A recent study challenges traditional views of how Earth’s continents formed, suggesting that subduction may not have been necessary. Its findings suggest that melting in the crust could explain the formation of the continents, casting doubt on the timing of plate tectonics and highlighting its influence on the origin of life.

The formation of Earth’s continents billions of years ago laid the groundwork for life to develop, but scientists still disagree on how these landmasses came to be and whether the geological processes involved are the same as those we see today.

A recent paper in the journal Nature Geoscience by David Hernandez Uribe of the University of Illinois at Chicago adds new information to the debate, refuting a leading theory of continent formation. Hernández Uribe used computer models to study the formation of magmas, which are believed to hold clues to the origin of the continents.

Geological processes and zircon research

Magma is molten material that cools to form rocks and minerals. Hernández Uribe was looking for magmas that matched the composition of deposits of rare minerals called zircons, dating back to the Archean period, 2.5 to 4 billion years ago, when scientists think continents first formed.

Last year, scientists from China and Australia published a paper arguing that Archean zircons could only have formed through subduction, when two tectonic plates collide underwater and push land up to the surface. This process continues today, causing earthquakes and volcanic eruptions and changing the shape of continental coastlines.

But Hernandez Uribe, associate professor of earth and environmental sciences, found that subduction was not necessary to form Archean zircons. Instead, the minerals could have formed due to the high pressures and temperatures associated with the melting of Earth’s thick primitive crust.

“Using my calculations and models, you can get the same signatures for zircons, and even a better match due to partial melting of the lower crust,” Hernández Uribe said. “So based on these results, we still don’t have enough evidence to say what process formed the continents.”

Plate tectonics and its impact on life on Earth

The results also increase uncertainty about when plate tectonics began on Earth. If Earth’s first continents formed through subduction, that would mean they began moving 3.6 to 4 billion years ago, just 500 million years into the planet’s existence. But the alternative theory of crustal melting forming the first continents means subduction and tectonics may have started much later.

“Our planet is the only planet in the solar system that we know of that has active plate tectonics,” Hernández Uribe said. “And that has to do with the origin of life, because the way the first continents moved controlled the weather, the chemistry of the oceans and everything else related to life.”