Gas-Pistoning Associated With the 2008 Summit Eruption of Kilauea Volcano, Hawai'i

Following several months of steadily increasing SO2 emissions and seismic tremor at the summit of Kilauea volcano, a small explosive eruption on March 19, 2008, opened a 35-m-wide vent on the south wall of Halema'uma'u crater. Since then, the new vent has exhibited fluctuating nighttime glow and is the source of a persistent ~1-km-high plume of gas and minor amounts of ash. Several relatively small explosive eruptions have punctuated this typical vent behavior and deposited juvenile and lithic tephra on the crater rim. Since April, the elevated seismic tremor has exhibited discrete phases of episodic bursts which correlate with observable fluctuations in infrasound, ground tilt, ash production (juvenile and lithic), and vent temperature and glow. Variations in gas emission and plume vigor also appear to correspond to the episodic tremor bursts. We interpret this behavior as resulting from a gas-piston process. A view into the vent during a helicopter overflight in early September allowed direct observation of the lava lake surface undergoing a gas- piston cycle (moderate bubbling followed by several minutes of intense spattering associated with a down- drop in lava level), which corresponded with a tremor burst episode. Similar bursts at East Rift eruptive vents have been correlated with contemporaneous variation in gas chemistry. Here we analyze the relative timing among different datasets and reconcile these time-series with previous observations of gas-pistoning at other locations on Kilauea. The transitions between steady (non-episodic) tremor and episodic tremor are also explored. Halema'uma'u's new vent is providing scientists with a unique opportunity to study sustained shallow magmatic processes at Kilauea's summit.