Dr. Arran Murch

The 2009 West Mata eruption is one of only two deep submarine eruptions for which both syn-eruptive visual observations and seafloor samples have been collected. The wealth of syn-eruptive data for the 2009 West Mata eruption provides the ideal opportunity to develop an eruption model of small scale mafic pyroclastic deep submarine volcanism.

West Mata volcano is in the volcanically active NE Lau Basin, West Pacific, ~ 140 km south west of Samoa. One of nine seamounts in the local area West Mata rises from maximum depth of approximately 2900 m below sea level (mbsl) to a summit at 1159 mbsl.

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In November 2008, a chemically unique particle plume discovered ~175 m above the summit of West Mata Volcano suggested active submarine volcanism, which was visually confirmed in May 2009 with ROV Jason2 (Resing et al., 2011). The eruption occurred from two vents named Hades (1200 mbsl) and Prometheus (1175 mbsl). Distinct pyroclastic activity occurred at each vent with the discontinuous release of 0.6-2m diameter bubbles that burst, quenched, and fragmented in the water column recorded at Hades. While more continuous low fountaining activity was observed from Prometheus. In addition, pillow lava flows up to 350-500 m long were erupted from Hades vent.