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Massive methane release triggered by seafloor erosion offshore southwestern Japan

Nathan L. Bangs, M. J. Hornbach, G. F. Moore and J. O. Park
Massive methane release triggered by seafloor erosion offshore southwestern Japan
Geology (Boulder) (November 2010) 38 (11): 1019-1022


Vast amounts of methane hydrate exist beneath continental margins, but whether this methane releases from sediment on a large scale and affects the oceans and atmosphere remains unclear. Analysis of newly acquired three-dimensional seismic images and drilling data from a large gas hydrate province reveal a recently eroded v-shaped depression. The depression sharply cuts through a relic bottom simulating reflection (BSR) and hydrate-laden sediments. The shape of the relic BSR indicates that the seafloor depression was once a large anticline that has recently been eroded and released an estimated 1.51X10 (super 11) m (super 3) of methane. We hypothesize that erosion of the seafloor via bottom-water currents unroofed buoyant hydrate-laden sediments and subhydrate overpressured free gas zones beneath the anticline. Once triggered, gas-driven erosion created a positive feedback mechanism, releasing gas and eroding hydrate-bearing sediment. We suggest that erosive currents in deep-water methane hydrate provinces act as hair triggers, destabilizing kilometer-scale swaths of the seafloor where large concentrations of underlying overpressured methane exist. Our analysis suggests that kilometer-scale degassing events are widespread, and that deep-water hydrate reservoirs can rapidly release methane in massive quantities.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 38
Serial Issue: 11
Title: Massive methane release triggered by seafloor erosion offshore southwestern Japan
Affiliation: University of Texas, Institute for Geophysics, Austin, TX, United States
Pages: 1019-1022
Published: 201011
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 25
Accession Number: 2010-100899
Categories: OceanographyApplied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2010282
Illustration Description: illus. incl. sects., sketch map
N33°00'00" - N33°30'00", E136°19'60" - E137°00'00"
Secondary Affiliation: University of Hawaii, USA, United StatesInstitute for Frontier Research on Earth Evolution, JPN, Japan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201052
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