Water was reaching deep inside Earth and helping fuel volcanic eruptions more than three billion years ago, according to a new analysis of ancient rocks from Western Australia. The finding suggests that the planet's early interior was interacting with surface water long before modern plate tectonics may have fully developed, challenging assumptions about when and how Earth's recycling systems began.
The researchers propose that water-rich pieces of crust periodically sank into the mantle through a process they call «dripduction.» Unlike modern subduction, in which rigid tectonic plates slide beneath one another and carry water downward, dripduction would have involved localized blobs of crust dripping into the deeper mantle. The buried water then lowered the melting point of surrounding rock, helping to produce magma that fed volcanic eruptions.
The evidence comes from ancient rocks in Western Australia, some of the oldest surviving material on Earth's surface. These rocks preserve chemical signatures indicating that water was present deep in the planet's interior at a time when the crust was likely hotter, thinner, and more mobile than it is today. The study adds to a growing body of research suggesting that early Earth was not a dry, stagnant world but one with active geological cycles.
If confirmed, the mechanism would help explain how volcanoes remained active on early Earth and how water moved between the surface and the deep interior. It would also push back the timeline for water-driven volcanism, placing it more than a billion years before the oldest widely accepted evidence of modern plate tectonics.
The work carries implications for understanding the origins of continents, the composition of the early atmosphere, and the conditions that made Earth habitable. Water cycling through the mantle influences long-term climate by regulating volcanic emissions of gases such as carbon dioxide and water vapor. A planet that recycled water early could have maintained a more stable surface environment than one without such a cycle.
The researchers do not claim that dripduction replaced plate tectonics. Instead, they present it as an earlier, perhaps transitional, mechanism that operated when Earth's lithosphere was too warm and buoyant to behave like modern plates. Over time, as the planet cooled, dripduction may have given way to the organized subduction zones that characterize plate tectonics today.
The study also raises questions about how much water early Earth stored in its interior and how that inventory changed over billions of years. Water trapped in the mantle can be released gradually through volcanism, shaping the oceans and atmosphere. If dripduction delivered significant amounts of water to the deep mantle, it could have influenced the planet's long-term water budget.
Scientists caution that the ancient rock record is fragmentary and that alternative explanations for the chemical signatures remain possible. Further fieldwork and laboratory analyses will be needed to test the dripduction hypothesis and to determine how widespread the process may have been. The rocks of Western Australia, however, continue to provide one of the few windows into Earth's earliest geological history.
The finding fits into a broader effort to reconstruct the first billion years of Earth's evolution, a period for which direct evidence is scarce. By combining geochemistry, petrology, and modeling, researchers are piecing together how the planet transitioned from a hot, chaotic youth to a world with stable continents, oceans, and a life-supporting climate.
