Our Earth is the only planet in the solar system on which life was born. This was made possible thanks to the presence of many of the components of which it consists, the hydrosphere, the atmosphere, and also the internal structure of the Earth and a certain distance to the Sun had an important influence. The planet is an ellipse-like body, consisting of several main shells, different in composition, chemical and physical properties.
The structure of the Earth is the subject of study by many scientists around the world, but so far only its upper part, the earth’s crust, has been thoroughly studied, and there are only theoretical assumptions about the remaining layers. The atmosphere and hydrosphere make up the gaseous and water shells of the Earth. And the internal structure of the Earth is represented by the crust, mantle and core.
The outermost shell is the atmosphere. It is gas, it consists mainly of oxygen and nitrogen. There is no longer a planet in the solar system with a similar chemical composition of the atmosphere, suitable for human life and all living things. Scientists consider its occurrence the result of a long biological and chemical evolution. In the atmosphere there are areas with different chemical composition, temperature, physical state, located in horizontal layers. Only the lowest layer is suitable for breathing and human life, the thickness of which does not exceed 4-5 km. The farther up, the more rarefied the atmosphere. Its density decreases three times every 8 km (in height), while the air temperature also decreases, which then increases at an altitude of 50 km in the stratosphere. Further, in the mesosphere, the temperature drops again, and then in the thermosphere (above 180 km) it increases significantly. At an altitude of more than 1000 km, the exosphere begins. From it, atmospheric gases are dissipated into outer space. An increase in temperature is interconnected with the ionization of atmospheric gases — the formation of electrically conductive layers called the ionosphere.
Another significant difference between the Earth and the rest of the planets in our system is the presence of a large number of surface waters, which are in proportionately distributed amounts in different aggregate states (solid, gaseous, and liquid). The water shell of our planet is called the hydrosphere. There are surface and internal waters on the planet.
The structure of the Earth - its bowels, is studied using the seismic method, since now mankind has reached such a level that it has the technical ability to drill a hole in the crust of a depth of only 12 km. Seismologists examine the propagation and occurrence of waves in different environments, at different depths. By changing their velocities and refraction, one can judge the heterogeneity and stratification of the deep layers of the planet. In addition to seismic, there are several equally effective methods by which the geological structure of the Earth is studied. Among them, the gravimetric method, magnetometric method, etc.
The Earth's crust is under the hydrosphere or atmosphere. Its structure depends on it. The continental crust differs from the oceanic crust in greater thickness and a different composition. The oceanic crust occupies approximately 56% of the Earth’s surface. Its capacity almost does not exceed 5-6 km, it is maximum in the immediate vicinity of the continents. It consists of three layers: sedimentary, basalt and a layer of full-crystalline igneous rocks.
The average thickness of the continental crust ranges from 35 to 40 km. It consists of three layers: sedimentary, a layer of the continental crust and granulite-mafic.
Between the crust and the mantle is the surface of Mokhorovichich (Moho). On the continents, it is located at a depth of 25 to 75 km. After Moho is the mantle. It distinguishes three layers that are slightly different from each other:
- upper mantle (up to 410 km in depth);
- middle mantle (from 410 to 670 km);
- lower mantle (670-2900 km).
The structure of the Earth is such that in its center is a core consisting of two parts:
- liquid outer part, located at a depth of 2900-5146 km;
- solid internal part, its depth - 5146-6371 km.
Most scientists claim that the core is iron with impurities of sulfur, nickel, and silicon. The main magnetic field of our planet is generated by convection of the outer core.