▽U.S. Geological Survey, Volcano Hazards Program ●04/17 21:43 April 15, 2025Volcanic gases reflect magma stalling and launching depthsMany open-vent arc volcanoes display two modes in their continuous gas emissions, one with a characteristic CO2/ ST ratio typical of periods of quiescent degassing and another punctuated by high CO2/ ST gas emitted in the weeks before eruption, a recently recognized eruption precursor. In this study we explore the origin of