Most of our knowledge about the interior of the earth is largely based on estimates and inferences. Yet, a part of the information is obtained through direct observations and analysis of materials. 
  • Volcanic eruption forms another source of obtaining direct information. As and when the molten material (magma) is thrown onto the surface of the earth, during volcanic eruption it becomes available for laboratory analysis. However, it is difficult to ascertain the depth of the source of such magma.  
  • Indirect Sources: Another source of information is the 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.  
  • The other indirect sources include gravitation, magnetic field, and seismic activity. 

Source: NCERT – XI Fundamentals of Physical Geography