Scientists studying some of the oldest rocks on Earth have uncovered new evidence that the planet’s first continents may have started forming through plate tectonics as early as 3.5 billion years ago.
The international research team analyzed tiny mineral crystals from the ancient Pilbara Craton, a region famous for preserving some of Earth’s oldest geological formations.
Their findings, published in Science Advances, could help solve one of geology’s biggest mysteries: how Earth’s earliest continents were created.
The study involved researchers from several institutions, including The University of Western Australia and Nanjing University.
For many years, scientists have debated how the first continental crust formed on the young Earth. One theory suggests it happened through subduction, the process where one tectonic plate slides beneath another and sinks deep into the planet. This movement carries water and other materials into Earth’s interior and helps create continents.
The competing theory argues that the early continents formed without plate tectonics. In this idea, extremely hot material rising from deep inside Earth, or even giant meteorite impacts, melted the crust and created continental rocks.
To investigate the question, the researchers examined zircon crystals found inside ancient granitic rocks in Western Australia. Zircon is an incredibly durable mineral that can survive for billions of years, preserving chemical clues about the conditions under which it formed.
By studying these crystals, the team discovered that the magma that created the granites gradually became richer in water and more oxidized between 3.5 billion and 3.2 billion years ago.
According to Professor Tony Kemp, this chemical change strongly suggests that water was being transported deep into Earth’s crust and mantle during that period.
Today, this type of water transport mainly happens through subduction zones, where tectonic plates collide and one sinks beneath the other. The process plays a major role in shaping Earth’s continents and recycling materials between the surface and the deep interior.
The new findings suggest that some form of plate subduction may already have been active incredibly early in Earth’s history.
“Our study implies that a very early form of plate subduction existed on Earth as far back as 3.5 billion years ago and could have had a role in the growth of ancient continents,” Kemp said.
If correct, the discovery means Earth’s surface may have started behaving more like the modern planet much earlier than scientists once believed.
The research also highlights how tiny mineral crystals can provide a window into Earth’s distant past, helping scientists reconstruct events that happened billions of years before the first life appeared on land.
