Tectonic Plates Drove Earth's Ancient Climate Swings, Study Reveals

Carbon released from Earth's spreading tectonic plates, not volcanoes, may have triggered major transitions between ancient ice ages and warm climates, new research finds. Published in Communications Earth & Environment, the study, led by researchers at the Universities of Melbourne and Sydney, reconstructed how carbon moved between volcanoes, oceans and deep within Earth over the last 540 million years. It provides insight into the magnitude of our rapidly changing climate today. Lead researcher, University of Melbourne Dr. Ben Mather from the School of Geography, Earth and Atmospheric Sciences said the findings challenge a long-held view that chains of volcanoes—formed by colliding tectonic plates—were Earth's main natural source of atmospheric carbon. "Our findings show that carbon gas released from gaps and ridges deep under the ocean from moving tectonic plates was instead likely driving major shifts between icehouse and greenhouse climates for most of Earth's history," Dr. Mather said. "We found that carbon emitted from volcanoes, around the Pacific ring of fire for example, only became a major carbon source in the last 100 million years, which challenges current scientific understanding." The work provides the first clear long-term evidence that the global climate was shaped mainly by carbon released where tectonic plates pull apart, rather than where they collide. "This new insight not only reshapes our understanding of past climates but also helps refine future climate models," Dr. Mather said. Co-author Professor Dietmar Müller from the University of Sydney's School of Geosciences described that by pairing global plate tectonic reconstructions with carbon-cycle modeling, the team were able to trace how carbon was stored, released and recycled as continents shifted. "Our study's findings help explain key historical climate shifts, including the late Paleozoic ice age, the warm Mesozoic greenhouse world, and the emergence of the modern Cenozoic icehouse, by showing how changes in carbon released from spreading plates shaped these long-term transitions to our climate," Professor Müller said. Dr. Mather said the research provides important context for our currently changing climate. "This research adds to a large pool of evidence that the amount of carbon in Earth's atmosphere is a key trigger to cause major swings in climate," he said. "Understanding how Earth controlled its climate in the past highlights how unusual the present rate of change is. Human activities are now releasing carbon far faster than any natural geological process that we've seen to have taken place before. The climate scales are being tipped at an alarming rate."