The image to the left, which shows all the Earth’s surface water in one place, gives you an idea of how big this discovery is.
Scientists have found, about 700 km deep in the Earth’s crust, a reservoir that holds about 3 times the water volume of the ocean. The water is trapped in a type of blue rock called ringwoodite, a “high-pressure polymorph of olivine that is formed at high temperatures and pressures”.
Picture credit: treehugger.com