Fact Check: The «Ocean» Beneath Our Feet Holds Water Three Times the Volume of All Oceans, But It’s Not What It Seems

Original article: Verificación: El “océano” de tres veces el volumen de los mares subterraeno, pero no es lo que parece

Verdict: DECEPTIVE. While science has confirmed the presence of a vast amount of water trapped in minerals within the Earth’s mantle, the «ocean» that supposedly holds three times the volume of all oceans underground is misleading. The viral claim suggests there are «three oceans» of liquid water beneath our feet, which distorts the truth: it’s neither liquid nor usable water, and the figure of «three times» is a conditional theoretical estimate, not a confirmed measurement. More accurate estimates reduce the real amount to between 0.2 and 1 equivalent ocean.

What the Original Study Says

The scientific basis for this story stems from a study published in 2014 in the journal Science by geophysicists Brandon Schmandt and Steve Jacobsen. By analyzing seismic waves beneath North America and combining them with high-pressure laboratory experiments, they concluded that the transition zone of the mantle (between 410 and 660 km deep) acts as a «major water reservoir».

Their finding was solid: they detected signals of dehydration melting, a process occurring when ringwoodite (a high-pressure blue mineral) transforms and releases the water captured in its crystalline structure. This water does not form pockets or underground rivers; it is chemically dissolved in the rock, in the form of hydroxide ions (OH⁻), similar to a solid sponge.

The Origin of the “Three Oceans” Figure

The «three times the oceans» figure originates from a hypothetical calculation that the authors themselves mentioned in their statements and media coverage. The reasoning was: if just 1% of the weight of all the rock in the transition zone contained water, the total amount would be nearly three times the volume of surface oceans.

That conditional «if» is the key detail that headlines overlooked. This referred to a potential storage capacity, not a confirmed measurement of how much is actually there or how it is distributed across the planet. A 2026 fact-check analysis succinctly summarizes: “The widely cited figure of ‘three times all oceans’ is a conditional upper limit assuming 1% water content; it is not a confirmed measurement”.

In fact, Jacobsen had direct evidence only that the hydrated rock was located beneath the United States; its global extent was a reasonable inference but not a measured certainty.

How Much Water Is There Really? The Most Rigorous Estimate

Subsequent scientific reviews have narrowed down the figure. A synthesis published in PMC (NIH) indicates that, according to the most reliable studies, the transition zone contains between 0.2 and 1 equivalent ocean of water, not three. The «three oceans» estimate is still mentioned in outreach, but the available petrophysical evidence places it at the most optimistic and uncertain end of the range.

The Physical Evidence That Did Materialize

In 2022, a diamond extracted from the Karowe mine (Botswana) provided direct evidence. The diamond contained inclusions of ringwoodite alongside other hydrated minerals, and analyses indicated it formed at about 660 km deep, at the boundary between the upper and lower mantle. Researchers concluded that the environment in which it crystallized was “rich in water” or “wet”, confirming that the transition zone contains water in a real sense, not merely theoretical.

However, even this diamond, which acted as a time capsule, does not allow for quantification of the total volume of the reservoir. It confirms the presence, not the global magnitude.

The Nuance That Changes Everything: The State of Water

Ringwoodite does not harbor liquid water. The water is structurally trapped in its crystal lattice, and extreme temperatures and pressures are needed to release it. This is water that does not flow, cannot be pumped, and is not potable in its current state. Comparing it to oceans is, according to a verification report, “fundamentally misleading without that clarification.”

What This Finding Actually Means

This discovery is significant. It alters our understanding of the deep water cycle: surface water sinks with tectonic plates in subduction zones and returns millions of years later through volcanism. It also supports the hypothesis that some of Earth’s water may have been inside the planet since its formation, rather than arriving exclusively via icy comets.

What it does not mean is that there is a «sixth liquid ocean» waiting to be discovered, nor that the surface water crisis can be solved by looking toward the mantle.

In summary: there is a vast amount of water down there, much more than previously believed, but not in the form, the exact quantity, or the availability that viral headlines suggest.