Modern plate tectonics may have gotten under way as early as 3.2 billion years ago, about 400 million years earlier than scientists thought. That, in turn, suggests that the movement of large pieces of Earth’s crust could have played a role in making the planet more hospitable to life.
Geologist Alec Brenner of Harvard University and his colleagues measured the magnetic orientations of iron-bearing minerals in the Honeyeater Basalt, a layer of rock that formed between 3.19 billion and 3.18 billion years ago. The basalt is part of the East Pilbara Craton, an ancient bit of continent in Western Australia that includes rocks as old as 3.5 billion years.
This craton, the researchers found, was on the move between 3.35 billion and 3.18 billion years ago, drifting around the planet at a rate of at least 2.5 centimeters per year. That’s a speed comparable to modern plate motions, the team reports April 22 in Science Advances.
The basalt layer, which burbled up as lava and hardened during the journey, contains iron-bearing minerals that can act as tiny signposts pointing the way toward Earth’s magnetic poles. While the lava was still molten, the minerals rotated, orienting themselves to align with either the north or south magnetic pole. By tracking the changes in orientation within the lava as more basalt formed during the journey, the researchers were able to determine how quickly the craton was moving.