meteorites the size of the one that killed the dinosaurs

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Each planet in the Solar System has characteristics that make it unique. Among the characteristics that make ours unique are the continents, large masses of land emerged from the oceans as a result of plate tectonics. And why is this happening on our planet? The answer that now seems most likely is not inside it but in the asteroids that collided with it. Asteroids, yes, of the caliber of the one that wiped out the dinosaurs millions of years later.

An ancient origin.
The history of the continents began about 3.6 billion years ago, when the Earth was barely 1 billion years old. This is how an international team of researchers, including scientists from Curtin University in Perth, in Western Australia, have deduced from their observations.

To be more specific, its origin would be due to the intense meteor shower that the Earth would have suffered in those times, with various impacts of force similar to that of the one that killed the dinosaurs.

These impacts would have created irregularities in the outer layers of the Earth, with thicker areas through a process of compression and “rebound”, but with greater geological activity at the impact site. Geological activity that would have stabilized later, forming what we know today as cratons.

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Cratons, the key piece.
Cratons are geological formations with a characteristic that makes them very relevant: their age. Cratons remain stable, away from tectonic activity and other ways rocks are altered. They therefore allow geologists to look back into the geological past.

The study recently published in the magazine Nature, turned to one of the oldest known cratons, located precisely in the region of Western Australia. The Pilbara Craton dates from the Archean Eon, the first geologic era after the formation of the Earth (the Hadean era), which spans the period between about 4 billion years ago and 2.5 billion years ago. Only two cratons are known from this age.

Three stages.
This craton did not arise suddenly but in three distinguishable stages. The oldest occurred about 3,600-3,400 million years ago. The study of the craton that emerged in this phase found evidence that the geological formation suffered a significant impact. This impact would have generated an enlargement of the earth’s crust in the area, creating new rock formations due to the high temperatures. Only large impacts would have been capable of initiating this process. Here interactions between the earth’s crust and mantle, volcanism and “dripping” would already appear.

The second stage of craton formation (between 3,400 and 3,000 million years ago) in which some areas suffered a process of fusion and rapid metamorphosis in which the sodic granites of the area were formed. In the third stage, the granite continued to form and the craton stabilized.

oxygen isotopes.
The proof of this process is in the oxygen isotopes. In Tim Johnson’s wordswho led the research, “studying the oxygen isotope composition in these zircon-rich crystals revealed a ‘top-down’ process beginning with melting of rocks near the surface and progressing deeper, consistent with the geological effect of giant meteorite impacts.”

Movements on Earth.
Understanding our geological past can be a useful tool for various goals, including understanding our geological present. We can better understand plate tectonics that generates continental drift, but also related to earthquakes and tsunamis.

We can also better predict what lies beneath our feet, facilitating the mining jobs that the world continues to rely on for electronics.

Our planet is the only one we know of with continents, but we continue to find planets around us and we have better and better tools to study them. Understanding our geological past can also help us understand the past of our solar system and the present of the planets that we can detect around us.

Find new data.
The team has not considered the issue settled. There are more than thirty cratons discovered in the world and this group of researchers wants to see if they can find evidence of this theory in more places.

In Johnson’s words, “Data relating to other areas of ancient continental crust on Earth seem to show patterns similar to those recognized in Western Australia. We would like to test our findings on these ancient rocks to see if, as we suspect, our model is widely applicable.”

Image | BIT

Each planet in the Solar System has characteristics that make it unique. Among the characteristics that make ours unique are…

Each planet in the Solar System has characteristics that make it unique. Among the characteristics that make ours unique are…

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