NSF GEO-NERC: Collaborative Research: A general model for bubble nucleation and growth in volcanic systems

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This project will be jointly funded by the National Science Foundation’s Directorate of Geosciences (NSF/GEO) and the National Environment Research Council (UKRI/NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with its own investigators and component of the work. The nucleation and growth of bubbles drives explosive volcanic eruptions. As such, quantitative modelling of these processes is essential if we are to predict eruptive style, as well as the nature of eruptive products. This project will produce a useful tool for the volcanological research community and enable our collective science to better understand and ultimately predict the nature, explosivity, and potential hazard of explosive eruptions. This most serious volcanic hazard arises from large ash eruptions. Ash poses local hazards to the region surrounding volcanoes, such as Mt. St. Helens, in 1980, and also threatens a much broader area with ash fallout that can contaminate surface water and agricultural soils, lead to respiratory stress, and in the case of very large eruptions, can temporarily alter global climate. As such, these eruptions threaten national and global security, and understanding them more fully is a science priority. Toward the goal of such understanding, this project aims to get to the heart of volcanoes- the nucleation of bubble that form, grow and drive explosive eruptions. The project includes international and domestic collaborations with cross-university mentoring of students and postdocs, including K-12 outreach and training of undergraduate and graduate students.This project will create and validate a unified numerical model for the nucleation and growth of bubbles in magma, across the range of compositions most commonly associated with explosive eruptions. At present, rigorous quantitative understanding of the physical controls on the nucleation and growth of bubbles is impeded by two knowledge gaps relating to nucleation processes and complex, evolving bubble growth. The project will combine novel experiments with theoretical modeling to overcome these knowledge gaps by 1) Conducting targeted experiments to constrain a novel, theoretically-grounded formulation that captures both homogeneous and heterogeneous nucleation; 2) Creating a numerical model of bubble growth that captures the ensemble behavior of cohorts of interacting bubbles, in which the distribution of nucleation sites may evolve in time and space; 3) Combining the nucleation formulation and bubble growth model to create a unified model. That ensemble bubble growth model will use the nucleation formulation to stochastically and iteratively assign nucleation events within a 3D volume of melt, and track the growth of the resulting bubbles using cohorts of shell models. This combined numerical model will allow users to determine the evolution of magma properties for natural eruption pathways, and set the stage for inverting from eruptive products to infer in-conduit eruptive conditions.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.