At the rim of many of Earth's oceans, ocean seafloor subducts beneath the less dense continents. This process causes large destructive earthquakes, explains the many earthquakes that occur hundreds of kilometers below Earth's surface, and also causes arcs of volcanoes (the ring of fire) above the subducted oceanic plate. These volcanoes and earthquakes are thought to occur as large amounts of water are carried down in the oceanic plate. Until now however, there has been little constraint on the amount of water that is carried particularly in the deeper part of the subducted plate. Tom Garth and Andreas Rietbrock show that fault zones that form in the deep oceanic trench offshore northern Japan persist to depths of up to 150 km in the subduction zone. These hydrated fault zones can carry large amounts of water, suggesting that subduction zones may carry much more water from Earth's ocean to the mantle than has previously been suggested. This supports the hypothesis that there are large amounts of water stored deep in the Earth.
Isotopically ultradepleted domains in the convecting upper mantle: Implications for MORB petrogenesis Benjamin L. Byerly and John C. Lassiter, Jackson School of Geosciences, University of Texas at Austin, 1 University Station, C1160, Austin, Texas 78712-0254, USA; firstname.lastname@example.org. Posted online 10 January 2014, http://dx.doi.org/10.1130/G34757.1.
Mid-ocean ridge basalts form by partial melting of material in Earth's convecting upper mantle. Abyssal peridotites are always found with mid-ocean ridge basalts and thus assumed to represent the solid residue from melt extraction. If so, both peridotite and associated basalt should be in isotopi
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