Abstract This paper illustrates the diversity of subsurface sediment mobilization features in tectonically mobile regions in a shale-rich environment. In the studied area of the southeastern Caribbean, new geophysical acquisition in Trinidad and Barbados spectacularly show the widespread development of mud volcanoes and massive sedimentary extrusions in the interference area between the southern part of the Barbados prism and the active turbidite system of the Orinoco. Mud volcanoes are well developed along ramp anticlines, or on top of sigmoid rises, which are oblique with respect to the trends of the main folds of the accretionary wedge. The area also exhibits trends of structures corresponding to massive extrusions of well preserved turbidite and hemipelagic sediments that cut the surrounding sediments. Some of these extrusion structures are complicated by the development of collapse structures, calderas, and superimposed mud volcanoes. On some active mud volcanoes, heat flow measurements show high positive anomalies and bottom simulating reflectors that are shallower compared to the surrounding areas and show high fluxes of fluid expulsion. The mobilized sediments expelled by the mud volcanoes are liquefied argillaceous and sandy material from deep horizons, and various shallower formations pierced by the mud conduits. Both in the Barbados prism and in Trinidad, the mud expelled is rich in thin, angular, and mechanically damaged quartz grains related to shearing and/or hydraulic fracturing processes. The exotic clasts and breccia result mostly from hydraulic fracturing. In Trinidad, the gas phase is mainly deep thermogenic methane associated with hydrocarbon generation at depth. This paper emphasizes that subsurface, clay-rich formation mobilization notably differs from salt mobilization by the role taken by the fluid dynamics that control overpressured shale mobilization, and induce sediment liquefaction. Mud volcanism corresponds to fluid displacement, whereas massive sedimentary extrusion corresponds to large movements of stratified solid levels for which the deep cause could be the intrusion of mud plugs. Both are dynamic phenomena controlled by the development of overpressure at depth, contributing to sediment mobilization by reducing the strength within the overpressured layer. The regime of the expulsion of the fluids varies according to cyclic phases. Low-frequency cycles, notably the catastrophic events, are controlled by the dynamic development of overpressure. They could be related to the fact that when high excess pore pressure occurs at depth, hydraulic fracturing is responsible for opening the fracture network favoring successive fluid release and cyclic pressure decrease. Such processes could be enhanced by a threshold effect when fluids are oversaturated in gas. In that case, massive degassing of a large volume of dissolved gas at depth is possible, resulting in a sudden rise in fluid pressure and damage to the sealing properties of the sediments above gas-charged mud chambers.