Self-healing volcanoes: mechanical response of magma failure, sealing and healing on outgassing

Cyclic patterns of eruptive activity and quiescent periods are commonly observed at silicic volcanoes (e.g. Santiaguito, Guatemala). Quiescence, characterised by outgassing and no magmatic emissions, can last from several minutes to several years. Eruptive activity is, by comparison, expressed as the extrusion of lava/ pyroclasts, lasting minutes to years, and the onset can be extremely sudden, especially during explosive eruptions. Previous studies have shown that the overpressure leading to explosive activity can be achieved through gas accumulation following the processes of pore collapse or fracture infill and healing, which act to obliterate permeable outgassing; subsequently, magma may fragment and erupt explosively once the pressure exceeds the tensile strength. Here, we build on these studies by systematically testing the effects of fracture opening and (mechanical) sealing as well as (physico-chemical) healing. The experimental data is used to model the kinetics of fracture healing and tensile strength recovery as well as to constrain the permeability of fractured media as a function of pressure in the system. We discuss how these fracture and healing processes may operate in the timescale of pressure build-up and outgassing observed at volcanoes, without a need to invoke the input of a new magma recharge in the upper conduit.