Flow and fragmentation of melts and magmas: developing a unified view through experimental, numerical and field investigations.

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Ten percent of the world's population (i.e. 100s of millions) live within 100 km of an active volcano. Furthermore, this number is set to rise with the increasing global population and growing demand for natural resources. When volcanoes erupt, they can behave effusively, explosively, or in a combination of both. Effusive activity produces lava flows and toxic gases, whereas explosive activity involves the breakage (fragmentation) of magma, dispersing molten droplets and, when the fragmentation is efficient, lethal ash clouds/flows that can travel several kilometres. Thus, the eruption style (effusive vs. explosive) directly controls the type, spatial footprint and magnitude of the hazard and therefore risk to populations. Thus, establishing the style of activity is of utmost importance to civil protection and hazard mitigation worldwide. Understanding eruption styles, particularly their transitions, ultimately allows us to predict eruption behaviour, perform accurate hazard assessments, protect local communities and better understand resultant deposits that can be of econnomic value.To determine the eruptive style of any volcano, we need to know how and when the magma breaks. There is a well-established theory for understanding the breakage of thick (high viscosity) magma, but this knowledge cannot be applied to runny (low viscosity) magmas. We do not currently understand how low viscosity magmas break and therefore cannot predict eruption style and accurately inform civil protection and hazard mitigation. This knowledge gap is particularly significant because the eruption of low viscosity magmas is the most frequent and volumetrically abundant form of volcanism on Earth, and on other planets. In this Future Leaders Fellowship, I will lead a team to fill this gap and provide the first quantification of how runny (low viscosity) magmas containing bubbles and/or crystals break. This key information, currently missing, will ultimately enable us to predict whether a volcano will erupt explosively or effusively. This goal will be achieved through a multidisciplinary and multicomponent approach, combining world-unique experiments developed in my lab, numerical modelling, field studies and novel community engagement methods. Scaled novel laboratory experiments will pull apart pure liquids (analogue melts) and mixtures of liquid, bubbles and/or particles (analogue magmas) at conditions relevant to natural volcanic eruptions. High-speed filming will record the stretching process and identify if, and how the liquid breaks. This will enable me to 'map out' the eruption conditions that lead to magma flow (effusive) or fragmentation (explosive). This 'behaviour map' will be the first of its kind that can be applied to bubble- and crystal-bearing magmas worldwide. Synthesis of these new experimental results with magma flow physics will allow me to produce a numerical model that will be able to forecast eruption style (effusive vs. explosive). Throughout the research, these outputs will be designed with volcano observatories to best support their operational use.To enhance the impact and reach of my work, I will deploy field techniques at Tseax volcano, British Columbia, Canada. Tseax is ~320 years old and represents the deadliest eruption in Canadian history, having resulted in the deaths of up to 2000 people and destroyed at least three Nisga'a First Nation villages. The volcano erupted low viscosity magma and crossed the explosive-effusive transition multiple times. Integration of field studies with the experimental results will uncover what caused the fatal explosive-effusive transitions. Bilateral exchange with the Nisga'a First Nation will integrate oral stories with scientific research to produce outreach materials that enthuse, engage and develop resilience in the community. My aim is that my novel approach could be used as a model to support other (Indigenous) communities affected by natural hazards worldwide.