Niuatahi

off-axis caldera, lying between the Northeast Lau Spreading Center (NELSC) and the northern Tofua arc; 15-km diam caldera with central cone Motutahi; SS11/2004 cruise: "the most spectacular retrieval of massively altered and sulfide-bearing lithologies was from Target O."; magnetic data also suggests active hydrothermal field (Kwak et al. 2006); Merle et al. (2008): tow t08c15; "Directly east of the NELSC the seafloor is dominated by an impressive circular volcanic caldera named Volcano “O”. Backscatter data acquired during our bathymetric surveys showed that Volcano O is the source of several lava flows covering large areas of the seafloor. Our plume surveys showed that Volcano O is also host to several active hydrothermal vents." (http://www.pmel.noaa.gov/vents/laubasin/lau-2008/lau08-nov27.html); Resing et al. (2010) indicate that this site may be confirmed active as of May 2009 ROV Jason II: "Observations of hydrothermal activity at two sites were made within the caldera at Volcano “O”"; May 2010 NOAA cruise report camera tow: "In response to the discovery of a very intense sulfur-rich plume over the dacite cone in the SE corner of Volcano O, Tow 8 found concentrated venting of sulfur near its summit at ~1280 m"; Baker et al. 2019: sites 41 and 42 in Table 2;