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  • 1
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    Rapid dispersal of a hydrothermal plume by turbulent mixing (2010)
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    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 57 (2010): 931-945, doi:10.1016/j.dsr.2010.04.010.
    Beschreibung: The water column imprint of the hydrothermal plume observed at the Nibelungen field (8°18' S 13°30' W) is highly variable in space and time. The off-axis location of the site, along the southern boundary of a non-transform ridge offset at the joint between two segments of the southern Mid-Atlantic Ridge, is characterized by complex, rugged topography, and thus favorable for the generation of internal tides, subsequent internal wave breaking, and associated vertical mixing in the water column. We have used towed transects and vertical profiles of stratification, turbidity, and direct current measurements to investigate the strength of turbulent mixing in the vicinity of the vent site and the adjacent rift valley, and its temporal and spatial variability in relation to the plume dispersal. Turbulent diffusivities Kp were calculated from temperature inversions via Thorpe scales. Heightened mixing (compared to open ocean values) was observed in the whole rift valley within an order of Kp around 10-3 m2 s-1. The mixing close to the vent site was even more elevated, with an average of Kp = 4 x 10-2 m2 s-1. The mixing, as well as the flow field, exhibited a strong tidal cycle, with strong currents and mixing at the non-buoyant plume level during ebb flow. Periods of strong mixing were associated with increased internal wave activity and frequent occurrence of turbulent overturns. Additional effects of mixing on plume dispersal include bifurcation of the particle plume, likely as a result of the interplay between the modulated mixing strength and current speed, as well as high frequency internal waves in the effluent plume layer, possibly triggered by the buoyant plume via nonlinear interaction with the elevated background turbulence or penetrative convection.
    Beschreibung: This work was supported by the Priority Program SPP1144 of the Deutsche Forschungsgemeinschaft; this is SPP 1144 contribution number 51. Funding for the ABE team from WHOI was provided by Grant # OE-2006-218 from NOAA's Ocean Exploration Program; funding for the MAPR work was provided by NOAA's Vents Program.
    Schlagwort(e): Physical oceanography ; Hydrothermal vents ; Diapycnal mixing ; Plume dispersal ; Mid-Atlantic Ridge ; Rift valleys
    Repository-Name: Woods Hole Open Access Server
    Materialart: Preprint
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  • 2
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    Flux measurements of explosive degassing using a yearlong hydroacoustic record at an erupting submarine volcano (2013)
    American Geophysical Union
    Details
    Publikationsdatum: 2022-05-25
    Beschreibung: 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): Q0AF07, doi:10.1029/2012GC004211.
    Beschreibung: The output of gas and tephra from volcanoes is an inherently disorganized process that makes reliable flux estimates challenging to obtain. Continuous monitoring of gas flux has been achieved in only a few instances at subaerial volcanoes, but never for submarine volcanoes. Here we use the first sustained (yearlong) hydroacoustic monitoring of an erupting submarine volcano (NW Rota-1, Mariana arc) to make calculations of explosive gas flux from a volcano into the ocean. Bursts of Strombolian explosive degassing at the volcano summit (520 m deep) occurred at 1–2 min intervals during the entire 12-month hydrophone record and commonly exhibited cyclic step-function changes between high and low intensity. Total gas flux calculated from the hydroacoustic record is 5.4 ± 0.6 Tg a−1, where the magmatic gases driving eruptions at NW Rota-1 are primarily H2O, SO2, and CO2. Instantaneous fluxes varied by a factor of ∼100 over the deployment. Using melt inclusion information to estimate the concentration of CO2 in the explosive gases as 6.9 ± 0.7 wt %, we calculate an annual CO2 eruption flux of 0.4 ± 0.1 Tg a−1. This result is within the range of measured CO2 fluxes at continuously erupting subaerial volcanoes, and represents ∼0.2–0.6% of the annual estimated output of CO2from all subaerial arc volcanoes, and ∼0.4–0.6% of the mid-ocean ridge flux. The multiyear eruptive history of NW Rota-1 demonstrates that submarine volcanoes can be significant and sustained sources of CO2 to the shallow ocean.
    Beschreibung: The National Oceanic and Atmospheric Administration Office of Ocean Exploration and Research, the NOAA Vents Program, and the National Science Foundation (OCE-0751776) for support.
    Beschreibung: 2013-05-29
    Schlagwort(e): Gas flux ; Ocean acoustics ; Seafloor volcanism
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 3
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    Volcanic eruptions in the deep sea (2012)
    The Oceanography Society
    Details
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © The Oceanography Society, 2012. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 25, no. 1 (2012): 142–157, doi:10.5670/oceanog.2012.12.
    Beschreibung: Volcanic eruptions are important events in Earth's cycle of magma generation and crustal construction. Over durations of hours to years, eruptions produce new deposits of lava and/or fragmentary ejecta, transfer heat and magmatic volatiles from Earth's interior to the overlying air or seawater, and significantly modify the landscape and perturb local ecosystems. Today and through most of geological history, the greatest number and volume of volcanic eruptions on Earth have occurred in the deep ocean along mid-ocean ridges, near subduction zones, on oceanic plateaus, and on thousands of mid-plate seamounts. However, deep-sea eruptions (〉 500 m depth) are much more difficult to detect and observe than subaerial eruptions, so comparatively little is known about them. Great strides have been made in eruption detection, response speed, and observational detail since the first recognition of a deep submarine eruption at a mid-ocean ridge 25 years ago. Studies of ongoing or recent deep submarine eruptions reveal information about their sizes, durations, frequencies, styles, and environmental impacts. Ultimately, magma formation and accumulation in the upper mantle and crust, plus local tectonic stress fields, dictate when, where, and how often submarine eruptions occur, whereas eruption depth, magma composition, conditions of volatile segregation, and tectonic setting determine submarine eruption style.
    Beschreibung: NSF-OCE 0937409 (KHR), OCE-0525863 and OCE-0732366 (DJF and SAS), 0725605 (WWC), OCE- 0751780 (ETB and RWE), OCE‐0138088 (MRP), OCE-0934278 (DAC), OCE-0623649 (RPD), and a David and Lucile Packard Foundation grant to MBARI (DAC and DWC).
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  • 4
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    Detection of an unusually large hydrothermal event plume above the slow-spreading Carlsberg Ridge : NW Indian Ocean (2010)
    American Geophysical Union
    Details
    Publikationsdatum: 2022-05-25
    Beschreibung: 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 Geophysical Research Letters 33 (2006): L10608, doi:10.1029/2006GL026048.
    Beschreibung: About 90% of Earth's volcanism occurs along the global mid-ocean ridge system. Here, sporadic volcanic and tectonic activity is thought to cause cataclysmic release of hydrothermal fluids, forming event plumes. Each plume often contains as much hydrothermal effluent and heat as chronic hydrothermal venting from a typical vent site discharges during a year. To date, only a few event plumes have been detected, and only above intermediate-rate spreading ridges in the Pacific. Here, we report the first evidence for an unusually large event plume that originated from the slow-spreading (3 cm/yr full-rate) Carlsberg Ridge in the NW Indian Ocean. At 70 km long, up to 4540 km3 in volume and with up to 24 × 1016 J of excess heat, this event plume was substantially larger than previous ones and demonstrates that dispersion of hydrothermal heat and biological products from slow spreading ridges may be more significant and effective than hitherto imagined.
    Beschreibung: This work was supported by the Natural Environment Research Council, UK; the National Oceanography Centre, Southampton (NOCS); the NOAA Vents Program.
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  • 5
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    Hydrothermal discharge during submarine eruptions : the importance of detection, response, and new technology (2012)
    The Oceanography Society
    Details
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © The Oceanography Society, 2012. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 25, no. 1 (2012): 128–141, doi:10.5670/oceanog.2012.11.
    Beschreibung: Submarine volcanic eruptions and intrusions construct new oceanic crust and build long chains of volcanic islands and vast submarine plateaus. Magmatic events are a primary agent for the transfer of heat, chemicals, and even microbes from the crust to the ocean, but the processes that control these transfers are poorly understood. The 1980s discovery that mid-ocean ridge eruptions are often associated with brief releases of immense volumes of hot fluids ("event plumes") spurred interest in methods for detecting the onset of eruptions or intrusions and for rapidly organizing seagoing response efforts. Since then, some 35 magmatic events have been recognized and responded to on mid-ocean ridges and at seamounts in both volcanic arc and intraplate settings. Field responses at mid-ocean ridges have found that event plumes occur over a wide range of eruption styles and sizes, and thus may be a common consequence of ridge eruptions. The source(s) of event plume fluids are still debated. Eruptions detected at ridges generally have high effusion rates and short durations (hours to days), whereas field responses at arc volcanic cones have found eruptions with very low effusion rates and durations on the scale of years. New approaches to the study of submarine magmatic events include the development of autonomous vehicles for detection and response, and the establishment of permanent seafloor observatories at likely future eruption sites.
    Beschreibung: Support for these efforts came from the NOAA Vents Program and the National Science Foundation, primarily through its long-term funding of the RIDGE and Ridge 2000 Programs, including grants OCE-9812294 and OCE-0222069. SOSUS detection efforts were supported from 2006 to 2009 by the National Science Foundation, grant OCE-0623649.
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    Materialart: Article
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  • 6
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    An authoritative global database for active submarine hydrothermal vent fields (2014)
    John Wiley & Sons
    Details
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Geophysical Union, 2013. 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 14 (2013): 4892–4905, doi:10.1002/2013GC004998.
    Beschreibung: The InterRidge Vents Database is available online as the authoritative reference for locations of active submarine hydrothermal vent fields. Here we describe the revision of the database to an open source content management system and conduct a meta-analysis of the global distribution of known active vent fields. The number of known active vent fields has almost doubled in the past decade (521 as of year 2009), with about half visually confirmed and others inferred active from physical and chemical clues. Although previously known mainly from mid-ocean ridges (MORs), active vent fields at MORs now comprise only half of the total known, with about a quarter each now known at volcanic arcs and back-arc spreading centers. Discoveries in arc and back-arc settings resulted in an increase in known vent fields within exclusive economic zones, consequently reducing the proportion known in high seas to one third. The increase in known vent fields reflects a number of factors, including increased national and commercial interests in seafloor hydrothermal deposits as mineral resources. The purpose of the database now extends beyond academic research and education and into marine policy and management, with at least 18% of known vent fields in areas granted or pending applications for mineral prospecting and 8% in marine protected areas.
    Beschreibung: For support to prepare this manuscript, we thank the National Science Foundation (OCE08-38923, GeoEd12-02977), the NOAA Vents (now Earth-Ocean Interactions) Program and the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) under NOAA Cooperative Agreement NA10OAR4320148, and WHOI.
    Beschreibung: 2014-05-19
    Schlagwort(e): Hydrothermal vent ; Deep-sea vent ; Hydrothermal activity ; Drupal
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 7
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    Eruptive modes and hiatus of volcanism at West Mata seamount, NE Lau basin : 1996–2012 (2014)
    John Wiley & Sons
    Details
    Publikationsdatum: 2022-05-26
    Beschreibung: 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 Geochemistry, Geophysics, Geosystems 15 (2014): 4093–4115, doi:10.1002/2014GC005387.
    Beschreibung: We present multiple lines of evidence for years to decade-long changes in the location and character of volcanic activity at West Mata seamount in the NE Lau basin over a 16 year period, and a hiatus in summit eruptions from early 2011 to at least September 2012. Boninite lava and pyroclasts were observed erupting from its summit in 2009, and hydroacoustic data from a succession of hydrophones moored nearby show near-continuous eruptive activity from January 2009 to early 2011. Successive differencing of seven multibeam bathymetric surveys of the volcano made in the 1996–2012 period reveals a pattern of extended constructional volcanism on the summit and northwest flank punctuated by eruptions along the volcano's WSW rift zone (WSWRZ). Away from the summit, the volumetrically largest eruption during the observational period occurred between May 2010 and November 2011 at ∼2920 m depth near the base of the WSWRZ. The (nearly) equally long ENE rift zone did not experience any volcanic activity during the 1996–2012 period. The cessation of summit volcanism recorded on the moored hydrophone was accompanied or followed by the formation of a small summit crater and a landslide on the eastern flank. Water column sensors, analysis of gas samples in the overlying hydrothermal plume and dives with a remotely operated vehicle in September 2012 confirmed that the summit eruption had ceased. Based on the historical eruption rates calculated using the bathymetric differencing technique, the volcano could be as young as several thousand years.
    Beschreibung: Support for R.W.E. during this study was by internal NOAA funding to the NOAA Vents Program (now Earth-Ocean Interactions Program). The NSF Ridge 2000 and MARGINS programs played a major role in the planning and justification for the 2009 rapid response proposal that funded the May 2009 expedition. MBARI provided support and outstanding postprocessing of the multibeam bathymetry from the D. Allan B. AUV multibeam sonar used in this study. NSF also provided major funding for the 2009 expedition (OCE930025 and OCE-0934660 to JAR) and for the 210Po-210Pb radiometric dating (OCE-0929881 and for the 210Po-210Pb radiometric dating (OCE-0929881 to KHR)). The NOAA Office of Exploration and Research provided major funding for the 2009 and 2012 field programs.
    Beschreibung: 2015-04-30
    Schlagwort(e): Seamount ; Lau ; Volcano ; Eruption ; Submarine ; Multibeam
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
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  • 8
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    Rapid dispersal of a hydrothermal plume by turbulent mixing (2010)
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 57 (8). pp. 931-945.
    Details
    Publikationsdatum: 2016-11-01
    Beschreibung: The water column imprint of the hydrothermal plume observed at the Nibelungen field (8 18'S 13 degrees 30'W) is highly variable in space and time. The off-axis location of the site, along the southern boundary of a non-transform ridge offset at the joint between two segments of the southern Mid-Atlantic Ridge, is characterized by complex, rugged topography, and thus favorable for the generation of internal tides, subsequent internal wave breaking, and associated vertical mixing in the water column. We have used towed transects and vertical profiles of stratification, turbidity, and direct current measurements to investigate the strength of turbulent mixing in the vicinity of the vent site and the adjacent rift valley, and its temporal and spatial variability in relation to the plume dispersal. Turbulent diffusivities K(rho) were calculated from temperature inversions via Thorpe scales. Heightened mixing (compared to open ocean values) was observed in the whole rift valley within an order of K(rho) around 10(-3) m(2) s(-1). The mixing close to the vent site was even more elevated, with an average of K(rho) = 4 x 10(-2) m(2) s(-1). The mixing, as well as the flow field, exhibited a strong tidal cycle, with strong currents and mixing at the non-buoyant plume level during ebb flow. Periods of strong mixing were associated with increased internal wave activity and frequent occurrence of turbulent overturns. Additional effects of mixing on plume dispersal include bifurcation of the particle plume, likely as a result of the interplay between the modulated mixing strength and current speed, as well as high frequency internal waves in the effluent plume layer, possibly triggered by the buoyant plume via nonlinear interaction with the elevated background turbulence or penetrative convection. (C) 2010 Elsevier Ltd. All rights reserved.
    Materialart: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.dsr.2010.04.010
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  • 9
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    Active submarine eruption of boninite in the northeastern Lau Basin (2011)
    Nature Research
    Details
    Publikationsdatum: 2022-04-26
    Beschreibung: Subduction of oceanic crust and the formation of volcanic arcs above the subduction zone are important components in Earth’s geological and geochemical cycles. Subduction consumes and recycles material from the oceanic plates, releasing fluids and gases that enhance magmatic activity, feed hydrothermal systems, generate ore deposits and nurture chemosynthetic biological communities. Among the first lavas to erupt at the surface from a nascent subduction zone are a type classified as boninites. These lavas contain information about the early stages of subduction, yet because most subduction systems on Earth are old and well-established, boninite lavas have previously only been observed in the ancient geological record. Here we observe and sample an active boninite eruption occurring at 1,200 m depth at the West Mata submarine volcano in the northeast Lau Basin, southwest Pacific Ocean. We find that large volumes of H2O, CO2 and sulphur are emitted, which we suggest are derived from the subducting slab. These volatiles drive explosive eruptions that fragment rocks and generate abundant incandescent magma-skinned bubbles and pillow lavas. The eruption has been ongoing for at least 2.5 years and we conclude that this boninite eruption is a multi-year, low-mass-transfer-rate eruption. Thus the Lau Basin may provide an important site for the long-term study of submarine volcanic eruptions related to the early stages of subduction.
    Materialart: Article , PeerReviewed
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