Ancient volcanic rocks in Western Australia’s Pilbara Craton reveal that water was cycling deep into Earth’s interior and driving volcanic activity more than three billion years ago, according to a study published in Nature Communications. Led by Adelaide University geochemist Dr. Eric Vandenburg, an international team examined preserved pillow lavas and discovered rare, water-rich boninite magmas that predate modern plate tectonics.
Pilbara Craton Yields Earth’s Oldest Extensively Preserved Boninites
The research focuses on the Whundo Group, a ten-kilometre-thick stack of volcanic rock laid down between 3.13 and 3.10 billion years ago in Western Australia, according to the study. Hammer sampling by the international team identified three distinct lava families: tholeiites, calc-alkaline basalts, and boninites. Boninite is a rare, water-rich, magnesium-heavy lava that today erupts almost exclusively at modern subduction zones where one tectonic plate grinds beneath another. The Whundo examples represent the oldest extensive boninites known to science.
By analyzing the chemical signatures locked inside the rocks, the research team estimated that the mantle feeding the Whundo boninites held between 0.8 and 1.5 percent water by weight. That figure lands squarely inside the range of present-day arc volcanoes, which hold between 0.1 and 2 percent water, according to the researchers’ findings published in The Conversation.
Did you know? Pillow lavas look like stone beanbags slumped over one another where molten rock hit cold seawater and stiffened instantly, preserving physical structures across the Pilbara Craton that have remained largely undisturbed for over three billion years.
How Dripduction Replaced Plate Tectonics on the Young Earth
Conventional subduction was mechanically difficult on a hotter, younger Earth with weaker, more ductile crust, raising questions about how surface water reached deep mantle depths. To solve this puzzle, researchers point to a geological mechanism known as dripduction, developed across modeling studies including work by Oliver Nebel and colleagues in Precambrian Research.
Under the dripduction model, dense and water-logged sections of the outer crust grew heavy enough to sag and founder, sinking into the hotter mantle below as lopsided blobs rather than sliding cleanly as rigid tectonic plates.
Implications for Early Earth and Missing Crust
The discovery addresses a major question in geology regarding when materials began moving between Earth’s surface and its deep interior. Cratons older than 2.8 billion years account for about seven percent of modern continents, meaning between 50 and 90 percent of evolved Archean crust is missing from the geological record.
According to the Adelaide University announcement, the crust built by dripduction was likely thin and chemically primed for destruction, which explains why so little of it survived three billion years of tectonic recycling. The study suggests that Whundo acts as a rare witness to processes that were already running early in Earth’s history.
Frequently Asked Questions
What are pillow lavas?
Pillow lavas are mound-shaped basaltic lava structures formed when molten rock erupts underwater and cools rapidly into distinctive pillow-like shapes.
What is dripduction?
Dripduction is a geological process where dense, water-rich segments of Earth’s early crust sag and sink into the mantle as blobs, serving as an early alternative to modern plate tectonics.
Where were these ancient rocks found?
The samples were collected from the Whundo Group within Western Australia’s Pilbara Craton by researchers from institutions including Adelaide University, Monash University, Curtin University, and the Geological Survey of Western Australia.
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