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At present, there are six continents emerged and 15 major tectonic plates, huge and rigid pieces of the crust of the planet that glide over the mantle, a lower layer, like ships adrift. But in the past the Earth had a very different look: we know that there was once a large supercontinent, Pangea , and that before this there were others. This is a result of plate tectonics, a process that, pushed by the tremendous pressures and temperatures of the interior of the planet, changes the shape of the continents and, in addition, generates mountain ranges, earthquakes, or volcanic eruptions.
Since when does this happen? Will there be an end? Many researchers have spent years trying to answer these and other questions. This week, a study published in the journal “Science Advances” has shown evidence that plate tectonics global era , that is to say, that occurred on the entire surface of the planet, at least 2,000 million years . These are the first signs of the global tectonics found up to now.
“It’s like talking about the invention of the internet,” he said in a press release Ross Mitchell , co-author of the study and a researcher at the Institute of Geology and Geophysics, Chinese Academy of Sciences (CAS). “Even though the internet existed in some form or another for decades, it was not until 1990 when he began the Era of the Information”, he added. The same thing happened with plate tectonics: there is evidence and models about when it started, but it is not known exactly when it was made global.
Traces of ancient movements
Some researchers place the origin of the tectonic makes up to 4,000 million years ago, only 560.000 years after his birth. On the other hand, the evidence of more direct locating it makes 1000 million years. Now, the team of researchers from the institution of china has concluded that the process was global for 2,000 million years.
How do you have found? We know that when the tectonic plates move and “collide” sometimes raised mountain ranges , such as the Himalayas or the Pyrenees. But the mountains are a result of the movements that are more recent in the geological scale, and do not allow to know what happened thousands of millions of years.
In this case, the researchers designed a study seismological to investigate the structure of old portions of the bark. For it came to several areas where the crust has been stable for a long time, as the region of Ordos, in the province of Shaanxi (China).
There, they found traces seismic discontinuity Mohorovičić, a transition zone between rocks of different composition that marks the boundary between the crust and the mantle. In particular, these signals were found to indicate ancient processes of subduction , a process by which one tectonic plate slips under another. The nature of the materials has allowed them to conclude that there was subduction in that region for thousands of millions of years. And that, therefore, there were tectonic movements.
Reconstruction of the subsurface thanks to seismological studies that indicate the presence of a process of subduction – IGG
This type of signal has been found, for example, in the Himalayas, where the indian plate is “sneaks” under the eurasian . But the novelty is that the researchers have been able to demonstrate that this phenomenon occurred in several regions of the planet, around 2,000 years ago million years, which supports the idea that the tectonic global era by then.
“researchers have done a great job describing their results and placing them in a larger context,” he said in a press release Peter Cawood , a researcher from the University of Monash (Australia) not involved in the study.
According to the authors of the study, these processes of subduction as old, linked to plate tectonics are global, they can interact with the tectonic movements that led to the formation of Nuna , possibly the first supercontinent of Earth.
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