Project Investigator Ryan Cahalan aims to quantify the potential hazards of magma-water interaction at the summit of Kīlauea and answer some key questions: (1) What is the rate of water entrainment into submerged volcanic jets? (2) What factors in wet volcanic jetting control the distance travelled by base surges and ballistics?
Experiments are being conducted at Washington State University Vancouver with Steve Solovitz to quantify water ingestion rates in eruption jets. We will answer the second question using a numerical model of underwater explosive eruptions that Ryan Cahalan developed during his PhD. The model will be updated from 2D to 3D and have conditions adjusted to simulate shallow-water environments. The experimental results will be used to validate the eruption model. The final goal was to develop a hazard map for eruptions through the water lake based on simulation results. This would aid to mitigate hazards if an eruption were to appear imminent.
The 2D subaqueous eruption model was improved by implementing in 3D, incorporating a Kīlauea digital elevation model into the 3D code, and testing out an air-water free surface condition for increased model accuracy. Each of these milestones were completed and are ready for further testing. In the December 20, 2021 Kīlauea summit eruption lava entered the water lake and boiled away the 50 m (164 ft) deep lake in 90-minutes. This produced a short lived, but tall (13,000 m, or about 43,000 ft, high) steam-rich plume in an otherwise docile eruption. While the immediate threat of hydrovolcanism vanished with the water lake, the eruption provided a uniquely well-constrained dataset. We have analyzed weather radar, infrasound and seismic data, camera footage, and field and satellite observations to constrain eruption timing, plume height time series, and plume rise rates. We introduced a method for measuring plume height using astrometry (star mapping). We examined the plume structure with 3D radar visualizations and found strong reflectivity zones coinciding indicative of the presence of large particles (possibly ashy raindrops or hail) that were transported downwind and deposited beyond sampled areas. The radar visualizations show an ice-dominated upper plume collocated with lightning flashes. With no ash detection from satellite, this suggests that ice charging is responsible for generating the lightning flashes. We utilized plume height measurements with 1D plume modeling to derive lake boiling rates to compare to lava-water interaction heat transfer models.
A manuscript is in preparation on the analysis of the 2020 Kīlauea eruption. This work was presented to the Volcano Science Center in June, in an HVO Volcano Watch in July, and will be presented at the American Geophysical Union Fall Meeting in 2021.