Harvard geoscientists have found the oldest direct evidence of plate tectonics on Earth, dating back 3.5 billion years. Analysis of ancient rocks from western Australia reveals early crustal drift and rotation. The discovery, published in Science, challenges notions of a rigid early planetary surface.
A team from Harvard University, led by Roger Fu and including lead author Alec Brenner, analyzed over 900 rock samples from more than 100 locations in the North Pole Dome area of the Pilbara Craton in western Australia. These rocks, from the Archean Eon around 3.5 billion years ago, preserve magnetic signals that act as a record of their past positions, similar to an ancient GPS system using paleomagnetism. The study required drilling cores, heating samples up to 590 degrees Celsius, and using sensitive magnetometers over two years. Brenner described the effort: 'We took a really big gamble... And boy, did it pay off! These results were beyond our wildest dreams.' The findings indicate that part of the East Pilbara region shifted in latitude from 53 degrees to 77 degrees and rotated clockwise by more than 90 degrees over about 30 million years, at rates of tens of centimeters per year. Movement slowed after roughly 10 million years. In contrast, rocks from the Barberton Greenstone Belt in South Africa remained near the equator and mostly stationary during the same period, suggesting varied crustal behaviors. Brenner noted: 'We're seeing motion of tectonic plates, which requires that there were boundaries between those plates and that the lithosphere wasn't some big, unbroken shell.' The research also detected the oldest known geomagnetic reversal. Fu emphasized plate tectonics' role: 'Almost everything unique about the Earth has something to do with plate tectonics at some level.' Published on March 19, 2026, in Science (DOI: 10.1126/science.adw9250), the study rules out a stagnant lid for early Earth but leaves open whether it had sluggish or episodic plate motion.
