Earth’s continental plates were moving 3.48 billion years ago

Earth’s continental plates were moving 3.48 billion years ago Skip to content Subscribe today Every print subscription comes with full digital access Subscribe Now Menu All Topics Health Humans Anthropology Health & Medicine Archaeology Psychology View All Life Animals Plants Ecosystems Paleontology Neuroscience Genetics Microbes View All Earth Agriculture Climate Oceans Environment View All Physics Materials Science Quantum Physics Particle Physics View All Space Astronomy Planetary Science Cosmology View All Magazine Menu All Stories Multimedia Reviews Puzzles Collections Educator Portal Century of Science Unsung characters Coronavirus Outbreak Newsletters Investors Lab About SN Explores Our Store SIGN IN Donate Home INDEPENDENT JOURNALISM SINCE 1921 SIGN IN Search Open search Close search Home INDEPENDENT JOURNALISM SINCE 1921 All Topics Earth Agriculture Climate Oceans Environment Humans Anthropology Health & Medicine Archaeology Psychology Life Animals Plants Ecosystems Paleontology Neuroscience Genetics Microbes Physics Materials Science Quantum Physics Particle Physics Space Astronomy Planetary Science Cosmology Tech Computing Artificial Intelligence Chemistry Math Science & Society All Topics Health Humans Humans Anthropology Health & Medicine Archaeology Psychology Recent posts in Humans Archaeology A new study questions when people first reached South America By Tom Metcalfe10 hours ago Health & Medicine Are pig organs the future of transplantation? 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These rocks hold the earliest known evidence on Earth of something resembling plate tectonics. Alec Brenner, Harvard University/Yale University By Douglas Fox 10 hours ago Share this:Share Share via email (Opens in new window) Email Share on Facebook (Opens in new window) Facebook Share on Reddit (Opens in new window) Reddit Share on X (Opens in new window) X Print (Opens in new window) Print The arid hills of Western Australia’s Pilbara region contain the earliest evidence yet of tectonic plates sliding across Earth’s surface. Tiny magnetic crystals locked in the bedrock recorded the terrain’s movement over time. Starting around 3.48 billion years ago, these rocks raced 2,500 kilometers poleward during a spurt lasting several million years, researchers report March 19 in Science. That pushes back the earliest physical evidence of plates moving by 140 million years. “This is the only planet we know of that has [well-established] tectonics” and it’s important to understand when that began, says Alec Brenner, a paleomagnetic geologist at Yale University.  Sign up for our newsletter We summarize the week's scientific breakthroughs every Thursday. Researchers believe that tectonics stabilized Earth’s environment, allowing complex life to evolve. But scientists have fiercely debated when it started. Estimates range wildly from 1 billion to 4 billion years ago. The researchers probably found “the only rocks in the world” that could convincingly show crustal movement so long ago, says Claire Nichols. The paleomagnetist at Oxford University wasn’t involved in the study but wrote an accompanying commentary. In modern tectonics, continental plates slowly drift and grind against one another, while thinner, denser plates bend, sink and melt under the edges of continents — a process called subduction that fuels volcanoes and the growth of mountain ranges such as the Himalayas and Andes. This recycling of Earth’s surface produces new rocks, which absorb carbon dioxide as they break down, stabilizing Earth’s levels of greenhouse gases and climate over geologic time. Scientists can reconstruct past continental movements by analyzing microscopic crystals of a mineral called magnetite. These crystals imprint the Earth’s magnetic field as they form; by measuring their compass-like orientation, scientists can estimate the latitude — that is, the distance from the equator — where the rocks were when they formed. Looking at rocks of different ages, they can track how tectonic plates moved over millions of years. But the older the rocks, the fainter the signal. Magnetism is “a very, very tenuous property,” easily obliterated by heat and pressure, says Roger Fu, a paleomagnetic geologist at Harvard University. Fu, Brenner and colleagues previously used paleomagnetic measurements in another part of Pilbara to show that this block of terrain drifted more than 5,000 kilometers over a 160 million-year period starting 3.34 billion years ago. But because they tracked only one piece of crust, they couldn’t entirely rule out the possibility that the Earth’s magnetic core had shifted — rather than crustal plates on the surface. As lava erupted onto the seafloor 3.5 billion years ago, it encountered cold seawater and rapidly cooled into the “pillow basalt” blobs seen here (so-called because they often resemble pillows). Hidden within these rocks are microscopic magnetic crystals; they reveal that this piece of the Earth’s crust rapidly drifted 2,500 kilometers over