Gas hydrates (clathrates) are crystalline solids consisting of gas molecules--usually (but not always) methane surrounded by a cage of water molecules in a relatively stable and compact composition (Fig.1). Gas hydrates are found in equilibrium under conditions of high pressures and low temperatures. These conditions are found onshore under permafrost in the polar regions and offshore along the continental shelf margins. One unit of gas hydrate when dissociated can produce approximately 164 units of gas (methane), so they are a very compact source of energy (Kvenvolden 1998). Secondly they are widely distributed around the world and several times greater than the amount of conventional natural gas resources.