Dynamics of carbon dioxide emission at Mammoth Mountain, California

Mammoth Mountain, a dormant volcano in the eastern Sierra Nevada. Californi a, has been passively degassing large quantities of cold magmatic CO2 since 1990 following a h-month-long earthquake swarm associated with a shallow m agmatic intrusion in 1989. A search for any link between gas discharge and volcanic hazard at this popular recreation area led us to initiate a detail ed study of the degassing process in 1997. Our continuous monitoring result s elucidate some of the physical controls that influence dynamics in flank CO2 degassing at this volcano. High coherence between variations in CO2 eff lux and variations in atmospheric pressure and wind speed imply that meteor ological parameters account for much. if not all of the variability in CO2 efflux rates. Our results help explain differences among previously publish ed estimates of CO2 efflux at Mammoth Mountain and indicate that the long-t erm (annual) CO2 degassing rate has in fact remained constant since similar to 1997. Discounting the possibility of large meteorologically driven temp oral variations in gas efflux at other volcanoes may result in spurious int erpretations of transients that do nut reflect actual geologic processes. ( C) 2001 Elsevier Science B.V. All rights reserved.