Geologists studying some of the planet's oldest volcanic rocks have uncovered new evidence that water was playing a major role in shaping Earth's interior and driving volcanic activity more than three billion years ago.
An international research team, led by Adelaide University geochemist Dr Eric Vandenburg , analysed ancient rocks from Western Australia's Pilbara Craton. They found signs that water had travelled deep beneath the Earth's surface before helping to generate magmas that formed volcanoes like those found in the Pacific "Ring of Fire" today.
The findings, published in Nature Communications, suggest that Earth was already running a version of the water-recycling processes that shape the planet today, despite conditions being dramatically different during the planet's infancy.
Dr Vandenburg, from the School of Physics, Chemistry and Earth Sciences, said the research provides a rare window into Earth's distant past.
"These rocks formed more than three billion years ago, when Earth was a very different place," he said.
Today, water is continually recycled through a process known as plate tectonics, where water from the oceans is carried down into the mantle at subduction zones, where one tectonic plate slides beneath another, feeding the volcanoes that build continents.
"The early Earth was too hot for plates to behave that way, so until now it has been unclear whether surface water could have made that journey more than three billion years ago, and if so, how.
"What surprised us was finding evidence that large amounts of water had already made their way deep into the Earth's interior and influenced the formation of volcanic rocks."
The new study suggests that while modern plate tectonics may not yet have existed, another process could have been transporting water into the mantle.
The researchers propose a mechanism they call "dripduction", in which dense, water-rich sections of Earth's cool outer crust sporadically sagged and collapsed into the hotter mantle below, carrying their water down with them.
As this material descended, the water it contained was released into the Earth's mantle, generating magmas that fed volcanic eruptions and later solidified into rocks that can still be studied today.
"The Earth wasn't operating exactly as it does now, but it appears some of the key processes were already in place," Dr Vandenburg said.
The discovery helps answer one of geology's biggest questions: when did Earth begin exchanging materials between its surface and deep interior?
Understanding when water first started moving deep underground is important because the process influences everything from volcanic eruptions to continental growth, and even life-crucial ingredients.
The findings also provide clues about how Earth's continents formed and how the planet evolved into the world we know today.
Because rocks this ancient are exceptionally rare, the Pilbara – where they are also unusually well preserved – is one of the few places to study the young Earth.
By analysing the chemical fingerprints preserved within the rocks, the researchers were able to reconstruct events that occurred 3.1 billion years ago.
The results suggest that Earth's interior and surface may have been connected far earlier than previously recognised, revealing a surprisingly dynamic young planet that was already recycling one of its most important ingredients: water.
The study involved researchers from Adelaide University, Monash University, the Geological Survey of Western Australia, Curtin University, the Australian National University, Cardiff University and the GEOMAR Helmholtz Centre for Ocean Research in Germany.
'Modern arc-like water content in the source of 3.1-billion-year-old volcanic rocks' is published in Nature Communications. DOI: 10.1038/s41467-026-74653-1
