fr en es pt
Contact the author rss astronoo

Life of the Earth

Layers of the Earth

 Automatic translation  Automatic translation Updated June 01, 2013

The Earth is a celestial object in which it made a tremendous heat at the center, about 6000°C and 20°C in mean surface.
These are the heat exchange between the center and the surface that sustain the Earth.
This heat melts the rocks at a depth of several tens of kilometers, is the manifestation of volcanism.
But part of this heat is also transformed into mechanical energy is the manifestation of earthquakes caused by tectonic plate movement.
That's life on Earth, disasters perceived by humans to determine the different layers of our planet. The recording stations, seismographs, placed everywhere on Earth tell us about the movements of the crust. The seismic waves that spread out from the epicenter, which spread very long in all directions and particularly in depth, are captured.
The time taken by these waves passing through the different layers of different physical properties, allows seismologists to determine the discontinuities of Earth strata. The first 400 kilometers are very well known and beyond the representation of the layers must be imagined and simulated experimentally. Seismology was able to reconstruct the structure of the Earth.
The major discontinuities are those between the crust, mantle and core. Between the crust and mantle is the Moho (MOHO), which lies about 70 km.
Between the mantle and the core is the Gutenberg discontinuity at about 2885 km.
Between the inner core and outer core is the Lehmann discontinuity at about 5155 km.

 The layers of the Earth

Image: The interior of the Earth consists of a succession of layers of different physical properties. The central core is divided into two parts, the solid inner core and liquid outer core. The mantle is divided into two parts, the solid lower mantle and upper mantle mainly plastic, called the asthenosphere. The crust or the crust is solid, it moves through the upper mantle during earthquakes.

Characteristics of the Earth
Average orbital radius  149 597 887 km (1 ua)
Orbital Circumference 9,4×108 km or
6,283 ua
Orbital eccentricity 0,016 710 22
Period of revolution
365,256 96 days
Orbital velocity
 29,783 km/s or
107 218,8 km/h
Orbital inclination 
Equatorial diameter
 12 756,28 km
(6 378,14 km)
Polar diameter
 12 713,55 km
(6 356,78 km)
Equatorial perimeter 40 075,02 km
surface 510 067 420 km²
volume 1,083 21 x 1012 km³
Mass 5,973 6 x 1024 kg
Average density 5515 kg/m³
Gravity (lat. 0°, alt. 0) 9,780 m/s²
Rotation period (sidereal day) 0,997 258 days, or 23,93419 h
Speed of rotation (equator) 1 674,38 km/h
Axis inclination 23,45°
Escape Velocity 11,186 km/s
Average atmospheric pressure at altitude 0 101,325 kPa

Structure of the Earth


The planets are assumed to consist of successive layers of increasing density.
The materials are in order of their density, the iron center and the iron sulfide, silicates, water, nitrogen, carbon dioxide, ammonia, methane, helium, hydrogen. There is yet no two identical planets in their structures, each with its own characteristics.
The native iron, first condensate  grains of solid chemicals and mineralogical birth fused in the nebulae, the following is called: the sequence of condensation. The first compounds that condense at 1300 ° C, are rich in titanium oxides, aluminum and calcium. To 1050 ° C condenses massive metallic iron and then to 950 ° C, the first case the silicate magnesium silicate and iron. To 800 ° C, to form silicates looser structures, feldspars and iron sulfide. At even lower temperatures condenses silicate containing water at 0 ° C and the water condenses into ice. abundant, is a constituent of the Earth's core.
Silicon, magnesium silicate and iron are essential components of Earth's mantle. Feldspar, condensate gives the basalt forms the floor of Earth's oceans. The internal structure of the Earth is divided into several successive envelopes, the earth's crust, mantle and core.
This representation is very simplified since the envelopes can themselves be decomposed. To identify these layers, seismologists use seismic waves, when the speed of a seismic wave suddenly changes, there is change of environment, so layer.
This method allowed, for example, determine the state of matter at great depths (deep mantle, core).
These layers are bounded by discontinuities such as the Moho between the crust and mantle, that of Gutenberg between the mantle and core.
The Earth formed by accretion of meteorites and the different layers are implemented in accordance with the density of its constituents.


The theory of plate tectonics is now recognized since the late 1960s and widely needed in the scientific world. In the 19th century it was hard to believe that entire continents could drift.
We know now that the solid mantle is driven by huge convection currents that flow over millions of years. The image we have now is a complex and active planet whose crust is composed of oceanic and continental plates of different mineral compositions, constantly moving under the combined action of convection currents and internal gravity land.
Continental blocks formed by collision of continental plates and tear, according to a cycle of 400 million years.
Oceanic plates are heavier, are participating in this ballet constant for several billion years and often end up diving in the Earth's interior by subduction, thus helping to recycle the Earth's crust whose thickness varies between a few kilometers and 65 km.
The seed (inner core) is a solid ball of 1220 km radius, located at the center of the Earth. Seismologists suspect the existence of an almond in it.
It is surrounded by the liquid core composed of an alloy of molten iron. It increases, by crystallization of liquid iron core cools slowly.

 structure of the Earth

Image: The structure of the Earth: crust solid surface has a thickness of 30 to 65 km, upper mantle viscosity, with a thickness of 670 km, the lower mantle elastic thickness of 2180 km, the liquid outer core With a thickness of 2270 km, the solid inner core with a thickness of 1220 km.

Life on Earth


Life is a mysterious and universal tendency of matter to associate, to organize, to become more complex. The living is characterized in that it draws energy in the environment, use this energy, waste and rejects expanding its organization. At the species level, the living is getting more complex since 4.5 billion years. Life is nothing else than a trivial mechanism, a particular form of matter which we will certainly discover the secret, as it is tenacious. We find that life evolves in time by taking a path defined by an infinite number of parameters, which makes it unpredictable and indefinable. But there is a biological definition of life: "an organism is alive when said exchange of matter and energy with its environment by maintaining its autonomy when it replicates and evolves by natural selection. "
All living organisms ensure their stability by responding to changes in their environment.
Life has a faculty of adaptation and learning.
Is it not rather that life?


But we also see by observing the galaxies, stars and planets, that matter is able to self-organize without being alive. However, a good definition of life must take into account this concept, ie, the ability of the material to gradually climb the ladder of complexity.
The tenacity of life is it not proof that it is present everywhere in the Universe, patiently waiting for favorable conditions to continue its path to complexity? It is difficult to believe that life exists on Earth, wherever there is liquid water, there is a possibility of life even under the icy crust of planets or satellites of planets. Life thrives in places where even the sun's energy does not penetrate, we see into the depths of our planet.
We recognize life when we see it!

Image: Note in the photo enlarged, the frail membrane of the Earth's atmosphere that protects life. Earth, like the cell, protected life inside a cell membrane.

 Planet Earth

1997 © − Astronomy, Astrophysics, Evolution and Ecology.
"The data available on this site may be used provided that the source is duly acknowledged."