Sunday, September 25, 2022

Evidence that giant meteorite impacts formed Earth’s continents

Giant impacts provide a mechanism for fracturing the crust.

Earth is the only planet known to have continents, although how they formed and evolved is unclear. Although the belief that the continents were first formed at the places of massive meteorite strikes has been around for a while, there hasn’t been much evidence to back it up.

A study by Curtin University offered the strongest evidence that Earth’s continents were formed by giant meteorite impacts that were particularly prevalent during the first billion years or so of our planet’s four-and-a-half-billion-year history.

Dr. Tim Johnson from Curtin’s School of Earth and Planetary Sciences said, “By examining tiny crystals of the mineral zircon in rocks from the Pilbara Craton in Western Australia, which represents Earth’s best-preserved remnant of ancient crust, we found evidence of these giant meteorite impacts.”

“Studying the composition of oxygen isotopes in these zircon crystals revealed a ‘top-down’ process starting with the melting of rocks near the surface and progressing deeper, consistent with the geological effect of giant meteorite impacts.”

The study offers the first convincing proof that massive meteorite strikes, comparable to those that wiped out the dinosaurs but billions of years earlier, were the catalyst for the processes that finally produced the continents. Understanding the formation and ongoing evolution of the Earth’s continents is crucial. These landmasses host most of Earth’s biomass, all humans, and almost all of the planet’s important mineral deposits.”

Dr. Johnson said, “Not least, the continents host critical metals such as lithium, tin, and nickel, commodities that are essential to the emerging green technologies needed to fulfill our obligation to mitigate climate change.”

“These mineral deposits are the result of a process known as crustal differentiation, which began with the formation of the earliest landmasses, of which the Pilbara Craton is just one of many.”

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

Journal Reference:

  1. Tim Johnson, Giant impacts and the origin and evolution of continents, Nature (2022). DOI: 10.1038/s41586-022-04956-y

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