Fumarole migration and fluid geochemistry at Poás Volcano (Costa Rica) from 1998 to 2001
O. Vaselli, F. Tassi, A. Minissale, G. Montegrossi, E. Duarte, E. Fernández, F. Bergamaschi, 2003. "Fumarole migration and fluid geochemistry at Poás Volcano (Costa Rica) from 1998 to 2001", Volcanic Degassing, C. Oppenheimer, D. M. Pyle, J. Barclay
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We report the results of a geochemical survey of fumaroles, thermal springs, and gas discharges from areas in and around the active crater lake of Poás volcano (Costa Rica) from February 1998 to February 2001. The springs are highly acidic-sulphate waters with temperatures approaching boiling point, whereas gas chemistry is characterized by typical magmatic species, such as SO2, HF, HC1, H2, and CO. From February 1998 new fumarolic fields formed inside the southern part of the crater. They moved anticlockwise from the S to the NE inner walls of the crater, while those located in the southern part of the crater and close to the pyroclastic cone south of the crater lake diminished or disappeared altogether, during 1999 and 2000. This shift was also characterized by chemical variation of the magmatic gas species. In spite of the chemical changes of fumaroles, the composition of the lake changed little during this time. This fact, together with the chemical profile with depth of the lake, suggests that the lake is a very efficient condenser of magmatic fluids. An apparent chemical stratification of the lake suggests that dilution with meteoric water is not complete, due to the presence of liquid sulphur at the lake bottom and/or due to the continuous influx of new magmatic components.
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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.