AMAZING - Massive underground water reservoirs exist, most notably a "hidden ocean" deep in the Earth's mantle (700km down) where water is chemically bound in the mineral ringwoodite, potentially holding thrice Earth's surface water, and vast aquifers in shallower crustal layers like the Great Artesian Basin in Australia or the Cascade Range. These aren't liquid oceans but water locked in minerals or porous rock, playing crucial roles in the planet's water cycle and geology, discovered through seismic waves and geological studies.
Deep Mantle Reservoir (The "Hidden Ocean")Location: Earth's mantle, around 700 km (400 miles) deep.
Form: Water is chemically bonded within a blue mineral called ringwoodite, not liquid water.
Significance: Could hold three times the water of all surface oceans, influencing Earth's water cycle and geology.
Discovery: Detected by seismic waves from earthquakes slowing down as they pass through this water-rich rock.











