9706251 Rutherford The phenocryst phases present in a subvolcanic magma, and the properties of the magma are controlled in part by the C-O-S volatile dissolved in the melt phase. In addition, exsolution of gas in subvolcanic magma systems will also affect their physical properties and related magmatic processes such as convection, eruption dynamics, magma degassing, and metal transport. The research to be conducted with this award is designed to understand (1) the controls on gas species solubility, (2) the composition of the excess gas phase, and (3) the effects these volatiles have on volcanic processes. The work involve experiments on natural volcanic rock compositions ranging from dacites such as those erupted from Mt. Pinatubo in 1991 to calc-alkaline and alkaline basalts. The third task involves a study if Mt. Vesuvius volcanic processes.