Earth’s tectonic plates were already shifting 3.5 billion years ago
The rocks didn’t look like much from the outside. Scattered across a remote stretch of western Australia called North Pole Dome, they were ancient, weathered, and largely ignored for the better part of Earth’s history. But locked inside those formations, in tiny magnetic minerals no larger than grains of dust, was a record of something that geologists have argued about for decades. Earth’s outer shell was moving. And it was doing so 3.5 billion years ago. A study published in Science, led by researchers from Harvard’s Department of Earth and Planetary Sciences, presents what the authors describe as the oldest direct evidence yet of plate movement. The work doesn’t end a long-running debate about when modern plate tectonics began. However, it does push the story much deeper into the planet’s past than many scientists expected. A Two-Year Hunt Inside Ancient Stone The researchers focused on the Pilbara Craton, a fragment of early Earth in western Australia that ranks among the best-preserved pieces of Archean rock on the planet. These formations date to a time when …
