"A seismologist at Washington University in St. Louis has made the first
3-D model of seismic wave damping - diminishing - deep in the Earth's
mantle and has revealed the existence of an underground water reservoir at
least the volume of the Arctic Ocean. It is the first evidence for water
existing in the Earth's deep mantle."
Full story : http://www.sciencedaily.com/releases/2007/02/070210171556.htm
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gautam