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

该项目将由国家科学基金会地球科学理事会(NSF/GEO)和英国国家环境研究理事会(UKRI/NERC)通过NSF/GEO-NERC牵头机构协议共同资助。该协定允许美国和英国提交一个单一的联合提案，并由该机构进行同行审查，该机构的调查员在预算中所占比例最大。在成功地联合确定一项裁决后，每个机构将为预算的比例以及与其自己的调查员和工作部分有关的调查员提供资金。气泡的成核和增长推动了火山爆发。因此，如果我们要预测喷发风格以及喷发产物的性质，对这些过程进行定量建模是必不可少的。该项目将为火山学研究界提供一个有用的工具，使我们的集体科学能够更好地了解并最终预测爆炸性喷发的性质、爆炸性和潜在危险。这种最严重的火山灾害是由大规模的火山灰喷发引起的。火山灰对火山周围的地区构成局部危险，例如山峰。1980年，圣海伦斯火山爆发，还威胁到更广泛的地区，火山灰会污染地表水和农业土壤，导致呼吸压力，在发生非常大的喷发的情况下，可能会暂时改变全球气候。因此，这些喷发威胁着国家和全球安全，更充分地了解它们是科学的优先事项。为了达到这种理解的目标，这个项目的目标是触及火山的核心--形成、生长和驱动爆炸性喷发的气泡的成核。该项目包括与跨大学学生和博士后辅导的国际和国内合作，包括对本科生和研究生的K-12推广和培训。该项目将创建和验证一个统一的数值模型，用于研究岩浆中气泡的成核和生长，涵盖最常与爆炸性喷发有关的成分范围。目前，对气泡成核和生长的物理控制的严格定量理解受到与成核过程和复杂的、不断演变的气泡生长有关的两个知识空白的阻碍。该项目将把新颖的实验与理论建模结合起来，通过以下方式克服这些知识空白：1)进行有针对性的实验，以约束同时捕获均匀和非均匀成核的新颖的、基于理论的公式；2)创建气泡增长的数值模型，该模型捕获相互作用的气泡队列的整体行为，其中成核位置的分布可能在时间和空间上演变；3)结合成核公式和气泡增长模型，创建统一的模型。该集合气泡生长模型将使用成核公式来随机和迭代地在3D熔体体积内分配成核事件，并使用壳层模型队列来跟踪所产生的气泡的生长。这个组合的数值模型将允许用户确定自然喷发路径的岩浆性质的演变，并为从喷发产物中反转以推断管道内喷发条件奠定基础。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.