When did plate tectonics begin?

This is one of Earth’s many unique features: unlike other known planets in the universe, Earth’s surface is composed of rigid plates that slide, collide with each other, and sink into the planet’s interior.

But when did the Earth’s surface break up into tectonic plates? And when did these plates start moving? 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 to the question of when plate tectonics emerged, with estimates ranging from 700 million years ago to about 4 billion years ago, when Earth was still in its infancy.

The oldest clear evidence of modern plate tectonics comes from the Neoproterozoic (1 billion to 541 million years ago), Robert Sterngeologist at the University of Texas at Dallas, told Live Science. That’s when the geological record reveals abundant ophiolites – pieces of ocean crust pushed onto the continents – and blueschists, or metamorphic rocks formed in subduction zonesor areas where plates collide and plunge into the planet’s interior. Subduction is a feature of plate tectonics, so these vast rocks certainly indicate that plates were colliding and sliding beneath each other.

However, many geologists consider Stern’s view too conservative.

Critics agree that rocks indicative of plate tectonics first became widespread 700 to 900 million years ago. However, they suggest that these rocks may have existed earlier and been eroded by time.

For example, the Indian subcontinent collided with southern Asia just 55 million years ago, and many of these rocks have already eroded away, he says Mark Harrisonprofessor emeritus of geology at UCLA. “The Tibet-India collision is not over yet,” Harrison told Live Science. If traces of tectonics disappear even when plates collide, what hope is there of finding the same rocks from a much more distant past?

Stern says there is evidence for a small subduction episode 1.8 billion years ago that didn’t quite lastsupporting his view that if plate tectonics had occurred consistently before about 800 million years ago, it would have been more evident in the rock record. (Other scientists see this moment as evidence that plate tectonics was already well underway.)

Many researchers considered the transition to plate tectonics much earlier. There are many indications of some type of geological shift during the Archean Eon (4 billion to 2.5 billion years ago), with estimates placing the exact period at 2.5 billion to 3.8 billion years ago. For example, at least one ophiolite has been preserved dates back 2.5 billion years.

Other evidence is the chemistry of the crust. If the crust is completely new volcanic rock, its chemical composition will resemble the mantle from which it comes. If it is melted down and recycled by plate tectonics, this chemistry will change. Some influential 2012 study found that around 3 billion years ago, more crust began to be recycled. This may mean a shift towards subduction, destruction and reworking of the crust, says the study’s co-author Chris HawkesworthProfessor Emeritus of Earth Sciences at the University of St. Andrews in the UK.

Research on zircons – minerals that survive even after the rocks around them melt and deform – suggest that the Earth’s crust moved earlier, 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 Nadja DrabonEarth scientist and planetary scientist at Harvard University, told Live Science. During this time, the crust also became shorter, again suggesting a subduction recycling process.

But does this transition reflect true plate tectonics? Zircon research published in 2023which examined Earth’s magnetic field conditions during mineral formation, suggests that these grains remained where they formed until 3.4 billion years ago, suggesting that land masses were not in motion until then.

Drabon noted that it is possible that different aspects of plate tectonics emerged at different times. Subduction may have started 3.8 billion years ago, but it took some time for the continents to start 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 comes from growing evidence that the newborn Earth was a surprisingly modern-looking place with oceans and continents – a conclusion drawn from zirconium research and chemistry of the oldest preserved rocks on Earth. Some studies of the oldest zircons on Earth, which date back to this mysterious period of geological history, have shown this to be the case they look uniquely like zircons that form in volcanic arcs over subduction zones today. Theoretical modeling shows that this is possible plate tectonics existing in Hadesian conditionsJun Korenaga, professor of Earth and planetary sciences at Yale University, told Live Science.

Each piece of evidence supporting each of these origin stories has weaknesses. For example, the vast majority of very old zircons come from one place, Jack Hills in Australia, and may not reflect what was happening on the rest of the planet. The oldest rocks may also be strange – perhaps they still hang around because they were unlike any other rocks on ancient Earth. And you don’t want to step in the middle of computer modelers as they argue about 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 Reiminek– a geologist from Pennsylvania State University told Live Science.