Today Earth has seven continents that together make up less than 30 percent of the planet’s landforms, while 70 percent of the water is left. Continental evolution has been the result of plate tectonics and crustal movements over millions of years, giving the planet its current landscape and geography.
However, a new study indicates that it all started with a bang, providing the strongest evidence that Earth’s continents were formed by the impact of giant meteorites. These effects were prevalent during the first billion years of our planet’s approximately 4.5 billion year old history. The research substantiates the long-held speculation that continents began to form around the sites of meteor strikes.
The study, published in the journal Nature, said that Earth is the only planet to have continents, although how they formed and evolved is unclear. “Massive impacts globally provide a mechanism for fracturing the crust and establishing long-term hydrothermal changes through interactions with the wider ocean,” the paper read.
it all started with a bang
Researchers analyzed tiny crystals of the mineral zircon in rocks from the Pilbara Craton in Western Australia. The region contains the best-preserved remains of Earth’s ancient crust and evidence of ancient meteor attacks on the planet. The team, led by researchers from Curtin University, studied the composition of the oxygen isotopes in these zircon crystals.
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Zircon is the oldest mineral on the planet, being about 4.4 billion years old and sometimes containing traces of uranium. They found an up-and-down process consistent with the geological impact of giant meteorite impacts, starting with the melting of rocks near the surface and progressing deeper.
(Graphic: Alex Kovrubias)
“Our research provides the first solid evidence that the processes that eventually formed continents began with giant meteorite impacts, which were responsible for the extinction of the dinosaurs, but which occurred billions of years ago,” said Dr Tim Johnson from the Curtin School of Earth and Planetary Sciences, said in a statement.
Why do we need to know?
Understanding the formation and ongoing evolution of Earth’s continents is important because these landmasses host most of Earth’s biomass, all humans, and nearly all of the planet’s important mineral deposits, the researchers said. The mineral deposits are the result of a process known as crustal differentiation, which began with the formation of the earliest landmasses.
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Dr Johnson said, “At least, the continents host important metals such as lithium, tin and nickel, which are essential commodities for the emerging green technologies needed to meet our obligation to mitigate climate change. “
The researchers also uncovered that data from other regions of ancient continental crust on Earth show patterns similar to those recognized in Western Australia.
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