Simulations of the emptying of a closed chamber by magma ascent dynamics based on self-organized fracture mechanisms

The emptying of a magma chamber can trigger eruptive series of events that can be very different in duration and explosivity degree. Usually, erupted magma is a mixture of magmas that originate at various depths and can significantly affect the style of the eruptive processes. In this work, possible correlations between depth of origin of magma and eruption size are investigated using a cellular automaton model that describes magma ascent in a buoyancy field as a diffusive dynamics on self-organized fracture networks. Interestingly, the model predicts that erupted magma is, generally, a mixture of magma that has continuously stopped during the whole ascent path from the chamber to the surface, except for eruptions above a given size threshold, for which it is possible to distinguish two dominant components deriving from specific depth ranges. Such a finding can provide a theoretical framework for the general feature of many volcanic eruptions whose deposits are characterized by two different magmas. Furthermore, in the repose times distribution, a timescale separation between short and long more probable repose times is found, which increases by deepening of the magma chamber. The identification of two different types of repose times suggests the presence of different patterns, which could help the understanding of magmatic processes responsible of different eruptive regimes that may characterize the life of a volcano.