New insights into lava flow dynamics during the 2018 eruption of Kīlauea

Abstract:

The 2018 lower East Rift Zone eruption of Kīlauea produced one of the most voluminous and destructive lava flows on the volcano in the past 200 years. The dominant flow, from fissure 8, was active for approximately two months and provided a unique opportunity to study the emplacement of a sustained, high-effusion rate (100-350 m³ s^-1 DRE) lava flow. We used a combination of ground-based and airborne visual and thermal observations to characterize the evolution of the flow through its lifespan.

Throughout the fissure 8 eruption, the proximal (<4 km from vent) perched channel remained stable, providing an efficient supply of lava to the distal flow. The medial braided channel (4–7 km), built over steeper slopes from overlapping pāhoehoe and ʻaʻā, showed only occasional changes with a progressive reduction in channel network complexity due to channel abandonment. The distal flow (7-13 km), emplaced on a broad, flat coastal plain, and composed mostly of ʻaʻā, was the most dynamic portion of the flow field. Channel backups led to overflows and significant flow thickening, which widened the distal flow via 1) lava from the flow interior squeezing out laterally along the margins (ooze-outs), and 2) levee breaching and channel diversions. The ocean entry exhibited cycles of activity over two months that began with direct supply from open channels, and transitioned as the channel crusted over, producing ooze-out (spiny pāhoehoe) entries fed by sub-crustal flow. These observations provide insight into how the flow dynamics were controlled by the interactions of internal and external emplacement parameters.

The substantial widening of the distal flow, via ooze-outs and channel diversions, highlights the late-stage hazards inherent to sustained flows emplaced on low slopes. While the primary advance of the fissure 8 flow destroyed approximately 400 structures, the secondary stage of channel backup, inflation, and widening consumed another 80 structures more than a month later. Thermal maps can reveal features and internal structures on channelized flows that are not evident to the naked eye, providing crucial detail on flow dynamics. This study emphasizes the value of repeat aerial thermal mapping for monitoring and understanding lava flow behavior.