Oldest Evidence of Plate Tectonics Found in Australian Rocks – 3.48 Billion Years Ago

WESTERN AUSTRALIA – Evidence of tectonic plate movement dating back 3.48 billion years has been discovered in the Pilbara region of Western Australia, pushing back the earliest known physical evidence of the process by 140 million years. The findings, published March 19 in the journal Science, suggest that plate tectonics – the driving force behind continental drift, earthquakes, and volcanic activity – may have begun much earlier in Earth’s history than previously thought.

Researchers analyzed microscopic magnetic crystals within ancient bedrock formations in the Pilbara Craton. These crystals record the orientation of Earth’s magnetic field at the time they formed. By measuring the crystals’ alignment, scientists were able to determine the latitude at which the rocks were located billions of years ago. The analysis revealed that a portion of the Pilbara Craton rapidly drifted approximately 2,500 kilometers towards the magnetic pole over a period of several million years, beginning around 3.48 billion years ago.

“This is the only planet we know of that has [well-established] tectonics,” said Alec Brenner, a paleomagnetic geologist at Yale University, “and it’s critical to understand when that began.”

The discovery challenges previous estimates of when plate tectonics began, which ranged from 1 billion to 4 billion years ago. Claire Nichols, a paleomagnetist at Oxford University who was not involved in the study, described the rocks examined as “the only rocks in the world” capable of providing such conclusive evidence of early crustal movement.

Plate tectonics plays a crucial role in regulating Earth’s climate. The process involves the recycling of Earth’s surface through subduction, where denser plates sink beneath continental plates. This process fuels volcanic activity and the formation of mountain ranges, like the Himalayas and Andes. Crucially, the recycling of rock also absorbs carbon dioxide, helping to stabilize greenhouse gas levels and maintain a habitable climate over geological timescales.

The Pilbara Craton is also notable as the location of the world’s oldest confirmed fossils of single-celled organisms, dating back roughly 3.48 billion years, according to a report in Scientific American. This proximity suggests a potential link between the emergence of plate tectonics and the evolution of life on Earth.

Previous research by Brenner and colleagues, also utilizing paleomagnetic measurements in the Pilbara region, indicated that a different section of the terrain had drifted more than 5,000 kilometers over a 160-million-year period starting 3.34 billion years ago. However, that earlier study was limited by tracking only one crustal fragment, leaving open the possibility that shifts in Earth’s magnetic core, rather than plate movement, were responsible for the observed changes.

The current study overcomes this limitation by analyzing rocks from North Pole Dome, a separate region within the Pilbara Craton. The team spent three years searching for a magnetic signal in the region, and their findings were corroborated by independent measurements showing that while the North Pole Dome was moving, rocks of the same age in South Africa remained stationary near the equator. This confirms that the observed movement was due to the independent motion of tectonic plates.

The rate of movement observed – 47 centimeters per year – was six times faster than current plate movements. Researchers attribute this to a warmer Earth interior and a more pliable crust in the planet’s early history, as stated by John Valley, a geochemist at the University of Wisconsin–Madison, who was not involved in the study.

Valley’s own research, based on the analysis of zircon crystals, suggests that some form of crustal recycling may have begun even earlier, as far back as 4.2 billion years ago, only 300 million years after Earth’s formation. However, he cautions that his findings do not definitively prove the existence of plate tectonics at that time, as subduction and plate movement are not necessarily synonymous.

The Pilbara Craton also contains evidence of a meteorite impact dating back 3.47 billion years, as reported in Nature, further complicating the understanding of the region’s geological history. Shatter cones – geological formations indicative of high-velocity impacts – were discovered within the crater floor, providing unequivocal evidence of the event.