Worldwide distribution of submarine mud volcanoes and associated gas hydrates

The list of known and inferred submarine mud volcanoes is presented in this paper. They occur worldwide on shelves, continental and insular slopes and in the abyssal parts of inland seas. Submarine mud volcanoes are distribut ed on the Earth more extensively than their subaerial analogs. The estimate d total number of known and inferred deep-water mud volcanoes is 10(3)-10(5 ). There are two key reasons for the formation of submarine mud volcanoes-h igh sedimentation rate and lateral tectonic compression. Submarine mud volc anoes form by two basic mechanisms: (1) formation on the top of a seafloor- piercing shale diapir; (2) formation due to the rise of fluidized sediments along faults. Fluid migration is critical to the formation of a mud volcan o. Gas hydrates are often associated with deep-water mud volcanoes and have many common features from one accumulation to another. Gas hydrates form b y conventional low-temperature hydrothermal process around the central part of a mud volcano and by metasomatic processes at its periphery. A prelimin ary global estimate of methane accumulated in gas hydrates associated with mud volcanoes is about 10(10)-10(12) m(3) at standard temperature and press ure. (C) 2000 Elsevier Science B.V. All rights reserved.