When Did the Earth’s Crust Start to Shift? Scientists Uncover Evidence of Plate Tectonics Happening 3.48 Billion Years Ago

A new study provides the oldest direct evidence of tectonic plate movement ever recorded

Sara Hashemi | Daily Correspondent

March 31, 2026

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The Earth’s crust is constantly changing. It’s currently made of many huge rock slabs called tectonic plates—seven major ones along with many more smaller plates—that fit together like puzzle pieces and move around atop the planet’s molten mantle layer.

When two tectonic plates shift against one another, the motion can form mountain ranges and volcanoes and trigger earthquakes. Long ago, the movement of these giant rocks is thought to have ushered in an atmosphere and climate that allowed complex life to evolve.

Exactly when and how plate tectonics started, however, is a matter of debate. Now, in a study published March 19 in the journal Science, rock samples from Western Australia hint that the Earth’s crust may have been moving as early as 3.48 billion years ago, roughly one billion years after our planet formed.

“Almost everything unique about the Earth has something to do with plate tectonics at some level,” says Roger Fu, a paleomagnetic geologist at Harvard University, in a statement. “At some point, the Earth went from something not that special, just another planet in the solar system with similar materials, to something very special. A very strong suspicion is that plate tectonics started Earth down this divergent track.”

In the new study, Fu and his colleagues focused on the Pilbara region of Western Australia—home to some of the oldest rocks in the world. Ancient grains of the mineral magnetite record traces of the Earth’s magnetic field during their formation, and analyzing them can reveal a rock’s orientation and distance from the equator at that time.

The researchers collected over 900 cylindrical rock samples, or sediment cores, by drilling into the ground at more than 100 sites. Then, they sliced the log-shaped cores—which preserved sediment ranging from 30 million to 3.48 billion years old—and put the slices into a device that demagnetized the samples and measured their waning magnetic signals, allowing the team to trace the rock’s history.

The roughly two-year analysis was “a big gamble,” says study co-author Alec Brenner, a paleomagnetic geologist now at Yale University, to Douglas Fox at Science News.

But the work paid off. During its earliest recorded history, part of the Pilbara formation spent several million years migrating toward one of Earth’s poles at a rate of about 18.5 inches per year and rotated clockwise by more than 90 degrees, the team found. Then, its movement significantly slowed. Meanwhile, other research hinted that ancient rock in South Africa was mostly stationary around 3.48 billion years ago.

That’s exciting because it “suggests there’s likely to be a plate boundary between the two [ancient pieces of crust],” indicating two plates moving independently, says Michael Brown, an emeritus geologist at the University of Maryland who was not involved in the work, to Marissa Grunes at Scientific American.

What’s more, the Earth’s magnetic field flips occasionally—which is why the researchers don’t know which direction the Pilbara formation traveled—and the team’s analysis revealed the earliest known evidence of a geomagnetic reversal, which took place around 3.46 billion years ago. The most recent one occurred roughly 780,000 years ago, causing the planet’s magnetic north to be in the Southern Hemisphere.

Both findings “demonstrate that [billions of years ago,] Earth was behaving very similar to today,” says Jun Korenaga, a geologist at Yale University who was not involved in the study, to Scientific American.

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Sara Hashemi is a science writer and fact-checker currently based in New York City. Her work has appeared in Sierra, The Body, Maisonneuve magazine and more.