Seafloor venting of microbial gases occurs at 2167 m water depth over the Blake Ridge diapir. Gas-rich plumes were identified acoustically in the water column up to 320 m above a pockmarked sea floor associated with active chemosynthetic biological communities. Plumes and venting fluids emanate from near a small fault that extends downward toward a dome in the bottom-simulating reflector, indicating that fluid and/or gas migration is associated with gas hydrate–bearing sediment below. These plumes might be caused by gas bubbles or buoyant clumps of gas hydrate that float upward from the seafloor.

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