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  • Springer  (2)
  • AAAS (American Association for the Advancement of Science)  (1)
  • 2015-2019  (3)
  • 1
    Publication Date: 2021-02-08
    Description: Seafloor elongated depressions are indicators of gas seepage or slope instability. Here we report a sequence of slope-parallel elongated depressions that link to headwalls of sediment slides on upper slope. The depressions of about 250 m in width and several kilometers in length are areas of focused gas discharge indicated by bubble-release into the water column and methane enriched pore waters. Sparker seismic profiles running perpendicular and parallel to the coast, show gas migration pathways and trapped gas underneath these depressions with bright spots and seismic blanking. The data indicate that upward gas migration is the initial reason for fracturing sedimentary layers. In the top sediment where two young stages of landslides can be detected, the slope-parallel sediment weakening lengthens and deepens the surficial fractures, creating the elongated depressions in the seafloor supported by sediment erosion due to slope-parallel water currents.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 2
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    AAAS (American Association for the Advancement of Science)
    In:  Science, 359 (6371). pp. 34-36.
    Publication Date: 2021-02-08
    Description: Research and regulations must be integrated to protect seafloor biota from future mining impacts Summary: As human use of rare metals has diversified and risen with global development, metal ore deposits from the deep ocean floor are increasingly seen as an attractive future resource. Japan recently completed the first successful test for zinc extraction from the deep seabed, and the number of seafloor exploration licenses filed at the International Seabed Authority (ISA) has tripled in the past 5 years. Seafloor-mining equipment is being tested, and industrial-scale production in national waters could start in a few years. We call for integrated scientific studies of global metal resources, the fluxes and fates of metal uses, and the ecological footprints of mining on land and in the sea, to critically assess the risks of deep-sea mining and the chances for alternative technologies. Given the increasing scientific evidence for long-lasting impacts of mining on the abyssal environment, precautionary regulations for commercial deep-sea mining are essential to protect marine ecosystems and their biodiversity.
    Type: Article , PeerReviewed
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  • 3
    Publication Date: 2019-09-23
    Description: This study presents 2D seismic reflection data, seismic velocity analysis, as well as geochemical and isotopic porewater compositions from Opouawe Bank on New Zealand’s Hikurangi subduction margin, providing evidence for essentially pure methane gas seepage. The combination of geochemical information and seismic reflection images is an effective way to investigate the nature of gas migration beneath the seafloor, and to distinguish between water advection and gas ascent. The maximum source depth of the methane that migrates to the seep sites on Opouawe Bank is 1,500–2,100 m below seafloor, generated by low-temperature degradation of organic matter via microbial CO2 reduction. Seismic velocity analysis enabled identifying a zone of gas accumulation underneath the base of gas hydrate stability (BGHS) below the bank. Besides structurally controlled gas migration along conduits, gas migration also takes place along dipping strata across the BGHS. Gas migration on Opouawe Bank is influenced by anticlinal focusing and by several focusing levels within the gas hydrate stability zone.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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