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New research reveals how Earth’s seven continents were actually created

It happened more than three-and-a-half billion years ago - before life on Earth began.

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By Mark Waghorn via SWNS

The seven continents were created by giant meteorite impacts - similar to the one that wiped out the dinosaurs, according to new research.

They happened more than three-and-a-half billion years ago - before life on Earth began.

It sheds fresh light on evolution. The landmasses host all humans and most of the planet's biomass and vital minerals.

Scientists analyzed microscopic grains of a mineral called zircon - which acts like a geological 'clock'.

They were dug from ancient rocks known as Pilbara Craton in Western Australia - dubbed "the oldest place on Earth."

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Lead author Dr. Tim Johnson said: "Studying the composition of oxygen isotopes in these zircon crystals revealed a 'top-down' process.

"It started with the melting of rocks near the surface and progressed deeper - consistent with the geological effect of giant meteorite impacts.

"Our research provides the first solid evidence the processes that ultimately formed the continents began with giant meteorite impacts.

"They were similar to that responsible for the extinction of the dinosaurs - but occurred billions of years earlier."

It led to the huge regions we know today as Asia, Africa, North America, South America, Antarctica, Europe and Australia - in order of size.

Dr. Johnson, of Curtin University in Perth, said the study even has implications for combating global warming.

He explained: "Not least, the continents host critical metals such as lithium, tin and nickel.

"These commodities are essential to the emerging green technologies needed to fulfill our obligation to mitigate climate change.

“These mineral deposits are the end result of a process known as crustal differentiation.

"It began with the formation of the earliest landmasses - of which the Pilbara Craton is just one of many."

Massive space rocks regularly smashed into the planet during the first quarter of its four-and-a-half-billion-year history.

It's known as the "Late Heavy Bombardment." Had it continued life as we know it would never have got started.

For decades it had been theorized the continents originally formed at these sites but there was no proof - until now.

Dr. Johnson said: "The Pilbara Craton represents Earth's best-preserved remnant of ancient crust.

"By examining tiny crystals of the mineral zircon in rocks we found evidence of these giant meteorite impacts."

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The study also pushes back when the first continents - called cratons - emerged from the ocean.

It was believed to have happened roughly 2.5 billion years ago. The findings in the journal Nature add to evidence it happened much earlier.

They eventually formed into one 'supercontinent' named Pangaea. It began breaking up 175 million years ago - with different segments drifting into those we see today.

Dr. Johnson said: "Earth is the only planet known to have continents - although how they formed and evolved is unclear."

A giant impact around 3.6 billion years ago would have triggered massive mantle melting to produce a thick nucleus, he explained.

Data related to other areas of the ancient continental crust on Earth appears to show patterns similar to those recognized in Western Australia.

The researchers plan to test the findings on these ancient rocks to see if - as they suspect - their model is more widely applicable.

Dr. Johnson said: "The search for evidence of the Late Heavy Bombardment on Earth
has been a long one.

"However, all along it seems the evidence was right beneath our feet."

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