An international team of geophysicists has announced a groundbreaking discovery that could fundamentally change our understanding of the Earth’s structure:
At around 700 kilometers beneath the surface, hidden in the Earth’s mantle, there may be a colossal reservoir of water — possibly holding as much as all of the planet’s surface oceans combined.
This water is not liquid like lakes or seas, but locked inside a blue mineral called ringwoodite, which can trap water in its crystal structure under extreme pressure.
“It’s not a traditional ocean with waves and shores, but a massive store of bound water inside the Earth,” said Steven Jacobsen, a geophysicist at Northwestern University.
“It’s possible that much of our surface water originally came from this deep reservoir.”
How the hidden ocean was found
The discovery was made using seismic waves from earthquakes, lab experiments, and microscopic inclusions found inside deep-origin diamonds.
Seismic waves travel more slowly through water-bearing rock than through dry material.
Researchers noticed that at about 700 km deep, there is a zone where the waves significantly slow down, which strongly suggests large amounts of bound water.
They also identified tiny inclusions of water-bearing ringwoodite in deep diamonds, providing direct evidence of water deep within the Earth.
“These findings confirm our long-held hypothesis that the mantle can store enormous amounts of water in solid form,” Jacobsen explained.
Why this water is so unusual
This water is not in liquid form. It is chemically bound to the crystal structure of ringwoodite, and can only exist under the extreme pressure and heat conditions of the mantle.
Yet this discovery could be key to understanding the global water cycle and the inner dynamics of our planet.
According to the scientists, this hidden reservoir might:
- Explain the origin of surface water, having slowly released vapor over billions of years
- Influence volcanic activity, since water lowers the melting point of mantle rock
- Help regulate the Earth’s internal temperature, by storing heat and changing mantle viscosity
- Enable plate tectonics to function, by reducing friction between slabs
- Act as a natural “water buffer” during major geological shifts
What we know so far about the “deep ocean”
| Parameter | Detail |
|---|---|
| Location | Mantle transition zone (between 410 and 700 km depth) |
| Average depth | Around 700 km below the surface |
| Form of water | Chemically bound within ringwoodite’s crystal lattice |
| Estimated quantity | As much or more than all surface oceans combined |
| Temperature | 1,400–1,600 °C |
| Pressure | About 23,000 times atmospheric pressure |
Ringwoodite can hold up to 1.5% of its weight in water, and because this mantle layer is so massive, it could contain billions of cubic kilometers of water.
This suggests that Earth’s water may not have arrived only via comets and asteroids, as long believed, but may have originated from inside the planet itself.
The researchers now plan deeper drilling and new high-pressure experiments to understand how this water interacts with the upper mantle and volcanic processes.
“We are literally living on top of a hidden ocean buried deep beneath our feet,” said Karen Lee of the Potsdam Geosciences Institute.
“This discovery could rewrite entire chapters of Earth’s history.”
