Query: “Underneath the permafrost there are sediments full of methane hydrates.

Relevant passages:
Permafrost <=SEP=> In geology , permafrost is ground , including rock or ( cryotic ) soil , at or below the freezing point of water 0 C for two or more years . Most permafrost is located in high latitudes ( in and around the Arctic and Antarctic regions ) , but alpine permafrost may exist at high altitudes in much lower latitudes . Ground ice is not always present , as may be in the case of nonporous bedrock , but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of the ground material . Permafrost accounts for 0.022 % of total water on earth and exists in 24 % of exposed land in the Northern Hemisphere . It also occurs subsea on the continental shelves of the continents surrounding the Arctic Ocean , portions of which were exposed during the last glacial period , with global weather implications .   A global temperature rise of 1.5 C-change above current levels would be enough to start the thawing of permafrost in Siberia , according to one group of scientists .

Permafrost carbon cycle <=SEP=> The Permafrost Carbon Cycle is a sub-cycle of the larger global carbon cycle . Permafrost is defined as subsurface material that remains below 0o C ( 32o F ) for at least two consecutive years . Because permafrost soils remain frozen for long periods of time , they store large amounts of carbon and other nutrients within their frozen framework during that time . Permafrost represents a large carbon reservoir that is seldom considered when determining global terrestrial carbon reservoirs . Recent and ongoing scientific research however , is changing this view .   The permafrost carbon cycle ( Arctic Carbon Cycle ) deals with the transfer of carbon from permafrost soils to terrestrial vegetation and microbes , to the atmosphere , back to vegetation , and finally back to permafrost soils through burial and sedimentation due to cryogenic processes . Some of this carbon is transferred to the ocean and other portions of the globe through the global carbon cycle . The cycle includes the exchange of carbon dioxide and methane between terrestrial components and the atmosphere , as well as the transfer of carbon between land and water as methane , dissolved organic carbon , dissolved inorganic carbon , particulate inorganic carbon and particulate organic carbon .

Clathrate gun hypothesis <=SEP=> The clathrate gun hypothesis is the popular name given to the hypothesis that increases in sea temperatures ( and/or drops in sea levels ) can trigger the sudden release of methane from methane clathrate compounds buried in seabeds and that are contained within seabed permafrost which , because methane itself is a powerful greenhouse gas , leads to further temperature rise and further methane clathrate destabilization -- in effect initiating a runaway process as irreversible , once started , as the firing of a gun .   In its original form , the hypothesis proposed that the `` clathrate gun '' could cause abrupt runaway warming on a timescale less than a human lifetime . It was thought to be responsible for warming events in and at the end of the last glacial maximum , however this is now thought to be unlikely .   However , there is stronger evidence that runaway methane clathrate breakdown may have caused drastic alteration of the ocean environment ( such as ocean acidification and ocean stratification ) and of the atmosphere of earth on a number of occasions in the past , over timescales of tens of thousands of years . These events include the Paleocene -- Eocene Thermal Maximum 56 million years ago , and most notably the Permian -- Triassic extinction event , when up to 96 % of all marine species became extinct , 252 million years ago .

Methane <=SEP=> Methane ( -LSB- ˈmɛθeɪn -RSB- or -LSB- ˈmiːθeɪn -RSB- ) is a chemical compound with the chemical formula ( one atom of carbon and four atoms of hydrogen ) . It is a group 14 hydride and the simplest alkane , and is the main constituent of natural gas . The relative abundance of methane on Earth makes it an attractive fuel , though capturing and storing it poses challenges due to its gaseous state under normal conditions for temperature and pressure .   Natural methane is found both below ground and under the sea floor . When it reaches the surface and the atmosphere , it is known as atmospheric methane . The Earth 's atmospheric methane concentration has increased by about 150 % since 1750 , and it accounts for 20 % of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases ( these gases do n't include water vapor which is by far the largest component of the greenhouse effect ) .

Permian–Triassic extinction event <=SEP=> The Permian -- Triassic ( P -- Tr or P -- T ) extinction event , colloquially known as the Great Dying , the End-Permian Extinction or the Great Permian Extinction , occurred about 252 Ma ( million years ) ago , forming the boundary between the Permian and Triassic geologic periods , as well as the Paleozoic and Mesozoic eras . It is the Earth 's most severe known extinction event , with up to 96 % of all marine species and 70 % of terrestrial vertebrate species becoming extinct . It is the only known mass extinction of insects . Some 57 % of all families and 83 % of all genera became extinct . Because so much biodiversity was lost , the recovery of life on Earth took significantly longer than after any other extinction event , possibly up to 10 million years . Studies in Bear Lake County near the Idaho city of Paris showed a quick and dynamic rebound in a marine ecosystem , illustrating the remarkable resiliency of life .   There is evidence for one to three distinct pulses , or phases , of extinction . Suggested mechanisms for the latter include one or more large meteor impact events , massive volcanism such as that of the Siberian Traps , and the ensuing coal or gas fires and explosions , and a runaway greenhouse effect triggered by sudden release of methane from the sea floor due to methane clathrate dissociation or methane-producing microbes known as methanogens ; possible contributing gradual changes include sea-level change , increasing anoxia , increasing aridity , and a shift in ocean circulation driven by climate change .