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Methane clathrate (CH 4 ·5.75H 2 O) or (4CH 4 ·23H 2 O), 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.
Naturally on Earth gas hydrates can be found on the seabed, in ocean sediments, [22] in deep lake sediments (e.g. Lake Baikal), as well as in the permafrost regions. The amount of methane potentially trapped in natural methane hydrate deposits may be significant (10 15 to 10 17 cubic metres), [ 23 ] which makes them of major interest as a ...
The existence and depth of a hydrate deposit is often indicated by the presence of a bottom-simulating reflector (BSR). A BSR is a seismic reflection indicating the lower limit of hydrate stability in sediments due to the different densities of hydrate saturated sediments, normal sediments and those containing free gas. [2]
Methane clathrate, also known commonly as methane hydrate, is a form of water ice that contains a large amount of methane within its crystal structure. Potentially large deposits of methane clathrate have been found under sediments on the ocean floors of the Earth, although the estimates of total resource size given by various experts differ by ...
The free gas zone is a zone of freed methane in a hydrate formation, beneath the hydrate stability zone. It can influence the rate of methane output at a ridge or ridge region. A large free gas zone makes more methane available to be released into the open ocean, and, thus, can likely be more influential on climate change than a smaller one. [11]
At water depths of 500 m to 1,000 m, and at the low temperatures typical of the seafloor (close to 4 °C), water and methane combine to create a substance known as methane hydrate. Within a few metres to hundreds of metres of the seafloor, the temperature is low enough for methane hydrate to be stable and hydrates accumulate within the sediment.
Methane ice at Southern Hydrate Ridge has been found within the shallow sediments, and more rarely exposed on the seafloor. Because Southern Hydrate Ridge is located on the upper continental slope , the regional hydrate stability zone (RHSZ) , which is controlled by the sediment pore pressure and temperature, [ 6 ] is very shallow. [ 7 ]
The low hydrate saturation can be explained due to the very small pore size and low permeability in clay-rich sediments, which hinder the mobility of both water and gas, necessary for hydrate formation (see UNEP Global Outlook on Methane Gas Hydrates (2012, in progress) for more details). In contrast, Japanese scientists were able to discover ...