Skip to main content
U.S. flag

An official website of the United States government

Forest-killing diffuse CO2 emission at Mammoth Mountain as a sign of magmatic unrest

January 1, 1995

MAMMOTH Mountain, in the western United States, is a large dacitic volcano with a long history of vo lean ism that began 200 kyr ago1 and produced phreatic eruptions as recently as 500 ± 200 yr BP (ref. 2). Seismicity, ground deformation and changes in fumarole gas composition suggested an episode of shallow dyke intrusion in 1989–90 (refs 3, 4). Areas of dying forest and incidents of near asphyxia in confined spaces, first reported in 1990, prompted us to search for diffuse flank emissions of magmatic CO2, as have been described at Mount Etna5 and Vulcano6. Here we report the results of a soil-gas survey, begun in 1994, that revealed CO2 concentrations of 30–96% in a 30-hectare region of killed trees, from which we estimate a total CO2flux of ≥1,200 tonnes per day. The forest die-off is the most conspicuous surface manifestation of magmatic processes at Mammoth Mountain, which hosts only weak fumarolic vents and no summit activity. Although the onset of tree kill coincided with the episode of shallow dyke intrusion, the magnitude and duration of the CO2 flux indicates that a larger, deeper magma source and/or a large reservoir of high-pressure gas is being tapped.

Citation Information

Publication Year 1995
Title Forest-killing diffuse CO2 emission at Mammoth Mountain as a sign of magmatic unrest
DOI 10.1038/376675a0
Authors C. D. Farrar, M. L. Sorey, William C. Evans, J. F. Howle, B.D. Kerr, B.M. Kennedy, C. -Y. King, J. R. Southon
Publication Type Article
Publication Subtype Journal Article
Series Title Nature
Index ID 70018903
Record Source USGS Publications Warehouse
USGS Organization California Water Science Center; Volcano Hazards Program