Ancient rocks reveal when Earth's tectonic engine 'switched on'

Scientists have discovered a critical moment in Earth's geological history where tectonic processes transformed from local to global, occurring around 2.5 billion years ago. This shift, which established the plate tectonics system we observe today, is now supported by a distinctive chemical signature found in ancient rocks. Dr. Janne Liebmann, the lead author of the study published in Proceedings of the Royal Society A, explained that the fingerprint is a result of the chemical composition of crust that formed about 4 billion years ago.

This signature was consistently found in rocks older than 2.5 billion years, indicating they were derived from a pool of ancient crust. However, after 2.5 billion years ago, the fingerprint vanished from the geological record, suggesting a fundamental change in how Earth's crust was formed and transformed. Professor Chris Kirkland, a co-author from Curtin University, emphasized that this discovery provides clear evidence of when the tectonic engine that drives modern Earth switched on, marking a significant transition in Earth's geodynamic regime.