Volcanology with emphasis on active volcanism. Geochemistry of fluids discharging from active volcanoes and hydrothermal systems. Flux of volatiles from magmas to the atmosphere during magma ascent and eruption. Element cycling from the mantle and crust to the atmosphere through volcanism and active faulting. Volatile composition of melts and their influence on eruption style. Diffuse degassing of CO₂ from continental rift systems. Field remote sensing, direct sampling and analyses of volcanic and hydrothermal fluids. Current field research areas are in Central America, the Aleutians, the East African Rift and Antarctica.  Current Chair of the Board of Directors for the Deep Carbon Observatory Deep Carbon Degassing (DCO-DECADE) Initiative.