A clathrate, consisting of methane trapped within a water-ice matrix, found mainly on and below the sea-floor at the lower edge of continental slopes, where low temperatures and high pressures permit it to exist. Some deposits also occur in permafrost regions. Enrichment in the 12C isotope shows the methane to be of organic origin. Estimates suggest that methane hydrate deposits are a potential reserve twice the size of the combined total for coal, oil, and conventional natural gas. Commercial exploitation is likely to be difficult, but preliminary tests have already begun.
Methane evolved through melting of methane hydrate has been proposed as one factor in sudden climatic change, including a surge in global temperatures at 55 × 106 bp, and changes at the end of the last ice age around 15 000 bp. It is also suspected to have caused major underwater slumping and consequent tsunami, particularly the Storrega submarine landslide off Norway, in c.8000 bp, when around 5 600 km3 of sediments slid downslope for about 800 km.
Subjects: Meteorology and Climatology.