A chemical fingerprint in ancient rocks suggests plate tectonics began 2.5 billion years ago

Résumé détaillé

Tectonic plates may have allowed life to form on Earth – but exactly when they started moving is a long-standing mystery.

Plate tectonics is one of the reasons Earth looks so different from its planetary neighbours.

The movement of enormous chunks of our planet’s crust builds mountain ranges, triggers earthquakes, shapes our oceans and continents, and helps regulate Earth’s climate and magnetic field over deep time.

This process may also be key to sustaining the kind of long-term habitability that allowed complex life to evolve. But exactly when it began has been a long-standing mystery.

In new research, we studied chemical fingerprints in more than 1,000 rocks to look for clues – and found clear evidence for when this remarkable shift occurred.

Many scientists believe plate tectonics provides the long-term stability that keeps our planet life-friendly, unlike tectonically “dead” worlds such as Venus and Mars.

But debate has raged over when this process began: has it run throughout Earth’s entire 4.5-billion-year history, or did it “switch on” at some point along the way?

For much of its early history, Earth may have been mostly covered by oceans, without the shifting, colliding plates that build tall mountains – which in turn erode away, supplying the nutrients to feed marine life.

The question is hard to settle because plate tectonics are very good at destroying the evidence. Where plates collide, some old crust is dragged back down into the mantle, and the crust that is thrust upward to form mountains also starts eroding away, which erases the geological record.

Often, all that survives are chemical fingerprints preserved in ancient rocks that have endured for billions of years, against the odds.

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