Quantification of the Mass Flux of H2O Gas (Steam) at Three Active Volcanoes Using Thermal Infrared Imagery

Abstract

We apply a measurement technique that utilizes thermal video of vapor-dominated volcanic plumes to estimate the H2O gas flux at three degassing volcanoes. Results are compared with H2O flux measurements obtained using other methods to verify the thermal camera-derived values. Our estimation of the H2O emission rate is based on the mass and energy conservation equations. H2O flux is quantified by extracting the temperature and width of the gas plume from the thermal images, calculating the transit velocity of the gas plume from the thermal video, and combining these results with atmospheric parameters measured on-site. These data are then input into the equations for conservation of mass and energy. Selected volcanoes for this study were Villarrica in Chile, Stromboli in Italy, and Santa Ana in El Salvador. H2O fluxes estimated from the thermal imagery were 38–250 kg s−1 at Villarrica, 4.5–14 kg s−1 for Stromboli’s Central Crater, and 168–219 kg s−1 at Santa Ana. These compare with H2O flux values estimated by other methods of 73–220, 3–70 and 266 kg s−1, at the three volcanoes, respectively. The good agreement between thermal image-derived results and those estimated by other methods seem to validate this method.