Ever imagined a gigantic ocean hidden deep beneath our feet, quietly shaping the very face of our planet? Well, scientists have just uncovered astonishing proof that such a reservoir not only exists but is truly mind-blowing in scale. Time to dust off your inner explorer!

An Ocean Three Times Bigger Than All Others

Picture this: deep below Earth’s surface, there is a secret reservoir containing as much as three times the volume of all the planet’s oceans combined. That’s not a typo, and no, this isn’t science fiction. This groundbreaking discovery could finally answer one of geology’s oldest riddles: where did Earth’s seas originate?

The sheer size of this buried water source has sparked new debates about our planet’s history. For ages, some geologists have argued that water hitched a ride to Earth on icy comets, slamming into our young world. Now, with this revelation, there’s compelling support for a different theory: maybe the oceans actually seeped out from the planet’s own interior over millions of years, kind of like Earth’s version of a slow cooker gone wild.

Following the Sound: How Scientists Tracked Down the Hidden Water

Steven Jacobsen from Northwestern University in Evanston, Illinois, led the discovery. According to him,

“It’s good evidence the Earth’s water came from within.”

Jacobsen suggests that this hidden water could even act as a stabilizer for the oceans above, possibly explaining how their size has remained so consistent through countless millennia.

The detective work behind the discovery is just as fascinating as the find itself. Jacobsen’s team deployed a staggering 2,000 seismometers across the planet to listen to the seismic symphony set off by more than 500 earthquakes. These seismic waves ripple through the planet’s interior—including all the way to the core—and, as Jacobsen humorously puts it,

“They make the Earth ring like a bell for days afterwards.”

By meticulously measuring how fast these waves traveled at different depths, the team deduced what kind of rocks the waves encountered. If the seismic speed dropped, that was a signal that the waves were moving through water-laden rock. After all, even seismic waves feel a bit sluggish when slogging through soggy terrain!

Meet Ringwoodite: The Unlikely Water Bearer

But how exactly does water hide deep inside solid rock? Enter ringwoodite—a blue crystal with a talent for hoarding water. Jacobsen didn’t leave anything to chance: he grew his own ringwoodite crystals in the lab, then subjected them to pressures and temperatures matching those a whopping 700 kilometers (over 430 miles) beneath Earth’s surface.

The results were stunning. Down in the so-called “transition zone,” which separates Earth’s upper and lower mantle, Jacobsen’s team discovered traces of wet ringwoodite. At those extreme depths, the conditions squeeze water out of the mineral.

“It’s rock with water along the boundaries between the grains, almost as if they’re sweating,”

Jacobsen explains.

Backed By Diamonds (And Science!)

Jacobsen’s work dovetails with recent findings by Graham Pearson from the University of Alberta, in Edmonton, Canada. Pearson’s team studied a diamond unearthed by a volcanic eruption—and discovered that it contained water-bearing ringwoodite. That diamond was the first concrete evidence that lots of water exists in the transition zone, backing up the seismic findings. (If you want the technical details, check Nature, doi.org/s6h.)

So, just how important is this great, unseen sea? Jacobsen doesn’t mince words:

“We should be grateful for this deep reservoir. If it wasn’t there, it would be on the surface of the Earth, and mountain tops would be the only land poking out.”

In other words, without this vast subterranean buffer, our planet might look a lot more like a watery world in a sci-fi blockbuster, with just the highest mountain peaks showing above the waves. The next time you gaze at the ocean, remember: there’s a lot more water beneath your feet than you ever imagined.