A shaded relief map of Mount Rainier with GPS track from the gas observation flight.

A shaded relief map of Mount Rainier with GPS track from the gas observation flight. The colors correspond to CO₂ levels in parts per million by volume (ppmv) that were measured during the flight. Yellow points indicate elevated CO₂ levels, which were located near visibly degassing volcanic gas vents. The small inset plot shows example CO₂ and SO₂ data. Note that clear CO₂ peaks (blue line, left axis) were observed as the aircraft passed over visibly degassing vents, but no corresponding SO₂ was detected (red line, right axis).