Greenland rocks provide evidence of Earth formation process

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Rocks dating back 3.4 billion years from south-west Greenland’s Isua mountain range have yielded valuable information about the structure of Earth during its earliest stages of development. In these rocks, which witnessed the first billion years of Earth’s history, a French-Danish team led by researchers from the ‘Magmas and Volcanoes’ Laboratory (CNRS / Université Blaise Pascal / IRD) have highlighted a lack of neodymium-142, an essential chemical element for the study of Earth’s formation.


This deficit supports the hypothesis that between 100 and 200 million years after its formation, Earth was made up of an ocean of molten magma, which gradually cooled. The work, which was carried out in collaboration with the Laboratoire de Géologie de Lyon (CNRS / Université Lyon 1 / ENS de Lyon) and the University of Copenhagen, was published on 1 November 2012, in the journal Nature.

Earth is believed to have formed 4.58 billion years ago, by accretion of material in the Solar System. The heat produced by the accretion process, as well as by the decay of radioactive elements, caused this material to melt. As a result, 100 to 200 million years after its formation, Earth must have been made up of an ocean of molten magma, in the center of which a metallic core formed. The ocean gradually cooled. Earth’s crust then appeared, and the process of continental drift began. The crystallization of the molten magma is likely to have been accompanied by the chemical layering of Earth: concentric layers with distinct chemical compositions became differentiated. It is the signature of these primordial inhomogeneities that the researchers found in the Isua rocks.

Written By: CNRS
continue to source article at sciencedaily.com

4 COMMENTS

  1.   @OP – Earth is believed to have formed 4.58 billion years ago, by accretion of material in the Solar System. 
    ▬▬▬▬▬▬▬▬▬▬▬▬▬
    The heat produced by the accretion process, as well as by the decay of radioactive elements, caused this material to melt.

    As a result, 100 to 200 million years after its formation, Earth must have been made up of an ocean of molten magma, in the center of which a metallic core formed.

    The ocean gradually cooled.
    Earth’s crust then appeared, and the process of continental drift began.
    The crystallization of the molten magma is likely to have been accompanied by the chemical layering of Earth: concentric layers with distinct chemical compositions became differentiated.

    It is the signature of these primordial inhomogeneities that the researchers found in the Isua rocks.

    It is interesting that rocks this old have been found to provide this sort of material.

    However, there is a further link from the article page to an earlier one to which I would have expected some reference to be made, rather more than a simple reference to “an accretion process” : –

    http://www.sciencedaily.com/re
    The common estimate of the moon’s age is as old as 4.5 billion years old (roughly the same age as the solar system) as determined by mineralogy and chemical analysis of moon rocks gathered during the Apollo missions.

    However, Lawrence Livermore National Laboratory scientist Lars Borg and international collaborators have analyzed three isotopic systems, including the elements lead, samarium and neodymium found in ancient lunar rocks, and determined that the moon could be much younger than originally estimated. In fact, its age may be 4.36 billion years old.

    The new research has implications for the age of Earth as well. The common belief is that the moon formed from a giant impact into Earth and then solidified from an ocean of molten rock (magma).

    “If our analysis represents the age of the moon, then the Earth must be fairly young as well,” said Borg, a chemist. “This is in stark contrast to a planet like Mars, which is argued to have formed around 4.53 billion years ago. If the age we report is from one of the first formed lunar rocks, then the moon is about 165 million years younger than Mars and about 200 million years younger than large asteroids.”

    The isotopic measurements were made by taking samples of ferroan anorthosite (FAN), a type of moon crustal rock, which is considered to represent the oldest lunar crustal rock type.

    The Earth Moon System seems to have been formed around this time by one of the versions of the “Giant impact hypothesis”  - 
    http://en.wikipedia.org/wiki/G… –
    so how this matches to the timing of the events is relevant.

    http://upload.wikimedia.org/wi

  2.   @OP:disqus   Earth is believed to have formed 4.58 billion years ago, by accretion of material in the Solar System.

    Just to expand a little more on this OP understatement:

    The Late Heavy Bombardment (commonly referred to as the lunar cataclysm, or LHB) is a period of time approximately 4.1 to 3.8 billion years ago (Ga) during which a large number of impact craters were formed on the Moon, and by inference on Earth, Mercury, Venus, and Mars as well.
    The LHB is “late” only in relation to the main period of accretion, when the Earth and the other three rocky planets first formed and gained most of their mass; in relation to Earth or Solar System history as a whole, it is still a fairly early phase. -  http://www.bbc.co.uk/science/e

    @OP:twitter  – This deficit supports the hypothesis that between 100 and 200 million years after its formation, Earth was made up of an ocean of molten magma, which gradually cooled.

    There is a nice little video clip explaining this:

    http://www.bbc.co.uk/science/e

    And a short series of 7 pictures showing the time-line of key events.
    http://www.bbc.co.uk/science/e

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