430 Miles Beneath the Surface of Earth, Scientists Have Located a 6th Ocean Scientists have discovered evidence of an enormous hidden “6th ocean” buried deep beneath Earth’s surface — roughly 430 miles down in the mantle. Unlike surface oceans, this vast reservoir is trapped inside a rare blue mineral called ringwoodite, capable of holding large amounts of water. The finding suggests that Earth’s interior may store more water than all surface oceans combined. • The water isn’t in liquid form — i