Complete image of Himalayan fault created

Sept. 15, 2009 at 2:31 PM
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CORVALLIS, Ore., Sept. 15 (UPI) -- An international team of scientists says it has created the most complete seismic image of the Earth's crust and upper mantle located under the Himalayas.

The scientists said their research identified some unusual geologic features that might explain how the world's largest mountain range formed.

Oregon State University Associate Professor John Nabelek, lead author of the study, said the team discovered that as the Indian and Eurasian tectonic plates collide, the Indian lower crust slides under the Tibetan crust, while the upper mantle peels away from the crust and drops down in a diffuse manner.

"The building of Tibet is not a simple process," said Nabelek. "In part, the mountain building is similar to pushing dirt with a bulldozer except in this case, the Indian sediments pile up into a wedge that is the lesser Himalayan mountains.

"However, an important component of the mass transfer from the upper crust of India to the Himalayas also occurs at depth through viscous processes, while the lower crust continues sliding intact farther north under the Tibet plateau."

The researchers said their findings are important because the piecemeal images gathered by previous research have led to a series of conflicting models of the lithospheric structure and plate movement.

The study that included scientists from France, Nepal, China and Taiwan is reported in the journal Science.

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