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  • Autonomous underwater vehicle  (2)
  • Bathymetry  (2)
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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2006. 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 7 (2006): Q05001, doi:10.1029/2005GC001086.
    Description: A 2002 multibeam sonar survey of Mauna Loa’s western flank revealed ten submarine radial vents and three submarine lava flows. Only one submarine radial vent was known previously. The ages of these vents are constrained by eyewitness accounts, geologic relationships, Mn-Fe coatings, and geochemical stratigraphy; they range from 128 years B.P. to possibly 47 ka. Eight of the radial vents produced degassed lavas despite eruption in water depths sufficient to inhibit sulfur degassing. These vents formed truncated cones and short lava flows. Two vents produced undegassed lavas that created ‘‘irregular’’ cones and longer lava flows. Compositionally and isotopically, the submarine radial vent lavas are typical of Mauna Loa lavas, except two cones that erupted alkalic lavas. He-Sr isotopes for the radial vent lavas follow Mauna Loa’s evolutionary trend. The compositional and isotopic heterogeneity of these lavas indicates most had distinct parental magmas. Bathymetry and acoustic backscatter results, along with photography and sampling during four JASON2 dives, are used to produce a detailed geologic map to evaluate Mauna Loa’s submarine geologic history. The new map shows that the 1877 submarine eruption was much larger than previously thought, resulting in a 10% increase for recent volcanism. Furthermore, although alkalic lavas were found at two radial vents, there is no systematic increase in alkalinity among these or other Mauna Loa lavas as expected for a dying volcano. These results refute an interpretation that Mauna Loa’s volcanism is waning. The submarine radial vents and flows cover 29 km2 of seafloor and comprise a total volume of ~2 x 109 m3 of lava, reinforcing the idea that submarine lava eruptions are important in the growth of oceanic island volcanoes even after they emerged above sea level.
    Description: This project was funded by NSF grants OCE-97-29894 to M.G. and OCE-9818744 to J.M.R.
    Keywords: Hawaii ; Mauna Loa ; Submarine volcanism ; Radial vents ; Bathymetry ; Igneous petrology
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: 10619596 bytes
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2008. 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 9 (2008):Q11T04, doi:10.1029/2008GC002070.
    Description: Four seafloor benchmarks were deployed with ROV Jason2 at frequently visited areas along the northern East Pacific Rise (NEPR) ridge crest near 9°50′N, within the Ridge2000 EPR integrated study site (ISS) bull's eye. When used in concert with established deep-ocean acoustic positioning techniques, these benchmarks provide navigational infrastructure to facilitate the integration of near-bottom data at this site by allowing efficient and quantitative coregistration of data and observations collected on multiple dives and over multiple cruises. High-resolution, near-bottom multibeam bathymetric surveys also were conducted along and across the ridge crest to provide a morphological and geological context for the benchmark areas. We describe the navigation and data processing techniques used to constrain the benchmark positions and outline operational details to effectively use benchmarks at this and other deep-ocean sites where multidisciplinary time series studies are conducted. The well-constrained positions of the benchmarks provide a consistent geospatial framework that can be used to limit navigational uncertainties during seafloor sampling and mapping programs and enable accurate spatial coregistration and integration of observations. These data are important to test a range of multidisciplinary hypotheses that seek to link geological, chemical, and biological processes associated with crustal accretion and energy transfer from the mantle to the hydrosphere at mid-ocean ridges.
    Keywords: Mid-ocean ridge ; Bathymetry ; Navigation ; Acoustic ; Hydrothermal vent
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
    Publication Date: 2022-10-26
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Wu, J., Parnell‐Turner, R., Fornari, D., Kurras, G., Berrios‐Rivera, N., Barreyre, T., & McDermott, J. Extent and volume of lava flows erupted at 9°50’N, East Pacific Rise in 2005–2006 from autonomous underwater vehicle surveys. Geochemistry Geophysics Geosystems, 23, (2022): e2021GC010213, https://doi.org/10.1029/2021gc010213.
    Description: Seafloor volcanic eruptions are difficult to directly observe due to lengthy eruption cycles and the remote location of mid-ocean ridges. Volcanic eruptions in 2005–2006 at 9°50′N on the East Pacific Rise have been well documented, but the lava volume and flow extent remain uncertain because of the limited near-bottom bathymetric data. We present near-bottom data collected during 19 autonomous underwater vehicle (AUV) Sentry dives at 9°50′N in 2018, 2019, and 2021. The resulting 1 m-resolution bathymetric grid and 20 cm-resolution sidescan sonar images cover 115 km2, and span the entire area of the 2005–2006 eruptions, including an 8 km2 pre-eruption survey collected with AUV ABE in 2001. Pre- and post-eruption surveys, combined with sidescan sonar images and seismo-acoustic impulsive events recorded during the eruptions, are used to quantify the lava flow extent and to estimate changes in seafloor depth caused by lava emplacement. During the 2005–2006 eruptions, lava flowed up to ∼3 km away from the axial summit trough, covering an area of ∼20.8 km2; ∼50% larger than previously thought. Where pre- and post-eruption surveys overlap, individual flow lobes can be resolved, confirming that lava thickness varies from ∼1 to 10 m, and increases with distance from eruptive fissures. The resulting lava volume estimate indicates that ∼57% of the melt extracted from the axial melt lens probably remained in the subsurface as dikes. These observations provide insights into recharge cycles in the subsurface magma system, and are a baseline for studying future eruptions at the 9°50′N area.
    Description: This project is supported by National Science Foundation grants OCE-1834797, OCE-1949485, OCE-194893, OCE-1949938, and by Scripps Institution of Oceanography's David DeLaCour Endowment Fund.
    Keywords: Submarine volcanism ; Mid-ocean ridges ; Autonomous underwater vehicle ; Eruption cycles ; Seafloor mapping
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
    Publication Date: 2023-02-16
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Fabbrizzi, A., Parnell‐Turner, R., Gregg, P., Fornari, D., Perfit, M., Wanless, V., & Anderson, M. Relative timing of off‐axis volcanism from sediment thickness estimates on the 8°20’N seamount chain, East Pacific Rise. Geochemistry, Geophysics, Geosystems, 23(9), (2022): e2022GC010335, https://doi.org/10.1029/2022gc010335.
    Description: Volcanic seamount chains on the flanks of mid-ocean ridges record variability in magmatic processes associated with mantle melting over several millions of years. However, the relative timing of magmatism on individual seamounts along a chain can be difficult to estimate without in situ sampling and is further hampered by Ar40/Ar39 dating limitations. The 8°20’N seamount chain extends ∼170 km west from the fast-spreading East Pacific Rise (EPR), north of and parallel to the western Siqueiros fracture zone. Here, we use multibeam bathymetric data to investigate relationships between abyssal hill formation and seamount volcanism, transform fault slip, and tectonic rotation. Near-bottom compressed high-intensity radiated pulse, bathymetric, and sidescan sonar data collected with the autonomous underwater vehicle Sentry are used to test the hypothesis that seamount volcanism is age-progressive along the seamount chain. Although sediment on seamount flanks is likely to be reworked by gravitational mass-wasting and current activity, bathymetric relief and Sentry vehicle heading analysis suggest that sedimentary accumulations on seamount summits are likely to be relatively pristine. Sediment thickness on the seamounts' summits does not increase linearly with nominal crustal age, as would be predicted if seamounts were constructed proximal to the EPR axis and then aged as the lithosphere cooled and subsided away from the ridge. The thickest sediments are found at the center of the chain, implying the most ancient volcanism there, rather than on seamounts furthest from the EPR. The nonlinear sediment thickness along the 8°20’N seamounts suggests that volcanism can persist off-axis for several million years.
    Description: This work was supported by National Science Foundation awards OCE-1356610, OCE-1356822, OCE-1357150, OCE-1754419, OCE-1834797, OCE-2001314, and OCE-2001331.
    Keywords: Off-axis seamounts ; East Pacific Rise ; Sediment thickness ; Seafloor morphology ; Autonomous underwater vehicle ; Eruption history
    Repository Name: Woods Hole Open Access Server
    Type: Article
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