The surface of the Earth is covered by water, revealing the continents and archipelagos. This water is part of the "Ocean" with a big O. Oceans cover about 361 million km2, or 70.8% of the surface of the planet and their average depth of 3 700 to 3 800 meters.
The total water volume reached 1.37 billion km3.
According to Francis Albarède, geochemist at the Laboratoire des Sciences de la Terre (CNRS / ENS Lyon / Université Claude Bernard), in an article published on 29.10.2009 in the journal Nature, all water on Earth is home extraterrestrial. It comes from the icy asteroid bombardment, the beginning of his training, there are 4.5 billion years, 80 to 130 million years after solar system formation.
The Earth has been at this time, enough water for the oceans were formed around the continents. Entering the mantle from the surface, water would have softened the earth and reduces the voltage at which the materials are broken. An event at the origin of the tectonic plates and the emergence of continents.
Image: The major tectonic plates, bounded by the lines of earthquakes. The plate of North America from South America, Eurasia, Africa, Pacific, Australia and Antarctica, are visible in this image.
Water is not from the fumes emitted during the intense volcanism beginning of the creation of our planet. To Francis Albarède, water is not part of the initial inventory of the Earth but from the stirring maintained in the outer solar system by giant planets.
The mantle rocks are poor in water, geochemists evaluate its concentration in two hundredths of a percent. It is the same on the sister planet of Earth, Venus and Mars. This is the main reason cited by Francis Albarède.
During the formation of the Solar System, the temperature would never come down low enough in the space between the Sun and the orbit of Jupiter, that the volatile elements can condense with the material world. The arrival of water on Earth then would correspond to an episode of the late planetary accretion.
The terrestrial planets are formed by agglomeration of asteroids, a few million years. This constant bombardment from the beginning is between objects located between the Sun and the asteroid belt.
This space windswept electromagnetic young Sun is too hot for water and volatile components are condensed.
The distribution of matter has the effect of cleaning the solar system's dust concentrating material in the planets in formation.
The gravity of giant planets distributed in all directions, asteroids covered with ice.
Image: distribution of matter has the effect of cleaning the solar system's dust concentrating material in the planets in formation.
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