Geophysics

Tearing Down Deep

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Science  27 Jun 2003:
Vol. 300, Issue 5628, pp. 2005-2007
DOI: 10.1126/science.300.5628.2005e

The greatest depth of the ocean, more than 11 km, is at the Marianas Trench in the western Pacific. One reason is that here some of the oldest, and thus coolest, ocean crust is subducted westward beneath Guam, and the trench is not filled with sediment. But the deepest part of the Marianas Trench, the Challenger Deep, is not southwest of Guam but southeast, where the trench bends to the west and much younger ocean crust is being subducted. Fryer et al. provide new geophysical data to explain why the Challenger Deep is so deep. Their data imply that the subducting ocean crust is torn here, not that there is a large strike-slip fault, as was previously thought. This tear has further influenced the deformation and dynamics of the overriding plate, and together these features have deepened what is already a deep subduction zone.—BH

Earth Planet. Sci. Lett. 211, 259 (2003).

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