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

Erin Fitch博士被授予NSF EAR博士后奖学金，以开发一种可扩展的火山喷发期间爆炸性岩浆-水相互作用的数值模拟。这项工作将在俄勒冈大学Josef Dufek博士的指导下进行。在水火山爆发期间，岩浆与外部的水或冰相互作用，导致剧烈的蒸汽爆炸。已知近30%的火山爆发涉及岩浆-水相互作用，并且可能在几乎没有预警的情况下发生，例如2019年的怀特岛和2014年的御竹岛，因此有必要开发专门用于岩浆-水相互作用的预测工具。岩浆-水相互作用的复杂性及其产生的危险条件使得这一过程难以研究，尤其是难以通过传统的现场方法进行量化。因此，我们将开发并验证一种新的岩浆-水相互作用的数值模拟，该模拟考虑了微观尺度的传热和破碎的过程，这些过程驱动了宏观尺度的爆炸膨胀、破碎和喷出物（凝固岩浆）的扩散。模拟将使我们能够估计岩浆水爆炸能量，为火山危险评估提供信息。此外，PI将积极参与俄勒冈大学的教育活动，开发特别侧重于将实地和实验室观察与数值模拟联系起来的教育材料，这是学术教育的一个不发达领域。这项工作的研究和教育目标直接影响喀斯喀特火山弧的危害评估，喀斯喀特火山弧以水火山作用和爆炸性喷发而闻名，而东道国机构就在那里。为了改进水火山作用危险性评价，本工作着重于岩浆-水相互作用过程的量化。以前，岩浆-水相互作用的能量学是基于矿床特征来量化的，这可能涉及很大的不确定性，因为岩浆气体膨胀和外部水都有助于岩浆岩的破碎和分散。然而，岩浆-水的爆炸性相互作用与熔岩-水爆炸和爆炸性融水实验是由相同的机制驱动的，因此我们可以用后者来理解前者。这种机制是熔融燃料-冷却剂相互作用（MFCI），其中“熔融燃料”是岩浆或熔岩，“冷却剂”是外部水。为了观察微尺度MFCI过程并确定它们在岩浆-水相互作用期间的进展情况，我们利用实验室实验和熔岩-水爆炸的新数据和现有数据的广度，使用灵活的工业标准软件开发了第一个可扩展的熔融-水混合数值模拟。我们的预期结果解决了自然系统中仍然知之甚少的过程，即(1)影响界面混合和不稳定性的因素，特别是气膜坍塌，(2)转化率与水/熔体质量比之间的关系，以及(3)通过快速传热驱动爆炸的活性颗粒的产生。这一模拟的持续发展将使其成为了解和预测与熔岩水爆炸和水火山爆发有关的危险的工具。研究金的教育方面包括编写教材，其中包括与数值模拟结合使用的实验室实验。该奖学金由地球科学部的岩石学和地球化学项目共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.