Mud Volcano and Its Evolution

Abstract

The term mud volcano refers to topographical expressions of naturally occurring volcanoshaped cone formations created by geologically excreted liquefied sediments and clay-sized fragments, liquids and gases. Ejected materials often are a mud slurry of fine solids suspended in liquids which may include water and hydrocarbon fluids. The bulk of released gases are methane, with some carbon dioxide and nitrogen. Mud volcanoes may be formed by a pressurized mud diapir which breaches the Earth's surface or ocean bottom. Flowing temperatures at the ocean bottom may be as low as freezing point and are associated with the formation of hydrocarbon hydrate deposits. Flowing temperatures can also be hot if associated with volcanic gases and heat escaping from deep magma which can turn groundwater into a hot acidic mixture that chemically changes rock into mud and clay-sized fragments. These mud volcanoes are built by a mixture of hot water and fine sediment that either pours gently from a vent in the ground like a fluid lava flow; or is violently ejected into the air as a lava fountain of escaping mud, volcanic gas, stream and boiling water. Mud volcanoes are most abundant in areas with rapid sedimentation rates, active compressional tectonics, and the generation of hydrocarbons at depth. Typically they are also found in tectonic subduction zones, accretionary wedges, passive margins within deltaic systems and in active hydrothermal areas, collisional tectonic areas, convergent orogenic belts and active fault systems, fault-related folds, and anticline axes. These structures act as preferential pathways for deep formation fluids to reach the surface. (see Pitt and Hutchinson, 1982, Higgins and Saunders, 1974; Guliyiev and Feizullayev, 1998; Milkov, 2000; Dimitrov, 2002; Kopf, 2002, Mazzini, 2009). The existence of mud volcanoes are controlled by tectonic activity where fluid escapes from areas undergoing complex crustal deformation as a result of transpressional and transtensional tectonics. Collisional plate interactions create abnormal pressure condition and consequently overpressured buildup of deep sedimentary sediment which in turn result in formation of diapirs. Over pressured zones typically are under-compacted sedimentary layers which have lower density than the overlying rock units, and hence have an ability to