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  • 1
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    Deep explosive volcanism on the Gakkel Ridge and seismological constraints on shallow recharge at TAG active mound (2013)
    Massachusetts Institute of Technology and Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-25
    Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2013
    Description: Seafloor digital imagery and bathymetric data are used to evaluate the volcanic characteristics of the 85°E segment of the ultraslow spreading Gakkel Ridge (9 mm yr-1). Imagery reveals that ridges and volcanic cones in the axial valley are covered by numerous, small-volume lava flows, including a few flows fresh enough to have potentially erupted during the 1999 seismic swarm at the site. The morphology and distribution of volcaniclastic deposits observed on the seafloor at depths of ~3800 m, greater than the critical point for steam generation, are consistent with having formed by explosive discharge of magma and CO2 from source vents. Microearthquakes recorded on a 200 m aperture seismometer network deployed on the Trans-Atlantic Geotraverse active mound, a seafloor massive sulfide on the Mid-Atlantic Ridge at 26°N, are used to image subsurface processes at the hydrothermal system. Over nine-months, 32,078 local microearthquakes (ML = -1) with single-phase arrivals cluster on the southwest flank of the deposit at depths 〈125 m. Microearthquakes characteristics are consistent with reaction-driven cracking driven by anhydrite deposition in the shallow secondary circulation system. Exit fluid temperatures recorded at diffuse vents on the mound during the microearthquake study are used to explore linkages between seismicity and venting.
    Description: My research was funded by a National Defense Science and Engineering Graduate Fellowship, the Woods Hole Oceanographic Institution Deep Ocean Exploration Institute fellowship, graduate support from the Woods Hole Oceanographic Institution Academic Programs Office, and NSF Award 0137329 for TAG active mound research (PI: Rob Sohn).
    Keywords: Volcanic eruptions ; Volcanology
    Repository Name: Woods Hole Open Access Server
    Type: Thesis
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  • 2
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    Toward extraplanetary under-ice exploration : robotic steps in the Arctic (2009)
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    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Journal of Field Robotics 26 (2009): 411-429, doi:10.1002/rob.20288.
    Description: This paper describes the design and use of two new autonomous underwater vehicles, Jaguar and Puma, which were deployed in the summer of 2007 at sites at 85°N latitude in the ice-covered Arctic Ocean to search for hydrothermal vents. These robots are the first to be deployed and recovered through ice to the deep ocean (〉 3500m) for scientific research. We examine the mechanical design, software architecture, navigation considerations, sensor suite and issues with deployment and recovery in the ice based on the missions they carried out. Successful recoveries of vehicles deployed under the ice requires two-way acoustic communication, flexible navigation strategies, redundant localization hardware, and software that can cope with several different kinds of failure. The ability to direct an AUV via the low bandwidth and intermittently functional acoustic channel, is of particular importance. Based on our experiences, we also discuss the applicability of the technology and operational approaches of this expedition to the exploration of Jupiter's ice-covered moon Europa.
    Description: This work was made possible in part through NSF OPP grant OPP-0425838, through the NASA ASTEP program through grant Z601701, through NSF Censsis ERC through grant EEC-9986821 and through funding from the Woods Hole Oceanographic Institution.
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 3
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    Effusive and explosive volcanism on the ultraslow-spreading Gakkel Ridge, 85°E (2012)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 13 (2012): Q10005, doi:10.1029/2012GC004187.
    Description: We use high-definition seafloor digital imagery and multibeam bathymetric data acquired during the 2007 Arctic Gakkel Vents Expedition (AGAVE) to evaluate the volcanic characteristics of the 85°E segment of the ultraslow spreading Gakkel Ridge (9 mm yr−1 full rate). Our seafloor imagery reveals that the axial valley is covered by numerous, small-volume (order ~1000 m3) lava flows displaying a range of ages and morphologies as well as unconsolidated volcaniclastic deposits with thicknesses up to 10 cm. The valley floor contains two prominent volcanic lineaments made up of axis-parallel ridges and small, cratered volcanic cones. The lava flows appear to have erupted from a number of distinct source vents within the ~12–15 km-wide axial valley. Only a few of these flows are fresh enough to have potentially erupted during the 1999 seismic swarm at this site, and these are associated with the Oden and Loke volcanic cones. We model the widespread volcaniclastic deposits we observed on the seafloor as having been generated by the explosive discharge of CO2 that accumulated in (possibly deep) crustal melt reservoirs. The energy released during explosive discharge, combined with the buoyant rise of hot fluid, lofted fragmented clasts of rapidly cooling magma into the water column, and they subsequently settled onto the seafloor as fall deposits surrounding the source vent.
    Description: We gratefully acknowledge the financial support of the National Aeronautics and Space Administration, the National Science Foundation (N.S.F.), the International Polar Year 2007–2008, and Woods Hole Oceanographic Institution; and the graduate support provided by N.S.F., the NDSEG Fellowship, and WHOI Deep Ocean Exploration Institute.
    Description: 2013-04-06
    Keywords: Mid-ocean ridge ; Seafloor morphology ; Submarine explosive volcanism ; Ultraslow spreading
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: text/plain
    Format: application/msword
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    Format: video/mp4
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  • 4
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    Microearthquake evidence for reaction-driven cracking within the Trans-Atlantic Geotraverse active hydrothermal deposit (2014)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 119 (2014): 822–839, doi:10.1002/2013JB010110.
    Description: We detected 32,078 very small, local microearthquakes (average ML = −1) during a 9 month deployment of five ocean bottom seismometers on the periphery of the Trans-Atlantic Geotraverse active mound. Seismicity rates were constant without any main shock-aftershock behavior at ~243 events per day at the beginning of the experiment, 128 events per day after an instrument failed, and 97 events per day at the end of the experiment when whale calls increased background noise levels. The microearthquake seismograms are characterized by durations of 〈1 s and most have single-phase P wave arrivals (i.e., no S arrivals). We accurately located 6207 of the earthquakes, with hypocenters clustered within a narrow depth interval from ~50 to 125 m below seafloor on the south and west flanks of the deposit. We model the microearthquakes as reaction-driven fracturing events caused by anhydrite deposition in the secondary circulation system of the hydrothermal mound and show that under reasonable modeling assumptions an average event represents a volume increase of 31–58 cm3, yielding an annual (seismogenic) anhydrite deposition rate of 27–51 m3.
    Description: This work was supported in part by the U.S. National Science Foundation, National Science and Engineering Graduate Fellowship, and the Woods Hole Oceanographic Institution Deep Ocean Exploration Institute.
    Description: 2014-09-19
    Keywords: Hydrothermal ; Microearthquake ; Sulfide ; Circulation ; Recharge
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: text/plain
    Format: application/pdf
    Format: application/postscript
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