Relevance of the work. Cryovolcanic phenomena in the permafrost zone of the Earth are at the very initial stage of study. Purpose of this paper is to form and study theoretical ideas about the nature and mechanism of formation of a cylindrical vent in order to obtain scientifically substantiated knowledge that can subsequently be useful in developing the methodology and content of field studies, laboratory experiments and predictive calculations. The implementation of this goal is based on the main working hypotheses of the formation of the studied cryogenic volcano and the cryogenic processes that caused it in the permafrost massif: gassing (gas saturation) associated with the existence of stratal underground ice and the response of permafrost to climate fluctuations; degassing, accompanied by pneumatic release of rock and ice to the adjacent territory. Attention is also drawn to a hypothesis based on the concept of the migration and accumulation of hydrocarbons in the permafrost strata as a result of macro- and micro-seepage of gases, leading to the formation of near-surface redox zones favorable for the biodegradation of hydrocarbons with the formation of secondary microbial gases, primarily, methane. Methodology of research provides for a comparative analysis of characteristics of the composition and properties of homogeneous elements of the object under study, identified as a result of primary measurements and visual examinations and presented theoretical hypotheses. Results of work and scope of their application made it possible to reveal the theoretical prerequisites for substantiating the hypothesis about the complex nature of the formation of a cylindrical vent of a cryogenic volcano, which is expressed by a combination of long-term mechanical and thermobiochemical processes in permafrost. Conclusions. The authors put forward a hypothesis about the significant contribution of biochemical processes with the participation of hydrocarbons, including in the liquid phase, in the formation of a primary cavity (vent) of a regular cylindrical shape in the rock mass at the stages preceding the explosive outburst of crater rocks. As an interconnected one, the authors theoretically substantiated the hypothesis of the formation of a meromictic reservoir with an established unmixed stratified anaerobic deep part in the cryovolcano vent after the explosive destruction of the heaving mound. An explanation of the nature of the source of gas ignition (from a spark formed during the collision of solid rock fragments at the time of cryovolcanic outburst of rocks), as well as the ferroelectric effect that occurs during deformation of frozen rocks is presented. Keywords: permafrost, ice, permafrost mound, cryovolcanism, vent, thermobiochemical process.