From discrete explosions to continuous fountains: quantifying contrasting explosive regimes at a single fissure from Kīlauea's 2018 lower East Rift Zone eruption

Authors:
Preprint
Publisher website
Google Scholar
Abstract
This study uses videography, image analysis, and ballistic modeling to quantify eruption source parameters and transport characteristics of pyroclasts at Fissure 17 (F17) during the 2018 lower East Rift Zone eruption of Kīlauea. The hazard posed by volcanic ballistic projectiles depends on their range and kinetic energy on impact, which, in turn depend on the source parameters of the eruption. Furthermore, analysis of clast trajectories can inform the evolution of eruption style and its subsurface drivers. F17 evolved from a ~500 m long, segmented fissure into two dominant, long-lived segments separated by ~275 m: Segment 1 (S1) in the west was characterized by discrete, archetypal (“normal”) Strombolian explosions involving andesitic magma; and Segment 4 (S4) in the east was characterized by continuous spattering to low, unsteady Hawaiian fountaining of basaltic-andesitic magma. We analyzed clasts from two observation periods (13–14 May and 18 May), quantifying their size, exit velocity, and launch angle. S1 strengthened markedly as the fissure focused from 13 to 18 May, reflected in the median exit velocity increasing from 16 m/s to 45 m/s while median clast diameter decreased from 0.33 m to 0.17 m. S4 showed a more modest shift in median exit velocities (14 to 20 m/s) with broadly stable clast sizes. Maximum modeled ballistic ranges were 338 m at S1 and 51 m at S4. We attribute the greater range of S1 clasts to their greater density (mean of 1640 kg/m3 for S1 versus 820 kg/m3 for S4), higher launch velocity, and broader launch-angle distribution than S4 clasts. These results show that vent localization can amplify eruptive vigor while preserving fundamentally different conduit flow regimes at different sites along a single fissure, and that Strombolian activity during Hawaiian fissure eruptions may pose an elevated risk compared with more typical lava fountain activity.

This publication has 32 references indexed in Scilit: