Scientists find evidence that the continents were formed by giant meteorite impacts

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Scientists have discovered what they believe is the strongest evidence yet that the continents were formed by giant meteorite impacts during Earth’s early history.

Meteorite impacts were “particularly prevalent during the first billion years or so of our planet’s four and a half billion year history,” according to Curtin University researchers.

The theory that the continents were originally formed at the sites of these impacts has been around for decades, but there is little hard evidence to support it, until now, says Dr Tim Johnson.

“Examining tiny crystals of the mineral zircon in rocks of the Pilbara Craton in Western Australia, which represents the best-preserved remnant of Earth’s ancient crust, we found evidence of such giant meteorite impacts,” said Dr. Johnson.

The mineral deposits around the iron-rich Pilbara are some of the oldest on Earth, and have previously been the site of the discovery of evidence of the oldest known terrestrial life.

A road leads to an open pit mine in the area known as the Pilbara region located in northwestern Western Australia
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A road leads to an open pit mine in the area known as the Pilbara region located in northwestern Western Australia

“The study of the oxygen isotope composition in these zircon crystals revealed a ‘top-down’ process that begins with the melting of the rocks near the surface and progresses deeper, according to the ‘geological effect of giant meteorite impacts,’ Dr Johnson explained.

“Our research provides the first strong evidence that the processes that eventually formed the continents began with giant meteorite impacts, similar to those responsible for the extinction of the dinosaurs, but occurring billions of years earlier.”

Understanding how Earth’s continents formed and continue to evolve is crucial, the scientists explained, because we depend so much on their mineral deposits, as well as the fact that land masses host most of our planet’s biomass.

“The continents are home to critical metals such as lithium, tin and nickel, commodities that are essential for the emerging green technologies needed to meet our obligation to mitigate climate change,” said Dr Johnson.

“These mineral deposits are the end result of a process known as crustal differentiation, which began with the formation of the first land masses, of which the Pilbara craton is just one of many.

“Data related to other areas of ancient continental crust on Earth appear to show similar patterns to those recognized in Western Australia. We would like to test our findings in these ancient rocks to see if, as we suspect, our model is more widely applicable .”

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