There is a new evidence to suggest that giant meteorite impacts played a significant role in the formation of continents.
- New Curtin research has provided the strongest evidence yet 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.
Key highlights
- Dr Tim Johnson, from Curtin’s School of Earth and Planetary Sciences, said the idea that the continents originally formed at sites of giant meteorite impacts had been around for decades, but until now there was little solid evidence to support the theory.
- 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, they found evidence of these giant meteorite impacts.
- The work was conducted on 26 rock samples containing fragments of zircon, dating between 3.6 and 2.9 billion years old.
- The research team carefully analyzed isotopes of oxygen; specifically, the ratios of oxygen-18 and oxygen-16, which have 10 and 8 neutrons, respectively.
- These ratios are used in paleogeology to determine the formation temperature of the rock in which the isotopes are found.
- Based on these ratios, the team was able to distinguish three distinct and fundamental stages in the formation and evolution of the Pilbara Craton.
- 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 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.
- Understanding the formation and ongoing evolution of the Earth’s continents was crucial given that these landmasses host the majority of Earth’s biomass, all humans and almost all of the planet’s important mineral deposits.
- Not least, the continents host critical metals such as lithium, tin and nickel, commodities that are essential to the emerging green technologies needed to fulfil our obligation to mitigate climate change.
- 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.
(Source: ScienceDaily)
