Pilbara rocks show surface water reached Earth's mantle 3.1 billion years ago

An international research group led by Adelaide University geochemist Dr. Eric Vandenburg reports that volcanic rocks from the Pilbara Craton in Western Australia preserve chemical evidence that surface water reached Earth's mantle more than three billion years ago, according to SciTechDaily covering a Nature Communications paper. The team analyzed chemical signatures in rocks more than three billion years old to reconstruct conditions 3.1 billion years ago. The chemistry suggests water entered the hot mantle layer beneath the crust and helped generate magma that later fed volcanoes that may have resembled those around today's Pacific Ring of Fire. The findings, reported in Nature Communications with the reference date 7 July 2026, suggest early Earth was already moving water between surface and interior through processes that performed some of the same functions as modern plate tectonics, even though the hotter young planet may not have supported rigid moving plates like today's subduction zones. The researchers propose a process they call dripduction, in which cooler outer crust absorbed or contained water, became dense enough to lose stability, and sagged or collapsed into the hotter mantle, carrying water-rich rock downward without a fully developed modern plate system. As sinking material heated, it released water that promoted melting and generated magma that could erupt and cool into the Pilbara rocks. Vandenburg said the rocks formed when Earth was a very different place and that what surprised the team was evidence that large amounts of water had already reached the deep interior and influenced volcanic rock formation. The study notes that ancient rocks preserving such records are uncommon and that the Pilbara is valuable because its rocks retained unusually clear chemical fingerprints of early processes.