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  • 1
    Online Resource
    Online Resource
    Newark :American Geophysical Union,
    Keywords: Biodiversity -- Galapagos Islands. ; Electronic books.
    Type of Medium: Online Resource
    Pages: 1 online resource (446 pages)
    Edition: 1st ed.
    ISBN: 9781118852569
    Series Statement: Geophysical Monograph Series ; v.204
    Language: English
    Note: Intro -- Geophysical Monograph Series -- Copyright -- Contents -- Contributors -- Foreword: Darwin's Perspective -- Foreword: The Galápagos as a Natural Laboratory -- References -- Acknowledgments -- Chapter 1 Introduction -- Chapter 2 Contrasting Volcanism in Hawai'i and the Galápagos -- 2.1. Introduction -- 2.2. Magma Supply -- 2.2.1. Competition for magma supply and interactions between volcanoes -- 2.2.2. Archipelago-scale magma supply -- 2.3. Magma Storage -- 2.3.1. Characteristics of magma storage -- 2.3.2. Magma storage beneath volcanic flanks -- 2.4. Volcano Morphology and Structure -- 2.4.1. Volcano shape -- 2.4.2. Pattern of eruptive fissures -- 2.4.3. Calderas -- 2.4.4. Intracaldera faulting -- 2.4.5. Flank instability -- 2.5. Volcanic Eruptions and Volcano Evolution -- 2.5.1. Eruption style -- 2.5.2. Volcano evolution -- 2.6. Conclusions -- 2.7. Acknowledgments -- References -- Chapter 3 Galápagos and Easter: A Tale of Two Hotspots -- 3.1. Introduction -- 3.2. The Galápagos Islands -- 3.3. Easter-Salas y Gómez Seamount Chain -- 3.4. Discussion -- 3.4.1. Plumes at the edges of the LLSVP -- 3.4.2. Plume-Ridge Interaction Effects -- 3.4.3. Orientation of the chemical boundary -- 3.4.4. Geochemical heterogeneity of the Pacific LLSVP -- 3.5. Conclusions -- 3.6. Acknowledgments -- 3.7. Author Contributions -- References -- Chapter 4 Eruption Rates for Fernandina Volcano: A New Chronology at the Galápagos Hotspot Center -- 4.1. Introduction -- 4.2. Sampling and Analytical Details -- 4.3. Constraints on Flow Mapping -- 4.4. Eruption Rate Estimate from Young Flows -- 4.5. Age of Oldest Lava Flows -- 4.6. Magmatic/Mantle Helium and Galápagos Geographic Variability -- 4.7. Conclusions -- 4.8. Acknowledgments -- References -- Chapter 5 Galápagos Magma Chambers -- 5.1. Introduction -- 5.2. Evidence from Volcanic History and Geomorphology. , 5.3. Evidence from Deformation and Gravity -- 5.4. Evidence from Magma Compositions and Crystals -- 5.5. Petrologic Monitoring of Eruptions -- 5.6. Summary of Interpretations -- 5.7. An Evolutionary Model for Mushy Magma Chambers -- 5.8. Conclusions: the Dynamic and Thermal Evolution of Galápagos Magma Chambers -- 5.9. Acknowledgments -- References -- Chapter 6 The Geology and Geochemistry of Isla Floreana, Galápagos: A Different Type of Late-Stage Ocean Island Volcanism -- 6.1. Introduction -- 6.2. Geologic Background -- 6.3. Methods -- 6.4. Results -- 6.4.1. Geologic development of Floreana -- 6.4.2. Petrography of Floreana lavas -- 6.4.3. Mineral compositions -- 6.4.4. Major element compositions -- 6.4.5. Trace element compositions -- 6.4.6. Strontium, Neodymium, and Lead isotopic ratios -- 6.4.7. Age determinations -- 6.5. Discussion -- 6.5.1. Geologic development of Floreana -- 6.5.2. Petrogenetic model -- 6.5.3. The trace element composition of the Floreana ("FLO") component -- 6.5.4. Late-stage volcanism in Galápagos -- 6.6. Conclusions -- 6.7. Acknowledgments -- References -- Chapter 7 Plate Tectonics, Evolution, and the Survival of Species: A Modern Day Hotspot -- 7.1. Introduction -- 7.2. Tectonic Setting -- 7.2.1. General description -- 7.2.2. Age of Galápagos Islands and geographical relationship to plate motions -- 7.3. Fauna and Flora, and East-West Colonization -- 7.3.1. General description of life on oceanic islands -- 7.3.2. Life on Galápagos: ancient dating -- 7.3.3. Why east-to-west colonization? -- 7.4. Conclusion of Plate Motions Linked to Biodiversity Movements -- 7.4.1. New islands and the saving of native and endemic species -- 7.5. Volcanism Versus Introduced Species in the Survival of Species -- 7.6. Case Study of Fernandina: Haven or Hell? -- 7.6.1. General description. , 7.6.2. Conclusion of Fernandina as a Refuge of Galápagos Biodiversity -- 7.7. Biodiversity, Introduced Species, and Plate Tectonics -- 7.7.1. Contamination through introduced species -- 7.8. Fate of Biodiversity -- 7.9. Conclusions -- 7.10. Acknowledgments -- References -- Chapter 8 A Paleogeographic Model of the Galápagos Islands and Biogeographical and Evolutionary Implications -- 8.1. Introduction -- 8.2. Ages of Island Emergence -- 8.2.1. Plate tectonic estimates -- 8.2.2. Direct age measurements of lavas -- 8.2.3. New age determinations -- 8.3. Biological Implications of the Islands' Ages -- 8.3.1. General models of island biogeography -- 8.3.2. Testing the general dynamic model -- 8.3.3. Modifications to the general dynamic model -- 8.4. Movement and Subsidence of the Galápagos Islands -- 8.4.1. Subsidence model -- 8.4.2. Paleogeography of the pleistocene Galápagos -- 8.5. The Proto-Galápagos and Evolutionary Geographic Pathways -- 8.5.1. Implications for phylogenetic divergence -- 8.5.2. Comparison with phylogenetic estimates -- 8.5.3. The progression rule -- 8.5.4. Dispersal and vicariance -- 8.6. Conclusions -- 8.7. Appendix I: Emergence Ages of the Individual Galápagos Islands -- 8.7.1. Isla Fernandina -- 8.7.2. Isla Isabela -- 8.7.3. Isla Santiago -- 8.7.4. Isla Pinzón -- 8.7.5. Isla Rabida -- 8.7.6. Isla Santa Cruz -- 8.7.7. Isla Floreana -- 8.7.8. Isla Santa Fe -- 8.7.9. Isla San Cristóbal -- 8.7.10. Isla Española -- 8.7.11. Islas Genovesa, Pinta, and Marchena -- 8.7.12. Islas Wolf and Darwin -- 8.8. Acknowledgments -- References -- Chapter 9 Hydrogeology of the Galápagos Archipelago: An Integrated and Comparative Approach Between Islands -- 9.1. Introduction -- 9.2. Constraints of Basaltic Islands and Advocated Methodology -- 9.3. Main Features of San Cristóbal and Santa Cruz Islands and their Significance for Water Resources. , 9.3.1. Geology and weathering processes -- 9.3.2. Climate and water budget -- 9.3.3. Geomorphology and surface hydrology -- 9.3.4. Groundwater -- 9.4. Discussion -- 9.5. Recommendations for Groundwater Management Practices in the Galápagos -- 9.6. Acknowledgments -- References -- Chapter 10 Controls on the Hydrological and Topographic Evolution of Shield Volcanoes and Volcanic Ocean Islands -- 10.1. Introduction -- 10.2. A General Framework for Volcanic Landscape Evolution -- 10.3. Insights from a Global Compilation of Volcanic Ocean Islands and Shield Volcanoes -- 10.4. Phenomena Driving Landscape Evolution -- 10.4.1. Soil development and dust deposition set the stage for landscape dissection -- 10.4.2. Chemical and physical erosion rates change throughout landscape evolution -- 10.4.3. Precipitation rate affects erosion and soil development -- 10.4.4. Flank collapses can hasten topographic dissection -- 10.4.5. Volcanic architecture and tectonics constrain the patterns of landscape evolution -- 10.5. Other Controls on Volcanic Landscape Evolution -- 10.6. Conclusions -- 10.7. Acknowledgments -- References -- Chapter 11 Climate and the Global Reach of the Galápagos Archipelago: State of the Knowledge -- 11.1. Climatic and Oceanographic Setting -- 11.2. Influence on the Equilibrium State of the Tropical Pacific -- 11.2.1. Numerical modeling -- 11.2.2. Observations -- 11.2.3. Global climate modeling -- 11.3. Relationship with Climate Variability and Change -- 11.3.1. Islands in the crosshairs -- 11.3.2. Role in interannual climate variability (ENSO) -- 11.3.3. Role in anthropogenic climate change -- 11.4. Recap and Future Directions -- 11.5. Acknowledgments -- References -- Chapter 12 Assessment of the Chile 2010 and Japan 2011 Tsunami Events in the Galápagos Islands -- 12.1. Introduction -- 12.2. Background -- 12.3. Method of Analysis. , 12.4. Results -- 12.4.1. Tsunami Maule, Chile 2010 -- 12.4.2. Tsunami Tohoku, Japan 2011 -- 12.5. Discussion -- 12.6. Conclusions -- References -- Chapter 13 Patterns in Galápagos Magmatism Arising from the Upper Mantle Dynamics of Plume-Ridge Interaction -- 13.1. Introduction -- 13.2. Methods -- 13.2.1. Mantle convection -- 13.2.2. Model mantle heterogeneity, melting, and magma composition -- 13.3. Results: Predicted and Observed Magma Flux -- 13.3.1. Model 1: Plume with low viscosity, without a dependence on water content -- 13.3.2. Model 2: High viscosity in the shallowest upper mantle with the dependence on water content -- 13.4. Results: Predicted and Observed Magma Compositions -- 13.4.1. Model 1 geochemical variations -- 13.4.2. Model 2 geochemical variations -- 13.4.3. Along-axis variations in incompatible element concentration -- 13.5. Discussion -- 13.5.1. Model limitations and robustness of model results -- 13.5.2. The case for a low-viscosity Galápagos plume -- 13.5.3. The nature of heterogeneity in the Galápagos plume and ambient mantle -- 13.5.4. Incompatible element concentrations along the Galápagos Spreading Center -- 13.6. Conclusions -- 13.7. Acknowledgments -- References -- Chapter 14 Variations in Crustal Thickness, Plate Rigidity, and Volcanic Processes Throughout the Northern Galápagos Volcanic Province -- 14.1. Introduction -- 14.1.1. The mechanics of plume-ridge and plume-lithosphere interaction -- 14.1.2. Along- and off-axis expressions of the Galápagos mantle plume -- 14.2. Data -- 14.3. Gravity Anomalies -- 14.3.1. Free air anomaly -- 14.3.2. Mantle Bouguer Anomaly -- 14.3.3. Residual Mantle Bouguer Anomaly -- 14.4. Gravity-Derived Crustal Thickness Variations -- 14.4.1. Inversion of MBA for crustal thickness -- 14.4.2. Inversion results -- 14.4.3. Other contributions to the MBA. , 14.5. Plate Flexure Associated with the Galápagos Lineaments.
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  • 2
    Publication Date: 2012-10-24
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 3
    Publication Date: 2022-05-25
    Description: Author Posting. © Elsevier B.V., 2007. 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 Earth and Planetary Science Letters 266 (2008): 256-270, doi:10.1016/j.epsl.2007.10.055.
    Description: Hotspot-ridge interaction produces a wide range of phenomena including excess crustal thickness, geochemical anomalies, off-axis volcanic ridges and ridge relocations or jumps. Ridges are recorded to have jumped toward many hotspots including, Iceland, Discovery, Galapagos, Kerguelen and Tristan de Cuhna. The causes of ridge jumps likely involve a number of interacting processes related to hotspots. One such process is reheating of the lithosphere as magma penetrates it to feed near-axis volcanism. We study this effect by using the hybrid, finite-element code, FLAC, to simulate two-dimensional (2-D, cross-section) viscous mantle flow, elasto-plastic deformation of the lithosphere and heat transport in a ridge setting near an off-axis hotspot. Heating due to magma transport through the lithosphere is implemented within a hotspot region of fixed width. To determine the conditions necessary to initiate a ridge jump, we vary four parameters: hotspot magmatic heating rate, spreading rate, seafloor age at the location of the hotspot and ridge migration rate. Our results indicate that the hotspot magmatic heating rate required to initiate a ridge jump increases non-linearly with increasing spreading rate and seafloor age. Models predict that magmatic heating, itself, is most likely to cause jumps at slow spreading rates such as at the Mid-Atlantic Ridge on Iceland. In contrast, despite the higher magma flux at the Galapagos hotspot, magmatic heating alone is probably insufficient to induce a ridge jump at the present-day due to the intermediate ridge spreading rate of the Galapagos Spreading Center. The time required to achieve a ridge jump, for fixed or migrating ridges, is found to be on the order of 105-106 years. Simulations that incorporate ridge migration predict that after a ridge jump occurs the hotspot and ridge migrate together for time periods that increase with magma flux. Model results also suggest a mechanism for ridge reorganizations not related to hotspots such as ridge jumps in back-arc settings and ridge segment propagation along the Mid-Atlantic Ridge.
    Description: Mittelstaedt, Ito and Behn were funded by NSF grant OCE03-51234 and OCE05-48672.
    Keywords: Ridge-hotspot interaction ; Ridge jump ; Magmatism ; Back-arc spreading ; Numerical modeling
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 4
    Publication Date: 2022-05-25
    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): Q04008, doi:10.1029/2011GC003991.
    Description: The relative heat carried by diffuse versus discrete venting of hydrothermal fluids at mid-ocean ridges is poorly constrained and likely varies among vent sites. Estimates of the proportion of heat carried by diffuse flow range from 0% to 100% of the total axial heat flux. Here, we present an approach that integrates imagery, video, and temperature measurements to accurately estimate this partitioning at a single vent site, Tour Eiffel in the Lucky Strike hydrothermal field along the Mid-Atlantic Ridge. Fluid temperatures, photographic mosaics of the vent site, and video sequences of fluid flow were acquired during the Bathyluck'09 cruise (Fall, 2009) and the Momarsat'10 cruise (Summer, 2010) to the Lucky Strike hydrothermal field by the ROV Victor6000 aboard the French research vessel the “Pourquoi Pas”? (IFREMER, France). We use two optical methods to calculate the velocities of imaged hydrothermal fluids: (1) for diffuse venting, Diffuse Flow Velocimetry tracks the displacement of refractive index anomalies through time, and (2) for discrete jets, Particle Image Velocimetry tracks eddies by cross-correlation of pixel intensities between subsequent images. To circumvent video blurring associated with rapid velocities at vent orifices, exit velocities at discrete vents are calculated from the best fit of the observed velocity field to a model of a steady state turbulent plume where we vary the model vent radius and fluid exit velocity. Our results yield vertical velocities of diffuse effluent between 0.9 cm s−1 and 11.1 cm s−1 for fluid temperatures between 3°C and 33.5°C above that of ambient seawater, and exit velocities of discrete jets between 22 cm s−1 and 119 cm s−1 for fluid temperatures between 200°C and 301°C above ambient seawater. Using the calculated fluid velocities, temperature measurements, and photo mosaics of the actively venting areas, we calculate a heat flux due to diffuse venting from thin fractures of 3.15 ± 2.22 MW, discrete venting of 1.07 ± 0.66 MW, and, by incorporating previous estimates of diffuse heat flux density from Tour Eiffel, diffuse flux from the main sulfide mound of ∼15.6 MW. We estimate that the total integrated heat flux from the Tour Eiffel site is 19.82 ± 2.88 MW and that the ratio of diffuse to discrete heat flux is ∼18. We discuss the implication of these results for the characterization of different vent sites within Lucky Strike and in the context of a compilation of all available measurements of the ratio of diffuse to discrete heat flux.
    Description: E. Mittelstaedt was supported by the International Research Fellowship Program of the U.S. National Science Foundation (OISE-0757920). Funding for the 2006, 2008, 2009, and 2010 cruises was provided by CNRS/ IFREMER through the MoMAR program (France), by ANR (France), the Mothseim Project NT05–3 42213 to J. Escartín and by grant CTM2010–15216/MAR from the Spanish Ministry of Science to R. Garcia and J. Escartín. T. Barreyre was supported by University Paris Diderot (Paris 7 – France) and Institut de Physique du Globe de Paris (IPGP, France).
    Description: 2012-10-19
    Keywords: Lucky Strike ; Diffuse venting ; Hydrothermal vents ; Video analysis
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2016. 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 43 (2016): 6205–6211, doi:10.1002/2016GL069430.
    Description: High-resolution geophysical data have been collected using the Autonomous Underwater Vehicle (AUV) Sentry over the ASHES (Axial Seamount Hydrothermal Emission Study) high-temperature (~348°C) vent field at Axial Seamount, on the Juan de Fuca Ridge. Multiple surveys were performed on a 3-D grid at different altitudes above the seafloor, providing an unprecedented view of magnetic data resolution as a function of altitude above the seafloor. Magnetic data derived near the seafloor show that the ASHES field is characterized by a zone of low magnetization, which can be explained by hydrothermal alteration of the host volcanic rocks. Surface manifestations of hydrothermal activity at the ASHES vent field are likely controlled by a combination of local faults and fractures and different lava morphologies near the seafloor. Three-dimensional inversion of the magnetic data provides evidence of a vertical, pipe-like upflow zone of the hydrothermal fluids with a vertical extent of ~100 m.
    Description: Royal Society of New Zealand Grant Number: GNS1003; New Zealand Ministry of Business, Innovation and Employment (MBIE) Grant Numbers: OCE-1131455, OCE-1337473, OCE-1131772; NSF
    Description: 2016-12-24
    Keywords: ASHES vent field ; Crustal magnetization ; Sentry AUV
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
    Publication Date: 2022-05-25
    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): Q05018, doi:10.1029/2012GC004093.
    Description: Anomalous volcanism and tectonics between near-ridge mantle plumes and mid-ocean ridges provide important insights into the mechanics of plume-lithosphere interaction. We present new observations and analysis of multibeam, side scan sonar, sub-bottom chirp, and total magnetic field data collected during the R/V Melville FLAMINGO cruise (MV1007; May–June, 2010) to the Northern Galápagos Volcanic Province (NGVP), the region between the Galápagos Archipelago and the Galápagos Spreading Center (GSC) on the Nazca Plate, and to the region east of the Galápagos Transform Fault (GTF) on the Cocos Plate. The NGVP exhibits pervasive off-axis volcanism related to the nearby Galápagos hot spot, which has dominated the tectonic evolution of the region. Observations indicate that ~94% of the excess volcanism in our survey area occurs on the Nazca Plate in three volcanic lineaments. Identified faults in the NGVP are consistent with normal ridge spreading except for those within a ~60 km wide swath of transform-oblique faults centered on the GTF. These transform-oblique faults are sub-parallel to the elongation direction of larger lineament volcanoes, suggesting that lineament formation is influenced by the lithospheric stress field. We evaluate current models for lineament formation using existing and new observations as well as numerical models of mantle upwelling and melting. The data support a model where the lithospheric stress field controls the location of volcanism along the lineaments while several processes likely supply melt to these eruptions. Synthetic magnetic models and an inversion for crustal magnetization are used to determine the tectonic history of the study area. Results are consistent with creation of the GTF by two southward ridge jumps, part of a series of jumps that have maintained a plume-ridge separation distance of 145 km to 215 km since ~5 Ma.
    Description: This work was supported by NSF grant OCE-0926637 and OCE-1030904 to DF and KH. DG’s work was supported by NSF grants EAR- 0838461 and EAR-1145271. Additional support was provided to E.M. by the Deep Ocean Exploration Institute at the Woods Hole Oceanographic Institution.
    Description: 2012-11-30
    Keywords: Hot spot ; Plume-ridge interaction ; Ridge jump ; Volcanic lineaments
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2018. 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 19 (2018): 3115-3127, doi:10.1029/2018GC007536.
    Description: While processes associated with initiation and maintenance of oceanic detachment faults are becoming better constrained, much less is known about the tectonic and magmatic conditions that lead to fault abandonment. Here we present results from near‐bottom investigations using the submersible Alvin and autonomous underwater vehicle Sentry at a recently extinct detachment fault near 13°48′N, Mid‐Atlantic Ridge, that allow documentation of the final stages of fault activity and magmatism. Seafloor imagery, sampling, and near‐bottom magnetic data show that the detachment footwall is intersected by an ~850 m‐wide volcanic outcrop including pillow lavas. Saturation pressures in these vesicular basalts, based on dissolved H2O and CO2, are less than their collection pressures, which could be explained by eruption at a shallower level than their present depth. Sub‐bottom profiles reveal that sediment thickness, a loose proxy for seafloor age, is ~2 m greater on top of the volcanic terrain than on the footwall adjacent to the hanging‐wall cutoff. This difference could be explained by current‐driven erosion in the axial valley or by continued slip after volcanic emplacement, on either a newly formed or pre‐existing fault. Since current speeds near the footwall are unlikely to be sufficient to cause significant erosion, we favor the hypothesis that detachment slip continued after the episode of magmatism, consistent with growing evidence that oceanic detachments can continue to slip despite hosting magmatic intrusions.
    Description: National Science Foundation (NSF) Grant Numbers: OCE‐1259218, OCE‐1260578, OCE‐1736547
    Description: 2019-03-14
    Keywords: Mid‐ocean ridge ; Oceanic detachment fault ; Near‐bottom geophysics ; Volatile geochemistry
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
    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 Matabos, M., Barreyre, T., Juniper, S., Cannat, M., Kelley, D., Alfaro-Lucas, J., Chavagnac, V., Colaço, A., Escartin, J., Escobar, E., Fornari, D., Hasenclever, J., Huber, J., Laës-Huon, A., Lantéri, N., Levin, L., Mihaly, S., Mittelstaedt, E., Pradillon, F., Lantéri, N., Levin, L. A., Mihaly, S., Mittelstaedt, E., Pradillon, F., Sarradin, P-M., Sarrazin, J., Tomasi, B., Venkatesan, R., & Vic, C. Integrating Multidisciplinary Observations in Vent Environments (IMOVE): decadal progress in deep-sea observatories at hydrothermal vents. Frontiers in Marine Science, 9, (2022): 866422, https://doi.org/10.3389/fmars.2022.866422.
    Description: The unique ecosystems and biodiversity associated with mid-ocean ridge (MOR) hydrothermal vent systems contrast sharply with surrounding deep-sea habitats, however both may be increasingly threatened by anthropogenic activity (e.g., mining activities at massive sulphide deposits). Climate change can alter the deep-sea through increased bottom temperatures, loss of oxygen, and modifications to deep water circulation. Despite the potential of these profound impacts, the mechanisms enabling these systems and their ecosystems to persist, function and respond to oceanic, crustal, and anthropogenic forces remain poorly understood. This is due primarily to technological challenges and difficulties in accessing, observing and monitoring the deep-sea. In this context, the development of deep-sea observatories in the 2000s focused on understanding the coupling between sub-surface flow and oceanic and crustal conditions, and how they influence biological processes. Deep-sea observatories provide long-term, multidisciplinary time-series data comprising repeated observations and sampling at temporal resolutions from seconds to decades, through a combination of cabled, wireless, remotely controlled, and autonomous measurement systems. The three existing vent observatories are located on the Juan de Fuca and Mid-Atlantic Ridges (Ocean Observing Initiative, Ocean Networks Canada and the European Multidisciplinary Seafloor and water column Observatory). These observatories promote stewardship by defining effective environmental monitoring including characterizing biological and environmental baseline states, discriminating changes from natural variations versus those from anthropogenic activities, and assessing degradation, resilience and recovery after disturbance. This highlights the potential of observatories as valuable tools for environmental impact assessment (EIA) in the context of climate change and other anthropogenic activities, primarily ocean mining. This paper provides a synthesis on scientific advancements enabled by the three observatories this last decade, and recommendations to support future studies through international collaboration and coordination. The proposed recommendations include: i) establishing common global scientific questions and identification of Essential Ocean Variables (EOVs) specific to MORs, ii) guidance towards the effective use of observatories to support and inform policies that can impact society, iii) strategies for observatory infrastructure development that will help standardize sensors, data formats and capabilities, and iv) future technology needs and common sampling approaches to answer today’s most urgent and timely questions.
    Description: The first workshop in Bergen was additionally funded by the K.G. Jebsen Centre for Deep Sea Research and the University of Bergen. The second workshop was supported by ISblue project, Interdisciplinary graduate school for the blue planet (ANR-17-EURE-0015) and co-funded by a grant from the French government under the program “Investissements d’Avenir”. Additional funding was provided by Ifremer, and the départment du Finistère. The operation and maintenance of the EMSO-Azores observatory is funded by the by the EMSO-FR Research Infrastructure (MESR), which is managed by an Ifremer-CNRS collaboration. The operation and maintenance of the Endeavour observatory is funded by the Canada Foundation for Innovation’s Major Science Infrastructure program and the Department of Fisheries and Oceans (Canada). The operation and maintenance of the Axial Seamount observatory is funded by the National Science Foundation as part of the Ocean Observatories Initiative Regional Cabled Array. MM, JS and PMS acknowledge funding from the EU Horizon 2020 iAtlantic project (Grant Agreement No. 818123). AC was supported by the Operational Program AZORES 2020, through the Fund 01-0145-FEDER-1279 000140 “MarAZ Researchers: Consolidate a body of researchers in Marine Sciences in the Azores” of the European Union. She was also supported by FCT – Foundation for Science and Technology, I.P., under the project UIDB/05634/2020 and UIDP/05634/2020 and through the Regional Government of the Azores through the initiative to support the Research Centers of the University of the Azores and through the project M1.1.A/REEQ.CIENTÍFICO UI&D/2021/010.
    Keywords: Essential ocean variables (EOVs) ; Essential biological variables (EBVs) ; Mid-ocean ridge (MOR) ; Sensors, seabed platforms ; Vent fluid dynamics ; Vent communities dynamics
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 9
    Publication Date: 2022-05-26
    Description: Author Posting. © Oxford University Press, 2016. This article is posted here by permission of Oxford University Press for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 205 (2016): 728-743, doi:10.1093/gji/ggw044.
    Description: While elasticity is a defining characteristic of the Earth's lithosphere, it is often ignored in numerical models of long-term tectonic processes in favour of a simpler viscoplastic description. Here we assess the consequences of this assumption on a well-studied geodynamic problem: the growth of normal faults at an extensional plate boundary. We conduct 2-D numerical simulations of extension in elastoplastic and viscoplastic layers using a finite difference, particle-in-cell numerical approach. Our models simulate a range of faulted layer thicknesses and extension rates, allowing us to quantify the role of elasticity on three key observables: fault-induced topography, fault rotation, and fault life span. In agreement with earlier studies, simulations carried out in elastoplastic layers produce rate-independent lithospheric flexure accompanied by rapid fault rotation and an inverse relationship between fault life span and faulted layer thickness. By contrast, models carried out with a viscoplastic lithosphere produce results that may qualitatively resemble the elastoplastic case, but depend strongly on the product of extension rate and layer viscosity U × ηL. When this product is high, fault growth initially generates little deformation of the footwall and hanging wall blocks, resulting in unrealistic, rigid block-offset in topography across the fault. This configuration progressively transitions into a regime where topographic decay associated with flexure is fully accommodated within the numerical domain. In addition, high U × ηL favours the sequential growth of multiple short-offset faults as opposed to a large-offset detachment. We interpret these results by comparing them to an analytical model for the fault-induced flexure of a thin viscous plate. The key to understanding the viscoplastic model results lies in the rate-dependence of the flexural wavelength of a viscous plate, and the strain rate dependence of the force increase associated with footwall and hanging wall bending. This behaviour produces unrealistic deformation patterns that can hinder the geological relevance of long-term rifting models that assume a viscoplastic rheology.
    Description: This work was supported by NSF grants OCE-11-54238 (JAO, MDB), EAR-10-10432 (MDB) and OCE-11-55098 (GI), as well as a WHOI Deep Exploration Institute grant and start-up support from the University of Idaho (EM).
    Keywords: Mid-ocean ridge processes ; Continental tectonics: extensional ; Lithospheric flexure ; Mechanics, theory, and modelling
    Repository Name: Woods Hole Open Access Server
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  • 10
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2016. 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 17 (2016): 1435–1453, doi:10.1002/2015GC006144.
    Description: Time-series measurements of diffuse exit-fluid temperature and velocity collected with a new, deep-sea camera, and temperature measurement system, the Diffuse Effluent Measurement System (DEMS), were examined from a fracture network within the ASHES hydrothermal field located in the caldera of Axial Seamount, Juan de Fuca Ridge. The DEMS was installed using the HOV Alvin above a fracture near the Phoenix vent. The system collected 20 s of 20 Hz video imagery and 24 s of 1 Hz temperature measurements each hour between 22 July and 2 August 2014. Fluid velocities were calculated using the Diffuse Fluid Velocimetry (DFV) technique. Over the ∼12 day deployment, median upwelling rates and mean fluid temperature anomalies ranged from 0.5 to 6 cm/s and 0°C to ∼6.5°C above ambient, yielding a heat flux of 0.29 ± 0.22 MW m−2 and heat output of 3.1± 2.5 kW. Using a photo mosaic to measure fracture dimensions, the total diffuse heat output from cracks across ASHES field is estimated to be 2.05 ± 1.95 MW. Variability in temperatures and velocities are strongest at semidiurnal periods and show significant coherence with tidal height variations. These data indicate that periodic variability near Phoenix vent is modulated both by tidally controlled bottom currents and seafloor pressure, with seafloor pressures being the dominant influence. These results emphasize the importance of local permeability on diffuse hydrothermal venting at mid-ocean ridges and the need to better quantify heat flux associated with young oceanic crust.
    Description: NSF Grant Numbers: OCE-1131772, OCE-1131455, OCE-1337473; University of Washington, and the NSF award Grant Number: OCE-0957938
    Description: 2016-10-27
    Keywords: ASHES hydrothermal field ; Diffuse heat flux ; Hydrothermal vents ; Mid-ocean ridges
    Repository Name: Woods Hole Open Access Server
    Type: Article
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