A giant reservoir of water has been discovered 400 miles beneath Earth's surface.
It could harbor three times the volume of water found in every ocean on Earth’s surface combined.
Yet this is no familiar liquid. It doesn’t course through hidden rivers or pool in vast underground chambers. Instead, it’s imprisoned inside ringwoodite, a mineral deep in the mantle that functions like a molecular sponge, clutching H₂O within its crystal lattice under crushing pressure and searing heat.
For decades, researchers speculated about such a subterranean reservoir, but this marks the most compelling proof to date. The revelation emerged from seismic waves: subtle variations in how earthquake vibrations propagate through Earth’s interior betrayed the signature of water-saturated rock.
The finding compels a radical overhaul of Earth’s hydrologic cycle. Conventionally, we viewed nearly all planetary water as confined to the surface and shallow crust. This concealed ocean, however, unveils a far-reaching, globe-spanning circuit that may shuttle water between oceans, mantle, and perhaps even greater depths across geologic timescales.
Lead geophysicist Steve Jacobsen suggests this buried trove could explain the origins of Earth’s abundant surface water. It may also govern volcanic eruptions and the restless drift of tectonic plates.
["Gigantic ocean of water found hidden beneath the Earth’s surface." Brighter Side of News, 30 April 2025]