Gas hydrates are icelike materials that form when specific conditions of temperature, pressure, and gas composition are simultaneously satisfied. Among the first descriptions of gas hydrates under natural conditions was that of Hammerschmidt (1940), who found them in pipelines used to transport natural gas. Milton (1976) indicates that conditions are suitable for the presence of gas hydrates in areas affected by permafrost and cites studies suggesting that large quantities of gas exist in hydrate form.

Sediment depth is given in mbsf. Routine shipboard analyses involve the use of two gas chromatographs (GC units). Gas samples are first analyzed by a Carle GC with a thermal conductivity detector, and from this analysis come the CO2 and C1 data. The Carle unit is relatively insensitive and a Hewlett-Packard GC is employed to quantify C2 and heavier hydrocarbons. Analysis via the Hewlett-Packard is a cold-trap technique in which C1 is not determined. For complete details, consult Whelan (1979).

Supplement to: Harrison, William E; Curiale, Joseph A (1982): Gas hydrates in sediments of Holes 497 and 498A, Deep Sea Drilling Project Leg 67. In: Abouin, J; von Huene, R; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 67, 591-594