Dynamics of CO2 Emission at Mammoth Mountain, California

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9909525KerrickUnderstanding the dynamics of diffuse magmatic CO2 degassing, which has caused over 50 ha of tree mortality on Mammoth Mountain since 1990, is the research focus of this proposal. We have recently documented the dynamic nature of CO2 efflux rates that indicate temporal variations must be taken into account in estimating the total CO2 discharge for an individual tree-kill area or the entire volcano. Prior studies of CO2 degassing at Mammoth Mountain have not addressed potential errors due to temporal variation in CO2 efflux rates; however, accurate estimates of CO2 efflux rates which take into account temporal variability are mandatory for monitoring long-term changes in the rate of CO2 degassing. The ability to numerically filter out short-term changes in CO2 efflux rates which occur due to external forcing (rather than reflecting a change in the deep source of CO2 degassing from beneath Mammoth Mountain) is also necessary. Accordingly, to shed light on the controls of CO2 degassing through the volcanic edifice at Mammoth Mountain, and to monitor for volcanic hazard, we have designed a comprehensive program for continuously monitoring CO2 emission at Mammoth Mountain, as well as elucidating the underlying physical and geologic principles that effect this phenomenon. This project is unique as there have been no long-term (greater than 72-hour) studies of continuous CO2 degassing on volcanoes or soil respiration. Because we are using new instrumentation with applicability to a broad range of gas transport phenomena in the unsaturated zone, the results of this study are particularly relevant to volcanic and/or geothermal degassing and to the transport and efflux of CO2 in the soil science, agriculture, and ecological subdisciplines. NSF Grant No. 98-10417 allowed us to acquire novel instrumentation and document the dynamic complexity of the volcanic CO2 degassing at Mammoth Mountain, but provided limited support for personnel. Our provisional study demonstrated that significant high-frequency variability in CO2 degassing rates exists at Mammoth Mountain - funding from grant EAR-9909525 will allow us to obtain a long-term record that will be even more meaningful. This grant will enable support for J. Rogie's Ph.D. thesis research on the driving forces for short and long-term temporal changes in CO2 degassing from Mammoth Mountain (using instrumentation purchased with NSF Grant No. 98-10417) and numerical modeling of gas transport in volcanic settings. This research will compliment the broad array of monitoring instruments and basic research in the active volcanic setting of Long Valley caldera and Mammoth Mountain via our collaboration with USGS researchers.