Seismology is the science in which earthquake waves are studied by marking the seismograph. The nature of these waves, their paths and directions are different. The variations in transmission and speed of these waves can be considered as the basis for knowing the internal structure of the Earth.
On this basis, the internal structure of the earth is divided into the following parts:
1. The crust: It is the topmost layer of the earth. Its average thickness is 30 km. This layer is made of heavy rocks and its density is 3 grams per cubic cm. The thickness of this crust is approximately 30 km on the continents. Under the mountainous parts, it has more depth. It is divided into two parts – 1. Internal crust 2. External crust. In this layer of earth, the prominence of a rock called granite is found. P and S waves are transmitted in this layer, which proves that this layer is made of rocks.
2. The mantle or substratum: This layer extends to a depth of 2,900 km below the crust. The upper part of the mantle is known as the Astheno Sphere. This part is the main source of lava that reaches the surface of the volcano during its eruption. S waves vanish after the depth of 2,900 km, that is, it is made from unrecognized concrete tiles. In this layer, the waves called P and S have been observed by Gonrad Sir. This layer gives the primacy of basalt rocks. The part between crust and mantle is called Moho – discontinuity,
3. The Core: The deepest part of the earth from 2900 km to 6371 km. is the most innermost part of the Earth whose average density is 11 grams per cubic cm. In this part, S waves cannot reach. In this layer, there are two parts – 1. External Core 2. Internal Core. The first part is in the liquid state, which extends from 2900 km to the depth of 5150 km. The boundary between the inelastic mantle and the core is called the Gutenberg discontinuity zone.
The inner core is a dense part which extends from 5150 km to 6371 km. The highest density in this part of the earth is 11 grams per cubic cm. It is made of highly rigid metallic content. These layers classified on the basis of earthquake science are depicted through the following diagrams.
