Eruption Evolution of West Mata Volcano, NE Lau Basin Using Hydroacoustic and Video Data

West Mata Volcano located in the NE Lau Basin is the site of the deepest observed submarine volcanic eruption, 1,200 meters below sea level. In May 2009, a research cruise collected video data of two eruptive vents showcasing different eruption styles. During the same research cruise, a BprobeTM portable hydrophone was deployed at the summit of West Mata and collected data that coincides with video recorded at the vents during ROV dives. These data sets were correlated to better understand the spectral signatures associated with the two eruptive vents. Both vents were near the summit, about 50 meters apart, and exhibit different eruptive styles. Hades vent exhibited bubble bursting described as Strombolian-style, while Prometheus vent exhibited active degassing, and slight lava fountaining referred to as Hawaiian-style. In December 2009, a moored hydrophone array consisting of four stations to the north, east, south, and west of West Mata collected data for up to two years. Short-term changes in eruptive behavior provide evidence of transitioning flow regimes. As Hades exhibited periods of singular bursting, while other times there were successive bursting events, it exhibited transitions from bubbly (successive bursts) to slug (singular bursts) flow. This switch in flow regime may have been caused by a slower magma rise rate that allowed bubble coalescence. Prometheus vent generated Hawaiian-style eruptions which also produced bubbly to slug flow regimes. Due to an eruptive vent filled with volcanic debris, bubbles were broken up as they moved through the rubble, thus producing the active degassing. Based on these observations, a time sequence of events is presented here to characterize the eruptive sequences at the West Mata vents, supported by the observed long-term trends in the hydrophone data and changes in bathymetry. These data are used to infer an evolution of the magmatic plumbing system during the 2009-2011 eruptive activity at West Mata