LONG-TERM HYDROACOUSTIC AND VIDEO INVESTIGATIONS OF SUBMARINE VOLCANIC ERUPTION DYNAMICS AT NW ROTA-1 AND WEST MATA

Studies of the dynamics of submarine volcanic eruptions provide a more comprehensive understanding of general volcanic and subduction processes. Many long-term eruptive studies exist for subaerial volcanoes, but visual observations of submarine volcanic eruptions have thus far only been short-term. Only two active, explosive seafloor eruptions have been witnessed at deep ocean volcanoes: West Mata and NW Rota-1 in the western Pacific Plate subduction margin. We present video and acoustic data from long-term observations at NW Rota-1 in 2006, and 2009-2010, and West Mata in 2009-2011. We use direct comparisons of video and acoustic data to describe how these two erupting submarine volcanoes behave and change over time. Synchronized hydroacoustic and video observations at these volcanoes have made it possible to relate hydroacoustic events with physical processes at each volcano. This project studies the hydroacoustic signals produced when these submarine volcanoes are erupting, and uses these comparisons to create a long-term timescale of submarine volcanic eruptive behaviors, noting changes in eruption style, eruption frequency, eruption duration, level of explosivity versus effusive activity, etc. For the times where video and hydroacoustic data are available, noteworthy events, such as explosive and/or effusive activity, pyroclasts, bubbles, etc. during each eruption have been identified in the video and their associated acoustic signatures are noted. These correlations allow for interpretations of eruptive behavior for time periods where video data are not available. This project demonstrates the utility of hydroacoustic data for interpreting the dynamics of seafloor eruptions, particularly when paired with available video data. Ultimately, this study will make it possible for future studies that may not have access to video data to be able to interpret submarine volcanic behaviors using hydroacoustic data. Hydroacoustic records may be used to compare prolonged submarine eruptions with prolonged subaerial eruptions such as Stromboli.