Thermal mapping of a pahoehoe laVa flow, Kilauea Volcano

Pahoehoe lava flows are a major component of Hawaiian eruptive activity, and an important part of basaltic volcanisth worldwide. In recent years, pahoehoe lava has destroyed homes and threatened parts of Hawaii with inundation and disruption. In this study, we use oblique helicopter-borne thermal images to create high spatial resolution (similar to 1 m) georeferenced thermal maps of the active pahoehoe flow on Kilauea Volcano's East Rift Zone. Thermal maps were created on 27 days during 2014-2016 in the course of operational monitoring, encompassing a phase of activity that threatened the town of Pahoa. Our results illustrate and reinforce how pahoehoe flows are multicomponent systems consisting of the vent, master tube, distributary tubes, and surface breakouts. The thermal maps accurately depict the distribution and character of pahoehoe breakouts through time, and also delineate the subsurface lava tube. Surface breakouts were distributed widely across the pahoehoe flow, with significant portions concurrently active well upslope of the flow front, often concentrated in clusters of activity that evolved through time. Gradual changes to surface breakout distribution and migration relate to intrinsic processes in the flow, including the slow evolution of the distributary tube system. Abrupt disruptions to this system, and the creation of new breakouts (and associated hazards), were triggered by extrinsic forcing namely fluctuations in lava supply rate at the vent which disrupted the master lava tube. Although the total area of a pahoehoe flow has been suggested to relate to effusion rate, our results show that changes in the proportion of expansion vs. overplating can complicate this relationship. By modifying existing techniques, we estimate time-averaged discharge rates for the flow during 2014-2016 generally in the range of 1-2 m(3) s(-1) (mean: 13 +/- 0.4 m(3) s(-1)) less than half of Kilauea's typical eruption rate on the East Rift Zone and suggestive of a weak eruptive regime during 2014-2016. We caution, however, that this discharge rate approach requires further independent corroboration. The thermal maps provide the first synoptic characterization of pahoehoe flow activity at high spatial resolution, essential both for operational hazard assessment and fundamental understanding of pahoehoe behavior. Published by Elsevier B.V.