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According to the study, mysterious blocks in the Earth's interior caused plate tectonics

According to the study, mysterious blocks in the Earth's interior caused plate tectonics

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View of two tectonic plates meeting on the surface in Thingvellir National Park (iconic image). © Zija Blahutar/Imago

When the Moon was forming, a Mars-sized body collided with the Earth. Was this also the cause of plate tectonics, which made life on Earth possible?

About 4.5 billion years ago, a Mars-sized object collided with the nascent Earth and broke off from our moon. Now a team of scientists suggests that this massive impact had an even bigger impact: the impact left mysterious clumps in the Earth's interior It could have helped move tectonic plates – The geological process that causes earthquakes and volcanoes and generally allows life to exist on our planet. This idea in one New study in the magazine Geophysical Research Letters Developed using computer models, it is an attempt to answer one of the fundamental questions about our homeworld.

We live on the only planet known to have a surface composed of rocky plates that slide and collide at their boundaries as the superheated interior moves. This subterranean drama usually goes unnoticed by human standards unless an earthquake or volcanic eruption occurs. However, most experts agree that this process is absolutely essential to life as we know it because it supports the planet's carbon cycle, which is important for keeping the climate habitable. What experts don't agree on is how plate tectonics emerged.

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Mysterious clumps in Earth's mantle: Do they come from a celestial body that struck Earth?

The new work builds on an earlier idea that attempts to explain a geological mystery. For decades, geologists have speculated about the presence of mysterious clumps in the Earth's mantle that were discovered through seismic imaging. These massive, dense masses appear to be made of a different material than the surrounding mantle, raising questions about their nature and how they were formed.

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A theory that appeared last year in the magazine nature The post provides an explanation, but it also raises some questions. It says that after the body that formed the Moon collided with our planet, parts of it landed intact inside the Earth.

The new study takes this idea a step further: About 200 million years after the impact, these submerged pieces may have generated hot exhaust gases inside the Earth, ripping off the emerging surface, cracking the crust, and allowing the circular plates to form. sink – a process called subduction.

Researchers say this process may explain why Earth's oldest minerals are zircon crystals, which appear to have sunk more than 4 billion years ago. In addition, they suspect that it may have contributed to the emergence of modern plate tectonics. “The giant impact not only caused the formation of our moon, but it also created the initial conditions for our Earth,” said Qian Yuan, a geologist at the California Institute of Technology and one of the authors of the study.

The theory raises a number of questions

Outside geologists said the model was fascinating but also raised a number of questions. The idea of ​​an initial subduction event caused by powerful mantle plumes shortly after the moon-forming impact is credible and supported by models and some geochemical data, Taras Geria, a geoscientist at ETH Zurich, said in an email. However, he added that he was unsure whether this would lead to modern plate tectonics or rapid global recycling of the entire crust, similar to what might have happened on the inhospitable planet Venus.

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Michael Brown, a geologist at the University of Maryland, said it is unclear how a circular subduction zone would give rise to global plate boundaries and the plate mosaics found in modern plate tectonics.

“It is almost certainly unknown and unknown.”

“We must remember that there is not enough evidence to know what tectonics looked like in the Archaean, which is the era that occurred between 4 and 2.5 billion years ago,” Brown said. “So from a philosophical point of view, it is almost certainly unknown and unknowable. I think that point is sometimes lost.”

I wrote. Mark Harrison, Distinguished Research Professor at the University of California, Los Angeles, recently wrote an article titled “We don't know when plate tectonics began.”. He questioned the assumptions built into the model and pointed out geochemical inconsistencies that cast doubt on the giant impact theory itself.

“If plate tectonics didn't exist, we wouldn't be having this conversation because our species wouldn't have existed,” Harrison said. “The best thing I can say to people is that my generation… has not been able to solve the most interesting question that still exists in science, which is how and under what conditions life arose.” He has a message for future scientists: “We have wrapped a little gift for you.”

About the author

Carolyn Johnson He is a science reporter. She previously covered health care and health care affordability for consumers.

We are currently testing machine translations. This article was automatically translated from English to German.

This article was first published in English on May 7, 2024 on “washingtonpost.com” was published as part of the collaboration, and is now also available in translation for readers of the IPPEN.MEDIA portals.