ALBERT

Description: West Mata is a submarine volcano located in the SW Pacific Ocean between Fiji and Samoa in the NE Lau Basin. West Mata was discovered to be actively erupting at its summit in September 2008 and May 2009. Water-column chemistry and hydrophone data suggest it was probably continuously active until early 2011. Subsequent repeated bathymetric surveys of West Mata have shown that it changed to a style of frequent but intermittent eruptions away from the summit since then. We present new data from ship-based bathymetric surveys, high-resolution bathymetry from an autonomous underwater vehicle, and observations from remotely operated vehicle dives that document four additional eruptions between 2012 and 2018. Three of those eruptions occurred between September 2012 and March 2016; one near the summit on the upper ENE rift, a second on the NE flank away from any rift zone, and a third at the NE base of the volcano. The latter intruded a sill into a basin with thick sediments, uplifted them, and then extruded lava onto the seafloor around them. The most recent of the four eruptions occurred between March 2016 and November 2017 along the middle ENE rift zone and produced pillow lava flows with a shingled morphology and tephra as well as clastic debris that mantled the SE slope. ROV dive observations show that the shallower recent eruptions at West Mata include a substantial pyroclastic component, based on thick (〉1 m) tephra deposits near eruptive vents. The deepest eruption sites lack these near-vent tephra deposits, suggesting that pyroclastic activity is minimal below ∼2500 mbsl. The multibeam sonar re-surveys constrain the timing, thickness, area, morphology, and volume of the new eruptions. The cumulative erupted volume since 1996 suggests that eruptions at West Mata are volume-predictable with an average eruption rate of 7.8 × 106 m3/yr. This relatively low magma supply rate and the high frequency of eruptions (every 1–2 years) suggests that the magma reservoir at West Mata is relatively small. With its frequent activity, West Mata continues to be an ideal natural laboratory for the study of submarine volcanic eruptions.

Description: Author Posting. © Oceanography Society, 2007. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 20, 4 (2007): 52-61.

Description: Human-occupied submersibles, towed vehicles, and tethered remotely operated vehicles (ROVs) have traditionally been used to study the deep seafloor. In recent years, however, autonomous underwater vehicles (AUVs) have begun to replace these other vehicles for mapping and survey missions. AUVs complement the capabilities of these pre-existing systems, offering superior mapping capabilities, improved logistics, and better utilization of the surface support vessel by allowing other tasks such as submersible operations, ROV work, CTD stations, or multibeam surveys to be performed while the AUV does its work. AUVs are particularly well suited to systematic preplanned surveys using sonars, in situ chemical sensors, and cameras in the rugged deep-sea terrain that has been the focus of numerous scientific expeditions (e.g., those to mid-ocean ridges and ocean margin settings). The Autonomous Benthic Explorer (ABE) is an example of an AUV that has been used for over 20 cruises sponsored by the National Science Foundation (NSF), the National Oceanic and Atmospheric Administration (NOAA) Office of Ocean Exploration (OE), and international and private sources. This paper summarizes NOAA OE-sponsored cruises made to date using ABE.

Description: Author Posting. © Oceanography Society, 2010. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 23, 1 (2010): 38-39.

Description: Axial Seamount is a hotspot volcano superimposed on the Juan de Fuca Ridge (JdFR) in the Northeast Pacific Ocean. Due to its robust magma supply, it rises ~ 800 m above the rest of JdFR and has a large elongate summit caldera with two rift zones that parallel and overlap with adjacent segments of the spreading center.