The “transition zone” in the Earth’s mantle earlier suspected to contain water trapped in rare minerals has been proven to have water trapped between the upper and lower mantle layers. A recent study conducted by scientists in the U.S. confirmed direct evidence of water trapped inside a water-rich mineral called ringwoodite between 410 and 660 kilometers underneath the surface of the Earth.
It has finally been validated that the world’s comprising many deep and spread out oceans conceals its largest ocean 400 to 600 kilometers beneath our feet.
Seismic waves travelling through the mantle were analyzed in the experiments as a result of which it was discovered that downward-flowing mantle material is melting at the area where it crosses the demarcation between the transition zone and the lower layer of mantle.
The researchers concluded that there has to be water in the transition zone because of the melting of the upper layer of the mantle. Melting is a way of getting rid of water, which is unstable under conditions in the Earth’s lower mantle, said the researchers.
Instead of being present in the form of liquid, ice or water, water is trapped in the molecular structure of ringwoodite as hydroxide ions or bonded oxygen and hydrogen atoms. Ringwoodite is a rare type of mineral that forms under very high pressures and temperatures such as those present in the mantle’s transition zone from a mineral called olivine. Olivine, also called peridot or chrysolite, is a magnesium iron silicate mineral common in the Earth’s sub-surface.
Scientists have earlier resorted to many approaches so as to unearth evidence of water under the Earth’s surface. However, this is the first time scientists have focused on the potential water-induced melting at the bottom of the transition zone.
Courtesy of this study, it is now known that the water in the Earth’s mantle comes from degassing of molten rock. What now needs to be understood is the amount of water inside the Earth as compared to that on the surface.