As the subsurface warms, the top of the gas hydrate stability zone moves downward (yellow arrows in the left panel). Warming results in gas hydrate dissociation in a gradually thickening zone (brown), releasing gaseous methane into the sediments (yellow bubbles). Bubble formation associated with this phase change creates over-pressured conditions. The right-hand panel shows how material may flow (red arrows) both laterally and vertically in response to overpressure. Displaced sediments rise upward to form the PLF and allow the gas to vent. As the pressure is dissipated through both the transfer of solids and degassing, subsidence in the area immediately surrounding the PLF (black arrows) creates the moat.
From collection: Frozen Heat - A Global Outlook on Methane Gas Hydrates