Why are most of the rocks on Earth so much younger than the planet itself?

(ORDO NEWS) — Not all rocks on Earth are the same age. Most of them are much younger than our planet.

The oldest patches of oceanic crust are believed to be 200 million years old, a blink of an eye compared to the billions of years the planet has lived. Why did it happen?

“Earth is an active planet,” explains Boyet, a geochemist at the University of Clermont-Auvergne in France. “This makes it different from other planets in our solar system, and also from the Moon.”

The plate tectonics of our planet is constantly processing rocks. When an oceanic plate meets a continental plate, it slides underneath it into the mantle, where the old rocks break down. Then new rocks are formed from the molten mantle.

Several very old rock strata have been found, such as the billion-year-old Nuvvuagittuk greenstone belt in Hudson Bay, as well as similar ancient rocks in Australia, China, Greenland, and South Africa. But even these ancient rocks had a complicated history.

“Exposure to high temperatures during the last collision can change the chemical composition,” says Boyet. “It breaks the isotope system we use to date rocks.”

Therefore, accurately determining the age of the Earth is not an easy task. The original breeds that existed in the earliest stages of its formation no longer exist. To determine the age of our planet, scientists had to look beyond the Earth.

Radiometric dating is used to confirm the age of rocks. Radioactive isotopes decay over a predictable amount of time, allowing geologists to determine the age of the sample.

The dating of the moon rock has given us a clearer idea of ​​the age of the solar system. Another key element was the radiometric dating of meteorites that formed in the first tens of millions of years of the formation of the solar system.

All this data allowed scientists to establish that the age of the Earth is approximately 4.5 billion years.

The absence of 4.5 billion-year-old rocks means that scientists still don’t know for sure what the Earth really was like when clouds of gas and dust condensed to form our planet.


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