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

摘要: Mammoth Mountain, in the western United States, is a large dacitic volcano with long history of volcanism that began 200 kyr ago 1 and produced phreatic eruptions as recently 500± yr BP (ref. 2). Seismicity, ground deformation changes fumarole gas composition suggested an episode shallow dyke intrusion 1989-90 (refs 3, 4). Areas dying forest incidents near asphyxia confined spaces, first reported 1990, prompted us to search for diffuse flank emissions magmatic CO 2 , have been described at Mount Etna 5 Vulcano 6 . Here we report results soil-gas survey, begun 1994, revealed concentrations 30-96% 30-hectare region killed trees, from which estimate total flux ≥1,200 tonnes per day. The die-off most conspicuous surface manifestation processes hosts only weak fumarolic vents no summit activity. Although onset tree kill coincided intrusion, magnitude duration indicates larger, deeper magma source and/or reservoir high-pressure being tapped.