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The Earth is formed by numerous layers, some external and some internal. The Earth structure It is organized into several groups according to their state: solid or semi-liquid, liquid or gas.
The crust of planet Earth is a thin layer formed by rigid plates that rest on the upper mantle. Together they form the lithosphere and float on the asthenosphere, a layer of hot and pasty materials that sometimes come out of a crack forming volcanoes.
Density and pressure increase towards the center of the Earth. In the core are the heaviest materials, metals. The heat keeps them in a liquid state, with strong movements. The inner core is solid.
The internal forces of the Earth generate movements that are noticeable outside. Rapid movements originate earthquakes; the slow form folds, like those that created the mountains.
The rapid rotational movement and the metal core generate a magnetic field that, together with the atmosphere, protects us from the harmful radiation of the Sun and the other stars of the universe.
Layers of the Earth
From the outside to the inside we can divide the Earth into five parts:
Atmosphere: It is the gaseous cover that surrounds the solid body of the planet. It has a thickness of more than 1,100 km, although half of its mass is concentrated in the lowest 5.6 km.
Hydrosphere: It consists mainly of oceans, but strictly speaking it comprises all the aquatic surfaces of the world, such as inland seas, lakes, rivers and groundwater. The average depth of the oceans is 3,794 m, more than five times the average height of the continents.
Lithosphere: Composed primarily by the Earth crust, extends to 100 km deep. The rocks of the lithosphere have an average density of 2.7 times that of water and are almost completely composed of 11 elements, which together form 99.5% of their mass. The most abundant is oxygen, followed by silicon, aluminum, iron, calcium, sodium, potassium, magnesium, titanium, hydrogen and phosphorus. In addition, 11 other elements appear in amounts smaller than 0.1: carbon, manganese, sulfur, barium, chlorine, chromium, fluorine, zirconium, nickel, strontium and vanadium. The elements are present in the lithosphere almost completely in the form of compounds rather than in their free state.
The lithosphere comprises two layers, the crust and the upper mantle, which are divided into about twelve rigid tectonic plates. The upper mantle is separated from the cortex by a seismic discontinuity, the Mohorovicic discontinuity, and the lower mantle by a weak zone, the asthenosphere. The plastic and partially molten rocks of the asthenosphere, 100 km thick, allow the continents to move across the earth's surface and the oceans to open and close.
Mantle: It extends from the base of the crust to a depth of about 2,900 km. Except in the area known as asthenosphere, it is solid and its density, which increases with depth, ranges from 3.3 to 6. The upper mantle is composed of iron and magnesium silicates such as olivine and the lower one of a mixture of oxides of magnesium, iron and silicon.
Nucleus: It has an outer layer of about 2,225 km thick with an average relative density of 10 Kg per cubic meter. This layer is probably rigid, its outer surface has depressions and peaks. On the contrary, the inner core, whose radius is about 1,275 km, is solid. Both core layers consist of iron with a small percentage of nickel and other elements. The temperatures of the inner core can reach 6,650 ° C and its average density is 13. Its pressure (measured in GigaPascal, GPa) is millions of times the surface pressure.
The inner core continuously radiates intense heat outward, through the various concentric layers that form the solid portion of the planet. The source of this heat is the energy released by the decay of uranium and other radioactive elements. Convection currents inside the mantle transfer most of the Earth's thermal energy to the surface.
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