There are the following ideologies about the interior of the earth
(1) The innermost hypothesis of the solid
German geophysicist Suisse has presented the notion that the melting point of every substance increases with an increase in pressure, but the experiment has shown that this is possible only to an extent. No mineral substance can remain solid at high temperatures. It is supported by volcanic eruptions, igneous rocks, and hot sources. British scholar Pitt and German geographer Ritter presented this idea. But in its opposition it has been said that during the tides, the spherical body of the earth acts as a solid body and the earthquake waves reach very deep; Which can be possible only in a solid spherical body. Other constellations are also solid like the Earth. In the year 1936, Letman proved with seismological evidence that the center of the earth can be solid.
- Write the Main Hypotheses Related to the Origin of the Earth.
- Discuss Theories Related to the Origin of the Earth
(2) Liquid innermost hypothesis
In favor of the liquid innermost hypothesis propounded by scientist Laplace, the phenomenon of volcanic eruption and interruption of earthquake waves is presented. Weichert, in 1890, presented the hypothesis of liquid innermost, which was proved by the geologist Oldham, but the following evidence is also found against it-
1. To generate tides in the ocean, there should be a solid spherical body of 400 km thickness below the hydrosphere. Due to the influence of all the forces on the liquid innermost surface, the folds of the earth are twisted twice. If the innermost surface of the earth were liquid, then the tides would rise on the surface of the earth, but in reality, this does not happen.
2. The solid layer above would have become solid and dense over so many ages. With the formation of a thick layer in the geographical ages, there would have been a continuous decrease in the eruptions of the volcano, but it is not so.
3. Like a solid, a liquid cannot remain at the bottom. As it solidifies, the bottom shell will settle down due to greater gravity. In this condition, the idea of the liquid innermost part of the earth had to be abandoned.
The Swedish scientist Arrhenius hypothesized that the Earth was made of metals and that the very deep part of it was filled with metals. Its upper part is solid, the middle is liquid and the lower part is in the gaseous state. But there are two difficulties in accepting this statement.
1. At the time of tide, the whole earth-mass acts like a solid body.
2. Earthquake waves travel as deep as they can in a solid body.
(3) Gaseous innermost hypothesis
Based on the rocks of the Earth’s crust and the density of the Earth, Newton determined that attraction. Power increases in proportion to the amount of matter in substances and decreases in proportion to the distance between them. According to this law, the density of the whole earth is 55, that of the crust is 2.7 and that of the central part is 8. This concludes that the interior of the Earth is made up of very heavy materials. The solidity of the Earth’s sphere, the Earth’s magnetism, and the significant fraction of iron and nickel compounds in meteors also come to support this fact. Therefore, the notion of gaseous innermost, introduced by Laplace, appears to be impractical.
The fibrous part of the Earth’s outer rocks is mainly composed of silica, in which there are minerals like felspar, mica, etc. The density of rocks made of silica varies greatly because there are two types of fibrous rocks, in which there are first, lighter silica rocks and second, dense silica rocks. The above points confirm the idea of a German scientist named Suiss that under the sedimentary rocks there is a layer of simple granite-like material which we call Siel. It contains a predominance of silica and aluminum. Its volume varies from 2.7 to 2.9. This makes up most of the continents. Below this is a substance of high density, which is rich in silica and magnesium, and we call it Sima. In comparison, only the original igneous rocks that are heavier can be retained. Syme’s representatives are rock basalt and gabbro. Its density is between 2.9 to 4.75. Its crust forms most of the oceans but is also located under the continents. The central part of the earth is made up of iron and nickel and is called Nife.
Suisse named the central part of the earth Nife after Sima. The density of its rocks is 8 to 11 in which iron and nickel predominate.
According to Suisse, the continent is Siel-made and the lower part of the continents and the ocean floor are made of Simrae.
Division of the earth’s layers
Based on the waves of the earthquake, three layers of the earth are also known-
1. The lithosphere – Its thickness is considered to be up to a depth of 100 km from the surface of the earth. It is formed by light watershed rocks. It is dominated by granite rocks, in which silica and aluminum metals predominate. In this, the speed of the main waves of the Earthquake is 51 km per second and that of the oblique waves is 3 km per second. The density of their rocks is 2.7.
2. Uttap Mandala- This is the intermediate part of the earth’s womb which is believed to be from 100 km to 2,900 km depth. These rocks are rich in silica and magnesium. In this, waves move 6 to 7 km per second and oblique waves move at 3 to 4 km per second. The density of this region of basalt rocks is 3.5.
3. Guru or Kendra-mandala- This part falls from 2,900 km depth to the center of the earth. It is one-third of the earth. Its density is 8 to 11. Iron or nickel predominates in this part. In this, the oblique waves cannot enter and the speed of the dominant waves decreases while entering the liquid. This part appears elastic, soft but firm.
Based on current investigations, it is concluded that the inner part of the Earth is not entirely composed of liquid matter, but in the lowest central part, there is a solid part with a 1,290 km radius, which has a density of 18. The fluid silicate formed in the center is about 2,250 km thick.
In support of the above hypothesis, the experimental study of the compressibility of rocks in the world-origin-shastra physics and meteorological evidence presents evidence.
Jeffrey’s theory and earthquake waves
Some scientists have also estimated the internal composition of the Earth from the study of earthquake waves. Waves travel faster in solid rocks than in soft rocks. In rocks of low density, these waves pass slowly at the same speed, but towards the interior, the speed becomes faster, whereas at greater depths the speed of the waves remains the same. Thus, based on three different geological movements of three classes, three layers of rocks are known- upper, intermediate, and substratum. The quality of granite is more in the upper layer, which includes sedimentary, metamorphic, and igneous rocks. Its thickness is considered to be 15. km.
This is a low-density level. Its density is 2.7. Its waves are called Pg, whose speed is 5.4 km per second. The second wave is called Sg, whose speed is 3.3 km per second. This speed is found up to a depth of 15 km. The level of granite rock is not found in the oceans.
Basalt predominates in the intermediate layer, which is 20 to 30 km deep. It has a definite chemical composition in the molten state, which may become fibrous by mixing different minerals under pressure and physical condition, or it may not become lava while changing to a solid state, it remains a liquid.
At this level, the speed of the main waves is 6 km per second and the speed of the secondary waves is 4 km per second. In this, the sediments of the oceans are based on basalt. The basalt layer is about 5 km thick.
Beneath the basalt layer, a layer of the mantle is found up to a depth of 2,900 km. Geologist Mohoro Visit has determined a boundary between the mantle rock and the earth’s surface. Mohoro Visit found a change or discontinuity in the earthquake waves in this belt at 35 km. It was given the name of Moho. Its density is 35. The density of the lower part of the mantle-shell belt is 5.7.
In the substratum, the outer-ground core is found up to 5,100 km from the mantle layer. The density of its lower part is 15.2. After this, up to 6,370 km from the center of the earth, an internal ground core is found, which has a density of 17.2. Excess density in these levels weakens the waves. The speed of the curves of the first waves. From the layer of mansard to the center of the earth, the predominance of iron and nickel is found. This part appears flexible and soft but firm.
American geologist Daly and Scottish mathematician Jeffrey consider this part to be made of basalt or las or tachylite, while Bergen and Holmes consider it to be made of amphibolite, but the substratum must be believed to be made of dense materials like basalt In which there is an abundance of olivine and minerals and these substances are in a bright state including self. It is related by Sun night. In this way, the study of seismic waves has been of great help in the knowledge of the internal structure of the Earth.