Editing Clathrate hydrate (section)

=== Natural gas hydrates ===
{{main|Methane clathrate}}
Naturally on [[Earth]] gas hydrates can be found on the [[seabed]], in ocean sediments,<ref>{{cite report |last1=Kvenvolden |first1=Keith A. |last2=McMenamin |first2=Mark A. |title=Circular |year=1980 |chapter=Hydrates of natural gas; a review of their geologic occurrence |doi=10.3133/cir825 |doi-access=free }}</ref> in deep lake sediments (e.g. [[Lake Baikal]]), as well as in the [[permafrost]] regions. The amount of [[methane]] potentially trapped in natural [[Methane clathrate|methane hydrate]] deposits may be significant (10<sup>15</sup> to 10<sup>17</sup> cubic metres),<ref>{{cite news |last1=Marshall |first1=Michael |date=26 March 2009 |title=Ice that burns could be a green fossil fuel |url=https://www.newscientist.com/article/dn16848-ice-that-burns-could-be-a-green-fossil-fuel/ |work=New Scientist }}</ref> which makes them of major interest as a potential energy resource. Catastrophic release of methane from the decomposition of such deposits may lead to a global climate change, referred to as the "[[clathrate gun hypothesis]]", because [[methane|CH<sub>4</sub>]] is a more potent greenhouse gas than [[carbon dioxide|CO]]<sub>2</sub> (see [[Atmospheric methane]]). The fast decomposition of such deposits is considered a [[geohazard]], due to its potential to trigger [[landslide]]s, [[earthquake]]s  and [[tsunami]]s. However, natural gas hydrates do not contain only methane but also other [[hydrocarbon]] gases, as well as [[Hydrogen sulfide|H<sub>2</sub>S]] and [[Carbon dioxide|CO<sub>2</sub>]]. [[Air hydrates]] are frequently observed in polar ice samples.

[[Pingo]]s are common structures in permafrost regions.<ref>{{cite journal |last1=Ussler |first1=W. |last2=Paull |first2=C. K. |last3=Lorenson |first3=T. |last4=Dallimore |first4=S. |last5=Medioli |first5=B. |last6=Blasco |first6=S. |last7=McLaughlin |first7=F. |last8=Nixon |first8=F. M. |title=Methane Leakage from Pingo-like Features on the Arctic Shelf, Beaufort Sea, NWT, Canada |journal=AGU Fall Meeting Abstracts |year=2005 |volume=2005 |pages=C11A–1069 |bibcode=2005AGUFM.C11A1069U }}</ref> Similar structures are found in deep water related to methane vents. Significantly, gas hydrates can even be formed in the absence of a liquid phase. Under that situation, water is dissolved in gas or in liquid hydrocarbon phase.<ref>{{cite journal |last1=Youssef |first1=Z. |last2=Barreau |first2=A. |last3=Mougin |first3=P. |last4=Jose |first4=J. |last5=Mokbel |first5=I. |title=Measurements of Hydrate Dissociation Temperature of Methane, Ethane, and CO<sub>2</sub> in the Absence of Any Aqueous Phase and Prediction with the Cubic Plus Association Equation of State |journal=Industrial & Engineering Chemistry Research |date=15 April 2009 |volume=48 |issue=8 |pages=4045–4050 |doi=10.1021/ie801351e }}</ref>

In 2017, both Japan and China announced that attempts at large-scale [[resource extraction]] of methane hydrates from under the seafloor were successful.  However, commercial-scale production remains years away.<ref>{{cite news |title=China claims breakthrough in 'flammable ice' |url=https://www.bbc.com/news/world-asia-china-39971667 |work=BBC News |date=19 May 2017 }}</ref><ref>{{cite journal |title=China and Japan find way to extract 'combustible ice' from seafloor, harnessing a legendary frozen fossil fuel |journal=National Post |date=19 May 2017 |url=https://nationalpost.com/news/world/china-japan-extracts-combustible-ice-from-seafloor-a-step-towards-harnessing-a-legendary-frozen-fossil-fuel }}</ref>

The 2020 Research Fronts report identified gas hydrate accumulation and mining technology as one of the top 10 research fronts in the geosciences.<ref>{{Cite web|url=https://discover.clarivate.com/ResearchFronts2020_EN|title=Web of Science}}</ref>