Dynamics of carbon dioxide emission at Mammoth Mountain, California

摘要

Mammoth Mountain, a dormant volcano in the eastern Sierra Nevada, California, has been passively degassing large quantities of cold magmatic CO_2 since 1990 following a 6-month-long earthquake swarm associated with a shallow magmatic intrusion in 1989. A search for any link between gas discharge and volcanic hazard at high popular recreation area led us to initiate a detailed study of the degassing process in 1997. Our continuous monitoring results elucidate some of the physical controls that influence dynamics in flank CO_2 degassing at this volcano. High coherence between variations in CO_2 efflux and variations in atmospheric pressure and wind speed imply that meteorological parameters account for much, if not all of the variability in CO_2 efflux rates. Our results help explain differences among previously published estimates of CO_2 efflux at Mammoth Mountain and indicate that the long-term (annual) CO_2 degassing rate has in fact remained constant since ～ 1997. Discounting the possibility of large meteorologically driven temporal variations in gas efflux at other volcanoes may result in spurious interpretations of transients that do not reflect actual geologic processes.