When did plate tectonics start?

This is one of Earth’s many unique features: unlike every other known planet in the universe, Earth’s surface is made up of rigid plates that move, crash into each other, and dive inside the planet.

But when did the Earth’s surface divide into tectonic plates? And when did these plates start to move? This is an important question because plate tectonics appears to drive the evolution and complexity of life.

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Surprisingly, geologists don’t have a good answer for when plate tectonics emerged, and estimates range from 700 million years ago to 4 billion years ago, when Earth was still in its infancy.

The oldest unambiguous evidence of modern plate tectonics dates back to the Neoproterozoic (1 billion to 541 million years ago), Robert Sterngeoscientist at the University of Texas at Dallas, told Live Science. This is when the geological record reveals abundant ophiolites – pieces of oceanic crust pushed onto continents – and blueschists, which are metamorphic rocks that form in subduction zonesor areas where plates collide and plunge into the planet’s interior. Subduction is a feature of plate tectonics, so these widespread rocks show with certainty that the plates were crushing and sliding beneath each other.

But many geologists think Stern’s view is too conservative.

Critics agree that the rocks indicative of plate tectonics first spread 700 to 900 million years ago. But these rocks could have existed earlier and been erased by time, they suggest.

For example, the Indian subcontinent collided with South Asia just 55 million years ago, and many of these rocks have already been eroded, said Marc Harrisonprofessor emeritus of geoscientist at UCLA. “The Tibet-India collision is not over yet,” Harrison told Live Science. If evidence of tectonics disappears even as plate-to-plate collision occurs, what hope is there of finding these same rocks from a much more distant past?

Stern argues that there is evidence of a small subduction episode 1.8 billion years ago which didn’t really lastreinforcing his view that if there had been consistent plate tectonics before about 800 million years ago, this would be clearer in the rock record. (Other scientists see this incident as evidence that plate tectonics was well advanced by then.)

Many researchers have advanced the transition to plate tectonics. There are many signs of some sort of geological change during the Archaean Eon (4 to 2.5 billion years ago), with estimates of the exact timing ranging from 2.5 to 3.8 billion of years. For example, at least one ophiolite preserved today dates back 2.5 billion years.

Another piece of evidence lies in the chemistry of the crust. If the crust is a brand new volcanic rock, its chemistry will be very similar to the mantle from which it came. If it is remelted and recycled by plate tectonics, this chemistry shifts. A influential 2012 study found that more crust began to be recycled around 3 billion years ago. This could mark the shift to subduction, destroying and reworking the crust, the study co-author said. Chris Hawkesworthprofessor emeritus of geosciences at the University of St. Andrews in the United Kingdom.

Research on zircons – minerals that survive even when the rocks around them melt and reform – suggests that the Earth’s crust moved earlier, around 3.8 billion years ago. “We are starting to see zircon structures that look more and more like what we see today in subduction zones,” study author Nadja Drabonan Earth and planetary scientist at Harvard University, told Live Science. The crust also became shorter at this time, again suggesting the recycling process of subduction.

But does this transition reflect real plate tectonics? Zircon Research published in 2023who studied the magnetic field conditions on Earth when minerals formed, suggests that these grains more or less remained where they were formed until 3.4 billion years ago, leaving to hear that the continental masses were not moving until then.

It’s possible that different aspects of plate tectonics arose at different times, Drabon noted. Subduction may have started 3.8 billion years ago, but it took time for continents to begin drifting around the globe.

A newer and more controversial idea suggests that Earth developed plate tectonics during the Hadean (4.5 to 4 billion years ago). This idea stems from growing evidence that the newborn Earth was a surprisingly modern place with oceans and continents – a conclusion drawn from zircon research and the chemistry of Earth’s oldest surviving rocks. Some studies of Earth’s oldest zircons, which date from this mysterious period in geological history, have revealed that they look remarkably like zircons that form in volcanic arcs on subduction zones today. And theoretical modeling shows that it is possible plate tectonics exists under Hadean conditionsJun Korenaga, professor of earth and planetary sciences at Yale University, told Live Science.

Every piece of evidence in each of these origin stories has weaknesses. For example, the vast majority of very old zircons come from one place, the Jack Hills in Australia, and may not represent what was happening on the rest of the planet. The oldest rocks can also be strange – maybe they’re still lying around today because they don’t look like all the other rocks on ancient Earth. And you don’t want to find yourself in the middle of computer modelers when they discuss hypotheses about the state of the mantle 4 billion years ago.

“Shockingly, there is no consensus on when (plate tectonics) began,” Jesse Reiminka geoscientist at Pennsylvania State University told Live Science.

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