Gas and hydrogen isotopic analyses of volcanic eruption clouds in Guatemala sampled by aircraft

Gas samples were collected by aircraft entering volcanic eruption clouds of three Guatemalan volcanoes. Gas chromatographic analyses show higher H₂ and S gas contents in ash eruption clouds and lower H₂ and S gases in vaporous gas plumes. H isotopic data demonstrate lighter isotopic distribution of water vapor in ash eruption clouds than in vaporous gas plumes. Most of the H₂O in the vaporous plumes is probably meteoric. The data are the first direct gas analyses of explosive eruptive clouds, and demonstrate that, in spite of atmospheric admixture, useful compositional information on eruptive gases can be obtained using aircraft.