Figure 1
From: Degassing during quiescence as a trigger of magma ascent and volcanic eruptions
Parts of a persistently degassing volcano and sketch of the magma dynamics in a dike.
(A) The deep and shallow reservoirs are hydraulically connected through a dike of length L. (B) Initially (
) the dike connecting the deep and shallow reservoirs is plugged (grey). The pressure in the shallow reservoir (
) decreases during quiescence, whereas the pressure in the deep reservoir (
) remains constant. After some time (
), the pressure in the shallow reservoir reaches a critical value (
), the rigid plug starts to replenish the reservoir and hotter melt (orange) ascends from the deep reservoir through the dike. During plug removal, the pressure in the reservoir remains constant (
) and the melt crystallizes near the dike walls. Two end-member scenarios can take place: (1) the plug is removed before the melt front stiffens and (2) the melt front stiffens before the plug is removed. When the former happens, pressurization of the shallow reservoir occurs. It is worth noting that a constant value for Ps means that the deep reservoir is in equilibrium with its surroundings and thus the pressure Ps is always lithostatic. In a more general case, the pressure change in the shallow reservoir during quiescence can be partially transmitted to the deep reservoir and thus Ps is not constant either. We also account for this possibility in the text.
