Giant meteorite impacts built Earth’s continents billions of years ago

• The study supports the theory that the Earth's continents were created by large meteorites.
• This process occurred during Earth's earliest period.
• If true, it would explain much of the abundance of zircon crystals in ancient pieces of Earth's crust.

A new study has revealed that the continents of the Earth were formed by enormous meteorite impacts during the first billion years of our planet's four and a half billion-year history.

Meteorite strikes are the best candidates for the process, discovered the Curtin University research, published on Wednesday.

The theory that the continents were first formed at the sites of massive meteorite impacts has been around for a while, but until recently, there wasn't much good evidence to back it up, according to Dr. Tim Johnson of Curtin's School of Earth and Planetary Sciences, Australia.

“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,” Dr. Johnson said.

“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.”

Dr. Johnson said it is imperative to comprehend how the Earth's continents formed and are still evolving, given that these landmasses are home to the vast majority of the biomass on Earth, all humans, and nearly all of the planet's significant mineral reserves.

“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,” Dr. Johnson said.

“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."

"Data from other old continental crust regions on Earth seem to reveal patterns resembling those found in Western Australia."

In order to determine whether our approach is more broadly applicable as we suspect, we would like to test our findings on these prehistoric rocks, the professor added.

For more, you can read about the study linked here.

Study abstract:

Earth is the only planet known to have continents, although how they formed and evolved is unclear. Here using the oxygen isotope compositions of dated magmatic zircon, we show that the Pilbara Craton in Western Australia, Earth’s best-preserved Archaean (4.0–2.5 billion years ago (Ga)) continental remnant, was built in three stages. Stage 1 zircons (3.6–3.4 Ga) form two age clusters with one-third recording submantle δ18O, indicating crystallization from evolved magmas derived from hydrothermally altered basaltic crust like that in modern-day Iceland. Shallow melting is consistent with giant impacts that typified the first billion years of Earth history. Giant impacts provide a mechanism for fracturing the crust and establishing prolonged hydrothermal alteration by interaction with the globally extensive ocean. A giant impact at around 3.6 Ga, coeval with the oldest low-δ18O zircon, would have triggered massive mantle melting to produce a thick mafic–ultramafic nucleus. A second low-δ18O zircon cluster at around 3.4 Ga is contemporaneous with spherule beds that provide the oldest material evidence for giant impacts on Earth. Stage 2 (3.4–3.0 Ga) zircons mostly have mantle-like δ18O and crystallized from parental magmas formed near the base of the evolving continental nucleus. Stage 3 (<3.0 Ga) zircons have above-mantle δ18O, indicating efficient recycling of supracrustal rocks. That the oldest felsic rocks formed at 3.9–3.5 Ga (ref. 13), towards the end of the so-called late heavy bombardment, is not a coincidence.