A Piece of North America Found in Australia Bolsters Theory of Two-Billion-Year-Old Supercontinent

Scientists recently discovered a region of Australia that was once part of North America, bolstering support for the idea that the two existed as a unified 'supercontinent' nearly two billion years ago.

A team led by researchers from Curtin University in Australia discovered that the sedimentary sandstone in the northern Australian region of Georgetown didn't bear much resemblance to other rock compositions in Australia, according to a Curtin University press statement. It did, however, bear quite a strong resemblance to rocks one might find in the North American landmass, known as Laurentia.

Specifically, it resembled geological features found in Canada, according to the Guardian. The researchers believe that the rock under modern-day Georgetown was once attached to North America's Laurentia, but broke away 1.7 billion years ago. After drifting for another 100 million years, it crashed into Australia. A paper describing the research was published in the scientific journal Geology

“This was a critical part of global continental reorganisation when almost all continents on Earth assembled to form the supercontinent called Nuna," co-author Adam Nordsvan, a student at Curtin University's School of Earth and Planetary Sciences, said in the press statement.

The most well-known supercontinent, Pangea, broke apart sometime around 175 million years ago, according to Live Science. But while Pangea may be the most famous, it wasn't the first; a number of supercontinents came before it, including Nuna (sometimes referred to as the Columbia supercontinent).

Nuna itself split into pieces another 300 million years after reaching Australia, according to the statement. But even as the rest of the landmass drifted away, the rock under what would later become Georgetown refused to budge, and has remained part of Australia ever since.

Researchers first started compiling evidence for Nuna's existence in 2002, according to a separate report from Live Science. While the scientific community believed that the landmass under northeast Australia had once been situated by North America, northern China or Siberia, there was never sufficient geological data to prove it. This is a big contribution to the body of evidence supporting Nuna.

“Ongoing research by our team shows that this mountain belt, in contrast to the Himalayas, would not have been very high, suggesting the final continental assembling process that led to the formation of the supercontinent Nuna was not a hard collision like India’s recent collision with Asia,” co-author Zheng-Xiang Li, a John Curtin Distinguished Professor in the School of Earth and Planetary Sciences, said in the press statement. “This new finding is a key step in understanding how Earth’s first supercontinent Nuna may have formed.”