Understanding the formation and ongoing evolution of the Earth’s continents is crucial, considering that these enormous landmasses host the vast majority of our planet’s biomass, all humans, and nearly all of the major mineral deposits on Earth.
Now, a research team led by Curtin University in Australia has found the strongest evidence yet that the Earth’s continents were formed by giant meteorite impacts which were particularly prevalent during the first billion years of our planet’s four-and-a-half billion years history. Although this hypothesis had been around for decades in the scientific community, there was little solid evidence to support it until now.
“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,” said study lead author Tim Johnson, an associate professor of Earth and Planetary Sciences at Curtin University.
“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. Our research provides the first solid evidence that the processes that ultimately formed the continents began with giant meteorite impacts, similar to those responsible for the extinction of the dinosaurs, but which occurred billions of years earlier.”
The deposits of critical metals such as lithium, tin, and nickel are all commodities that are essential to the emerging green technologies needed to mitigate climate change. Better understanding the formation and development of these deposits could help scientists devise innovative ways of extracting and using them to safeguard our planet.
“These mineral deposits are the end 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,” explained Professor Johnson.
Since the researchers based their study on materials collected in Western Australia, further research is needed to see whether their model could be generalized for other regions.
“Data related to other areas of ancient continental crust on Earth appears to show 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,” Professor Johnson concluded.
The study is published in the journal Nature.