A chemical fingerprint found in ancient rocks across the globe indicates that Earth’s plate tectonics may have switched on 2.5 billion years ago.
Researchers at Curtin University identified this shift by tracking a specific signature that disappears from the geological record at that time.
The team analyzed more than 1,200 rocks from ancient landmasses in Australia, Africa, North America, and Europe. Spanning nearly four billion years of Earth’s history, the study utilized both newly analyzed samples and data compiled from earlier research. The researchers searched for a chemical signature left behind when new crust is created through the melting of older, existing rock.
According to the study, this specific fingerprint is preserved in certain minerals, such as sulfide minerals and feldspar, allowing it to remain largely undisturbed for billions of years.
“We found it consistently in rocks older than 2.5 billion years,” lead author Janne Liebmann, a research fellow at Curtin's Timescales of Mineral Systems Group, said, which indicates they originated from a pool of ancient crust that formed approximately four billion years ago. During this early period, the material was repeatedly melted and remelted to form the granite-like rocks that comprised the earliest continents.
However, the signal vanishes abruptly around 2.5 billion years ago. The researchers examined hundreds of younger rocks and found that the distinctive signature of those ancient crustal reservoirs never appeared again.
Janne Liebmann, a research fellow at Curtin’s Timescales of Mineral Systems Group, said that the fingerprint offers a rare glimpse into the evolution of Earth’s earliest crust.
The disappearance of this fingerprint marks how the planet's crust construction changed, moving toward the dynamic system observed today. Co-author Chris Kirkland, a professor in Curtin’s School of Earth and Planetary Sciences, described the shift as a transition from an early Earth where ancient crust was reworked in place to a system capable of recycling crust on a much larger scale.
Plate tectonics is the mechanism responsible for building mountain ranges, triggering earthquakes, and shaping oceans and continents. This process is also fundamental to regulating Earth’s climate and magnetic field over deep time, potentially providing the long-term habitability required for complex life to evolve.
While the start of plate tectonics has been a subject of debate—with some studies of mineral crystals suggesting earlier beginnings—the ability to identify when the process became global has been hindered by the tendency of tectonic activity to destroy its own evidence.
By recycling crust deep into the planet, the process often erases the geological record. The researchers state that their findings offer a new piece of the puzzle regarding how Earth’s unique tectonic engine began to function, helping to explain why Earth evolved so differently from planetary neighbors like Venus and Mars.
The research, titled “Loss of ancient crustal reservoirs marks a shift in Earth’s geodynamic regime,” was published in Proceedings of the Royal Society A. Scientists continue to investigate the specific triggers that initiated this tectonic shift.