Hidden ocean found 700 km inside Earth’s mantle

Exam-focused facts from the 28 March 2026 current affairs briefing.

Key facts

A water-saturated reservoir located roughly 700 km beneath Earth’s surface has been detected in the mantle transition zone (410–660 km deep).
The water is chemically bound within ringwoodite, a high-pressure mineral that can store hydrogen and water in its crystal structure.
The trapped water volume is estimated to equal or exceed the combined volume of all surface oceans.
Ringwoodite samples recovered in volcanic diamonds and xenoliths confirm the mineral’s water-bearing capacity under mantle conditions.