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Massive methane release triggered by seafloor erosion offshore southwestern Japan

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 r...

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Bibliographic Details
Published in:Geology (Boulder) 2010-11, Vol.38 (11), p.1019-1022
Main Authors: Bangs, Nathan L, Hornbach, M. J, Moore, G. F, Park, J. O
Format: Article
Language:English
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Summary: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 1.51×1011 m3 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
1943-2682
DOI:10.1130/G31491.1