“A water reservoir located approximately 700 kilometers below Earth's surface contains more water than all of Earth's oceans combined.”

Extensive studies have agreed that the transition zone is a major water reservoir, but the water storage in the lower mantle is poorly constrained. The water contents summarized in Table 1 indicate that the upper mantle, mantle transition zone and lower mantle contain 0.04, 0.2–1 and <2 oceans of water, respectively.

Current evidence suggests that a considerable amount of water may be located deep within the Earth's mantle, far below the Earth's crust. Situated about 700 kilometres below the Earth's crust, this body of water is not in a liquid state but is instead locked in within minerals, according to Brookhaven National Laboratory. Its potential volume is considerable, even surpassing that of all the oceans on the Earth's crust, thus reinvigorating research on the Earth's water cycle.

The researchers have estimated that even if water makes up just 1% of the weight of the total rock in that region, it would still add up to roughly three times the volume of the total water in the Earth's oceans. That said, this isn't the kind of water you could swim in or scoop up with a bucket. Instead, it exists as hydroxyl radicals, chemically bound to a mineral's crystal structure, specifically ringwoodite.

This new discovery suggests that water is stored deep in a mysterious region of the Earth's interior called the transition zone, located roughly 250 to 410 miles beneath North America. “If just one percent of the weight of the mantle rock in the transition zone is water, that would be nearly three times the volume of all Earth's oceans combined,” says Northwestern geophysicist Steve Jacobsen, co-author of the study.

Scientists at Northwestern University in Illinois, United States, have discovered a massive water reservoir hidden beneath the Earth's surface. The hidden ocean, thought to be three times the size of all the oceans combined, is located around 700 kilometres beneath the Earth's surface. This vast underground ocean, contained within a mineral known as ringwoodite, contradicts our previous understanding of the origins of the Earth's water.

Scientists have discovered a massive water reservoir locked within rocks deep in Earth's mantle transition zone, potentially exceeding the volume of all surface oceans. This water, trapped in minerals like ringwoodite, was confirmed by a diamond from Brazil and supported by seismic studies. Nearly 660 kilometers below the surface, in a region called the mantle transition zone, researchers found proof that vast amounts of water may be locked inside rock.

The seismic data suggest that the mantle's water is widespread, Schmandt says, perhaps containing as much water as all of Earth's oceans or even more. Many geologists think the water gets trapped about 410 to 660 kilometers beneath Earth's surface, where the upper mantle transitions into the partially molten lower mantle. A recent analysis of a battered diamond that made the 400-kilometer trek from mantle to surface in an estimated 10 hours revealed a tiny bit of the sapphire-blue mineral ringwoodite — a mineral that's especially good at holding water in the form of hydroxide ions.

Researchers from Northwestern University and the University of New Mexico report evidence for potentially oceans worth of water deep beneath the United States. Though not in the familiar liquid form — the ingredients for water are bound up in rock deep in the Earth's mantle — the discovery may represent the planet's largest water reservoir. If just one percent of the weight of mantle rock located in the transition zone is H2O, that would be equivalent to nearly three times the amount of water in our oceans, the researchers said.

At an astonishing depth of approximately 400 miles beneath our planet's surface, there is an abundant reservoir of water trapped in ringwoodite. To offer some perspective on the sheer volume of this subterranean water body: if the ringwoodite rock contained a mere 1% water, the Earth's crust would be sheltering a water volume thrice that of all the oceans combined on its surface.

After decades of searching scientists have discovered that a vast reservoir of water, enough to fill the Earth's oceans three times over, may be trapped hundreds of miles beneath the surface, potentially transforming our understanding of how the planet was formed. The water is locked up in a mineral called ringwoodite about 660km (400 miles) beneath the crust of the Earth, researchers say.

The volume of water in the oceans is enormous: 1.37 billion cubic kilometers (1.37 × 10^9 km^3, or 0.328 × 10^9 mi.^3). The world's oceans comprise 97.3% of the total water on earth and consists of 5 oceans: Atlantic, Pacific, Indian, Arctic, and Southern. The current range for the volume of the world's ocean is from 1.3 to 1.5 billion cubic kilometers.

The dense minerals wadsleyite and ringwoodite can (unlike the olivine at lesser depths) store large quantities of water—in fact so large that the transition zone would theoretically be able to absorb six times the amount of water in our oceans. “So we knew that the boundary layer has an enormous capacity for storing water,” Brenker says. “However, we didn't know whether it actually did so.”

More than just a place of molten rock, earth's mantle apparently harbors a watery zone able to hold an ocean of water. Analysis of a diamond volcanically coughed up from deep in the earth and recovered in Brazilian river gravel has serendipitously revealed water-containing ringwoodite, a testimony to the presence of both water and the elusive olivine polymorph under the earth.