BY TIM CLAREY, PH.D. * |
THURSDAY, NOVEMBER 08, 2018

Since the 1990s, cross-section images of mantle tomography have shown visible slabs of oceanic lithosphere (which includes oceanic crust) descending hundreds of miles beneath ocean trenches into subduction zones.1 These descending plates have been imaged all the way down to the top of the earth’s outer core2 and are composed of cold, brittle, dense rock about 62 miles thick.

Researchers from the University of Colorado recently reported finding that some of the subducted slabs stagnate at depths of about 670 km (416 mi) to 1000 km (620 mi) and appear to travel horizontally.3

Publishing in Nature Geoscience, Wei Mao and his co-author, Shijie Zhong, present seismic tomography that show descending plates beneath the Honshu and northern Mariana subduction zones in the western Pacific. The plates stop in the mantle transition zone and move horizontally for more than 1500 km (930 mi) to the west beneath East Asia.3

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