• Saturday March 28,2020

Layers of the Earth

We explain what are the layers of the Earth and the characteristics of each. In addition, the discontinuities of Mohorovicic and Gutenberg.

The layers of the earth are the crust, the mantle and the nucleus.
  1. What are the layers of the Earth?

Planet Earth is a spheroid planet of 12, 742 kilometers of equatorial diameter, with a slight flattening at the poles. Humanity, together with other forms of life, inhabit its surface (the biosphere). But inside, the planet is made up of a set of concentric layers of different composition and dynamics.

The set of these layers forms the geosphere . As with other rocky planets, the layers of the Earth become more dense as we move towards its center, where the planetary nucleus is located. On the other hand, the deeper we go, the more heat there will be, and the closer we will get to the geological past, that is, to the traces of the planet's formation itself.

The layers of the Earth, then, are three: crust, mantle and core, each of which comprises various intermediate strata and has certain characteristics, which we will see below separately.

See also: Soil layers

  1. Earth crust

In the earth's crust live all living beings.

It is the most superficial layer of the planet, on which we live living beings, even those that inhabit the depths of the soil.

The deepest hole that we humans have dug, called Kola Super Deep Well (former Soviet Union) is 12, 262 meters deep, and is within the range of the earth's crust. It extends from the surface itself (0 km) to 35 kilometers deep .

All continents are part of the continental crust. Its composition is mostly of felic rocks (sodium, potassium and aluminum silicates) with an average density of 2.7 g / cm 3 .

More in: Land Crust

  1. Mohorovicic discontinuity

At an average depth of 35 kilometers (70 on the continents and 10 in the oceans) is the so-called Mohorovicic Discontinuity or “Mold”, a transition zone between the earth's crust and the mantle . It serves as a transition between the less dense crust and the denser rocks of iron silicate and magnesium that start the mantle.

  1. Lithosphere

The lithosphere is formed by tectonic plates.

The lithosphere is another name that receives the upper layer of the Earth, between 0 and 100 kilometers deep, that is, it covers the entire earth's crust and the first kilometers of the upper mantle or the asthenosphere.

Its name literally means "stone sphere." It is fragmented into a set of tectonic plates on which the crust rests, on whose edges the geological accidents known as faults or magmatism occur, giving rise to the mountains and depressions (orogenesis).

The lithosphere can be continental or oceanic, depending on what type of crust is above it, being thicker in the first case and thinner in the second.

  1. Asthenosphere

Located below the lithosphere, between 100 and 400 kilometers deep, is the upper area of ​​the mantle known as asthenosphere. It is composed of silicate materials of high ductility, either in solid state or semi-molten by pressure and high temperatures.

This layer allows movement over it of the tectonic layers, thus allowing continental drift. As we approach its lower edge, however, the asthenosphere loses its properties and quickly acquires rigidity.

  1. The earth's mantle

The layer that follows the crust, strictly speaking, is the earth's mantle, which is also the widest stratum on the planet, covering 84% of the Earth . It extends from 35 kilometers deep to 2890, where the earth core begins.

It becomes progressively hotter as you move towards the core. It oscillates between temperatures of 600 C to 3500 C between its upper strip and the vicinity of the nucleus.

The mantle contains rocks in a state of viscous paste, due to the high temperatures and the enormous pressure, although contrary to what would be thought, as you move towards the core the rocks tend to be more sym ss idas, due to the gigantic pressures that force them to occupy the minimum possible space.

The command is subdivided into two regions:

  • Upper mantle From Moho to 665 kilometers deep, where peridothetic, ultrabasic rocks predominate, mostly composed of magnesium olivine and pyroxene (80% and 20% respectively).
  • Lower mantle Extending from 665 kilometers deep to the so-called Gutemberg discontinuity at about 2900 kilometers deep, it is a very solid and low plasticity area, of much higher density, despite its temperatures between 1000 and 3000 C. It is thought that it could house more iron than the upper layers, given its proximity to the nucleus.
  1. The Gutenberg Discontinuity

In the discontinuity of Gutenberg the magnet is born that creates northern lights.

Between the earth's mantle and the planet's core is another discontinuity, located almost three thousand kilometers deep. His name pays homage to his discoverer, the German geologist Beno Gutenberg, who came into existence in 1914.

It is the region where the electromagnetic waves that generate the Earth's magnetosphere are born, thanks to the rubbing of the outer core, composed of ferromagnetic metals, and the mantle.

  1. The Earth Core

The innermost zone of all earth layers is the nucleus. It is almost 3, 000 kilometers deep and extends to the very center of the planet.

It is the densest region on the planet, which is pretty much to say, since Earth is the densest planet in the Solar System (5515 kg / m 3 on average). This means that the pressure in the nucleus is millions of times that of the surface, and that its temperatures reach up to 6700 C .

The core is composed of two distinct parts:

  • The external nucleus, which reaches 3400 km deep and is semi-solid in nature, probably composed of a mixture of iron, nickel and traces of other elements such as oxygen and sulfur.
  • The inner core, which is a solid sphere of 1220 km radius, composed mostly of iron, although with a minor presence of nickel and other heavy elements, such as mercury, gold, cesium and titanium. It is possible that the inner core rotates faster than the rest of the layers, and that its gradual cooling generates part of the enormous amount of internal heat of the planet.

Continue with: Earth Rotation

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