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The discovery is said to be the first for a very large body of water near the Earth's mantle---which definitely conjures up images of Brendan Fraser floating on a raft in a sea underneath the Earth's crust (Journey to the Center of the Earth 3D)---but this is real, not a movie.
The discovery was made by seismologist Michael Wysession of Washington University in St. Louis and former graduate student Jesse Lawrence, who had been analyzing seismic records from China. The area was of particular interest due to it's seismic activity. The two studied 600,000 seismograms from instruments all over the world.
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It has been theorized that if a part of the ocean's floor sinks towards the mantle, it would take water down with it, which heats up the deeper it goes, until the rock deteriorates and loses the water.
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While Wysession doesn't mention anything about an underground ocean, there are those who believe that the Earth is hollow.
Join Brendan Fraser in Journey to the Center of the Earth 3D.
Save gas! Convert your car to burn water.