Characterising the trigger mechanisms of volcanic eruptions

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Although considerable progress has been made in the quantitative characterisation of volcanic eruptions, we still have relatively little knowledge of the physicochemical processes that control volcanic activity. Obtaining this knowledge is essential to the accurate prediction of eruptions, and this will only be achieved through the integration of multi-temporal and multi-spatial geochemical, geophysical and remote sensing studies. The objectives of my research program are thus to understand the evolution of magmatic volatiles from the mantle to the atmosphere and to seek surface evidence of their associated physical effects. The intrusion of fresh, gas-rich magma into a reservoir is often the trigger for an eruption, and the extent and rate of this interaction with the ponded magma will affect the nature of the eruption. By understanding the phenomenon of magma degassing, we will be better able to evaluate the evolution of volcanic activity and interpret signals that may be precursors to eruptions. Although there is agreement that crystallisation and the exsolution of volatiles from magmas exert a strong control on magma ascent, the rates at which these processes occur are not well known. Temporal variations in CO2/SO2 and HCl/SO2 ratios in the gas phase have been used for decades to infer changes in magmatic and hydrothermal systems, and are important in forecasting changes in volcanic activity. However, it is only with the recent advances in direct and indirect field measurements of volcanic gas compositions and fluxes, and higher precision analyses of melt inclusion compositions, that it is now possible to accurately determine the concentrations of the principal pre- and post-eruptive magmatic volatiles and thus quantify the volcano degassing budget. Nevertheless, fundamental questions remain regarding the evolution of H2O, CO2, SO2, HCl and HF during magma ascent, the role of separate gas phases on magma evolution and degassing, and the effects of divergent pathways on volcanic emissions measured on the surface. By understanding the evolution of magmatic volatiles from source to sink, this research has the potential to significantly advance our knowledge of how volcanic systems develop from dormancy through to eruption.