Methane clathrate (CH
4·5.75H
2O) or (4CH
4·23H
2O), also called
methane hydrate,
hydromethane,
methane ice,
fire ice,
natural gas hydrate, or
gas hydrate, is a solid
clathrate compound (more specifically, a
clathrate hydrate) in which a large amount of
methane is trapped within a
crystal structure of water, forming a solid similar to
ice. Originally thought to occur only in the outer regions of the
Solar System, where temperatures are low and water ice is common, significant deposits of methane clathrate have been found under
sediments on the
ocean floors of the
Earth.