Mud volcanoes - a significant source of atmospheric methane

Mud volcanoes are recognized as a significant geological source of atmospheric carbon, particularly as methane gas. This paper considers the total number of mud volcanoes, types and frequency of their activity, quantities of emissions during quiescence and eruption, and composition of venting gases. Mud volcanoes approximate 1,950 prominent individuals worldwide and about 60 to 65 erupt every year. They sporadically or continuously emit to the atmosphere considerable volumes of gas, mainly methane, in average volumes of 3.3 to 3.6x10(6) m(3) per year during quiescent periods, and about 12x10(6) m(3) to more than 350x10(6) m(3) per single eruption. The total annual amount of methane emitted to the atmosphere through mud volcanoes is estimated to be about 5 Tg, containing almost equal quantities of fossil and modern carbon.