Degassing processes of Popocatépetl and Volcán de Colima, Mexico
To understand the behaviour of a volcano and try to predict future eruptive activity, it is imperative to investigate its degassing processes. Areas of study include direct degassing of the magma through the conduit, the interaction between the hydrothermal system and volcanic gases and fluids, and diffuse degassing through the volcanic edifice. Various aspects of the degassing processes of Popocatepetl and Volcan de Colima in Mexico have been studied. The results are summarized in this chapter, and new data on diffuse degassing at both volcanoes and analyses of fumarolic gases from Volcan de Colima are presented.
Variations in the flux of SO2 at both volcanoes have led to models of the degassing processes. At Colima, isotopic analyses of condensates suggest a shallow degassing magma body. Volcan de Colima showed geochemical precursors prior to its 1998/9 eruption and variations in certain parameters continue to relate to the behaviour of the volcano during its on-going eruption. Both volcanoes yield interesting data on their diffuse degassing of CO2 and radon: at Popocatepetl, the large plume degassing contrasts with a small diffuse contribution. Volcan de Colima has anomalous concentrations of diffuse CO2 associated with faults. The challenge is how to interpret the geochemical data to provide a fresh insight into the mechanics of the volcanic system.
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Humans have long marvelled at (and feared) the odorous and colourful manifestations of volcanic emissions, and, in some cases, have harnessed them for their economic value. The degassing process responsible for these phenomena is now understood to be one of the key factors influencing the timing and nature of volcanic eruptions. Moreover the surface emissions of these volatiles can have profound effects on the atmospheric and terrestrial environment, and climate. Even more fundamental are the relationships between the history of planetary outgassing, differentiation of the Earth’s interior, chemistry of the atmosphere and hydrosphere, and the origin and evolution of life. This book provides a compilation of 23 papers that investigate the behaviour of volatiles in magma, the feedbacks between degassing and magma dynamics, and the composition, flux, and environmental, atmospheric and climatic impacts of volcanic gas emissions.