The Formation and Evolution of Mud Volcano: The Significance of Scientific Research on the Earth System

Mud volcanoes are not volcanoes, the formation of mud volcanoes is the same as that of mud diapirs. It is the result of the pressure release of internal trap fluid in the strata. Because their eruption way and accumulation formed after eruption are similar to the volcanoes, hence the name (Milkov, 2000; Dimitrov, 2002; Wan et al., 2015). Mud volcanoes are of great significance to many aspects of scientific research on the earth system. The material erupted by mud volcanoes are mainly muddy sediments, water, gas and oil, etc., which contribute to revealing deep geological information (Dimitrov, 2002; Feseker et al., 2014). The formation of mud volcanoes is directly related to hydrocarbons accumulation and gas hydrates mineralization, so mud volcanoes can be used as important indicators for hydrocarbons and gas hydrates resources evaluation (Milkov, 2000; Abrams, 2005). Besides, mud volcanic fluid eruption activities will affect drilling, pipeline laying and other projects (Normile, 2008). Furthermore, the large amount of methane gas erupted by mud volcano will also cause greenhouse effect and climate change (Dimitrov, 2003; Kopf, 2005). Last but not least, mud volcanoes are significant symbol of neotectonic movement and are closely related to earthquake activities and faulted structure (Manga, 2012; Bonini et al., 2016). At present, there are more than 1,800 mud volcanoes found on the earth, mainly distributed in Indonesia, Russia, Trinidad and Barbados island. Among them, Java island in Indonesia, Baku in Azerbaijan, Makran in Iran, Buza in Romania and Yellowstone National Park in the United States are more well-known (Milkov, 2000; Kopf,