To elucidate the phenomenon of self-preservation of gas hydrates, the decomposition rates of methane hydrates prepared from dilute electrolyte solutions were measured while the temperature was increased from 233 to 273 K at atmospheric pressure. Decomposition was significantly suppressed near the eutectic temperature (T-E) of the electrolyte+water system. When the concentration of the electrolyte was relatively high, however, a transitory upsurge in the decomposition rate occurred at T-E. We speculate that the presence of electrolyte crystals increases the mobility of water molecules. This promotes the formation of a contiguous layer of ice that acts as an obstacle to diffusion of methane. This mechanism becomes marked as the temperature increases. When the temperature exceeds T-E, however, the occurrence of stable liquid causes local melting of the ice layer with attenuation of the barrier for methane diffusion. (C) 2013 Elsevier Ltd. All rights reserved.