Bob Dziak¹, Del Bohnenstiehl², Ed Baker³

¹OSU/NOAA, HMSC, Newport, OR 97365 (Robert.p.dziak@noaa.gov)

²Dept of Marine, Earth, and Atmospheric Sciences, NCSU, Rayliehgh NC, delwayne_bohnenstiehl@ncsu.edu

³NOAA, Pacific Marine Environmental Laboratory, Seattle, WA 98115 (Edward.Baker@noaa.gov)

            During two cruises in November 2008 and May 2009, a spectacular explosive eruption was discovered at the summit of West Mata Volcano in the northeast Lau Basin (Resing et al. 2009).  This submarine volcano is located ~150 km southwest of Samoa, between 15°00’S and 15°10’S. In December of 2009, we re-initiated acoustic monitoring of the West Mata system by deploying four hydrophone moorings during a research cruise of opportunity. This array, recovered in late April 2010, was configured in a diamond-shaped geometry encompassing the summit and a set of nearby volcanic edifices known as the North Matas (Fig. 1).  Each mooring contained a single sound-channel moored hydrophone (~300-1000 m depth) with a sample-rate of 1 kHz. The southern mooring in the array also contained two optical backscatter and temperature sensors (MAPRs) attached to the mooring line (at 1800 and 2250 m depth) to detect plumes of volcanic debris that detach from the flank of West Mata.  

The presence of prolonged and intense eruptive activity makes the northeastern Lau Basin an ideal system to gain insight on deep-ocean volcanism and its impacts on the ocean. We would like to combine our hydrophone and in situ MAPR data with other ship-based water column and geophysical measurements to investigate several first-order processes.

            We hypothesize that: 1) Volcano-acoustic signals from the Northern Lau Basin are produced by multiple, some yet undiscovered, sources along the summit of West Mata. This creates a natural laboratory through which we can study the impact of water depth on submarine eruptions.  2) Variable frequency harmonic tremor observed at submarine volcanoes like West Mata can be modeled as a series of discrete explosion events.  Such a discovery would alter the existing paradigm for submarine tremor generation, which relates this process to resonance within the magma conduit. 3) The relative production of volcanic ash and debris plumes, as monitored by the in situ MAPRs deployed near West Mata, can be correlated with the intensity and style of acoustic signals sourced from the volcanic edifice.  This work seeks to unravel the time history of volcano growth and the transport of clastic material from the summit.