Helium/Carbon dioxide ratios as premonitors of volcanic activity

The composition of the gaseous emissions of two fumaroles at the summit of Kilauea Volcano was monitored for m?re than 2 years. Magma was released from the summit reservoir on three occasions during this period; prior to or during each event the ratios of helium to carbon dioxide in the fumarole gases decreased substantially from that observed during periods of quiescence.