Evolution of the Fissure 8 lava flow on Kilauea's Lower East Rift Zone

New eruptive activity began on Kilauea's Lower East Rift Zone on May 3, 2018, initiating the most destructive eruption in Hawai`i's historical record. The initial two weeks of the eruption were dominated by the opening of numerous small fissures, producing spattering and low-volume lava flows. Later fissures in May erupted more fluid lava at higher rates, producing longer, more voluminous lava flows fed by low fountains. The eruption focused at a single vent, Fissure 8, in late May. The flow from this vent traveled 13 km over several days, reaching the coast and forming a sustained ocean entry. As of late July, Fissure 8 has erupted continuously for two months, with preliminary estimates of dense-rock effusion rate of roughly 50-150 cubic meters per second. The Fissure 8 flow has destroyed hundreds of homes, large areas of cropland, and numerous local landmarks.

The sustained nature of the Fissure 8 lava flow has allowed observations and measurements of lava flow activity in unprecedented detail. Flow monitoring was accomplished via airborne thermal mapping, time-lapse camera imagery, lidar surveys, and regular unmanned aerial system (UAS) mapping. The proximal section of the flow consists of a perched channel of pahoehoe lava. The medial portion consists of transitional pahoehoe-`a`a with braided channels. The distal region, near the coast, is composed of a broad fan of `a`a fed via a changing channel system.

The distal fan has been the most dynamic portion of the flow field. Thermal mapping reveals daily changes to the geometry of this region, controlling the expansion of the flow margins into coastal residential areas. Weeks after the initial emplacement of the distal flow in early June, lava began seeping laterally from the margins in a series of lava "ooze-outs", which created significant secondary expansion of the flow. These ooze-outs were supplied by lava within the flow interior, beneath the rubbly crust, and may have been the result of lateral injection due to inflation and overplating of lava around the channel. Ooze-outs destroyed scores of homes, well after the initial flow margin stalled, and highlight the hazards of secondary mobilization of lava within inflated `a`a flows. The Fissure 8 lava flow is notable for its persistence and property destruction, and we summarize the processes controlling the flow behavior.