"We found that supercontinents appear to assemble through two alternating processes of extroversion and introversion," lead author Professor Zheng-Xiang Li, from Curtin University, said in a statement.
"More intriguingly, these two alternating processes determine not only whether the superocean survives, but also whether the circum-superocean Ring of Fire – like the present-day Pacific Ring of Fire – survives."
Professor Li added: "Such alternating ways of supercontinent assembly, along with the survival or regeneration of the superocean and the Ring of Fire, led to the presence of an Earth cycle twice as long as the 600-million-year supercontinent cycle and influenced the formation of some of the planet's resources."
In the model proposed by the researchers, Nuna broke up and then turned into Rodinia via the introversion method, so the crust of the global ocean didn’t change during that period. But after Rodinia split, it then took the extroversion path, with its ocean lost to the Earth’s interior.
While the idea is certainly intriguing and there's supporting evidence, it's possible there isn't a true double-cycle but instead two potential options. Currently, the former superocean, now the Pacific, is shrinking, which would be seen as an extroversion movement. But maybe this trend will change and things will go back according to the introversion approach. Either way, there is still 50 to 200 million years to go before the next supercontinent.