Gas hydrate stability zone

marine environment at which methane clathrates naturally exist in the Earth's crust

sediments due to the different densities of hydrate saturated sediments, normal sediments and those containing free gas.^[2]

meters.^{1[citation needed]} The maximal depth of the hydrate stability zone is limited by the geothermal gradient. Along continental margins the average thickness of the HSZ is about 500 m.^[3] The upper limit in oceanic sediments occurs when bottom water temperatures are at or near 0 °C, and at a water depth of approximately 300 meters.^{1[citation needed]} The lower limit of the HSZ is bounded by the geothermal gradient. As depth below seafloor increases, the temperature eventually becomes too high for hydrates to exist. In areas of high geothermal heat flow, the lower limit of the HSZ may become shallower, therefore decreasing the thickness of the HSZ. Conversely, the thickest hydrate layers and widest HSZ are observed in areas of low geothermal heat flow. Generally, the maximum depth of HSZ extension is 2000 meters below the Earth's surface.^{1,3[citation needed]} Using the location of a BSR, as well as the pressure-temperature regimen necessary for hydrate stability, the HSZ may be used to determine geothermal gradients.^{2[citation needed}

Landslides of rock or sediment above the hydrate stability zone may also impact the hydrate stability. A sudden decrease in pressure can release gasses or destabilize portions of the hydrate deposit.^[5] Changing atmospheric and oceanic temperatures may impact the presence and depth of the hydrate stability zone, however, is still uncertain to what extent. In oceanic sediments, increasing pressure due to a rise in sea level may offset some of the impact of increasing temperature upon the hydrate stability equilibrium.^{1[citation needed}