A continuing effort by the Submarine Ring of Fire team to explore the submarine portions of the intra-oceanic volcanic arcs of the western Pacific. The 2004 dive program on the Mariana Arc was extraordinarily rich in discoveries. Highlights of the expeditions include: (1) the first observations and sampling of an actively erupting submarine arc volcano; (2) the discovery of a field of copiously discharging "CO2 vents" emitting droplets of liquid CO2 (only the second such site found anywhere), surrounded by an ecosystem of apparently high biological productivity; (3) the discovery of overlapping chemosynthetic and photosynthetic ecosystems on a shallow volcano; and (4) the recovery of at least 10 new macrofauna species at the various volcanoes. The first year of this proposal (2005) is a collaborative program with two New Zealand research groups to use the Hawaii Undersea Research Laboratories PISCES IV and V human occupied vehicles to dive on hydrothermally active volcanoes of the Kermadec Arc lying northeast of New Zealand. Together with our New Zealand collaborators, dives will be made on 6 or 7 volcanoes. An international, interdisciplinary team of geologists, chemists, microbiologists and macrobiologists will comprise the science team.