Scientists have identified a major turning point in Earth’s geological history, when the processes shaping the planet’s crust changed dramatically and began to resemble the plate tectonics we see today – about 2.5 billion years ago.
Plate tectonics shapes Earth’s continents and oceans and helps regulate its climate and magnetic field over deep time, but scientists have struggled to determine when it began because the process destroys much of its own evidence by recycling Earth’s crust deep inside the planet.
Curtin University researchers have now found a distinctive chemical fingerprint preserved in rocks from around the world that pinpoints a major shift in Earth’s geological record about 2.5 billion years ago.
Lead author Dr Janne Liebmann, Research Fellow in Curtin’s Timescales of Mineral Systems Group in Curtin Frontier Institute of Geoscience Solutions, said the chemical fingerprint provided a rare glimpse into how Earth’s earliest crust evolved.
“New crust often forms by melting older rock, leaving behind a distinctive chemical fingerprint,” Dr Liebmann said.
“We searched for this fingerprint in thousands of rocks from around the world, spanning almost four billion years of Earth’s history.
“We found it consistently in rocks older than 2.5 billion years, showing they were derived from a pool of ancient crust that formed about four billion years ago.
“But after 2.5 billion years ago, that fingerprint disappears from the geological record – and despite examining thousands of rocks, we never see it again.
“That tells us something fundamental changed in the way Earth’s crust was being formed and transformed, marking a transition towards the dynamic tectonic system we see today.”
Study co-author Professor Chris Kirkland, from the Timescales of Minerals Systems Group within Curtin’s School of Earth and Planetary Sciences, said the findings helped explain when Earth acquired one of the features that sets it apart from tectonically inactive planets such as Venus and Mars.
“Plate tectonics is fundamental to the way Earth has evolved over billions of years, continually reshaping the continents and oceans and influencing the planet’s atmosphere and climate,” Professor Kirkland said.
“What makes this finding remarkable is that we can see the fingerprints of an ancient Earth disappear from the geological record at a very specific point in time.
“It marks the transition from an early Earth where ancient crust could be repeatedly melted and reworked in place, to a system capable of moving and recycling crust on a much larger scale.
“This gives us our clearest geological evidence yet for when the tectonic engine that drives the modern Earth ‘switched on’.”
The study, ‘Loss of ancient crustal reservoirs marks a shift in Earth’s geodynamic regime’, was published in Proceedings of the Royal Society A and can be found online here: https://doi.org/10.1098/rspa.2026.0587
