Volcanic flame: source of fuel and relation to volcanic gas-lava equilibrium

Flame formation at or near volcanic vents is a somewhat unusual phenomenon, but during October 1970 true flames were observed to issue at intervals from a series of vents in a lava tube or from spatter cones associated with the new eruptive center (Mauna Ulu) on the southeast rift of Kilauea volcano, Hawaii. This situation was similar to that under which successful volcanic gas collections have been made in the past in Hawaii and elsewhere. After several attempts two gas samples were collected successfully between flaming episodes. Analysis showed these to be chiefly water vapor with a small amount of hydrogen and carbon dioxide. The probable source of the hydrogen in the gas is explained on the basis of the high-temperature equilibria involved. The flame-forming properties of dilute mixtures of hydrogen and non-combustible gas were studied and the most dilutemixtures that would produce flames under volcanic conditions were measured (flammability limit). Intermittent flaming can be ascribed to the periodic attainment of the flammability limit for hydrogen in the volcanic gas mixture, which was found to be achieved in one of the collected samples.