Dehydration melting at the top of the lower mantle

Abstract

Cycling water through the transition zone The water cycle involves more than just the water that circulates between the atmosphere, oceans, and surface waters. It extends deep into Earth's interior as the oceanic crust subducts, or slides, under adjoining plates of crust and sinks into the mantle, carrying water with it. Schmandt et al. combined seismological observations beneath North America with geodynamical modeling and high-pressure and -temperature melting experiments. They conclude that the mantle transition zone—410 to 660 km below Earth's surface—acts as a large reservoir of water. Science , this issue p. 1265