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The oldest continents may be the result of giant meteorite collisions

The oldest continents may be the result of giant meteorite collisions

So far, Earth is the only planet that we know of with continents.

However, the way these formed and developed not clear. We know, for example, because the edges of the continents separated by thousands of kilometers coincide – long ago the land mass was concentrated in a large area. subcontinent.

Since the planet is not like this nowadays, it is unanimous Something had caused this giant continent to disintegrate. A new investigation has shown data that appears to indicate that the effects of giant meteorites She played an important role.

Deny this doubt Zirconium metal crystals It was excavated in a craton in Western Australia, a piece of Earth’s crust that has been stable for over a billion years.

known as Pilbara CratonThis is a piece of the crust Best save on the planet…the zirconium crystals within them contain evidence of ancient meteorite traces before the breakup of the continents.

“A study of the oxygen isotope composition in these zircon crystals revealed a Top-down processwhich begins with melting He explained that the rocks are near the surface and are progressing deeper, consistent with the geological impact of giant meteorite impacts.” Tim Johnson, Geologist at Curtin University in Australia.

Our research presents the first hard evidence That the processes that eventually formed the continents began with the impacts of giant meteorites, similar to those responsible for the extinction of the dinosaurs, but that it happened billions of years ago“.

Work published in the magazine temper naturein 26 rock samples It contains fragments of zirconium dating between 3.6 and 2.9 billion years old. The team of researchers carefully analyzed the oxygen isotopes. Specifically, the ratios of oxygen-18 and oxygen-16, which contain 10 and 8 neutrons respectively. These ratios are used in paleobiology to determine temperature rock formation at any isotopes.

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Based on these ratios, the team was able to distinguish Three distinct stages And essential in the formation and development of the Pilbara Craton, as he says Science alert.

The first stage is shaping A large proportion of zircon Consistent with partial dissolution of the crust. The researchers showed that this partial melting was most likely the result of meteorite bombardmentwhat or what warmed up Planetary crust upon collision. The oldest set of these zircons, according to the team’s interpretation, were the result of a single giant impact that led to kraton formation.

The second stage was a period Rework And the basic stability From the crust, followed by the third stage – the period of melting and formation of granite. Then, much later, this stable core would evolve into the continents of today, like the cratons found on Earth. other continents around the world.

However, many meteorites have already hit Earth in eons past, by the numbers much superior number of continents. It’s only the largest of the effects that can generate enough heat to form a kraton, which appears to be twice the size. thickness from the surrounding lithosphere.

These results fixed with Previously Suggested Models to form kratons around the world — but they constitute, the researchers said, the strongest evidence yet for this theory.

However, this is just one kraton, out of a total About 35 acquaintances. To make the evidence stronger, the team will need to compare their results with more samples from other cratons to see if their model is correct. globally consistent.

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Data on other regions of the ancient continental crust on Earth seem to show Patterns similar to those recognized In Western Australia, Johnson said. “We would like to test our results on these ancient rocks to see if our model is applicable to a larger scale, as we think.”

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