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 Automatic translation  Automatic translation Category: Earth
Updated Apr 13, 2015
  structure of the Earth

Image: Earth placed in an aquarium. The structure of the Earth is divided into several layers, the atmosphere, the Earth's crust (continental and oceanic crust), mantle (upper and lower) and the core (internal and external). Each layer has a thickness of several tens of kilometers. If one converts each layer of the same density thickness, for example that of water (1) it gives this representation where the earth's crust is insignificant (continental crust in blue sky and oceanic crust in white) and the atmosphere non-existent.
The continental crust on the surface has a thickness of 30 to 65 km (1 blue pixel on the display), the oceanic crust on the surface has a thickness of 1 to 12 km (one white pixel), the viscous upper mantle has a thickness 670 km (≈100 brown pixels), the elastic lower mantle has a thickness of 2180 km (≈230 navy blue pixels), the liquid outer core has a thickness of 2270 km (≈160 green pixels) and the solid inner core has a 1220 km thickness (8 red pixels).

Peridotite is an igneous rock mainly composed of olivine associated with other ferromagnesian silicates, mainly pyroxenes. It constitutes the major part of Earth's mantle. Peridotite often has a green tint or greenish-yellow. Mohorovičić discontinuity (or Moho) marks the boundary between the Earth's crust and upper mantle. It is on average 35 km deep. The Moho is a physicochemical discontinuity between two layers, so the Earth's crust is composed of rocks, ≈3 density basaltic (in the oceans), granitic (under continents), while the mantle is composed of peridotites from ≈4 density. The speed of seismic waves (vibrations Ground during an earthquake) is amended by geological structures through which they pass. By measuring the propagation speed of the seismic waves that seismologists can analyze the structure of the Earth.

1997 © − Astronomy, Astrophysics, Evolution and Earth science.

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