Scientists using 3-D scanning of the deep interior of Earth have found evidence of a vast water reservoir beneath eastern Asia that is at least the volume of the Arctic Ocean -the first time such a large body of water has found in the planet’s deep mantle.
The finding, made by Michael Wysession, a seismologist at Washington
University in St. Louis, and his former graduate student Jesse
Lawrence, now at the University of California, San Diego, was made by
analyzing more than 600,000 seismograms—records of waves generated by earthquakes traveling through the Earth—collected from instruments located around the planet.
The team discovered a region beneath Asia where seismic waves appeared to dampen, or “attenuate,” and also slow down slightly. “Water slows the speed of waves,” Wysession explained. “Lots of damping and a little slowing match the predictions for water very well.”
Their research proved out earlier predictions that calculated that
if a cold slab of the ocean floor were to sink thousands of miles into
the Earth’s mantle, the hot temperatures would cause water stored
inside the rock to evaporate out.
The researchers estimate that up to 0.1 percent of the rock sinking
down into the Earth’s mantle in that part of the world is water, which
works out to about an Arctic Ocean’s worth of water.
Wysession has dubbed the new underground feature the “Beijing anomaly,” because seismic wave attenuation was found to be highest beneath the Chinese capital city (see image left above showing increased attenuation in Asia) . Wysession first used the moniker during a presentation of his work at the University of Beijing.
“They thought it was very, very interesting,” Wysession said. “China is under greater seismic risk than just about any country in the world, so they are very interested in seismology.”
Water covers 70 percent of Earth’s surface and one of its many functions is to act like a lubricant for the movement of continental plates.
“Look at our sister planet, Venus,” Wysession said. “It is very hot and dry inside Venus, and Venus has no plate tectonics. All the water probably boiled off, and without water, there are no plates. The system is locked up, like a rusty Tin Man with no oil.”
Posted by Jason McManus.
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