Thermodynamics of freezing soil closed system saturated with gas and water

Abstract Natural eruptions in shallow permafrost with formation of large craters reported lately from gas-producing regions of the Russian Arctic may result from pressure buildup in freezing closed zones of gas-saturated unfrozen soil (taliks). Under certain conditions, increasing pressure may lead to hydraulic fracture of the overlying permafrost, with ensuing eruption of talik material and crater formation. The conditions of pore moisture freezing in gas-saturated taliks and related pressure buildup have been modeled by thermodynamic calculations. The model uses elegant equations to provide constraints on the freezing temperature of pore fluids containing dissolved salts and gases, which depends on free gas pressure, composition and contents of dissolved pore gases (methane, carbon dioxide, and their mixtures), and salinity. Pressure increase in these conditions is limited thermodynamically by the onset of gas hydrate formation.