Catastrophic methane release has been suggested as a possible cause of mass extinction. Methane clathrate is an ice-like substance formed from water and methane in the sea bed, arctic lakes and permafrost. It forms where the temperature is at freezing or a little above and where the pressure of overlying water and sediment creates the right conditions. A temperature rise causes the methane in the clathrate to be released as gas. Global warming results and causes further clathrate heating and methane release. The resultant soaring temperature causes such stress to plant and animal life that mass extinction follows.