An enduring question in geology involves the question of when the tectonic plates of the Earth’s crust began pushing and pulling in a process that formed the planet’s continents, oceans, and other landforms. Some researchers theorize it happened about 4 billion years ago. Others say it was closer to 1 billion.
Clues can be found in very old rocks. Looking at some, a team led by Harvard researchers show that these plates were moving at least 3.2 billion years ago on the early Earth.
In a portion of the Pilbara Craton in Western Australia, one of the oldest pieces of the Earth’s crust, scientists found a latitudinal drift of about 2.5 centimeters a year. They found the motion went back 3.2 billion years and confirmed it using a novel magnetic microscope.
The researchers believe this shift is the earliest proof that modern-like plate motion happened between 2 and 4 billion years ago, suggesting that the plates pushed and pulled in ways unlike those seen earlier periods, when the Earth’s crust moved less. It adds to growing research that tectonic movement occurred on the early Earth and offers hints about the conditions under which the earliest forms of life developed.
The work was published in Science Advances on Earth Day.
“Basically, this is one piece of geological evidence to extend the record of plate tectonics on Earth further back in Earth history,” said Alec Brenner, one of the paper’s lead authors and a member Harvard’s Paleomagnetics Lab. “Based on the evidence we found, it looks like plate tectonics is a much more likely process to have occurred on the early Earth, and that argues for an Earth that looks a lot more similar to today’s than a lot of people think.”