Gas hydrates that outcrop on the sea floor: stability models

 The detection of sea-floor gas hydrates (GHs) proves that they can coexist in contact with seawater. We calculate that sea-floor hydrates undergo rapid dissolution, yet they are maintained by the constant high rate of upward migration of gas-saturated waters. If upward migration originates from a point source, then the thickness of sea-floor hydrates varies with distance from the center of the upwelling (depending on heat flow). However, near-surface fracturing may control the actual points of exit onto the sea floor above. If gas migration rates decrease from the center of the mud volcano to its periphery, a concentric pattern in distribution of temperature, methane concentration, and GH contents can be described.