Eruption of South Sarigan Seamount, Northern Mariana Islands: Insights into Hazards from Submarine Volcanic Eruptions


The eruption of South Sarigan Seamount in the southern Mariana arc in May 2010 is a reminder of how little we know about the hazards associated with submarine explosive eruptions or how to predict these types of eruptions. Monitored by local seismometers and distant hydrophones, the eruption from ~ 200 m water depth produced a gas and ash plume that breached the sea surface and rose ~ 12 km into the atmosphere. This is one of the first instances for which a wide range of preand post-eruption observations allow characterization of such an event on a shallow submarine volcanic arc volcano. Comparison of bathymetric surveys before and after the eruptions of the South Sarigan Seamount reveals the eruption produced a 350 m diameter crater, deeply breached on the west side, and a broad apron downslope with deposits > 50 m thick. The breached summit crater formed within a pre-eruption dome-shaped summit composed of andesite lavas. Dives with the Japan Agency for Marine-Earth Science and Technology Hyper-Dolphin remotely operated vehicle sampled the wall of the crater and the downslope deposits, which consist of andesite lava blocks lying on pumiceous gravel and sand. Chemical analyses show that the andesite pumice is probably juvenile material from the eruption. The unexpected eruption of this seamount, one of many poorly studied shallow seamounts of comparable size along the Mariana and other volcanic arcs, underscores our lack of understanding of submarine hazards associated with submarine volcanism.



South Sarigan Seamount, Volcanic eruptions, Cratering, Mariana arc

"We are grateful to the NOAA Vents Program (now Earth Oceans Interaction Program) and the NOAA Office of Ocean Exploration and Research for long-term funding support of the Mariana arc explorations. JAMSTEC provided funding for Y. Tamura, the Hyper-Dolphin ROV dives, and the support vessel Natsushima. This work was supported in part by the JSPS Grant-in-Aid for Scientific Research (B) (23340166)]. The 2002 and 2013 mapping cruises were supported by the National Science Foundation (2013 cruise OCE-0841074). We thank the crews and science teams on the research vessels T.G. Thompson, Ewing, Melville, and Natsushima for their hard work at sea. We are grateful to J. White, M. Perfit, G. McGimsey, and J. Chaytor for their helpful reviews and C. Searcy and D.N. Greene for informative discussions about the history of seismic and hydro-acoustic monitoring in the southern Mariana arc. PMEL contribution number 4139."


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