In contrast to the seismic and infrasonic energy released from quiescent and erupting volcanoes, which have long been known to manifest episodes of highly periodic behavior, the spectral properties of volcanic gas flux time series remain poorly constrained, due to a previous lack of high‐temporal resolution gas‐sensing techniques. Here we report on SO2 flux measurements, performed on Mount Etna with a novel UV imaging technique of unprecedented sampling frequency (0.5 Hz), which reveal, for the first time, a rapid periodic structure in degassing from this target. These gas flux modulations have considerable temporal variability in their characteristics and involve two period bands: 40–250 and 500–1200 s. A notable correlation between gas flux fluctuations in the latter band and contemporaneous seismic root‐mean‐square values suggests that this degassing behavior may be generated by periodic bursting of rising gas bubble trains at the magma‐air interface. Key Points Distinct periodic structure in volcanic degassingCorrelation between gas flux fluctuations and contemporaneous seismic RMS valuesPeriodic bursting of rising gas bubble trains at the magma‐air interface