Figure 2.10. Dehydration in slab leads to peridotite melting. Water is released from hydrated ocean crust (spilite) and subducted sediment as the downgoing slab is heated and metamorphosed. Water loss is shown schematically by the blue colors in the figure. The water released from slab dehydration reactions seeps into the peridotite of the overlying lithosphere and causes partial melting. The yellow region in the overlying mantle is the zone of peridotite partial melting identified by Grove and others (2006) based on their laboratory experiments. Mantle melt is shown schematically by the red blobs. Because magma is less dense than the melting rock, partial melt liquids coalesce and rise toward the surface.