Metastability of gas hydrate

Marine occurrences of gas hydrate are normally confined to the top few hund red meters of sediments along deep continental margins. The zone of stabili ty for gas hydrate is limited in depth by increases in temperature below th e seafloor. We use thermodynamic calculations to show that gas hydrate can exist in a metastable state below the usual base of the stability zone. We estimate that gas hydrate can be overheated by several degrees and that it may persist in this metastable state in the seafloor for as long as 10(6) y ears. Sudden decomposition of metastable hydrate should produce substantial pore pressure in the sediments, contributing to slope failure in locations where gas hydrate is found. Such a mechanism might help to explain why slu mping appears to be more frequent than average during the interval around t he last glacial maximum.