Models for in situ hydrate formation

The first type of hydrate is finely disseminated. Due to their disseminated nature, these hydrates may dissociate rapidly, frequently within the time span of a core s trip from the seafloor to shipboard, leaving residual traces of pore water freshening, or low temperatures, because of the endothermic heat of dissociation. As discussed in this section, disseminated hydrates represent the large majority of hydrates in the ocean. 

Nodular hydrates up to 5 cm in diameter may occur, such as found in the Green Canyon Gulf of Mexico the gas in these hydrates may be of thermogenic origin that migrated from depth. 

Layered hydrates are separated by thin layers of sediments, such as cores recovered from the Blake-Bahama Ridge. Such hydrates probably occur both offshore and in permafrost regions. 

Low gas fluxes result in mineralization, such as carbonate mounds, cones, and chimneys, with very localized and poorly developed chemo-synthetic communities, and highly biodegraded hydrocarbons. 

Moderate gas fluxes result in gas hydrate mounds, dense diverse chemo-synthetic communities, (Beggiatoa, tube worms, clams), and moderately degraded hydrocarbons. 

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