Can rainfall trigger volcanic eruptions? A mechanical stress model of an active volcano: 'Piton de la Fournaise', Reunion Island

This paper relates the hydrology of a volcano to its eruptive activity, whi ch seem to be correlated. Based on the groundwater pattern previously deter mined by hydrologic and thermal modelling, we formulate hypotheses for the mechanisms linking rainfall and volcanic eruptions. We focus on: mechanical loading by the weight of the infiltrated rain, which might favour magma ov erpressure or slope instability on the eastern volcanic flank; unloading of the infiltrated water, discharged toward the ocean, which could increase t he tangential tensile stress above the magma chamber. We test the sensitivi ty of the model to the magma chamber geometry and the rainfall distribution . The mechanical unloading of the infiltrated water is the mechanism most l ikely to trigger eruptions. However, the presence of a sliding surface and rainfall loading could favour the development of tensile stress in the 'she ll' surrounding the magma chamber but with a lower intensity than in the pr evious case.