for National Geographic News
A giant blob of water the size of the Arctic Ocean has been discovered hundreds of miles beneath eastern Asia, scientists report.
Researchers found the underground "ocean" while scanning seismic waves as they passed through Earth's interior.
But nobody will be exploring this sea by submarine. The water is locked in moisture-containing rocks 400 to 800 miles (700 to 1,400 kilometers) beneath the surface.
"I've gotten all sorts of emails asking if this is the water that burst out in Noah's flood," said the leader of the research team, Michael Wysession of Washington University in St. Louis.
"It isn't an ocean. [The water] is a very low percentage [of the rock], probably less than 0.1 percent."
Given the region's size, however, that's enough to add up to a vast amount of water.
Earthquakes Reveal "Ocean"
Wysession and former graduate student Jesse Lawrence discovered the damp spot by observing how seismic waves from distant earthquakes pass through Earth's mantle.
The wet zone, which runs from Indonesia to the northern tip of Russia, showed up as an area of relatively weak rock, causing the seismic waves to lose strength much more rapidly than elsewhere (see map of Asia.)
The water got there by the process of plate tectonics, in which sections of the Earth's crust shift. This process caused the ocean bottom to be pulled beneath continental plates all around the Pacific Rim.
Normally, Earth's internal heat bakes the water out of the rocks before it gets more than 60 miles (100 kilometers) deep. The water then escapes upward as volcanic gas.
But along the eastern Pacific Rim, conditions allow the rock to be drawn much deeper before the moisture is cooked out.
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