Figure 2. Map of the Western Pacific and Mariana, Izu-Bonin, and Northern Mariana Seamount Province volcanic arcs. Solid circles = existing drill holes; most coring that occurred prior to Sites 800-802 failed to penetrate the complete sedimentary section and/or had poor recovery. Shaded seafloor includes Pigafetta Basin (PB) and Magellan Seamount, where alkalic Cretaceous overprint predominates. Solid triangles = active volcanoes. Site BON-8A and Hole 801C are proposed drill sites. Ogasawara Fracture Zone-Magellan Seamount Flexural Moat (OFZ-MSM) after Abrams et al., 1992 (their fig. 2). Curved arrows = instantaneous trajectories for the Pacific Plate relative to the Philippine Plate, after Seno et al., (1993). Dashed curves = continuation of trajectories beneath the arc. EMB = East Mariana Basin. N. Smt. Prov. = Northern Seamount Province. Gray shaded boxes show Leg 125 and 126 drilling areas and the Izu Crosschains. The Izu Crosschains shaded box shows the location of a cruise in 1995 that conducted detailed sampling of the Izu Crosschain seamount volcanoes. These samples provide excellent controls on spatial and temporal variations in slab outputs across the Izu-Bonin arc.