Potential effects of gas hydrate on human welfare

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   Figure 1

   A 12-fold multichannel seismic reflection profile from the crest and eastern flank of the Blake Outer Ridge. The strong BSR is inferred to represent the base of the gas hydrate stability zone. Modified from ref. 3.

   
   
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   Figure 2

   Phase diagram showing boundary between free methane gas (no pattern) and methane hydrate (pattern) for a pure water and pure methane system. The addition of salts, such as NaCl, to water shifts the curve to the left. Adding CO₂, H₂S, C₂H₆, or C₃H₈ to methane (CH₄) shifts the boundary to the right, thus reducing the pressure for gas-hydrate stability at a given temperature. Depth scale assumes lithostatic and hydrostatic pressure gradients of 10.1 kPa⋅m⁻¹. Redrawn after Katz et al. (4).

   
   
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   Figure 3

   The Earth showing locations of known and inferred gas-hydrate deposits in oceanic sediment of outer continental margins and in permafrost (continental) regions. Modified from ref. 7.

   
   
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   Figure 4

   Changing magnitude of estimates of the methane content (×10¹⁵ m³) of worldwide gas-hydrate deposits from 1980 to 1998.

   
   
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   Figure 5

   Map of a portion of the Beaufort Sea continental shelf offshore from Alaska showing station locations and concentrations of methane (in nM) in water samples collected when ice was present and absent from 1993 through 1995. Based on data from refs. 50 and 51.

   
   
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   Figure 6

   Diagram showing the effects of changes in sea level on submarine gas hydrate and the resulting failures and gas release. Adapted from McIver (57).