Editing Extinction event (section)

===== Clathrate gun hypothesis =====
{{Main|Clathrate gun hypothesis}}
[[Clathrates]] are composites in which a lattice of one substance forms a cage around another. [[Methane clathrate]]s (in which water molecules are the cage) form on [[continental shelf|continental shelves]]. These clathrates are likely to break up rapidly and release the methane if the temperature rises quickly or the pressure on them drops quickly – for example in response to sudden [[global warming]] or a sudden drop in sea level or even [[earthquake]]s. Methane is a much more powerful [[greenhouse effect|greenhouse]] gas than carbon dioxide, so a methane eruption ("clathrate gun") could cause rapid global warming or make it much more severe if the eruption was itself caused by global warming.

The most likely signature of such a methane eruption would be a sudden decrease in the [[Isotope analysis|ratio of carbon-13 to carbon-12]] in sediments, since methane clathrates are low in carbon-13; but the change would have to be very large, as other events can also reduce the percentage of carbon-13.<ref>{{cite magazine | vauthors = Hecht J | title=Methane prime suspect for greatest mass extinction | magazine=[[New Scientist]] | date=2002-03-26 | url=https://www.newscientist.com/article/dn2088-methane-prime-suspect-for-greatest-mass-extinction/}}</ref>

It has been suggested that "clathrate gun" methane eruptions were involved in the [[Permian–Triassic extinction event|end-Permian extinction]] ("the Great Dying") and in the [[Paleocene–Eocene Thermal Maximum]], which was associated with one of the smaller mass extinctions.