Research Progress of Seafloor Pockmarks in Spatio-Temporal Distribution and Classification

Seafloor pockmarks are important indicators of submarine methane seepages and slope instabilities. In order to promote the understanding of submarine pockmarks and their relationship with sediment instabilities and climate changes, here we summarize the research results of pockmarks in the spatio-temporal distributions and shaping factors. Most of pockmarks occur along active or passive continental margins during the last 25 kyr B.P.. Circular and ellipse are the most common forms of pockmarks, whereas pockmarks in a special crescent or elongated shape are indicators of slope instabilities, and ring-shape pockmarks are endemic to the gas hydrate zones. Further researches should be focused on the trigger mechanism of climate changes based on the pockmarks in the high latitudes formed during the deglaciation periods, and the role of gas hydrates in the seafloor evolution should be elucidated. In addition, the feature of pockmarks at their early stage (e.g., developing gas chimneys and gas driving sedimentary doming) and the relations between pockmarks and mass movements, mud diapirs could be further studied to clarify the influences of rapid methane release from submarine sediments on the atmospheric carbon contents.