Dense gas from deep traps as the cause of large rapid and long-runout landslides

Abstract

This paper presents a cause hypothesis of dense gas from deep crustal traps to logically, consistently and universally explain and interpret the large rapid and long-runout landslides. They are also called rapid giant landslides, rock avalanche-debris flows and/or rockslide-debris flows. Up to now, their cause and mechanism are still an unsolved problem. Based on field observations and theoretical studies, this paper points out, analyses and evaluates that landslides can be a result of endogenic geological and geophysical actions that originate in the interior of the Earth. A large amount of dense gas mass can rapidly escape out of deep crustal traps and migrate via geological faults or discontinuities to the slope soil and rock mass near the ground surface, which can be a form of outgassing of the Earth in mountains. The dense gas mass can have a huge amount of physical volumetric expansion energy and/or chemical explosive energy to suddenly deform and rupture stable slope rock mass. Its dynamic energy can expand, uplift, erupt and eject large rock mass. Together with the gravity potential energy, the gas expansion energy can rapidly accelerate the originally static broken rock mass to gain high vertical and horizontal velocities so that the solid debris can quickly run and flow long horizontal distances on gentle and/or flat ground and have the peculiar features. A simplified dynamic and mechanical model is used to describe this type of large rapid and long-runout landslides. The associated governing equations are developed according to the law of idealized gas, linear elastic theories of fracture mechanics, and Newton’s law of motion. Some numerical results are given and show that the volumetric expansion of dense gas with high pressure and sizeable volume can offer the required additional energy so that there is no need to have a huge reduction of ground frictional resistant work.