The question of the formation of the first continents is still strongly and permanently debated. The question is the difficulty of finding elements dating back more than 4 billion years. However, a new study has updated the hypothesis of the origin associated with major meteorite impacts.
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[EN VIDÉO] A billion years summed up in 40 seconds: plate tectonics Researchers have modeled the motions of plate tectonics over the past billion years.
So today The amount of continental crust remains relatively stable Representing about 30% of the Earth’s surface, this was not always the case. Originally, our planet was made up of only one huge ocean the silhouette. It’s from this rocky ocean in fusion from the beginning continental crust formed, and gave birth to the first Continents. If we know today that continental growth is mainly related to volcanoes Subduction zones, mechanisms involved in the formation of the first masses Continental is still not clearly defined, the tectonic plates in which subduction participates It did not exist 3.8 billion years ago. However, we found some metal typical of the continental crust, zirconwhich shows a much higher age: more than 4 billion years.
Several theories to explain the formation of the first continental crust
Thus, there are several theories to explain the formation of the first continents from the ocean of primitive magma. Some scholars suggest that it all starts with training of a primitive crust completely different from that of our present-day continents, but could have served as a “base” for the generation of the first continental crust. Others involve giant meteorite impacts.
Although it has been proposed for several decades, this second hypothesis is not clearly supported by the Elements Solid. in A new study published in temper naturea team of scientists from Curtin University (Western Australia) is updating this theory by providing new elements.
The first continental rocks formed under the heat of the impact of a meteorite?
As with other studies on the origin of the first continents, Tim Johnson and colleagues themselves relied on the study of zircon from carton From Pilbara, Western Australia. The batons are already zones a land The oldest and most likely it contains traces, albeit very weak, of the origin of the first continental crust. After analyzing the chemical composition of zircon, in particular, different proportions isotopes Oxygen, the researchers suggest that the first continental rocks may have formed from an episode of surface melt that evolved to the depth rather than the other way around. However, this finding is consistent with the impact caused by a large meteorite impact.
So it was possible to start the formation of the first continental rocks in the affected areas meteorites Giants, such as those that, after billions of years, caused the disappearance of dinosaurs. This type of catastrophic event was far from rare 4 billion years ago. Then the land was subjected to intense bombardment.
Scientists now want to bolster their theory by analyzing zircons from other regions of the world, in order to show that it is indeed a global mechanism rather than a local specificity.
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