EAR-PF: Investigating the Explosive Effect of External Water on Volcanic Eruptions: Developing a Scalable Simulation of Explosion Energetics

Fitch, Erin Piper, Honolulu HI

Investigators

Abstract

Dr. Erin Fitch has been awarded an NSF EAR Postdoctoral Fellowship to develop a scalable, numerical simulation of explosive magma–water interaction during hydrovolcanic eruptions. This work will be pursued under the mentorship of Dr. Josef Dufek at the University of Oregon. During hydrovolcanic eruptions, magma interacts with external water or ice, resulting in vigorous steam explosions. Almost 30% of volcanic eruptions are known to involve magma–water interactions and can occur with very little warning, like at White Island in 2019 and Ontake in 2014, necessitating the development of forecasting tools that account specifically for magma–water interactions. The complexity of magma–water interactions and the hazardous conditions they create make this a difficult process to study, and especially difficult to quantify by traditional field methods. We will therefore develop and validate a new numerical simulation of magma–water interactions, which takes into account the progression of micro-scale heat transfer and fragmentation that drives macro-scale explosive expansion, fragmentation, and dispersal of ejecta (solidified magma). The simulation will allow us to estimate magma–water explosion energy to inform volcanic hazard assessments. Additionally, the PI will be actively involved in educational activities at the University of Oregon by developing educational material specifically focused on tying field and laboratory observations to numerical simulations, which is an underdeveloped area of academic education. The research and education goals of this work directly impact the hazard assessment of the Cascade Volcanic Arc, known for hydrovolcanism and explosive eruptions, where the host institution is located. In order to improve hydrovolcanism hazard assessment, this work focuses specifically on the quantification of processes occurring during magma–water interactions. Previously, the energetics of magma–water interactions was quantified based on deposit characteristics, which can involve a significant amount of uncertainty, because magmatic gas expansion and external water both contribute to the fragmentation and dispersal of tephra. However, explosive magma–water interactions are driven by the same mechanism as lava–water explosions and explosive melt–water experiments, so we can use the latter to understand the former. This mechanism is Molten-Fuel-Coolant Interaction (MFCI) where the “molten fuel” is magma or lava and the “coolant” is external water. In order to take observations of micro-scale MFCI processes and determine how they progress during magma–water interactions, we use the breadth of new and existing data on laboratory experiments and lava–water explosions to develop the first scalable numerical melt–water mixing simulation, using flexible industry-standard software. Our expected results address processes that are still poorly understood for natural systems, namely (1) the factors affecting interfacial mixing and instabilities, especially vapor film collapse, (2) the relationship between the conversion ratio and water/melt mass ratio, and (3) the production of active particles, which drive the explosion through rapid heat transfer. Ongoing development of this simulation will enable it to be used as a tool to understand and forecast hazards associated with lava–water explosions and hydrovolcanic eruptions. Educational aspects of the fellowship include developing educational materials that include laboratory experiments used in conjunction with numerical simulations. This fellowship received co-funding from the Petrology and Geochemistry program in the Earth Science division. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.