Computer models are becoming more and more important to transforming all our measurements and ideas into things we can try and measure. This is as true for the universe as a whole as it is for our home planet, Earth. We can’t go back in time and see directly how the continents have moved and evolved over the planet’s five billion-year history. We can, however, find the world’s oldest rocks and use them to place limits on what might have happened in the past.
We’ve known for about a century that all the modern continents once fit together into a single supercontinent named Pangaea. More recent work has found evidence of two older supercontinents and a 600 million-year continental cycle. Has that always been the case? Without evidence, it wasn’t something a model alone could sort, so researchers found the oldest rocks out there, and went looking for magnetic evidence of how those rocks were once aligned with the Earth’s magnetic field.
Based on these new measurements and models of our world, this team concluded, to quote Zheng-Xiang Li: We can almost rule out the existence of a long-lived single supercontinent before two billion years ago (2 Ga), although transient supercontinents may have existed. More likely, there could have been two long-lived clusters of cratons, or supercratons, before 2 Ga that were geographically isolated from each other, never forming a singular supercontinent.
This work is published in the journal Geology, with first author Yebo Liu, who adds: This study surely isn’t the final word on the debate, but it’s certainly a step in the right direction and we need to collect data from a lot more similar rocks to further test the hypotheses.
Curtin University press release
“Archean geodynamics: Ephemeral supercontinents or long-lived supercratons,” Yebo Liu et al., 2021 March 22, Geology