Possible mechanism of lithospheric crack development

An equation of crack channel propagation is derived under the assumption that the crack opening is a slow process. The equation contains only one phenomenological parameter: time $\tau$ of melt free flow in a crack channel (free flow means that the hydrodynamic drag is absent). Time $\tau$ is found to be about 10 s. A solution to this equation is checked as applied to the Great Tolbachin Fissure Eruption, which occurred in 1975–1976. Satisfactory agreement between calculated and observed data for the magma eruption rate ($V$ = 0.15 m/s) and crack opening time ($T$ = 8.4 days) is obtained.