Cyclic lava effusion during the 2018 eruption of Kīlauea Volcano

INTRODUCTION The 2018 flank eruption and summit collapse of Kīlauea Volcano was one of the largest and most destructive volcanic events in Hawai‘i in the past 200 years. The eruption occurred on the volcano’s lower East Rift Zone (ERZ), draining magma at a high rate from the summit reservoir and triggering incremental collapse of the overlying caldera floor. Lava flows erupted for 3 months, destroying several residential subdivisions and burying miles of roads. The eruption rate exhibited cyclic behavior on multiple time scales, resulting in repeated lava breakouts and overflows. Multidisciplinary observations provide insight into the nature of these variations, driving forces in the magmatic system, and implications for hazard. RATIONALE Volumetric eruption rate is a primary control on the vigor and hazard of lava flows, but the processes that control its temporal variations are not well understood because of limited observational data. We integrated field observations, photos and video from time-lapse cameras and unmanned aircraft systems, seismic tremor, and infrasound to track the time scales and magnitude of fluctuations in eruption rate at the primary vent for the 2018 eruption on Kīlauea’s LERZ. We combined these data with documentation of summit caldera collapses to investigate the origins and impacts of these fluctuations. RESULTS Cyclic variations in eruption rate occurred on two disparate time scales. First, short-term fluctuations (“pulses”) in eruption vigor had periods of 5 to 10 min, but had no major implications for lava flow hazard. Flow rate in the lava channel was inversely related to fountaining and outgassing intensity at the vent. Second, long-term fluctuations (“surges”) had periods of 1 to 2 days and began within minutes of episodic caldera collapse events at the summit, 40 km upslope. These surges triggered overflows from the channel that produced hazardous enlargement of the lava flow field, which could be forecast several hours in advance. We also show that seismic tremor and infrasound were correlated with lava flow eruption rates. CONCLUSION We conclude that the two types of eruption rate cycles were controlled by two distinct processes. Short-term pulses were driven by changes in outgassing efficiency of the lava at shallow depths. Long-term surges in eruption rate were driven by pressure transients induced by the summit collapses and transmitted through the magma conduit over a distance of 40 km. The pressure-driven surges in eruption rate demonstrate that the episodic rhythm of summit caldera collapse sequences may be imparted on the accompanying flank eruption. The surges also help to constrain the efficient hydraulic connection between Kīlauea’s summit magma system and rift zones and demonstrate that pressure communication over distances of 40 km can occur on a time scale of minutes. Seismic tremor and infrasound may be effective proxies for lava flow eruption rates, allowing for improved tracking of lava flow hazards. Our multidisciplinary data provide a clear link between eruption rate fluctuations and their driving processes in the magmatic system.