When did plate tectonics begin?

It’s one of the many unique things about Earth: unlike any other known planet in the universe, Earth’s surface is made up of rigid plates that move, collide with each other, and sink into the planet’s interior.

But when did the Earth’s surface split into tectonic plates? And when did those plates start moving? It’s an important question because plate tectonics appears to fuel the evolution and complexity of life.

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

The earliest clear evidence of modern plate tectonics dates from the Neoproterozoic (1 billion to 541 million years ago), Robert Sterna geoscientist at the University of Texas, Dallas, told Live Science. Then the geologic record reveals abundant ophiolites—chunks of oceanic crust pushed onto continents—and blueschists, which are metamorphic rocks that form in subduction zonesor areas where plates collide and sink into the planet’s interior. Subduction is a feature of tectonic plates, so these splayed rocks definitely show that the plates collided and slid under each other.

But many geologists believe that Stern’s view is too conservative.

Critics agree that rocks indicative of plate tectonics first spread 700 billion 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 southern Asia only 55 million years ago, and many of these rocks have already eroded away, he said Mark Harrisonprofessor emeritus of geoscience at UCLA. “The Tibet-India collision is not over yet,” Harrison told Live Science. If evidence of tectonics disappears even when a plate collision occurs, what hope is there of finding the same rocks from the much more distant past?

Stern argues that there is evidence for a small subduction episode 1.8 billion years ago that didn’t last longreinforcing his view that if plate tectonics had existed consistently before about 800 million years ago, it would be clearer in the rock record. (Other scientists see this point as evidence that plate tectonics was in full swing by then.)

Many researchers made the transition to plate tectonics much earlier. There are numerous signs of some sort of geological change during the Archean Eon (4 billion to 2.5 billion years ago), with estimates of the exact time ranging from 2.5 billion to 3.8 billion years ago. For example, at least one ophiolite preserved today dating back 2.5 billion years.

Another line of evidence is in the chemistry of the crust. If the crust is brand new volcanic rock, its chemistry will look a lot like the mantle from which it came. If it is melted and recycled by plate tectonics, this chemistry changes. A influential 2012 study found that more crust began to be recycled about 3 billion years ago. This could mark the shift to crustal destruction and reworking by subduction, the study’s co-author said Chris Hawkesworthprofessor emeritus of geosciences at the University of St. Andrews of Great Britain.

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

But does this transition reflect the true plate tectonics? Zircon research published in 2023who investigated the magnetic field conditions on Earth when the minerals formed, suggests that these grains remained more or less where they were produced until 3.4 billion years ago, suggesting that the land masses did not -they found out in motion until that moment.

Different aspects of plate tectonics may have arisen at different times, Drabon noted. Subduction may have started 3.8 billion years ago, but it took time for the continents to start floating around the globe.

A newer and more controversial idea suggests that Earth developed plate tectonics in the Hadean (4.5 billion 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 the chemistry of the oldest surviving rocks on Earth. Some studies of the oldest zircons on Earth, dating from this mysterious period of geologic history, have found that they they look remarkably like zircons that form in volcanic arcs over subduction zones today. And theoretical modeling shows it’s possible plate tectonics to exist under Hadean conditionsJun Korenaga, professor of Earth and planetary sciences at Yale University, told Live Science.

Each piece of evidence for each of these origin stories comes with weaknesses. For example, the vast majority of very old zircons come from one location, Jack Hills in Australia, and may not represent what is happening on the rest of the planet. The oldest rocks might also be strange—perhaps they’re still around today because they weren’t like all the other rocks on ancient Earth. And you don’t want to get in the middle of computer modelers arguing about hypotheses about the state of the mantle 4 billion years ago.

“It’s shocking to realize that there is no consensus on when (plate tectonics) started,” Jesse Reiminka Pennsylvania State University geoscientist told Live Science.

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