Earth's plate tectonics began roughly 2.7 billion years ago, evidenced by a distinctive lead isotope fingerprint in ancient rocks.
The lead isotope signature appears in rocks older than 2.76 to 2.63 billion years and disappears in younger rocks. This pattern was observed yesterday.
This abrupt disappearance marks a fundamental shift in crust formation, leading to the dynamic plate tectonic system that shapes modern continents, regulates climate, and generates earthquakes.