A new study of more than 1,200 ancient rocks suggests that plate tectonics may have begun around 2.5 billion years ago, marking a major turning point in Earth’s geological history.
Plate tectonics is the process through which enormous sections of Earth’s outer crust move, collide and separate. These movements shape continents and oceans, build mountain ranges and trigger earthquakes. They also play an important role in regulating Earth climate and magnetic field over long periods.
Scientists believe this geological process may have helped create the stable conditions necessary for life to evolve and flourish. However, exactly when plate tectonics first began has remained a subject of scientific debate.
Researchers analysed more than 1,200 rocks collected from ancient landmasses across Australia, Africa, North America and Europe. The samples covered nearly four billion years of Earth’s history.
The team examined chemical fingerprints preserved in minerals such as feldspar and certain sulfide minerals. These fingerprints can survive for billions of years, providing valuable information about how Earth’s continental crust formed.
New continental crust does not always develop directly from molten material rising from Earth’s mantle. In many cases, it forms when older rocks within the crust melt and are transformed into new rocks. This process leaves behind distinctive chemical signatures that scientists can use to trace the origins of ancient crust.
The study revealed a striking pattern. Rocks older than approximately 2.5 billion years consistently contained a chemical signature linked to extremely ancient crustal material that appears to have formed around four billion years ago.
For more than a billion years, this ancient material was repeatedly melted and recycled, producing granite like rocks that formed much of Earth’s earliest continents.
However, the researchers found that this distinctive chemical fingerprint disappeared abruptly around 2.5 billion years ago. Despite examining hundreds of younger rocks, they could no longer identify the same signature.
Scientists believe this disappearance indicates a fundamental change in the way Earth’s continental crust was being produced.
Before this transition ancient continental material was repeatedly melted to create new crust, with relatively little contribution from other sources.
Around 2.5 billion years ago, however, the process appears to have changed. New crust began forming through a combination of older recycled material and fresh material from Earth’s mantle.
This pattern resembles modern geological activity at tectonic plate boundaries, where molten material rises from the mantle while older crust is also recycled.
Researchers therefore suggest that this major shift could mark the beginning of plate tectonics.
Other geological evidence also points to significant changes around the same period, including changes in rock chemistry, crustal thickness and composition, as well as the formation of Earth’s first supercontinent.
The findings suggest that approximately 2.5 billion years ago, Earth underwent a major reorganisation of its geological system. This transformation may have helped shape the planetary environment that eventually supported the development and expansion of life.
However, scientists still do not know exactly what triggered the beginning of plate tectonics. Further research will be needed to understand how Earth’s geological engine first became active.
The study led by researchers including Janne Liebmann of Curtin University, provides an important new clue to one of the biggest unanswered questions about Earth’s early history.