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Five years of sawing, crushing, dissolving, and analyzing later, they have coaxed from those rocks a secret hidden for eons: the era when plate tectonics began.
Earth’s fractured carapace of rigid, interlocking plates is unique in the solar system. Scientists increasingly connect it to our planet’s other special features, such as its stable atmosphere, protective magnetic field and menagerie of complex life. But geologists have long debated exactly when Earth’s crust broke into plates, with competing hypotheses spanning from the first billion years of the planet’s 4.5-billion-year history to sometime in the last billion. Those estimates have wildly different implications for how plate tectonics affects everything else on Earth.The spreading, smashing, and plunging of tectonic plates shapes far more than just geography. The recycling of Earth’s surface helps to regulate its climate, while the building of continents and mountains pumps vital nutrients into the ecosystem. Indeed, plate tectonics, if it began early enough, may have been a major driver of the evolution of complex life. And by extension, shifting plates could be a prerequisite for advanced life on distant planets as well.
Now, a study of the rocks from the Australian Outback by Tusch, Münker and their co-authors, published in Proceedings of the National Academy of Sciences, has captured “a snapshot” of the advent of plate tectonics, said Alan Collins, a geologist at the University of Adelaide in Australia. The team’s analysis of tungsten isotopes in the rocks reveals Earth in the act of transitioning to plate tectonics around 3.2 billion years ago.
“Plate tectonics gives a very organized way of moving the surface,” said Carolina Lithgow-Bertelloni, a geophysicist at the University of California, Los Angeles. “You can then understand why there are earthquakes where there are earthquakes, why there are mountains where there are mountains.”