When did plate tectonics begin?

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

But when did the Earth’s surface splinter 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 to the question of when plate tectonics originated, and estimates range from 700 million years ago to 4 billion years ago, when the Earth was still in its infancy.

The oldest unequivocal 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 LiveScience. That’s when the geological record reveals abundant ophiolites – pieces of oceanic crust that have slid onto continents – and blueschists, which are metamorphic rocks that form in subduction zonesor areas where the plates collide and plunge into the interior of the planet. Subduction is a hallmark of plate tectonics, so these widespread rocks show conclusively that plates collided and slid under each other.

But many geologists find Stern’s view too conservative.

Critics agree that rocks indicative of plate tectonics first became widespread 700 billion to 900 million years ago. But these rocks could have existed earlier and been swept away by time, they suggest.

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

Stern states that there is evidence for a small episode of subduction 1.8 billion years ago that did not last all the wayreinforcing his position that if there had been consistent plate tectonics before about 800 million years ago, it would be more evident in the rocks. (Other scientists see this blip as evidence that plate tectonics was already in full swing.)

Many researchers started the transition to plate tectonics much earlier. There are numerous signs of some kind of geological shift during the Archean Eon (4 billion to 2.5 billion years ago), with estimates of exactly when ranging from 2.5 billion to 3.8 billion years ago. For example, at least one ophiolite has been preserved dates from 2.5 billion years ago.

Another piece of evidence lies in the chemistry of the crust. If the crust is brand new volcanic rock, its chemistry will be very similar to the mantle it came from. When it is melted again and recycled through plate tectonics, the chemistry changes. A influential study from 2012 found that more crust was recycled about 3 billion years ago. This could mark the shift toward subduction, which destroys and reworks the crust, the study co-author said Chris HawkesworthEmeritus Professor of Geosciences at the University of St. Andrews in Great Britain.

Research into zircons – minerals that survive even as the rocks around them melt and reform – suggest that the Earth’s crust has shifted before, around 3.8 billion years ago. “We are starting to see zircon structures that increasingly resemble what we see today in subduction zones,” study author wrote. Nadja Drabonan Earth and planetary scientist at Harvard University told LiveScience. Crust also became shorter-lived around that time, again indicating the recycling process of subduction.

But does this transition reflect true plate tectonics? Zircon research published in 2023that examined Earth’s magnetic field conditions as the minerals formed suggests that these grains remained more or less where they were created until 3.4 billion years ago, indicating that landmasses were not moving until that point.

It’s possible that different aspects of plate tectonics emerged at different times, Drabon noted. Perhaps subduction began 3.8 billion years ago, but it took time for the continents around the world to begin drifting.

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 comes from mounting evidence that the newborn Earth was a surprisingly modern-looking place with oceans and continents – a conclusion drawn from zircon research and the chemistry of the oldest extant rocks on Earth. Some studies of the oldest zircons on Earth, which date from this mysterious period of geological history, have shown that this is the case are remarkably similar to zircons that form in volcanic arcs today about subduction zones. And theoretical models show that this is possible plate tectonics exists under Hadean conditionsJun Korenaga, professor of earth and planetary sciences at Yale University, told LiveScience.

Every piece of evidence for each of these origin stories has weaknesses. For example, the vast majority of very old zircons come from one location, Australia’s Jack Hills, and may not represent what happened on the rest of the planet. The oldest rocks can be weird too; maybe they’re still hanging around today because they weren’t like all the other rocks on ancient Earth. And you don’t want to find yourself in the middle of computer modelers discussing assumptions about the state of the mantle 4 billion years ago.

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